SPARK IGNITION,

DIRECT INJECTION

ENGINE R&D 

2001

ANNUAL

PROGRESS

REPORT

U.S. Department of Energy

Energy Efficiency and Renewable Energy

Office of Transportation Technologies
ACKNOWLEDGEMENT

We would like to express our sincere appreciation to Argonne

National Laboratory and Computer Systems Management, Inc.,

for their artistic and technical contributions in preparing and

publishing this report.

In addition, we would like to thank all our program participants

for their contributions to the programs and all the authors who

prepared the project abstracts that comprise this report.
U.S. Department of Energy

Office of Transportation Technologies

1000 Independence Avenue, S.W.

Washington, DC 20585-0121

FY 2001

Progress Report for the Spark Ignition Direct 

Injection R&D Program

Energy Efficiency and Renewable Energy

Office of Transportation Technologies

March 2002
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

CONTENTS

 Page

ii

I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

II. FUNDAMENTAL COMBUSTION AND MODELING STUDIES . . . . . . . . . . . . . . . . . . . . .9

A. Gasoline Fuel Spray Studies Using Synchrotron X-Rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

B. University SIDI Combustion Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

C. Spark-Ignited Direct-Injected (SIDI) Homogeneous Combustion Research and Development . . . . . . . . . . . . . 19

D. Computer Modeling to Support GDI Engine Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

E. Active Flow Control for Maximizing the Performance of Internal Combustion Engines . . . . . . . . . . . . . . . . . 27

III.ENGINE AND COMPONENT R&D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

A. Development of Near-Frictionless Carbon Coatings for SIDI Fuel System Components . . . . . . . . . . . . . . . . . 36

B. Development of an Advanced Non-Impingement SIDI Combustion System and Associated Low Pressure Fuel 

System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

C. Variable Compression Ratio Engine Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

D. Performance of Plasmatron-Enhanced Lean-Burn SI Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

E. On-Board Distillation of Gasoline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

IV. EMISSION SENSOR DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

A. Exhaust Gas Sensors CRADA (HC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

B. Advanced Ion-Mobility NOx Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

C. Exhaust Gas Sensor Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

D . NOx Sensor for Monitoring Vehicle Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

E. Improved Exhaust Emissions and Fuel Economy through the Use of an Advanced NOx Sensor . . . . . . . . . . . 71

F. Fuel Vapor Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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II. INTRODUCTION

Advancing Fuel Efficient Automotive Technologies Through SIDI R&D

On behalf of the Department of Energy’s Office of Transportation 

Technologies (OTT), I am pleased to introduce the Fiscal Year (FY) 2001 

Annual Progress Report for the Spark Ignition Direct Injection Engine 

R&D Program. Together with DOE National Laboratories and in 

partnership with private industry and universities across the United States, 

OTT engages in R&D that provides enabling technology for fuel efficient 

and environment-friendly vehicles. The Program is focused on exploring 

the fundamental combustion characteristics of spark ignition, direct 

injection (SIDI) engines, development of components specific to SIDI 

engines such as new fuel injection systems, development of exhaust 

emission control devices, and development of new sensors to control fuel 

injection and emission control systems. This report marks the conclusion 

of the SIDI R&D Program within DOE, though its many developments 

have broad utility and will live on as part of other DOE R&D Programs.

SIDI engines use direct in-cylinder fuel injection of gasoline which results in a more efficient engine 

because of less need for intake air throttling and because they can be operated with lean air/fuel ratios. Under 

laboratory conditions simulating congested urban driving, SIDI engines have demonstrated the potential for 

fuel economy improvements of up to 30 percent. Under less congested driving conditions, the gains are likely 

to be about half this amount. SIDI engines have advantages in noise and vibration, cost, and specific power 

output relative to compression ignition, direct injection (CIDI) engines (an advanced version of the diesel 

engine) which makes them viable contenders for use in future, more fuel efficient vehicles using gasoline as 

fuel. SIDI engines have the potential to lower engine-out hydrocarbons because less fuel is quenched in 

crevices, and precise fuel metering reduces the need for cold start enrichment. They are more tolerant of 

exhaust gas recirculation (EGR), which can help to control NOx.

SIDI Technology Status

In Europe and Japan, SIDI vehicles are being deployed to improve the efficiency of light-duty vehicles 

using gasoline. Mitsubishi, a leader in SIDI technology has four-, six-, and eight-cylinder SIDI engines in 

production, and all the cars it builds in Europe have SIDI engines. Mitsubishi has built SIDI engines since 

1996, and has produced close to 1 million to date. Audi has just announced a four-cylinder, 2-liter SIDI engine 

for use in Europe, and Volkswagen has announced a similar four-cylinder, 1.6 liter SIDI engine. Nissan 

recently announced that they will soon have a complete line of four-, six-, and eight-cylinder SIDI engines that 

will be capable of meeting the 2005 Euro-IV emission standards. Saab implemented SIDI by incorporating the 

fuel injector with the spark plug in experimental versions of their engines that will be able to meet the 

California ULEV-II emission standards.

Orbital Engine Company is a leading international developer of SIDI fuel systems for all types of lightduty engines. Orbital and Siemens Automotive created a 50:50 joint venture called Synerject to manufacture 

air-assisted direct injection fuel systems (Synerject is located in Newport News, Virginia). In the fall of 2001, 

Orbital announced several new developments:

Rogelio Sullivan, Program Manager
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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• They signed a technical transfer and license agreement 

giving Delphi Automotive Systems rights to manufacture 

and sell Orbital direct-injection technology.

• General Motors unveiled a V-8 concept engine 

incorporating Orbital air-assisted direct-injection fuel 

system.

• Four motorcycle manufacturers announced new products 

using Orbital direct-injection fuel injection systems.

• Orbital teamed with Johnson Matthey to develop a test 

vehicle with 12 percent better fuel economy while 

meeting Euro-IV emission standards. Besides improved 

fuel economy, this combination of Orbital direct-injection 

technology and Johnson Matthey catalyst technology does 

not require ultra-low sulfur gasoline. However, with 

ultra-low sulfur gasoline, significant further reductions in 

NOx emissions are possible with this system.

SIDI development in the U.S. is likely to take a slightly 

different path than the SIDI engines being developed in Europe and Japan. SIDI engines have not been 

introduced into the U.S. because of their additional cost over conventional port injection engines, and 

uncertainty about their ability to meet future emissions regulations (more stringent than those of Japan and 

Europe). The first U.S. SIDI engines are likely to maintain a stoichiometric air/fuel ratio over most of the 

operating range because that will allow use of proven 3-way catalyst technology. Despite forgoing the 

advantages of lean-burn, these SIDI engines will likely still be more efficient than similar port fuel injected 

gasoline engines because of the ability to use higher compression ratios and less throttling. As lean-NOx

emission control devices improve and U.S. gasoline sulfur content is reduced, SIDI engines should be able to 

employ lean-burn operation, resulting in additional fuel economy improvements.

Technical Leadership

The SIDI R&D Program sharply focused on improving SIDI combustion and emission control 

technologies through cost-shared projects with industry partners. Substantial progress was made in the areas 

of new emission sensors, fundamental combustion analysis and modeling, fuel spray imaging, and low-friction 

coatings. These advancements have furthered progress in overcoming the critical technical barriers associated 

with SIDI engines, namely, higher than desired levels of NOx and particulate matter (PM) in the exhaust, 

expansion of the stratified charge operating regime, and higher cost fuel systems. But just as importantly, these 

advancements are equally applicable to development of other advanced engine technologies with CIDI engines 

being the foremost example. DOE could not provide this leadership without the cooperative assistance of 

General Motors, DaimlerChrysler and Ford through participation in the Partnership for a New Generation 

Vehicle (PNGV) technical teams and the Low Emission Partnership (LEP).

The unique scientific capabilities and facilities of the national laboratories offered us the opportunity to 

target those technical areas of highest priority and those that require high-risk R&D that are often overlooked 

by industry. The National Laboratories are a much valued asset in this endeavor. We worked with industry and 

through the PNGV technical teams to ensure that National Laboratory R&D activities fulfilled industry’s needs 

for basic scientific understanding and development of new research tools, materials, and processes. The R&D 

projects conducted were reviewed each year internally and by representatives from the auto manufacturers and 

emission control device manufacturers. This assures that the work completed was relevant to the ultimate 

users of the technologies.

Cross-Section of the Synerject Air-Assisted 

Injector (Courtesy of Synerject)
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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ACCOMPLISHMENTS

Fundamental Combustion and Modeling Studies

The projects in the Fundamental Combustion and Modeling area are aimed at developing research tools, 

collecting engine data, and providing a more complete understanding of SIDI in-cylinder phenomena. To 

achieve high efficiency and low emissions, parameters such as air/fuel ratio and EGR will have to be pushed to 

the limits of stable combustion. The research in this portion of the SIDI Program identifies these limits 

through the development of models and analytical tools. The key processes that have been explored include: 

fuel injection; fuel vaporization; fuel-wall interaction; fuel-air mixing; ignition; and flame propagation and 

combustion. The projects have been conducted primarily at national laboratories and universities, using 

advanced diagnostics in optical research engines and a variety of air flow and combustion simulation 

capabilities. Detailed models of SIDI combustion chambers were created in KIVA and simulations of fuel 

sprays and combustion were performed to verify the experimental results. The tools and data developed are 

being shared with SIDI engine developers to assist them in devising strategies to achieve high efficiency with 

low emissions.

Argonne National Laboratory Advances Fuel Spray Imaging Technology

Argonne National Laboratory (ANL) demonstrated that 

the combination of high intensity x-ray beams from wideband-pass x-ray optics and a fast 2-D x-ray detector can 

collect the radiographic images of gasoline injector sprays 

much more efficiently. The image collection time has been 

reduced from 1 week to a few hours per injection condition. 

This advancement makes this method practical as a 

diagnostic technique for fuel injection equipment 

manufacturers and the auto industry to use in designing new 

injectors. Using a Delphi injector, ANL has clearly shown 

the ability to measure the asymmetry of the spray cone and 

variations in the density of the spray. Spatial temporal 

resolution and mass distribution of the entire spray event 

can be captured in unprecedented detail. This measurement 

technique is so precise that pressure waves are detected 

emanating from the injector. This is the first time this 

phenomena has been observed, and this project was 

awarded ANL’s Director’s Award in June 2001 because of it. 

This work paves the way to a comprehensive understanding 

of the dynamic characteristics of high-pressure fuel spray in 

near-nozzle regions that can potentially benefit designers of 

fuel injectors for SIDI engines, and other applications.

X-Ray Snapshot of Direct Injection Fuel Spray 

Showing Density Waves Emanating from the Injector
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Sandia National Laboratory Identifies Improved Fuel Blend for Laser-Induced Fluorescence 

Studies

Using evaporation experiments, Sandia National 

Laboratory (SNL) demonstrated that 3-pentanone is 

preferentially evaporated from isooctane-3-pentanone 

mixtures commonly used for laser-induced fluorescence 

(LIF) measurements of direct injection fuel spray inside 

the cylinder. By blending the two fluorescent fuel tracers 

being used in an optimized ternary fuel mixture, SNL 

found that a much more uniform LIF signal is obtained 

during the evaporation process. This results in LIF being 

able to accurately track fuel vapor concentration during 

fuel injection and evaporation in SIDI engines. These 

results and tests of the ternary fuel/tracer blend in a fired 

SIDI engine have been submitted for publication.

Los Alamos National Laboratory Develops Multicomponent Fuel Model for Modeling SIDI 

Combustion

Los Alamos National Laboratory (LANL) improved the 

modeling capabilities of KIVA-3V by developing a 

multicomponent fuel model and by incorporating it into the the 

spray and wall film submodels of KIVA-3V. This model (unlike 

others), tracks temperature and mass concentration variations 

within the interior of the fuel droplet or wall film using an 

efficient computational scheme. LANL found that tracking 

internal variations inside the fuel is necessary in order to capture 

the complex spatial and temporal variations that occur during 

multicomponent fuel evaporation. The results of this work have 

been published and several presentations have been made at 

meetings during the past year.

University of Michigan Uses Active Flow Control to Design SIDI Combustion Systems

The cycle-to-cycle variation in turbulence and fuel-airresidual exhaust gas mixing is of primary importance to 

stratified charge SIDI engines. Recent research has shown a 

significant interaction between the mean flow and the 

fluctuating parts of the in-cylinder velocity. In order to 

design better lean burn engines, one has to have a better 

understanding of the flow patterns during the compression 

stroke and a way needs to be found to reduce cycle-to-cycle 

variation. If cycle-to-cycle variation is reduced, the incylinder flows are more predictable and thus one could 

employ leaner combustion without large torque variability 

or misfire. The objective of this study was to investigate the 

effects of perturbing the flow in the engine cylinder using 

controlled acoustic excitation. This study was conducted 

using a 1999 model year Ford cylinder head with 4 valves 

Motor

Nitrogen+Biacetyl

UV Lenses

Laser Mirror

Intake

Exhaust
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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and double overhead cams. A flat-head, optical access piston was used in the experiment. Molecular Tagging 

Velocimetry (MTV) was used to measure the velocity profiles at a tumble plane which is located at the center 

of the cylinder, about 2 cm from each side of the cylinder wall. The most advantageous operation of the 

system showed a 25 percent reduction in the variation of in-cylinder flow velocities. 

Engine and Component R&D

The objective of the projects in the Engine and Component Research portion of the SIDI Program is to 

address the system level barriers to commercialization of SIDI engines. These barriers include: lack of 

effective and durable NOx emission control devices; excess injector and combustion chamber deposits; the cost 

of fuel injection system components; and quantification and control of PM emissions. The projects in this 

portion of the SIDI Program are being conducted by national laboratories, universities, and through 

cooperative agreements with industry. Each of the individual projects is focused on a research topic that has a 

high potential to overcome one or more of the key barriers to commercialization. Each project is closely tied to 

a potential customer or system developer through a cooperative agreement or similar mechanism to transfer 

technology to industry.

Argonne National Laboratory Demonstrates Durability of Low-Friction Injector Coatings

Argonne National Laboratory (ANL) has developed 

low-friction coatings for SIDI fuel injectors. These 

coatings may help offset the reduced lubricity of lowsulfur fuels. Million-cycle wear tests were conducted 

using two different coating formulations and seven 

different gasolines plus pure ethanol. The fuels 

represented summer and winter blends, premium and 

regular octane levels, and some contain additives under 

consideration for future blends. The low-friction 

coatings were found to provide clear reductions in 

friction over the uncoated fuel injectors. One coating 

showed 27% lower friction, while use of the other 

coating resulted in a friction reduction by nearly a factor 

of two. Equally important, is the reduction in wear that the coatings provide. Because of the high level of 

precision and tight tolerances in injector tips, any wear or erosion can be very detrimental to spray quality. The 

ANL coatings have been shown to dramatically reduce wear (and potentially deposit accumulation), helping to 

maintain injector performance over its useful life.

Delphi Advances Development of a Low-Pressure Direct Injection Fuel System

Delphi Energy & Engine Management Systems has been 

developing a low-pressure direct injection fuel system that 

would enable SIDI engines to meet their efficiency targets. Low 

fuel pressure is beneficial in that less energy is needed to 

generate good fuel spray characteristics, and only a single pump 

is needed, which reduces cost. However, getting sufficiently 

atomized fuel becomes more difficult as fuel injection pressure 

is reduced. A total of 42 initial injector atomizer designs were 

considered, and five were tested during the past year. Of these 

five, three underwent extensive testing and one has emerged as 

having the best combination of performance characteristics. For 

the fuel pump, an internal gear pump was found to be the best to 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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develop the required pressure. Improved performance was achieved by minimizing clearances, optimizing 

valve ports, and improving the design of the interface between the pump and drive mechanism. Optimization 

of the fuel pump durability continues through material selection, lubrication, and optimum application of 

pressure balancing. Additional component development will be performed and a final report will then be 

issued.

Emission Sensor Development

The projects in the Sensor Development portion of the SIDI Program are directed towards the development 

of new sensors to control SIDI engine operation, diagnostics, and emission control systems. However, 

practical sensors must be capable of withstanding harsh engine environments while being highly species 

selective, fast responding, and inexpensive. Examples of the sensors that are being developed include those 

that can detect hydrocarbons (HCs) and NOx with high precision and fast response, and sensors that can 

measure a wide-range of oxygen in the exhaust gases. Through industry feedback and technical collaboration, 

the feasibility of particular sensor concepts is evaluated at the outset of each project. Prototype sensors are 

evaluated against performance targets using bench rigs, and those that show promise will be evaluated for 

robustness and durability through engine tests. All of the projects include industry partners who perform these 

tests. 

Los Alamos National Laboratory Develops Low-Cost Solid-State Non-Methane HC Sensor

Los Alamos National Laboratory (LANL) has developed low-cost, solid-state non-methane hydrocarbon 

sensors that will be useful to control SIDI emission control systems. These sensors are based on thin-film 

transition metal oxide catalyst/noble metal composites deposited on oxygen ion conducting solid-state 

electrolytes. These sensors are very small and have demonstrated 

the ability to reproducibly measure hydrocarbon emissions under 

laboratory conditions for long time periods. They exhibit almost no 

cross sensitivity for nitric oxide, water vapor or carbon dioxide 

gases. They have better than 95 percent device-to-device response 

uniformity and the response time has been improved from a minute 

to less than 3 seconds. The automotive Cooperative Research and 

Development Agreement (CRADA) partners for this project have 

also extensively tested these devices under laboratory and engine 

exhaust conditions. A number of automotive sensor suppliers have 

expressed interest in the possible testing and subsequent 

commercialization of this sensor. 

Pacific Northwest National Laboratory Advanced NOx Sensor Development

SIDI engines will likely need to rely on sensors to control regeneration of NOx adsorption catalysts. The 

signal for regeneration will be when the NOx

catalyst approaches full adsorption and NOx

escapes from the catalyst outlet. Pacific Northwest 

National Laboratory compared several variations of 

two-stage zirconia-membrane based prototype NOx

sensors and the important parameters investigated 

included: electrode thickness, triple phase boundary 

lengths, pore size/distribution, and primary grain 

size/distribution. They discovered that optimal 

design and fabrication of diffusion channels to 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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control gas flow to the oxygen pump cavity is critical for developing accurate and sensitive sensor elements, 

and that carefully optimized grain morphology and pore structure in the electrode is required to obtain the 

desired electrocatalytic reduction behavior from electrode structures. As quantification of these relationships 

is completed, PNNL will provide recommendations for optimal NOx sensor designs. 

Honors and Special Recognition

Jin Wang, Ramesh Poola, Chris Powell, and Yong Yue of Argonne National Laboratory were finalists in 

the Discover Awards, for their work on using x-rays to image and measure fuel injector spray patterns. The 

award is issued by Discover Magazine.

Patents

1. Matthews, R.D.,R. Stanglmaier, G.C. Davis, and W. Dai, "On-Board Gasoline Distillation for Reduced 

Hydrocarbon Emissions at Start-Up", U.S. Patent No. 6,119,637, issued Sept. 19, 2000.

2. "Mixed potential hydrocarbon sensor with low sensitivity to methane and carbon monoxide" R. 

Mukundan, E.L. Brosha, F.H. Garzon inventors. Patent pending - case #94675.

3. "Enhanced Electrodes for Solid State Gas Sensors" F.H. Garzon and E.L. Brosha inventors. U.S. Patent 

Granted.

Summary

The remainder of this report highlights progress achieved during FY 2001 under the Spark Ignition Direct 

Injection R&D Program. The following 16 abstracts of industry and national laboratory projects provide an 

overview of the exciting work conducted to tackle tough technical challenges associated with SIDI engines, 

including fuel injection, fuel/air mixing, combustion chamber design, sensor development, and catalytic 

exhaust treatment devices for controlling emissions. The commitment of Japanese and European 

manufacturers to SIDI technology and the recent interest by U.S. manufacturers and suppliers suggests a bright 

future for SIDI engines and more efficient vehicles because of them. 

I would like to personally thank all of the researchers at the national laboratories, universities, and in 

industry, for all your contributions to this Program. Your hard work and ingenuity have resulted in a 

measurable advancement in the state of knowledge about the real potential and remaining challenges for SIDI 

engines.

Rogelio Sullivan, Program Manager

Office of Advanced Automotive Technologies

Office of Transportation Technologies
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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II. FUNDAMENTAL COMBUSTION AND MODELING STUDIES

A. Gasoline Fuel Spray Studies Using Synchrotron X-Rays

Jin Wang (Primary Contact) and Roy Cuenca

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

(630) 252-9125, fax: (630) 252-9303, e-mail: wangj@aps.anl.gov

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Characterize gasoline spark-ignited, direct-injection (SIDI) engine fuel injector hollow-cone spray 

structure and dynamics in the region near the nozzle. 

• Develop highly efficient, highly quantitative and time-resolved radiographic methods and 

instrumentation to achieve the above goal.

• Obtain the axial, radial, and angular distribution of mass flux in fuel injector sprays to characterize the 

core and study the mechanism leading to spray breakup and atomization.

Approach

• Use the combination of high intensity x-ray beams from wide-band-pass x-ray optics and a twodimensional (2-D) x-ray detector to collect the radiographic images of the gasoline sprays more 

efficiently. 

• Develop data analysis methods and computational programs to process the image data for quantitative 

evaluation of such spray characteristics as fuel mass distribution and flux.

• Use theoretical modeling and computational approaches to improve the understanding of the hollowcone sprays.

Accomplishments

• We have demonstrated that the combination of high intensity x-ray beams from wide-band-pass x-ray 

optics and a fast 2-D x-ray detector can collect the radiographic images of the gasoline sprays much 

more efficiently. The image collection time has been reduced from 1 week to a few hours per injection 

condition. Therefore, the method is practical as a diagnostic technique for injection equipment 

manufacturers and the auto industry.

• We have studied thoroughly the fuel sprays from a Delphi gasoline direct injection (GDI) system. 

Tomographic-type measurements have been performed with high image quality, revealing never-seenbefore characteristics of hollow-cone gasoline sprays.

• We have developed a comprehensive analysis program to quantitatively evaluate the fuel distribution 

at any given time and spatial location.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Future Directions

• We plan to develop and implement a system consisting of dedicated x-ray optics and detectors suitable 

for 2-D data collection to further improve the efficiency of the testing.

• We will perform the spray measurement of the Delphi injector under high pressure and temperature 

environments to simulate actual gasoline engine cylinder conditions.

• We will develop better software so that the data analysis can be performed in a more automated mode.

Introduction

Using synchrotron X-radiography and mass 

deconvolution techniques, this research reveals 

never-before-seen structure characteristics of the 

direct injection (DI) gasoline hollow-cone sprays in 

the near-nozzle region, paving a way for a revolution 

in gasoline direct injection (GDI) technology. A 

series of experiments were conducted with the 

world’s most brilliant monochromatic X-ray beams. 

Employed to measure gasoline sprays, Xradiography allows quantitative determination of the 

fuel distribution in this optically impenetrable region 

with a time resolution of better than 1 μs, revealing 

the most detailed near-nozzle mass distribution of a 

fuel spray ever detected. Based on the X-radiographs 

of the spray collected from four different 

perspectives, enhanced mathematical and numerical 

analysis was developed to deconvolute the mass 

density of the gasoline hollow-cone spray. This lead 

to efficient and accurate regression curve fitting of 

the measured experimental data to obtain essential 

parameters of the density distribution, which are then 

utilized in reconstructing the cross-sectional density 

distribution at various times and locations. The fuel 

density distribution of the near-nozzle region may 

greatly affect the fuel’s atomization further 

downstream in GDI systems. The quantitative 

observation of the severe asymmetry associated with 

the sprays will allow the automobile industry to 

design better injection nozzles and combustion 

engines with a clearer understanding of the key 

components that affect the spray’s structure in this 

region. 

Approach/Results

In this research, a series of intensive experiments 

have been conducted to measure the DI gasoline 

sprays in the near-nozzle region at the APS and 

Cornell High Energy Synchrotron Source (CHESS). 

A GDI injection system with an outwardly opening 

injector was employed. Injection was performed into 

a spray chamber filled with nitrogen gas at 

atmospheric pressure and room temperature. The 

spray chamber (10.16 cm in width, 12.7 cm in height, 

20.32 cm in depth) is designed to hold the injector, 

contain the spray plume, and allow the nitrogen to 

scavenge the fuel vapors. The chamber has 63.5-

mm-long by 63.5-mm-wide windows of Kapton film 

that provide line-of-sight access for the x-rays. A 

gentle flow of nitrogen was maintained through the 

chamber to scavenge the fuel spray mist. The fuel 

used in this study was a blend of calibration-type 

gasoline fuel (Viscor) and a cerium-containing 

additive with a final cerium concentration of 4.2% by 

weight. Table 1 provides a summary of the injection 

system, test fuel, and test conditions employed for 

the x-ray absorption measurements. The focused Xray beam was collimated by a pair of X-Y slits to a 

size of about 13 mm (horizontal) x 2.5 mm (vertical). 

The collimated beam then passed into the injection 

chamber for probing the fuel sprays. An extremely 

brilliant monochromatic x-ray beam tuned to 6.0 keV 

was used; this x-ray photon energy is slightly above 

the several cerium L resonance absorption edges near 

Parameters Quantity and Properties

Injection system GDI with outwardly 

opening injector

No. of orifices 1

Orifice diameter, mm 1.9

Fill gas and pressure, MPa N2, 0.1

Fill gas temperature, °C 25 to 30

Fuel Viscor (the calibration 

fluid) with Ce- additive

Specific gravity, g/mL 0.8405

Spray duration, μs 1000

Spray cone-angle 65° (nominal)

Table 1. Parameters of the GDI system and the injection 

conditions
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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5.7 keV. This maximizes absorption by the fuel jet. 

The transient x-ray attenuation signal due to the fuel 

spray was measured by using a fast-response x-ray 

area detector, pixel array detector (PAD) with a 

temporal resolution of better than 1 ms. The 

transmission image was averaged for 20 cycles in 

order to improve the signal/noise ratio. A data 

processing program was developed to quantitatively 

determine X-ray transmission values, incorporating a 

noise-reduction technique. Then the program 

calculates the integrated mass distribution of fuel, 

which results in a time-resolved mass measurement. 

Videos of the gasoline spray have been produced 

from a group of transmission snapshots by modified 

commercial image processing software. The 

snapshots demonstrated the details of dynamic 

characteristics of the mass distribution of the hollowcone gasoline spray at near-nozzle regions. These 

include time-dependent irregular density distribution 

and extremely high frequency pressure waves within 

the sprays, never-before discovered or reported by 

any conventional non-optical or optical spray 

diagnostic technique. Tomographic-type of xradiographs have been collected to facilitate the 

model-dependent deconvoluting theme from four 

angles: 0°, 45°, 90°, and 135°.

Figure 1 shows a group of 2-D reconstructed 

transmission x-ray snapshots of the fuel spray at 

different time instances, which clearly displays the 

Figure 1. Transmission snapshots of x-ray measurement 

of fuel spray (beam rotation angle is 45o); (a) 

time=26.657 s, when the spray is just exiting 

the nozzle; (b) time=55.365 s, when the 

spray is forming its hollow-cone shape; (c) 

time=96.376 s, when the spray is extended to 

its full range; (d) time=123.034 s, after the 

nozzle is closed.

Figure 2. Diagram illustrating the reconstruction of the 

cross-sectional density distribution rings from 

mass deconvolution fitting at four directions.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

12

transience of gasoline sprays. Features such as 

asymmetry, local "streak," and pressure waves are 

readily evident in these snapshots. The circles on 

Figure 1(a) pinpoint the asymmetry of the spray that 

is present upon its exit from the nozzle. Although 

such asymmetry seems to moderate as the spray 

continues, quantitative analysis later revealed that the 

irregularity still existed throughout the duration of 

the spray. The streaks of local density peaks, labeled 

in Figure 1(c), demonstrate further asymmetry in the 

angular distribution of density. Another neverbefore-observed phenomenon is the pressure waves, 

shown in Figure 1(b), appearing as high-density 

columns. To illustrate more clearly the deconvolution 

method, Figure 2 depicts the 4-way tomographictype of analysis which has been performed on the 

image data collected at the location 20 mm from the 

nozzle and at ca. 110.73 μs after the injection. Figure 

3 displays the deconvolution regression fits at time 

110.73 μs, 15 mm from the nozzle, on all four 

rotational angles. There are large differences in 

density in the angular direction. The radius of the 

annular cross-section also changes from one 

rotational angle to another, indicating the cross 

section of the spray cone is not perfectly circular. 

Figure 4 shows the cross-section rings of density 

distribution constructed from the calculated matrix, 

using a contour color fill graphing technique, at four 

distances, 5, 10, 15, and 20 mm from the nozzle, all 

at time 110.73 μs after the start of the injection. They 

are denoted as a, b, c, d, respectively. Some important fitting parameters are listed in Table 2.

Conclusions

In light of the precise analysis that was performed on 

the experimental data obtained from measuring the 

fuel spray with X-radiography, we can conclude that 

observing the near-nozzle regions of the hollow-cone 

Figure 3. Experimental mass calculations and mass 

deconvolution model fitting at time 110.73 μs, 

15 mm from the nozzle; (a) rotation angle 0°; 

(b) rotation angle 45°; (c) rotation angle 90°; 

(d) rotation angle 135°.

Figure 4. Reconstructed density distribution rings at 

110.73 μs; cross-section slice (a) 5mm from 

nozzle, (b) 10mm from nozzle, (c) 15mm from 

nozzle, (d) 20mm from nozzle.

Distance 

from Nozzle 

(mm)

Average 

Radius 

(mm)

Max. 

Density 

(μg/mm3

)

Min. 

Density 

(μg/mm3

)

5 4.088 1.600 0.256

10 7.538 1.000 0.120

15 10.513 0.800 0.064

20 14.213 0.550 0.066

Table 2. Density Distribution Variation on the Fuel 

Spray’s Cross-Sectional Rings
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

13

gasoline spray with non-intrusive monochromatic xrays is an effective method to study and document 

the characteristics of the never-before-seen area of 

the fuel injection process. The mathematical and 

numerical analysis presented in this study was able to 

efficiently and accurately construct a mass 

deconvolution model that fit the experimental data 

extremely well. From the parameters obtained from 

these models of various rotation angles of the spray, a 

cross-sectional density distribution model was 

reconstructed to fully represent the characteristics of 

the hollow-cone spray with its many irregularities. 

This successful cross-sectional construction can be 

readily compiled into a three-dimensional image 

model that will better show the continuity of the 

density distribution changes through time and space. 

The promising finding and novel methodology 

described in this work pave the way to a 

comprehensive understanding of the dynamic 

characteristics of high-pressure fuel spray in nearnozzle regions that can potentially benefit liquidpropellant rockets, gas turbines, internal-combustion 

engines, and even other industrial areas.

References

1. Quantitative Measurements of Direct-Injection 

Gasoline Fuel Sprays in Near-Nozzle Region 

Using Synchrotron X-Ray, Y. Yue, C. F. Powell, 

R. Poola, J. Wang, M.-C. Lai, S. E. Parrish, SAE 

paper SAE 2001-01-1293, 2001.

2. Synchrotron X-Ray Measurement of Direct 

Injection Gasoline Fuel Sprays, Y. Yue, C. 

Powell, R. Cuenca, R. Poola, J. Wang, ASME 

paper, accepted, 2001.

3. X-ray Propagation-Based Phase-Enhanced 

Imaging of Fuel Injectors, W.-K. Lee, K. Fezzaa 

and J. Wang, ASME paper, accepted, 2001.

Awards

1. Director’s Award, Argonne National Laboratory, 

June 2001.

2. Finalist, Discover Magazine Award, June 2001.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

14

B. University SIDI Combustion Projects

Jay Keller

Sandia National Laboratories

P.O. Box 969, MS 9053

Livermore, CA 94550-9053

(925) 294-3316, fax: (925) 294-1004, e-mail: jokelle@sandia.gov

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Introduction

A significant part of the overall OAAT engine combustion program is a well-coordinated University 

program. These projects were awarded from a carefully crafted competitive bid process; as a result, they form 

an integral part of the overall engine combustion program. Sandia National Laboratories provides technical 

management of these projects to ensure a well-focused overall program. Biannual meetings where recent 

research results are presented and future directions are discussed between the University projects, the National 

Laboratory projects, and the Industrial partners insure the program remains well focused and collaborative. 

University research includes both compression ignition direct-injection (CIDI) and spark ignition directinjection (SIDI) work; following are the individual reports on SIDI work performed during phase II of these 

contracts (June 2000 to May 2001). For information on the CIDI projects, refer to the 2001 Annual Report on 

Combustion and Emission Control for Advanced Engines. 

Objectives and Approach

The University of Texas is studying mixture 

formation, emissions sources, and fuel composition 

effects in spark-ignited, direct-injection (SIDI) 

engines. These experimental studies are being 

conducted in a 4-cylinder GM Twin Cam engine and 

an analog single-cylinder optical engine having an 

identical cylinder head. Both engines have one 

cylinder converted to SIDI operation. The emissions 

impact of the mixture formation phenomena 

observed in the optical engine is to be measured in 

the Twin Cam engine and extended to higher engine 

speeds and loads. The conversion to SIDI operation 

has been completed in both engines. A 

programmable engine controller has been built to 

allow independent control of the direct-injection 

cylinder and the other three port-injected cylinders in 

the Twin Cam engine. In the optical engine we have 

studied spray/flow interactions; wall wetting; and 

how the equivalence ratio near the spark gap is 

related to the injection timing, bulk flow, injector 

cone angle, and engine speed. In addition, we have 

studied particulate matter emissions under cold-start 

conditions and the origins of hydrocarbon emissions 

resulting from fuel wetting of the piston.

Results

We have found that the type of in-cylinder flow 

field has a tremendous effect on wall wetting and 

fuel/air mixing and that fuel composition affects 

hydrocarbon emissions. Using schlieren imaging, 

we found that fuel vapors can evaporate from the 

piston surface late during the power stroke, forming 

dense regions of fuel vapor that remain close to the 

SIDI Mixture Formation, Emissions Sources, and Fuel Composition Effects

Ronald D. Matthews and Matthew J. Hall

The University of Texas at Austin

Grant Number DE-FG04-99AL66262
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

15

piston surface. This behavior may be a cause of high 

hydrocarbon emissions observed from SIDI engines. 

We have found that clouds of particulates can form as 

a result of pool fires on the piston. The particulates 

form during the power stroke at the point at which incylinder temperatures are too low to complete 

oxidation, leading to high particulate emissions. 

Work on the metal Twin Cam engine has been 

completed and the control system is being calibrated 

to operate the engine for the emissions and fiber 

optic spark plug measurements. 

A new set of fiber optic spark plug 

measurements were completed in the optical engine 

to measure the effects of bulk flow and injection 

timing on fuel/air mixing under firing operation. 

Both parameters have a strong effect on engine 

indicated mean effective pressure (IMEP) and 

measured emissions. A tradeoff was found between 

wall wetting and mixing as a function of injection 

timing for early injection. Later injection timings 

resulted in less wall wetting, but also less time for 

sufficient mixing of the fuel and air to occur. The 

optimum timing for early injection was found to be 

120 degrees after top dead center (ATDC) of intake. 

This resulted in minimal surface wetting yet 

sufficient time for mixing. It was found that at the 

earliest injection timing examined (60 degrees ATDC 

intake), between 10% and 15% of the injected fuel 

was lost to surface wetting for all of the bulk flows 

examined. 

For late injection timings, a strong correlation 

was found between the measured equivalence ratio at 

the time of ignition and the measured IMEP. Higher 

equivalence ratios at the time of ignition resulted in 

higher IMEP. The equivalence ratio at the time of 

ignition was strongly dependent upon both the bulk 

flow and the injection timing. It was found that the 

cycle-to-cycle variation in the equivalence ratio at 

the time of ignition increased as the injection timing 

was retarded. These cycle-to-cycle variations were 

found to correlate well with cyclic variability in 

IMEP. In general, the strong bulk flows typified by 

tumble and swirl resulted in faster mixing, but also 

greater convection of inhomogeneities past the spark 

plug. This made engine performance for these flows 

more sensitive to both injection and ignition timing. 

The weaker bulk flows typified by reverse-tumble 

and low-tumble resulted in slower mixing, but a 

more stable charge near the spark plug.

The effect of piston wetting on particulate 

emissions was investigated in the metal Twin Cam 

engine. The engine was operated on 90% propane 

fuel while an injection probe was used to inject 10% 

liquid fuel onto the top of the piston. The liquid fuels 

were chosen to examine the effects of fuel volatility 

and molecular structure on the PM emissions. 

A nephelometer was used to characterize the PM 

emissions. Mass measurements were compared with 

gravimetric filter measurements and particulate size 

measurements were compared with scanning 

electron microscope photos of particulates captured 

on filters. The engine was run at 1500 rpm at the 

Ford world-wide mapping point with an overall 

equivalence ratio of 0.9. The liquid fuels examined 

were California Phase II gasoline, n-pentane, isooctane, toluene, and undecane.

With the injection of liquid fuel onto the piston, 

particulate matter mass emissions increased greatly 

over operation on propane alone and over operation 

where a similar fraction of the liquid fuel was port 

injected. Toluene and n-pentane had the highest 

mass emissions, reflecting the effects of fuel 

structure and volatility. They also had the largest 

mean particulate size. The particulates had mean 

scattering diameters in the range of 500 to 1000 nm. 

Time-resolved measurements taken at 2 second 

intervals showed the temporal variation of PM 

characteristics.

Particulate mass emissions correlated well with 

prior measurements of unburned hydrocarbon 

emissions taken under the same conditions.

Publications

1. Alger, T., Huang, Y., Hall, M.J., and Matthews, 

R.D., "Liquid Film Evaporation Off the Piston of 

a Direct Injection Gasoline Engine," Society of 

Automotive Engineers Paper 2001-01-1204, 

2001.

2. Mehta, D., Alger, T., Hall, M. J., Matthews, R. 

D., and Ng, H. "Particulate Characterization of a 

DISI Research Engine using a Nephelometer and 

In-Cylinder Visualization," Society of 

Automotive Engineers Paper, to be presented at 

the SAE Fuels and Lubricants Meeting, Orlando, 

FL, May, 2001.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

16

3. Warey, A., Huang, Y., Matthews, R. D., Hall, M. 

J., and Ng, H. "Effects of Piston Wetting on Size 

and Mass of Particulate Matter Emissions in a 

DISI Engine," submitted to Society of 

Automotive Engineers for 2002 World Congress, 

February, 2002.

4. Alger, Matthews, R. D., and Hall, M.J. "Effects 

of In-cylinder Flow on Fuel Concentration at the 

Spark Plug and Engine Performance and 

Emissions in a DISI Engine," submitted to 

Society of Automotive Engineers for 2002 World 

Congress, February, 2002.

Mixture Preparation and Nitric Oxide Formation in an SIDI Engine Studied by 

Combined Laser Diagnostics and Numerical Modeling

Profs. Volker Sick and Dennis N. Assanis

The University of Michigan

Grant No. DE-FG04-99AL66236

Objectives

Through the combination of advanced imaging 

laser diagnostics with multi-dimensional computer 

models, a new understanding of the performance of 

direct-injection gasoline engines (SIDI) is being 

pursued. The work focuses on the fuel injection 

process, the breakup of the liquid into a fine spray 

and the mixing of the fuel with the in-cylinder gases. 

Non-intrusive laser diagnostics will be used to 

measure the spatial distribution of droplets and 

vaporized fuel with very high temporal resolution. 

These data along with temperature measurements 

will be used to validate a new spray breakup model 

for gasoline direct-injection. Experimental data on 

near wall fuel distributions will be compared with 

modeled predictions of the spray-wall interaction and 

the dynamics of the liquid film on the surface. 

Quantitative measurements of local nitric oxide 

concentrations inside the combustion chamber will 

provide a critical test for a numerical simulation of 

the nitric oxide formation process. This model is 

based on a modified flamelet approach and will be 

used to study the effects of exhaust gas recirculation.

Experimental Approaches and Achievements

A single-cylinder optical SIDI engine was built 

that allows access to the entire combustion chamber 

for the observation of spray formation, fuel/air 

mixing, flame propagation and nitric oxide 

formation. The introduction and mixing of fuel (isooctane) with air was studied via PLIF (planar laserinduced fluorescence) using toluene as a trace 

because of its unique quenching properties that yield 

a fluorescence signal that is directly proportional to 

the fuel/air ratio. Figure 1 shows an example of an 

instantaneous φ distribution that was measured in the 

pentroof of the engine very close to the spark plug.

To assist the interpretation of the fuel/air mixing 

data, flow fields were investigated using Particle 

Image Velocimetry (PIV). It was found that the 

center of a strong swirl shifts as the engine speed is 

changed.

Figure 1. Equivalence Ratio Map, Measured Close to 

the Spark Plug at 600 rpm
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

17

Modeling Approaches and Achievements

A spray/wall impingement submodel was 

developed and integrated into the KIVA-3V 

multidimensional computational fluid dynamics 

(CFD) environment to simulate the behavior of a 

spray impacting solid surfaces. The performance of 

the model was assessed by comparing numerical 

results to the data obtained from measurements 

conducted at the University of Michigan of a hollow 

cone spray impinging normally onto a flat plate 

under ambient conditions. The spray/wall 

impingement model conserved the mass, momentum, 

and energy of an impinging parcel before and after 

impact. Three splashing parcels and one wallfilm 

parcel were used to represent the shattering of an 

incoming droplet upon impact with the surface as 

shown in Figure 2.

The model showed improvements over the 

current KIVA-3V impingement model as shown in 

Figure 3 in predicting on-the-wall spray penetrations. 

Publications

1. Sick, V., Stojkovic, B., 2001, "Attenuation 

Effects on Imaging Diagnostics of Hollow-Cone 

Sprays," Applied Optics, 40, (15) pp. 2435 - 

2442

2. Stojkovic, B., Sick, V. 2001, "Evolution and 

Impingement of an Automotive Fuel Spray 

Investigated with Simultaneous Mie/LIF 

Techniques," Applied Physics B 72, pp. 1-9

3. Grover, R., Assanis, D., 2001, "A Spray Wall 

Impingement Model Based Upon Conservation 

Principles," Proceedings of The 5th Int. 

Symposium on Diagnostics and Modeling of 

Combustion in Internal Combustion Engines, 

Nagoya, Japan, 2001.

Figure 2. Splash of an Impinging Parcel

Figure 3. Comparison of the Normal Penetration 

Predictions of New Impingement Submodel 

and KIVA-3V Model with Experimental Data

Hydrocarbon Emission Formation Mechanisms in Direct-Injection Engines

Prof. Jaal B. Ghandhi

University of Wisconsin-Madison

Grant No. DE-FG04-99AL66264

Objective

The objective of this project is to investigate the 

major hydrocarbon emission formation mechanisms 

in a gasoline direct-injection (SIDI) engine. The two 

major sources of hydrocarbon emissions are the 

incomplete combustion of fuel in the lean regions of 

the stratified fuel-air mixture, and the evaporation of 

liquid fuel films from the combustion chamber 

surfaces following the flame propagation through the 

cylinder. An experimental approach has been taken 

to separately investigate both of these mechanisms.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

18

Results

1) The first direct observation of the lean flame 

quench phenomena in an engine — Lean flame 

quenching has been postulated to occur in stratifiedcharge engines, contributing to hydrocarbon 

emissions, but it has never been directly observed. 

Using a combination of planar laser-based imaging 

techniques, lean flame quenching has been directly 

observed in an engine for the first time. Planar laserinduced fluorescence (PLIF) of 3-pentanone was 

used to mark the fuel, and PLIF of the hydroxyl 

radical was used to identify the product region. The 

engine was run at both 600 and 1200 rpm, an overall 

equivalence ratio of 0.3, and with naturally aspirated 

intake conditions. A clearly defined region of 3-

pentanone fluorescence (fuel) was always observed 

late in the expansion stroke at the edge of the piston 

bowl. This region was also always found to be 

devoid of OH fluorescence. This combination 

provides evidence that the flame had not propagated 

into this region of the fuel cloud. Further, the late 

timings of these observations — up to 75 degrees after 

top dead center — indicate that further chemical 

conversion is not possible.

2) Correlation of the lean flame quench 

phenomena with the engine operation — Once lean 

flame quenching was observed, a series of 

experiments were performed to investigate the 

necessary in-cylinder conditions for avoiding the 

phenomena and the accompanying hydrocarbon 

emissions. Two types of tests were performed, both 

with the goal of increasing the end gas temperature. 

The first test involved advancing both the injection 

and ignition timings to phase the heat release earlier 

within the cycle. In spite of the slight increase in end 

gas temperature, flame quenching was still observed 

for the range of conditions that allowed acceptable 

combustion. The second test involved throttling the 

engine while maintaining a constant injected fuel 

mass. At an intake absolute pressure of 69 kPa the 

flame was observed to propagate across the entire 

combustion chamber, and quenching was not 

observed. There are two possible causes for this 

behavior: increased homogeneity due to the increase 

in the overall fuel-air ratio (although it is still well 

lean of stoichiometric) and the increase in the end 

gas temperature.

3) Development of a robust fiber optic fuel film 

temperature measurement system — A diagnostic has 

been developed to allow continuous single-point fuel 

film temperature measurement through the dual 

wavelength observation of the fluorescence of BTBP, 

which is doped into the fuel. The system uses a 

single optical fiber for both delivery of the laser light 

and collection of the fluorescence, and provides 

spatial resolution of 100 μm. The calibration has 

been made extremely robust so that fibers can be 

interchanged in the system without a change in the 

temperature calibration. Thus, multiple fibers from 

an engine can be used with no change in the system 

response, although the magnitude and time history of 

the fluorescence signals will be different.

4) Preliminary fuel film temperature 

measurements in a firing direct-injection engine — 

The fiber-based fuel film temperature system has 

been employed in a firing gasoline direct-injection, 

and preliminary data have been acquired. The fibers 

were mounted in the piston crown and were removed 

from the engine via a linkage within the Bowditch 

piston. No fiber durability issues were encountered. 

The results showed that the mean fuel film 

temperature was very close to the piston crown 

temperature, which was measured simultaneously 

with a thermocouple. No interference from 

combustion luminosity was observed. Further 

testing will be pursued in the near future. 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

19

C. Spark-Ignited Direct-Injected (SIDI) Homogeneous Combustion Research 

and Development

Richard Steeper and Greg Fiechtner

Sandia National Laboratories

PO Box 969, MS 9053

Livermore, CA 94551-0969

Steeper: (925) 294-2618, fax: (925) 294-1004, e-mail: steeper@sandia.gov

Fiechtner: (925) 294-3161, fax: (925) 294-1004, e-mail: gjfiech@sandia.gov

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Characterize the fuel injection process in SIDI engines.

• Determine the extent and location of wall-wetting, and identify its effects on combustion and 

emissions.

• Characterize the in-cylinder fuel-air mixing process, emphasizing fuel distribution in the vicinity of 

the spark plug at the time of ignition.

• Improve laser-induced fluorescence (LIF) diagnostic to achieve quantitative measurements of incylinder air-fuel ratio distribution.

Approach

• Apply LIF and laser elastic scattering methods to record bench-top and in-cylinder injector 

performance over a range of fuel temperatures and ambient pressures.

• Use flood LIF to measure fuel films that form on the piston window. Record simultaneous flame 

images and soot scattering images to identify pool fires that burn above the piston-top films and soot 

that is produced by the fires.

• Record in-cylinder fuel-vapor distributions using LIF of gasoline as well as custom fuel/tracer blends.

• Characterize the commonly used LIF fuel/tracer blend isooctane/3-pentanone, and test potentially 

improved octane/ketone blends.

• Present research results to industry, National Laboratories, and university partners, soliciting feedback 

and disseminating acquired information.

Accomplishments

• Collected comprehensive data documenting the formation of persistent piston-top fuel films, the 

ignition of pool fires, and the associated production of soot using current, high-pressure swirl injectors 

with 53° and 74° cone angles.

• Documented the non-ideal evaporative behavior of isooctane/3-pentanone mixtures used for LIF 

measurements. Identified an alternative ternary blend of isooctane/3-pentanone/3-hexanone that 

achieves improved fuel/tracer co-evaporation.

Future Directions

• Funding for SIDI engine research at Sandia National Laboratories was withdrawn at the end of FY01.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

20

Introduction

The spark-ignition direct-injection (SIDI) engine 

is a promising alternative to compression-ignition 

direct-injection (CIDI) engines, approaching the fuel 

efficiency of the diesel engine while retaining the 

specific power of the gasoline engine. Several 

liabilities in current CIDI engine performance 

including higher particulate and NOx emissions, 

lower specific power, lower public acceptability, 

higher noise, and lower fuel availability make the 

development of alternative strategies a wise 

investment.

Current SIDI engine designs incorporate both 

homogeneous charge and stratified charge operating 

modes. The SIDI engine program at Sandia 

comprises two laboratories configured to investigate 

the two different operating modes. One laboratory 

houses an engine configured with a vertical, centrally 

mounted injector and a flat piston, and the second 

contains an engine with an inclined injector mounted 

between the intake valves and targeted toward a 

sculpted piston. Both facilities are used to investigate 

fuel-air mixing, wall-wetting, combustion, and 

emission formation during homogeneous-mode 

operation.

Approach

Both research engines provide extensive optical 

access, enabling the application of advanced optical 

diagnostics. Planar LIF is used to characterize both 

liquid fuel distribution during injection and vapor 

fuel distribution at the time of spark. Flood LIF 

identifies liquid films that form in the cylinder. 

Laser-elastic scattering is applied for spray 

visualization as well as for soot detection. Direct 

flame imaging records premixed flame combustion 

as well as pool fires formed when fuel films on 

cylinder and piston surfaces ignite.

Results

A set of current-design swirl injectors were 

obtained for both engines, and the optical methods 

developed in FY00 were applied to the side-inject 

engine operating with the new injectors. In bench 

tests, the new injectors produced more symmetric 

sprays with reduced pre-and post-sprays than prior 

injectors tested. In the engine, however, the newer 

injectors performed similarly to old injectors. 

Increased ambient (in-cylinder) pressure decreased 

the axial penetration of all sprays. Increased fuel 

temperature caused an increased droplet entrainment 

toward the spray centerline, forming a radially 

compact fuel cloud that penetrated to the piston 

crown in most cases. Both 54° and 74° injectors 

significantly wet the piston over a range of injection 

timings. Low radial penetration meant that the spray 

did not impinge directly on the cylinder walls. As 

with the old injectors, piston-top fuel films 

frequently ignited and burned as pool fires.

Evaporation experiments definitively 

demonstrated that 3-pentanone is preferentially 

evaporated from isooctane-3-pentanone mixtures 

commonly used for LIF measurements of in-cylinder 

fuel fraction. Figure 1 presents histories of the batch 

evaporation of several mixtures of isooctane and 

ketone tracers. LIF was used to measure the tracer 

concentration of saturated air leaving the evaporation 

chamber. In the figure, the LIF signal is normalized 

by the value recorded at the start of the experiment. 

The plots are read from right to left as remaining 

liquid fraction progresses from 1 to 0.

The triangle symbols in Figure 1 represent an 

initial mix of 10 vol% 3-pentanone in isooctane, and 

they indicate a dramatic drop in tracer concentration 

as the evaporation proceeds. The 3-pentanone 

Figure 1. LIF tracer signal history of the vapor phase 

evaporating from three fuel/tracer mixtures at 

90°C. Component volume percents for the 

three mixtures are: 10% 3-pentanone / 90% 

isooctane (triangles); 10% 3-hexanone / 90 

isooctane (diamonds); 1% 3-pentanone / 9% 3-

hexanone / 90% isooctane (squares).
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

21

evaporates far faster than isooctane initially, 

depleting its concentration in the liquid phase and 

leading to a low vapor-phase concentration of the 

tracer late in the evaporation. These results imply 

that using this fuel/tracer blend in LIF engine 

experiments to track fuel (octane) concentrations will 

lead to incorrect results.

The diamond symbols in Figure 1 present the 

evaporation history of a 10 vol% mix of 3-hexanone 

in isooctane. This is a heavier ketone, and its vaporphase concentration is seen to increase with time. But 

by blending the two tracers in a ternary mixture, a 

much more uniform LIF signal is obtained during the 

evaporation process, as shown by the square 

symbols. The fluorescent tracers in the 1:9:90 vol% 

mix of 3-hexanone/3-pentanone/isooctane coevaporate with the isooctane and can be expected to 

faithfully track octane vapor concentration. These 

results and tests of the ternary fuel/tracer blend in a 

fired SIDI engine were submitted for publication.

Publications/Presentations

1. R. R. Steeper and E. J. Stevens, 

"Characterization of Combustion, Piston 

Temperature, Fuel Sprays, and Fuel-Air Mixing 

in a DISI Optical Engine," SAE Paper 2000-01-

2900, presented at the Fall Fuels and Lubes 

Meeting, Baltimore, October, 2000.

2. E. Stevens and R. Steeper, "Piston Wetting in an 

Optical DISI Engine: Fuel Films, Pool Fires, and 

Soot Generation," SAE Paper 2001-01-1203, 

presented at the SAE Congress, March, 2001.

3. R. R. Steeper and E. J. Stevens, "Effects of 

Piston Wetting in an Optical DISI Engine,"

Gasoline Direct Injection Engines Conference, 

presented in Cologne, Germany, June, 2001.

4. D. Han and R. R. Steeper, "Examination of 

Isooctane/Ketone Mixtures for Quantitative LIF 

Measurements in a DISI Engine," submitted to 

SAE, SAE Paper 02P-294, 2001.

5. M. Davy, P. Williams, D. Han, and R. R. Steeper, 

"Evaporation Characteristics of the 3-Pentanone/

Isooctane Binary System," submitted to 

Experiments in Fluids, 2001.

6. Presented research reports at two DOE Review 

Meetings convening DOE, National Lab, 

industry, and university partners.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

22

D. Computer Modeling to Support GDI Engine Research

David J. Torres (Primary Contact), Peter J. O’Rourke

Fluid Dynamics Group T-3, MS B216

Los Alamos National Laboratory

Los Alamos, NM 87545

(505) 667-2638, fax (505) 665-5926, e-mail: dtorres@lanl.gov

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov 

Objectives

• Provide 3-D Computational Fluid Dynamics (CFD) modeling support to research and production 

Gasoline Direct Injection (GDI) engines being experimentally tested at Sandia National Laboratories 

in Livermore, CA.

- Interpret experimental data

- Understand fuel/air mixture preparation

- Improve computer submodels

• Implement a multicomponent model into KIVA-3V.

• Publish a description of the model and demonstrate its use in performing KIVA-3V calculations of 

multicomponent fuel sprays. 

Approach

• Continue to perform engine simulations using the latest submodels in KIVA-3V and compare 

computations with experimental results.

• Research literature regarding multicomponent fuel evaporation.

• Develop equations for multicomponent fuel evaporation for spray and wall film.

• Implement multicomponent model into KIVA-3V.

• Present and publish multicomponent spray results at meetings and in journals.

• Use next-generation code CHAD (Computational Hydrodynamics for Advanced Design) when fullengine-cycle simulation capability is available in CHAD.

FY 2001 Accomplishments

• Compared measured and computed spray distributions in benchtop experiments using iso-octane and 

gasoline. 

• Implemented a multicomponent fuel model into the fuel spray and wall film in KIVA-3V.

• Presented multicomponent description and multicomponent simulations

- CRADA meeting in Livermore, CA, January 2001

- ILASS meeting in Dearborn, MI, May 2001

- University working group meeting, Madison, Wisconsin, June 2001
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

23

• Published "A Discrete Multicomponent Fuels Model for GDI Engine Simulations" in ILASS Americas 

Proceedings, 2001.

• Will submit "A Discrete Multicomponent Fuel Model" to Atomization and Sprays by mid-October 

2001.

Future Directions

• Incorporate multicomponent fuel model into CHAD.

• Validate newly incorporated multicomponent fuel model by comparing KIVA-3V calculations with 

experimental measurements of liquid fuel spray and liquid film locations as well as vapor fuel 

distribution.

• Model the interior of a fuel injector to determine the sensitivity of the spray to fuel pressure, radius of 

curvature of surfaces, and azimuthal velocities.

• Continue to perform KIVA-3V calculations modeling Sandia research and production engines using 

latest submodels.

Introduction and Approach

Internal combustion engine performance relies 

on spatial and temporal fuel vapor distributions that 

produce efficient and reliable combustion. 

Predicting where and when liquid fuel will vaporize 

is invaluable information to designers of modern 

fuel-injected engines. KIVA-3V is a code developed 

at Los Alamos that is used extensively in industry as 

well as universities for engine studies. KIVA-3V has 

traditionally used a single component fuel in engine 

modeling. In order to model gasoline and diesel 

fuels, which are composed of many components, a 

representative fuel was traditionally used in KIVA3V calculations. While this representative fuel can 

mimic many important features of a multicomponent 

fuel, it cannot account for certain effects arising from 

the differing volatilities of fuel components. These 

effects include preferential gas-phase vaporization of 

volatile fuel components that results in 

inhomogeneous fuel vapor distributions, or the 

accumulation of low-volatility liquid fuel 

components on a piston crown.

To improve KIVA-3V’s modeling capabilities, 

we have developed a multicomponent fuel model and 

have implemented it into the spray and wall film 

submodels of KIVA-3V. Our model (unlike other 

models, Zeng and Lee 2000) tracks temperature and 

mass concentration variations within the interior of 

the droplet or wall film using an efficient 

computational scheme. We found that tracking 

internal variations inside the fuel is necessary in 

order to capture the complex spatial and temporal 

variations that occur during multicomponent fuel 

evaporation. 

Fiscal Year 2001 Results

During the last year we have continued to 

compare experimental and KIVA computational 

results. Benchtop injection into a known quiescent 

room temperature and pressure was used to provide a 

controlled environment under which one could 

conduct comparisons. Iso-octane spray comparisons 

were made for injection fuel temperatures of 30°C 

and 90°C. Gasoline spray comparisons were made 

for injection fuel temperatures of 30°C. KIVA-3V 

computations of gasoline were performed with a 

preliminary multicomponent model.

Liquid fuel spray locations and penetration 

continue to differ between KIVA-3V and the 

experiment. Experimental laser-induced 

fluorescence images show significant spray cone 

filling, while KIVA-3V shows the spray structure to 

maintain a hollow cone shape. This difference in 

spray has led us to consider other liquid sheet 

breakup models. We also did not consider in our 

computations initial transients in the injector spray 

before the injector spray builds up enough angular 

momentum to achieve a steady shape. Modeling the 

interior and immediate external spray of a GDI 

injector with KIVA-3V may resolve how initial 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

24

transients and liquid sheet breakup affect the overall 

spray behavior. 

Much of our effort the past year has been 

devoted to developing the multicomponent model. 

We show that a multicomponent fuel behaves much 

differently than a single-component fuel by 

comparing single droplet evaporation and 2-D 

axisymmetric spray calculations.

Figure 1 shows how a multicomponent fuel 

blend (syn. fuel - composed of iso-pentane, 

cyclohexane, iso-octane, toluene, ethylbenzene, ndecane, and napthalene) designed to mimic gasoline 

(Greenfield et. al. 1998) compares with a single 

component "KIVA gasoline" used in the past to 

model gasoline. The 20 micron diameter droplet 

temperature was initially 90°C and evaporates in a 

30°C, quiescent, 1 atmosphere environment. The 

multicomponent syn. fuel evaporates much more 

slowly than KIVA gasoline. While only the least 

volatile components (n-decane and napthalene) 

remain in the syn. fuel droplet after 40 milliseconds, 

these components allow the droplet to survive for 

300 milliseconds (30 times longer than the single 

component KIVA gasoline). Figure 2 shows the 

same syn. fuel and KIVA gasoline droplet at 90°C 

which now evaporates in a 120°C, quiescent, 2.6 

atmosphere environment. In this environment, the 

syn. fuel droplet evaporates faster, but still at a rate 

2.5 times slower than the KIVA gasoline droplet. 

The dramatically different rates of evaporation 

between the single-component and multicomponent 

droplets have significant implications in predicting 

where and when the vapor fuel cloud will be 

available for combustion.

Figures 3 and 4 show a 2-D axisymmetric spray 

calculation of 90°C syn. fuel and KIVA gasoline 

respectively injected into a 1 atmosphere, 30°C 

chamber full of air. We see dramatic differences in 

how the spray behaves. The KIVA gasoline spray 

penetrates further and its spray angle has been 

reduced. The KIVA gasoline fuel vapor cloud is also 

more concentrated near the spray axis. The vapor 

cloud from the syn. fuel is more disperse and dilute.

Figures 5 and 6 show a 2-D axisymmetric spray 

calculation of 90°C syn. fuel and KIVA gasoline 

respectively injected into a 2.6 atmosphere, 120°C 

chamber full of air. Although the increased pressure 

reduces the spray penetration for both fuels 

(compared to Figures 3 and 4), we see that KIVA 

gasoline continues to penetrate further than syn. fuel. 

Significant differences in the fuel vapor cloud 

concentration and location are again evident.

Figure 1. Droplet radius squared versus time for a 90°C 

single droplet evaporating in a 30°C, 1 

atmosphere quiescent environment. Two fuels 

are shown—a 7 species multicomponent 

"gasoline" called syn. fuel and a singlecomponent fuel, KIVA gasoline.

Figure 2. Droplet radius squared versus time for a 90°C 

single droplet evaporating in a 120°C, 2.6 

atmosphere quiescent environment. Two fuels 

are shown—a 7-species multicomponent 

"gasoline" called syn. fuel and a singlecomponent "gasoline", KIVA gasoline.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

25

Conclusions

We have continued to compare KIVA-3V 

computational and experimental results. Work needs 

to be done in matching experimental spray 

morphology and evolution. The main difficulty in 

matching the spray is that KIVA-3V’s spray model 

(Han et al 1997) characterizes the injector based only 

on injector pressure, injector diameter, and cone 

angle. Such a reduced number of injector parameters 

may be insufficient to describe the spray emitted 

from the interior of a GDI injector.

We have developed a multicomponent fuel 

model and implemented the model into the spray and 

wall film submodels of KIVA-3V. We have 

published a paper describing the preliminary model 

and have presented our results at conferences. We 

are presently using the multicomponent model in 

3-D engine simulations. Numerical simulations 

show dramatic differences in how multicomponent 

and single-component fuels behave. We believe that 

the automotive industry would benefit from adopting 

a multicomponent fuel model in their engine 

computations due to the large differences we 

encountered when comparing multicomponent and 

single-component fuels. It simply does not suffice to 

average the multicomponent fuel species properties 

to generate a single-component fuel.

Figure 3. Spray droplets and total fuel vapor mass 

fraction for 90°C multicomponent syn. fuel 

injected into a 30°C, quiescent, 1 atmosphere 

axisymmetric chamber.

Figure 4. Spray droplets and total fuel vapor mass 

fraction for 90°C KIVA gasoline injected into 

a 30°C, quiescent, 1 atmosphere axisymmetric 

chamber.

Figure 5. Spray droplets and total fuel vapor mass 

fraction for 90°C multicomponent syn. fuel 

injected into a 120°C, quiescent, 2.6 

atmosphere axisymmetric chamber.

Figure 6. Spray droplets and total fuel vapor mass 

fraction for 90°C KIVA gasoline injected into 

a 120°C, quiescent, 2.6 atmosphere 

axisymmetric chamber.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

26

References

1. Amsden, A.A., O’Rourke, P.J., and Butler T.D., 

"The KIVA-II Computer Program for 

Chemically Reactive Flows with Sprays," Los 

Alamos National Laboratory LA-11560-MS 

(1989).

2. Greenfield, M.L., Lavoie, G.A., Smith, C.S., 

Curtis, E.W., "Macroscopic Model of the D86 

Fuel Volatility Procedure," SAE Paper 982724 

(1998).

3. Han, Z., Parrish, S., Farrell, P.V., and Reitz, R.D., 

"Modeling Atomization Processes of PressureSwirl Hollow-Cone Fuel Sprays," Atomization 

and Sprays 7, 663 (1997).

4. O’Rourke, P.J. and Amsden, A.A., "A Particle 

Numerical Model for Wall Film Dynamics in 

Port-Injected Engines," SAE Paper 961961 

(1996).

5. O’Rourke, P.J. and Amsden, A.A., "A Spray/

Wall Interaction Submodel for the KIVA-3 Wall 

Film Model," SAE Paper 2000-01-0271 (2000).

6. Zeng, Y., and Lee, C.F., "Modeling of Spray 

Vaporization and Air-Fuel Mixing in Gasoline 

Direct-Injection Engines," SAE Paper 2000-01-

0537 (2000).
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

27

E. Active Flow Control for Maximizing the Performance of Internal Combustion 

Engines 

Harold J. Schock (Primary Contact), Alvin Goh, Giles J. Brereton, Tom I-P Shih, Manoochehr M. 

Koochesfahani

Automotive Research Experiment Station 

Michigan State University

East Lansing, Michigan 48824

(517) 353-9328, fax: (517) 432-334, e-mail: schock@egr.msu.edu 

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Develop an understanding of the factors that influence the performance of a stratified charge (SC) 

internal combustion engine with emphasis on cycle-to-cycle variability.

• Determine how active flow control can be used to manage the air motion and fuel-air mixing in an 

internal combustion engine.

• Demonstrate the influence that active flow control has on the combustion process in a stratified charge 

engine using a 4-ohm speaker in the engine inlet system.

Approach

• Construct a motored optical engine assembly to be used to conduct evaluations of selective active flow 

technologies on the in-cylinder flowfield of a SC engine.

• Implement molecular tagging velocimetry to measure in-cylinder flows and develop the necessary 

diagnostic software to evaluate selected flow control technologies.

• Develop and implement the necessary simulation tools based on KIVA to allow for a numerical 

evaluation of the active flow control strategies.

• Demonstrate the influence that the most promising flow control strategy has on the variability in SC 

engine combustion.

Accomplishments

• The amplitude effect experiment showed that the largest amplitude (28 V) of the perturbation gave the 

maximum U rms and V rms reduction.

• Free-run perturbation at 270 CAD and 600 rpm showed that the effective perturbation frequency range 

is from 50 Hz to 400 Hz. For U rms, the best reduction case was 400 Hz. It showed about 25%-30% 

reduction at certain region of the flow field. As for V rms, the best reduction case was 200 Hz.

• Fixed-time perturbation from 0 CAD to 180 CAD, at 270 CAD and 600 rpm showed that the U rms 

was reduced about 20%-30%, when perturbed at 300 Hz and 400 Hz. As for V rms, the best reduction 

cases were at 400 Hz and 600 Hz.

• The sweeping perturbation experiment (sweeping frequency started at 100 Hz) showed that the U rms 

and V rms were reduced to about 20%. The best reduction case for U rms was sweeping from 100 Hz 

to 1200 Hz. The best reduction case for V rms was sweeping from 100 Hz to 800 Hz.

• The rest of the experiments for 270 CAD and 600 rpm did not show clear trends or huge U rms and V 

rms reductions.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Introduction

Cycle-to-cycle variation in turbulence and fuelair-residual exhaust gas mixing is of primary 

importance to premix, stratified charge SIDI engines. 

In recent years, a significant amount of work has 

been done to improve the engine’s performance and 

fuel efficiency. Recent research has shown a 

significant interaction between the mean flow and 

the fluctuating parts of the in-cylinder velocity [1]. 

Due to cycle-to-cycle variation, the engine fuel 

injector is operated to over-fuel the combustion 

chamber to avoid partial burns or misfires. In order to 

design better lean burn engines, one has to have a 

better understanding of the flow patterns during 

compression stroke and also needs to find a way to 

reduce cycle-to-cycle variation. If cycle-to-cycle 

variation is reduced, the in-cylinder flows are more 

predictable and thus one could employ leaner 

combustion without large torque variability or 

misfire. In return, this would improve fuel economy 

in engines. The ultimate goal of this study is to find a 

way of controlling the flow and reducing the cycleto-cycle variation. As a result, one could provide 

control of the mixing and burning rates in an internal 

combustion engine.

The present study is intended to explore the 

extent to which in-cylinder fluid motion late in the 

compression stroke can be more regularized with less 

cycle-to-cycle variation using judicious acoustic 

excitation of shear layers adjacent to the intake 

valves during the intake stroke.

Approach

Optically Accessible Research Engine

A schematic of the optically accessible research 

engine is shown in Figure 1, and the engine 

specifications are listed in Table 1. This study was 

conducted with a 1999 model year Ford cylinder 

head with 4 valves and double overhead cams. The 

engine cylinder head was part of the left bank of a V8 

prototype engine. A flat-head, optical access piston 

was used in the experiment. The bore and stroke 

were 90.2 mm and 90.0 mm, respectively. The 

length of the connecting rod was 150.7 mm. The 

cylinder used in the experiment was made from 

quartz so that it would be optically accessible. 

The cylinder was mounted on a single-cylinder 

research engine that served as a reciprocating 

mechanism. The engine was first-order balanced in 

forces and moments and connected through a rubberdamped coupling to a 10 HP electrical motor. Two 

different belt drive setups were connected to the 

exhaust camshaft that would allow interchanging 

between the two engine stroke variants. The exhaust 

camshaft was linked by a roller-chain to the intake 

camshaft. The intake valve diameter was 37 mm and 

the exhaust valve diameter was 30 mm. The 

maximum valve lift was 10.02 mm at 120° crank 

angle. The valves of the investigated cylinder were 

the only valves activated. A 4-ohm, 4.5 inch midFigure 1. Schematic of the Research Engine Setup

Model and Make Ford 4-Valve 4.6L

Bore and Stroke 90.2 mm / 90.0 mm

Connecting Rod Length 150.7 mm

Valve Activation DOHC

Intake Valve Diameter 37.0 mm

Exhaust Valve Diam. 30.0 mm

Maximum Valve Lift 10.02 mm /120 CAD

Zero CAD Intake TDC

Intake Valve Opening 6 CAD Before TDC

Intake Valve Closure 250 CAD After TDC

Exhaust Valve Opening 126 CAD After TDC

Exhaust Valve Closure 16 CAD After TDC

Compression Ratio 9.85 : 1

Piston Top Flat

Table 1. Engine Specifications

Motor

Nitrogen+Biacetyl

UV Lenses

Laser Mirror

Intake

Exhaust
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29

woofer speaker was mounted at the intake manifold. 

The speaker power was 40 W, and it was driven by 

an input signal from a function generator. Before the 

input signal was fed into the speaker, it was 

amplified by a Hafler P1000 amplifier. The amplifier 

had a full power bandwidth of 0.1 Hz to 100 kHz.

Molecular Tagging Velocimetry (MTV) Setup

The velocity measurements were made using 

Molecular Tagging Velocimetry (MTV). MTV is a 

full-field optical diagnostic that allows for the nonintrusive measurement of a velocity field in a 

flowing medium. For gas-phase applications, MTV 

uses nitrogen as a working fluid and biacetyl as a 

long-lived luminescence tracer mixed with the 

nitrogen [6]. A pulsed UV laser is used to tag the 

flow in the regions of interest. The regions of 

interest are imaged at two successive times using a 

CCD camera. The measured Lagrangian 

displacement vector and the time over which the 

displacement occurred provide the velocity vector. 

For MTV, a Lambda Physik LPX 210i UV (308nm) 

laser operating at approximately 290 mJ (20 kV) 

provided the energy to generate phosphorescence 

from a working fluid mixture of nitrogen and 

biacetyl. Figure 2 shows the optical setup for the 

experiment. In order to measure the velocity field 

throughout a region, a series of vertical and 

horizontal laser lines were generated. These lines 

were orthogonal to each other. At this point, images 

were recorded by the intensified CCD camera. These 

images were considered as reference images. At 

certain delay later (normally it was about 200 

microseconds for 270 CAD measurement) the tagged 

region was recorded again using the intensified CCD 

camera. These images were considered as delayed 

images. Post-processing by correlation-based 

techniques allowed the instantaneous planar velocity 

field to be deducted from the reference and delayed 

images. The MTV experiments were done with a 

field of view approximately 5 cm x 5 cm. The top of 

the grids was located about 1 cm below the intake 

and exhaust valves, and the edges of the grids were 

about 2 cm from the cylinder wall. The incoming 

laser beam was first split to form horizontal and 

vertical beams. Each laser beam was focused using a 

combination of two cylindrical lenses with focal 

lengths of 150 mm and 50 mm. By going through 

these two lenses, a very thin laser sheet was

generated for each beam. Beam blockers with series 

of thin slits cut through them were used in each beam 

path to generate a series of 12 lines for the horizontal 

and 15 lines for the vertical. 

Data Acquisition and Processing

A Xybion CCD video camera, model ISG-350 

with a Nikkor 50mm f1.2 lens was used to take 

images in the experiment. An engine encoder was 

coupled to the camshaft to produce a 5-V TTL signal 

at a desired crank angle. The signal was then used to 

trigger the laser. The delay time for the laser beam to 

reach the engine cylinder was 1.3 microseconds. The 

software used together with the acquisition board 

was the MV-1000 Grab Sequence Application 

version 1.3 for Windows NT. A total of 500 

instantaneous velocity fields were measured for each 

measurement condition. A convergence experiment 

was conducted to determine the number of 

instantaneous realizations needed to produce a good 

average. The results showed that 500 instantaneous 

realizations were sufficient to produce a good 

average. 

Figure 2. Optical Setup for the Experiment

Incoming Laser Beam

Beam Splitter

Mirror

Mirror

150mm Cylindrical Lens

50mm Cylindrical Lens

50mm Cylindrical Lens

Beam Blocker

Beam Blocker

CCD Camera

Engine Cylinder

Mirror

Beam Block

Engine Cylinder

Vertical Laser

Grid

Horizontal Laser Grid
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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The data processing process was performed 

using an in-house code developed over the past few 

years. When processing the data, the main objective 

was to determine the displacement vector of the 

tagged regions with the highest possible sub-pixel 

accuracy in order to increase the dynamic range of 

the velocity measurements. The displacement of the 

tagged regions was determined using a direct digital 

spatial correlation technique. The details of this 

approach can be found in Gendrich and 

Koochesfahani 1996 [2]. The basic idea of this 

approach is that a small window called a source 

window is selected from a tagged region in the 

reference or zero-delay image. It is then spatially 

correlated with a larger roam window in the delayed 

image. A well-defined correlation peak occurs at the 

location corresponding to the displacement of the 

tagged region by the flow. The displacement peak is 

found by using a multi-dimensional polynomial fit. 

Results and Discussion

The experiment was carried out at an on engine 

speed of 600 rpm, at 270 CAD. The reason 270 

CAD was chosen is because in-cylinder preflame air 

motion has been known to have a dominant effect on 

the firing behavior of internal combustion engines 

[3,4,5]. The flow patterns during compression stroke 

influence the succeeding combustion of SIDI 

engines. 

An experiment was performed to determine the 

amplitude effect of the acoustic perturbations. The 

experiment was done on three different amplitude 

cases with the engine running at 600 rpm and 

perturbation at 50 Hz. The three different amplitudes 

included a small amplitude of 675 mV, a medium 

amplitude of 10 V and a large amplitude of 28 V. 

The crank angle of investigation was at 270 CAD. 

The results of the experiment showed that as the 

amplitude of the perturbation increased, the U rms 

and V rms were reduced. In other words, the trend of 

the experiment was the higher the amplitude, the 

lower the cycle-to-cycle variation. As for the U 

mean and V mean, the results showed that there were 

some changes in their means as the amplitude 

increased, but the increments were small. Thus, from 

the experiment, the highest amplitude (28 V) was 

chosen as the best parameter for the rest of the 

research and experiments.

Free-run Perturbation Method 

In this mode, the speaker was run freely with the 

engine without any timing. The perturbation was 

done throughout the crank angles with the desired 

frequency at the maximum amplitude (28 V). It was 

initially thought that the best cycle-to-cycle variation 

reduction would occur in a high frequency range, 

namely 1000 Hz onwards. However, from this 

experiment, it was found that the best reduction 

occurred at a lower frequency, below 400 Hz. In the 

experiment, the range of frequencies investigated 

was from 50 Hz to 4000 Hz. However, the best cases 

were only in the range of 50 Hz to 400 Hz. Beyond 

400 Hz, there was no significant reduction in velocity 

rms or cycle-to-cycle variation. 

Figure 3 shows the results for U mean and U rms 

taken from running the engine at 600 rpm, 270 CAD. 

The color contour shows the U rms that gives the 

information on the average deviation of the 

instantaneous flows from the U mean flow. In other 

words, the cycle-to-cycle variation and turbulence 

are reduced if the rms value is reduced. The trend of 

the results was as the frequency of the perturbation

Figure 3. Free-Run Perturbation, U Mean and U rms at 

600 rpm, 270 CAD
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increased, the U rms decreased until 400 Hz. After 

400 Hz, the U rms increased back again. Comparing 

the perturbed cases with the unperturbed case, one 

could notice that the contour color gets less red or 

yellow and becomes more green and blue. 

According to the color scale, the rms value is smaller 

when it is green or blue in color. Figure 4 shows the 

results for V mean and V rms. The trend of V rms 

was the same as with U rms. As the frequency 

increased, the V rms was reduced, but after 400 Hz, 

the V rms increased again. 

Figures 5a and 5b, and 6a and 6b show graphs 

taken along a line at y=-1.2, about 1.2 cm below the 

intake and exhaust valves. It is obvious that the 

perturbation did not effect the U mean and V mean. 

The U mean and V mean stayed about the same 

values throughout all frequencies. However, the 

perturbation had huge effect on the U rms that 

represents the cycle-to-cycle variation and 

fluctuating velocity field. As the frequency 

increased, the U rms decreased. The largest 

reduction among all was the 400 Hz case. It showed 

about 25% to 30% reduction at certain region of the 

flow field. As for V rms, the reduction was only 

about 20%, and the best case was again 400 Hz.

Fixed-time Perturbation Method

In this experiment, the starting and ending points 

of the perturbation were timed. The timing of the 

perturbation was done by using the burst mode of a 

function generator. The speaker would only start 

perturbing when the piston reached Top Dead Center 

(TDC). It would continue to perturb from 0 CAD to 

180 CAD and then stop when the piston reached 180 

CAD. The engine condition was the same as in the 

previous experiment. The experiment was done at 

600 rpm and 270 CAD. The range of frequencies 

investigated was from 50 Hz to 4000 Hz. Each 

frequency case had an average from 500 continuous, 

instantaneous flows. The reason of choosing the 

frequency range was based on the previous 

experiment (free-run experiment). From the 

Figure 4. Free-Run Perturbation Method, V Mean and V 

rms at 600 rpm, 270 CAD

Figure 5. Effect of Perturbations on the U Mean and U 

rms at Horizontal Line about 1.2 cm below the 

Intake and Exhaust Valves
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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experiment, it was found that the perturbation had no 

effect beyond 4000 Hz or below 50 Hz. The results 

had the same trend as the free-run results. There was 

a noticeable reduction in U rms and V rms at 300 Hz 

and 400 Hz. The reduction was about 20%-30%. As 

the frequency increased, the U rms and V rms 

decreased until 400 Hz, and it increased at 

frequencies over 400 Hz. In the previous free-run 

perturbation experiment, the U mean and V mean of 

the flow did not change for cases with or without 

perturbation. However, for this fixed-time 

perturbation, the U mean and V mean of the flow 

decreased in velocity. They appeared to be slowing 

down with the perturbation. See Figure 7 for more 

information.

Figure 8 shows results for V mean and V rms taken at 

600 rpm and 270 CAD. Each of the frequency cases 

had an average of 500 instantaneous flows. The 

results did not show any clear trend as found in U 

mean and U rms previously. They appeared to have 

less rms reduction compared with U mean and U 

rms. The best V rms reduction cases were 400 Hz 

and 600 Hz. Figures 9a and 9b show graphs taken 

along a line at y=-3.1, about 3.1 cm below the intake 

and exhaust valves. From the graphs, it is obvious 

that the perturbation had some effects on the U mean 

flow. The U mean decreased as the frequency 

increased. In some places of the flow, the U mean 

decreased as much as 70% to 80% of the unperturbed 

flow. The flow direction had changed too in some 

places of the flow. As for the U rms, the perturbation 

had a huge effect on the U rms that represents the 

cycle-to-cycle variation and fluctuating velocity 

field. As the frequency increased, the U rms 

decreased until 400 Hz and then it increased beyond 

400 Hz. The largest reductions were at 300 Hz and 

400 Hz. In the 300 Hz case, it showed about 20% to 

30% reduction at certain region of the flow field.

Figures 10a and 10b show that the perturbation 

had some effects on the V mean flow, the same 

effects that could be found on U mean flow. The V 

mean decreased as the frequency increased. In some 

places of the flow, the V mean decreased as much as 

40% to 50% of the unperturbed flow. As for the V 

Figure 6. Effect of Perturbations on the V Mean and V 

rms at Horizontal Line about 1.2 cm below the 

Intake and Exhaust Valves

Figure 7. Fixed-Time Perturbation Method, U Mean and 

U rms at 600 rpm, 270 CAD
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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rms, the perturbation had some effects on the V rms 

too. As the frequency increased, the V rms decreased 

until the frequency reached between 400 Hz and 600 

Hz. It increased beyond 600 Hz. The largest 

reductions were all at 400 Hz and 600 Hz. In the 400 

Hz case, it showed about 20% to 30% reduction at 

certain region of the flow field.

Sweeping Perturbation Method (sweeping 

frequencies from 100 Hz to 2000 Hz)

This experiment was done with the sweeping 

mode of the function generator. As in the previous 

experiments, all the perturbation frequencies were 

fixed. For example, when the flow was said to be 

perturbed at 400 Hz, it was done by perturbing the 

flow constantly at 400 Hz throughout the experiment 

using free-run method or fixed-time method. 

However, in this experiment, the perturbed 

Figure 8. Effect of Perturbations on the U Mean and U 

rms at Horizontal Line about 3.1 cm below the 

Intake and Exhaust Valves

Figure 9. Fixed-Time Perturbation Method, V Mean and 

V rms at 600 rpm, 270 CAD

Figure 10. Effect of Perturbations on the V Mean and V 

rms at Horizontal Line about 3.1 cm below the 

Intake and Exhaust Valves
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

34

frequencies increased linearly but at a fixed starting 

point of perturbation, which was at TDC. Each case 

of experiment was done by perturbing the flow 

starting at 100 Hz and then sweeping linearly to the 

respective end frequency. Nevertheless, the duration 

of the sweeping was still only from 0 CAD to 180 

CAD. In the case of the engine running at 600 rpm, 

the duration of sweeping was 0.05 seconds. 

This experiment was necessary because the 

intake valves opened in a linear manner during the 

intake stroke. If the perturbation were fixed at a 

certain frequency, the flow would not be perturbed at 

that frequency during the period of the valves 

opening. In order to improve the maximum effect of 

the perturbation to the flow, the perturbation was 

done by sweeping the frequencies linearly. The 

range of frequencies investigated in the experiment 

was from 200 Hz to 2000 Hz. The first case of 

sweeping frequencies was sweeping from 100 Hz to 

200 Hz, and the last case was sweeping from 100 Hz 

to 2000 Hz. 

The cases investigated were as follows: 

sweeping from 100 Hz to 200 Hz

sweeping from 100 Hz to 300 Hz

sweeping from 100 Hz to 400 Hz

sweeping from 100 Hz to 600 Hz

sweeping from 100 Hz to 800 Hz

sweeping from 100 Hz to 1000 Hz

sweeping from 100 Hz to 1200 Hz

sweeping from 100 Hz to1400 Hz

sweeping from 100 Hz to 1600 Hz

sweeping from 100 Hz to 1800 Hz

sweeping from 100 Hz to 2000 Hz

The range of U rms and V rms reductions were 

from 20% to 25% in the experiment. The best 

reduction case for U rms was sweeping from 100 Hz 

to 1200 Hz, and the best reduction case for V rms 

was sweeping from 100 Hz to 800 Hz. Figures 11 

and 12 show the results. The U mean and V mean 

did not change much.

Conclusions

• The amplitude effect experiment showed that 

the largest amplitude (28 V) of the 

perturbation gave the maximum U rms and V 

rms reduction.

• Free-run perturbation at 270 CAD and 600 

rpm showed that the effective perturbation 

frequency range is from 50 Hz to 400 Hz. 

For U rms, the best reduction case was 400 

Hz. It showed about 25%-30% reduction at 

certain region of the flow field. As for V 

rms, the best reduction case was 200 Hz.

• Fixed-time perturbation from 0 CAD to 180 

CAD, at 270 CAD and 600 rpm showed that 

the U rms was reduced about 20%-30%, 

Figure 11. Sweeping Perturbation Method, U Mean and 

U rms at 600 rpm, 270 CAD

Figure 12. Sweeping Perturbation Method, V Mean and 

V rms at 600 rpm, 270 CAD
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

35

when perturbed at 300 Hz and 400 Hz. As 

for V rms, the best reduction cases were at 

400 Hz and 600 Hz.

• The sweeping perturbation experiment 

(sweeping frequency started at 100 Hz) 

showed that the U rms and V rms were 

reduced to about 20%. The best reduction 

case for U rms was sweeping from 100 Hz to 

1200 Hz. The best reduction case for V rms 

was sweeping from 100 Hz to 800 Hz.

• The rest of the experiments for 270 CAD and 

600 rpm did not show clear trends or huge U 

rms and V rms reductions.

Acknowledgments

This research work was financially supported by 

the Ford Motor Company and Michigan State 

University in addition to the U.S. Department of 

Energy.

References

1. Hascher, H. G., Jaffri, K., Novak, M., Lee, K., 

Schock, H., Bonne, M., Keller P., "An 

Evaluation of Turbulent Kinetic Energy for the 

In-cylinder Flow of a Four-Valve 3.5L SI Engine 

Using 3-D LDV Measurements," SAE 970793, 

1997.

2. Gendrich, C. P. and Koochesfahani, M. M., "A 

Spatial Correlation Technique for Estimating 

Velocity Fields Using Molecular Tagging 

Velocimetry," Experiments in Fluids, Vol. 22, pp. 

67-77, 1996.

3. Lancaster, D. R., Krieger, R. B., Sorenson, S. C., 

and Hull, W. L., "Effects of Turbulence on 

Spark-Ignition Engine Combustion," SAE Paper 

760160, 1976.

4. Davis, G. C., Tabaczynski, R. J., Beire, R. C., 

"The Effect of Intake Valve Lift on Turbulence 

Intensity and Burn Rate in SI Engines," SAE 

Paper 840030, 1984.

5. Hascher, H. G., Novak, M., Stuecken, T., 

Schock, H. J., and Novak, J., "The 3-D InCylinder Charge Motion of a Four-Valve SI 

Engine under Stroke, Speed and Load Variation," 

SAE 2000-01-2798, 2000.

6. Stier, B. and Koochesfahani, M. M., "Molecular 

Tagging Velocimetry (MTV) Measurements in 

Gas Phase Flows," Experiments in Fluids, Vol. 

26, pp. 297-304, 1999.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

36

III. ENGINE AND COMPONENT R&D

A. Development of Near-Frictionless Carbon Coatings for SIDI Fuel System 

Components

George R. Fenske (Primary Contact), Oyelayo Ajayi, John Woodford, Ali Erdemir, and Jeff 

Hershberger

Argonne National Laboratory

9700 S. Cass Ave.

Argonne, Illinois 60439

(630) 252-5190, fax: (630) 252-4798, e-mail: gfenske@anl.gov

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Develop low-friction, highly wear-resistant coatings for critical engine components needed to meet 

national emission goals, most notably fuel injection and valvetrain components for spark-ignited 

direct-injected (SIDI) gasoline engines.

• Evaluate the friction and wear resistance of Argonne’s Near-Frictionless Carbon (NFC) coatings in 

tests simulating service conditions of SIDI engine components.

• Tune deposition parameters to optimize performance of NFC coatings on critical components in SIDI 

engines.

Approach

• Perform benchtop wear tests under conditions of load, speed, etc. which simulate service conditions of 

SIDI engine components.

• Apply coatings and perform wear tests on production fuel injector plungers.

• Use very-long-term (1 million cycle) wear tests to determine rates and mechanisms of wear which 

occur in extended service lifetimes.

• Introduce a variety of production gasolines into the wear contacts to include chemical interactions 

experienced in working engines.

• Investigate both conventional and reformulated gasolines. 

• Characterize worn surfaces and determine failure mechanisms.

• Use advanced analytical techniques and post-testing characterization to guide optimization of NFC 

coating parameters and to recommend other surface treatments which may also improve component 

longevity.

• Upgrade custom-built benchtop Fretting Tester system to enable testing under the ISO12156 fuel 

lubricity standard.

• Perform Ball-On-Three-Disc (BOTD) industry standard wear tests on steel discs in gasolines and 

compare the data to the results of injector tests.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

37

• Analyze gasoline wear debris using Scanning Electron Microscopy (SEM), Energy Dispersive 

Analysis of X-rays (EDAX), and Transmission Electron Microscopy (TEM).

Accomplishments

• Optimized NFC deposition plasma parameters for coating thickness on production fuel injectors.

• Modified Fretting Tester to hold a production fuel injector as a wear counterface instead of a steel ball.

• Completed a matrix of 1-million-cycle lifetime wear tests comparing the performance of fuel injector 

tips with two NFC coatings to uncoated fuel injector tips.

• Performance of NFCs were investigated in seven varieties of gasoline in addition to the baseline 

ethanol.

• Completed a matrix of BOTD comparisons to fuel injector tests in the same fuels.

• Upgraded Fretting Tester to ISO12156 compliance.

Introduction

Spark-ignited, direct-injected (SIDI) engines are 

being developed because of their ability to meet 

stringent emission standards, their potential for high 

fuel efficiency, and their relatively mature state of 

commercial development. Such engines will operate 

at higher injection pressures than today’s portinjected engines and will utilize low-sulfur fuels that 

are being marketed to protect catalytic emission 

control devices. The tighter tolerances required on 

fuel delivery components to inject at higher pressures 

(e.g. approx. 100 bar vs. 4 to 5 bar for port injection) 

coupled with the low lubricity of gasoline (especially 

low-sulfur gasoline) will require advanced fuel 

delivery system designs and materials to meet 

reliability and durability goals.

Approach

The guiding principle of this project is to develop 

NFC coatings for SIDI engine applications via 

thorough wear testing and understanding of the wear 

mechanisms. The current year of effort builds upon 

the accomplishments of the previous year, where test 

materials and prototype engine components were 

successfully coated with NFC and the deposition 

parameters given initial adjustment. NFC coatings 

on steel balls and flats provided great improvements 

over uncoated metals in wear tests in gasoline, 

indicating compatibility of the coating with the 

conditions encountered in the engine environment. 

This year, development of the NFC coating for SIDI 

engines has focused on wear testing of production 

fuel injection parts, extension of tests to one-millioncycle lifetime duration, and exploration of what 

effects the next-generation fuels needed for working 

SIDI engines will have on the wear couples.

The central set of results discussed below are the 

friction and wear data from one-million-cycle wear 

tests of NFC2-coated, NFC6-coated, and uncoated 

fuel injectors in seven reformulated gasolines plus 

ethanol. The fuels used include summer and winter 

blends, premium and regular octane levels, and some 

contain additives under consideration for future 

blends. These friction and wear data are shown in 

Figures 1-4. Complementing this information are the 

industry standard BOTD fuel lubricity tests 

performed on uncoated discs in Figures 5-6. Further 

forensic examination of wear couples aids 

Figure 1. Friction of NFC-Coated and Uncoated Fuel 

Injectors in Several Gasolines
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

38

interpretation of friction and wear data; microscopy 

and other characterization results are shown in 

Figures 7-10.

Trends in the friction data may be found by 

studying the averages of friction results for each 

coating over the seven gasolines used, and by 

averaging the friction results for each gasoline over 

the three coatings used. Table 1 shows the friction 

result for each of the three surface treatments 

averaged over the seven gasolines.

The NFC coatings provide clear improvements 

in friction over the uncoated fuel injectors. NFC6 

gives 27% lower friction, while use of NFC2 results 

in a friction reduction of nearly a factor of two. This 

has important ramifications for part longevity, such 

as reducing local heat buildup at the contact point 

and the tendency to bind in close tolerances. 

Examining the other friction results, averaging the 

three coatings for each gasoline, gives tightly 

grouped numbers, each of which carries a large 

standard deviation. In other words, the major factor 

influencing friction is the coating, not the gasoline. 

Notable exceptions are ethanol and Gasoline G, 

which provide relatively low friction.

Similarly, trends in the wear data may be 

observed by averaging results for each coating over 

the seven gasolines, and by averaging the results for 

each gasoline over the three coatings. Attention to 

the differences between injector wear, flat wear, and 

the total wear reveal additional information. Table 2 

shows the trends.

Applying NFC coatings on the injectors again 

provided clear improvements in total wear rate and 

wear rate of the flats compared to the uncoated 

injectors. These improvements ranged from an over 

one-third reduction of wear to over a factor of four 

Figure 2. Wear Rate of Steel Flats Worn Against NFCCoated and Uncoated Fuel Injectors in Several 

Gasolines

Figure 3. Wear Rate of NFC-Coated and Uncoated Fuel 

Injectors in Several Gasolines

Figure 4. Combined Wear Rate of Steel Flats and 

Counterfaces of NFC-Coated and Uncoated 

Fuel Injectors Worn in Several Gasolines

Surface 

treatment

Friction coefficient 

average Improvement

Uncoated 0.29

NFC6 0.22 27% reduction 

over uncoated

NFC2 0.15 48% reduction 

over uncoated

Table 1. Friction for Three Surface Treatments Averaged 

over Seven Gasolines
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

39

wear reduction. In the case of the coated injectors 

themselves, NFC6 provided a wear rate very similar 

to that of the uncoated surface while the NFC2 

coating wore significantly faster than NFC6 and the 

uncoated part. Taking into account the extremely 

low friction provided by NFC2 in the tests, we may 

speculate that the NFC2 may be slowly sacrificing 

itself in order to reduce both friction and counterface 

wear. In contrast, NFC6 provides reductions of both 

friction and wear non-sacrificially. To consider the 

other wear results, averaging the three coatings for 

each gasoline, we see trends similar to that in the 

friction. Wear rate averages are tightly grouped but 

the averaged numbers (for different coatings) are 

highly variable. Gasolines A and B and ethanol 

produced somewhat higher wear on both flats and 

injectors, while Gasolines C and D lowered wear, but 

in general, the major factor influencing wear is the 

surface treatment, not the gasoline. 

The BOTD test results shown in Figures 5 and 6 

were produced on a Falex BOTD machine modified 

to provide output of friction data to a computer. The 

BOTD test is an industry standard which specifies a 

test duration, load, and an amount of fuel to be used. 

All tests were performed on uncoated steel discs, per 

the standard specification, to provide a measure of 

the lubricity of the gasoline. The friction and wear 

results are quite consistent, with fuels providing low 

friction also providing low wear. However, the 

differences in friction and wear among the fuels are 

relatively small. This is consistent with the 

observations above, that the gasoline is not the major 

factor influencing wear. At first glance, the friction 

and wear results appear inconsistent with the 

observations above regarding the effects of the 

gasolines on friction and wear rate for injector-onflat contacts. However, closer examination of the 

data reveals that the differences are a result of 

inclusion of the coated materials in the previous 

results. Taking into account only the data from the 

uncoated injectors, to match the uncoated BOTD 

discs, results in a high degree of consistency between 

the two sets of results.

Figures 7 through 9 show the results of the 

advanced analytical techniques used to characterize 

the wear contact area. Figure 7 is a top-down view 

of a 3-D optical micrograph of a wear scar on an 

injector; the low areas are dark colors while the high 

areas are light. The curvature of the spherical 

injector tip has been mathematically removed, 

changing the image from a curved surface with a flat 

scar to a flat surface with a bowl-shaped scar. This 

aids visualization and quantification of the wear 

volume. In this image, the boundary between the 

coating and the substrate is clearly visible; the 

coating has worn smoothly, while the areas of 

exposed steel and the coating next to it are rough. 

Only a very small amount of substrate has been worn 

off in this experiment. Figure 8 is a standard optical 

Surface 

treatment

Flat wear 

reduction

Injector 

wear 

reduction

Total 

wear 

reduction

Uncoated Worst flat 

wear

-47% from 

NFC2

Worst 

total wear

NFC6 -56% from 

uncoated

-40% from 

NFC2

-39% from 

uncoated

NFC2 -77% from 

uncoated

Worst injector wear-36% from 

uncoated

Table 2. Wear Rates for Three Surface Treatments 

Averaged over Seven Gasolines, Stated in Terms 

of Reduction from Worst Case

Figure 5. Friction in BOTD Lubricity Tests on Uncoated 

Steels in Several Gasolines

Figure 6. Wear Scar Diameter in BOTD Lubricity Tests 

in Several Gasolines
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

40

micrograph of the steel flat worn by that injector. 

Again the differences between the areas worn by 

NFC and the areas worn by the exposed substrate are 

clearly visible, despite the fact that the entire sample 

shown is steel. Figure 9 shows the friction trace of 

this test, indicating a sharp momentary rise in friction 

when the fresh steel substrate was exposed at 

approximately cycle 500,000. Figure 10 shows a set 

of Raman spectroscopy scans used to interpret the 

results of a different test. The response from the 

NFC coating on a worn injector is shown, which was 

substantially the same as the response from an 

unworn injector area. From this we know that the 

atomic structure of the NFC is not changed by the 

wear process. The response from the exposed 

substrate steel of the injector tip was also similar to 

that of the worn steel flat. A fragment of wear debris 

on the flat was also scanned, revealing it to be NFC.

Conclusions

Argonne’s NFC coatings have now been shown 

to provide outstanding benefits of friction and wear 

reduction for production fuel injectors in conditions 

simulating an operating engine environment. NFC6 

reduces friction an average of 22% compared to 

uncoated parts while reducing the wear rate by 

approximately 40%. For applications where even 

more friction reduction and counterface wear 

protection is desired, NFC2 can be used, which 

provides a friction reduction of a factor of two and a 

mating-part wear reduction of over a factor of four 

by slowly sacrificing its own volume and still 

providing excellent lifetime performance.

Figure 7. 3-D Optical Micrograph of a Wear Scar on an 

NFC-Coated Fuel Injector after a 1-million 

Cycle Lifetime Test

Figure 8. Optical Micrograph of Steel Flat Worn Against 

NFC-Coated Injector Shown in Figure 7 

(above)

Figure 9. Friction Trace of 1-million Cycle Lifetime Test 

of Figures 7 and 8 (above)

Figure 10. Raman Spectroscopy of NFC-Coated 

Injector, Steel Counterface, and Wear Debris 

after 1-million Cycle Lifetime Test
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

41

B. Development of an Advanced Non-Impingement SIDI Combustion System and 

Associated Low Pressure Fuel System

Paul VanBrocklin (Principal Investigator and Program Manager)

Delphi Energy & Chassis Systems

P. O. Box 20366

Rochester, New York 14602-0366

(716) 359-6797, fax (716) 359-6061, e-mail: paul.g.vanbrocklin@delphiauto.com

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Subcontractors: The Pennsylvania State University, State College, PA

Objectives

• To develop a non-impingement gasoline Spark Ignited Direct Injection (SIDI) combustion concept 

meeting modified Partnership for a New Generation of Vehicles (PNGV) objectives:

• To develop a low-pressure fuel injection system that allows an engine to meet the above requirements, 

which is consistent with the overall commercial considerations. 

• To understand EGR and ignition requirements for a non-impingement SIDI system. 

Approach

1. Determine the feasibility of a Jet-Stratified combustion system approach using Computational Fluid 

Dynamics (CFD) analysis, optical and single-cylinder engine testing.

2. Develop a Low Pressure Fuel System based on sub-system requirements generated earlier in the 

program, using analytical and experimental methods.

3. Implement developed sub-systems on a single cylinder research engine to demonstrate the 

performance of the combined systems.

Engine characteristics, units Range or Goal

Number cylinders 4

Total Displacement, cc 2000

Power output, kW Approx. 55

Peak efficiency target, % 35-37

Cost Within 10% of SI

Durability, hours >5000

NOx emissions, engine-out, g/kWh <1.4

PM emissions, engine-out, g/kWh <0.05

HC emissions, engine-out, g/kWh <3.0

CO emissions, engine-out, g/kWh <41.0
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

42

Accomplishments

This program is approximately 80% complete. 2001 accomplishments to date include:

• Engine Hardware

- Jet 4a and Jet 4b cylinder head designs were developed and built. The design of Jet 5 hardware has 

been recently completed and is being built. This Jet 5 concept will use a dedicated supplemental 

energy atomizer injection system on both the single-cylinder engine (SCE) and the optical engine 

(OE).

• Firing Single-Cylinder Engine

- Jet 2, 4a, and 4b combustion systems have been run. 

• Optical Engine at Delphi

- Particle Image Velocimetry (PIV) to map engine flow fields has been run on Jet 3 and 4b 

hardware. The ability to fire the OE and capture combustion images has also been developed.

• Optical Engine at Penn State University

- Additional testing using simultaneous Mie scattering and planar laser-induced fluorescence (PLIF) 

of two different Delphi injectors has been conducted to determine the liquid and vapor contents of 

the fuel spray. 

• Computational Fluid Dynamics

- Kiva 3v was used to model Jet 4a, determining that the optimal injector orientation for the Jet 4 

design was approximately 7.5° from vertical. This resulted in the Jet 4b design. Correlation of 

simulated to experimental PIV results for Jet 2 was successful. Difficulties with the correlation for 

the Jet 3 and 4 design are being evaluated.

• Injector/Atomizer

- The concept evaluation process reduced potential design approaches from five to three. First 

iteration hardware design, build and test loops on these three concepts have been completed. The 

second iteration of hardware build is in process. 

• Fuel Pump

- Two distinctly different designs using the same general gear pump concept have been designed, 

built, and undergone preliminary testing. The second design, although a radical departure from 

conventional gear pump designs, shows significant promise in the areas of reduced wear and 

friction. 

Future Directions

• Aside from the formidable technical challenges of developing high efficiency combustion systems, 

atomizers, and pumps, a significant non-technical issue has arisen during the course of the program. 

The DOE has elected to not continue funding in the area of SIDI research in 2002. This has resulted in 

the OTT not having the funds to test a multi-cylinder engine at the National Lab of their choice. Since 

a multi-cylinder engine was intended to be the final deliverable of this program, a change in program 

direction was required. It was decided to not build a multi-cylinder SIDI engine, but to continue 

development and refinement in the areas of fuel pumps, injector/atomizers and combustion chamber 

design using a single-cylinder engine. This continued work is outlined in the respective Approach/

Results to Date sections. The program will conclude at the end of Q1 2002 as before, but with a report 

centering on engine performance data comparing a high efficiency pressure orifice atomizer and 

supplemental energy devices.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

43

Introduction

Aside from significant vehicle level systems 

issues, the basic performance of today’s production 

SIDI engines do not benefit from the years of 

refinement that port fuel injected (PFI) SI engines 

have had. Because of this, current systems have high 

costs and small efficiency improvements over current 

PFI systems, questioning the value of such SIDI 

systems in North America. By developing SIDI 

systems that meet the PNGV requirements, the goals 

and objectives of both the DOE and Delphi are met. 

This report builds upon last year’s report published in 

the OTT 2000 Annual Progress Report.

The stratification mechanism currently employed 

in SIDI systems is to "bounce" injected fuel off a 

surface (typically the top of the piston) in 

combination with in-cylinder air motion to re-direct 

fuel to the spark plug. By impinging the piston, some 

portion of fuel is spread over a surface, leading to 

unburned hydrocarbons. An alternate, but unproven 

SIDI approach, is non-impingement or Jet 

stratification. Jet stratification is the principle of 

directing the fuel, as a well atomized jet, directly at 

the spark plug to avoid wetting combustion chamber 

surfaces. Because this type of system is in its 

infancy, Delphi Automotive Systems considers this 

approach to meet the DOE / PNGV requirements, 

while remaining commercially feasible, to be of 

higher risk than would normally be pursued. 

Participating in this cost-shared project with the 

DOE has allowed for participation in such a high-risk 

project, and it puts Delphi in the forefront of 

evolving technology. 

Approach / Results to Date

An essential goal of the project is to obtain 35-

37% overall engine efficiency. This efficiency target 

is significantly above the 22-28% efficiencies that 

current PFI or SIDI engines attain. To determine the 

individual goals of the project, the efficiency target 

was broken down into the areas of the base engine, 

injector and fuel supply system. This allows for 

power consumption to be used as an independent 

criteria for selection of engine, injector and fuel 

pump concepts. For example, an injector concept 

isn’t viable if it uses significantly more than the 

allotted power. However, since the target is overall

efficiency, there will be some power allocation tradeoffs as the project progresses and individual concepts 

are grouped into complete systems. Figure 1 

illustrates the efficiency breakdown of engine losses 

comparing empirical values for a production piston 

impingement SIDI engine to the predicted values for 

an Advanced Jet Stratified SIDI engine.

A governing direction of the project is to use 

lower fuel pressure (2.5 MPa) compared to current 

SIDI (5-10 MPa). This low pressure is beneficial in 

two areas of the project. 1) Less energy is expended 

to develop the required fuel pressure, thus helping to 

increase the overall energy efficiency. 2) By having 

a lower pressure, a single pump can be used, 

eliminating a significant amount of the cost 

associated with an engine-driven high-pressure pump 

that is required for current systems. 

The project is broken into 3 functional areas: the 

combustion system, atomizer, and fuel supply. 

Figure 1. Comparison of Engine Power Usage Between 

a Production SIDI and Advanced SIDI
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

44

Engine / Combustion System

Existing Delphi gasoline DI injectors have been 

used to conduct engine experiments to date. Kiva 3v 

has been used along with particle image velocimetry 

in an optical engine to understand and predict engine 

performance, with the end result being the 

development of engine hardware. PIV has been used 

to validate the Kiva 3v model. Good results have 

been obtained with the Jet 2 design that uses a flat 

top piston. Correlation between the Jet 3 and 4 

concepts that use a dome piston with a deep bowl has 

proven more difficult. Kiva 3v was used to predict 

that changing the angle of the centerline of the 

injector from vertical to 7.5° from vertical would 

increase the time over which an ignitable amount of 

vapor was in the location of the spark plug. Refer to 

Figure 2 for a plot of the coefficient of variation 

(COV) of indicated mean effective pressure (IMEP) 

(combustion stability) as a function of the air to fuel 

ratio for these two cases. The Pennsylvania State 

University has also conducted simultaneous Mie 

scattering and Laser Induced Florescence to 

determine vapor concentration of various Delphi 

injectors. 

Atomizer

A main goal of the atomizer program is to 

develop injectors that provide lower spray 

penetration (velocity) by having lower inlet pressure, 

while maintaining a well atomized spray. Developing 

well atomized sprays with fuel having lower initial 

energy requires significant advancements in the area 

of injector atomizers. This can be done either by 

more efficient use of available energy stored in the 

fuel as pressure, or by adding external sources of 

energy to help atomize the fuel. To save 

development time, existing injector actuators were 

used and only improved atomizers were developed. 

Of 42 initial concepts, five were brought forward 

into calendar year 2001. Initial hardware was built 

for the feasible concepts and bench testing was 

completed. Three concepts remain: a high efficiency 

pressure orifice atomizer and two supplemental 

energy pressure orifice devices.

A Taguchi designed experiment was completed 

on the high efficiency pressure orifice atomizer to 

gain an understanding of general design features and 

their relevance with respect to atomization. Figure 3 

shows spray volume distribution results from this 

experiment. CFD modeling using Fluent was 

completed on the best design and correlated within 

1% for flow. The calculated turbulent kinetic energy 

(TKE) output obtained from the CFD model was 

then used as a baseline indicator of atomization for 

comparative studies. Additional Taguchi Robust 

Engineering studies were completed to optimize the 

design for maximum TKE. Remaining work will 

include fabrication, assembly and testing of the 

second iteration of the high efficiency pressure 

orifice atomizer.

The second atomizer concept carried forward, a 

supplemental energy pressure orifice device, uses 

electrostatic repulsive forces to atomize and disperse 

fuel. Tasks completed on this concept include an 

evaluation of predictive software, charge flux 

modeling of initial concepts and design and 

fabrication of initial hardware. Remaining work will 

include completion of the Robust Engineering study 

for concept evaluation.

The third atomizer concept, also a supplemental 

energy device, was added to the program mid-year 

2001. This concept, previously evaluated at Delphi, 

demonstrated spray/penetration performance 

meeting most of the atomizer requirements. As 

such, it is currently the leading atomizer concept. 

Detailed spray and flow testing as well as 

combustion testing will be the remaining focus for 

this concept.

Figure 2. Combustion Stability Jet 4a (vertical injector) 

vs. Jet 4b (7.5° from vertical injector)
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

45

Pump

Concept development originally identified an 

internal gear type pump as the most viable concept 

for the pressure range under consideration. The main 

development challenges for this technology have 

been flow performance and durability. Development 

for improved flow performance has involved 

reducing internal leakage by minimizing the 

clearance or bypass flow paths between moving 

parts. This has been done by optimizing valve ports 

and by improving the design of the interface between 

the pump and the drive mechanism. To improve 

durability, material selection, lubrication, and 

pressure balancing have been the main focus. The 

use of hydrodynamic lubrication, or the 

establishment of fluid films under dynamic 

conditions, is the primary focus for areas of relatively 

large surface area (flat plate type interfaces). In highforce/small-area interfaces, such as the interface 

between a gear rotating on a shaft, material selection 

is the primary direction. Finally, pressure balancing, 

or eliminating the pressure differentials between the 

two faces of the gear, is being used to minimize high 

wear forces. Dynamic modeling of a gear type pump 

has proven to be very difficult. For this reason, an 

empirical build and test loop has been the primary 

method of component development. Figure 4 shows 

an example of how face clearance affects flow 

performance.

Conclusions

Development, testing, and analysis to date has 

resulted in several key findings:

• Not all methods of entraining air into the fuel 

spray to provide an ignitable mixture are 

equally robust. 

• An injector using supplemental energy for 

atomization may provide higher overall 

engine efficiencies due to the ability to 

operate with extreme residual levels. 

• The division of allowable tolerance stackups within the gear section of the pump for 

high-pressure operation is not the same as 

that of gear pumps used in Port Fuel 

Injection applications today. 

Figure 3. High Effective Pressure Orifice Atomizer 

Configuration 1 vs. Configuration 6 Spray 

Volume Distribution

Figure 4. Effect of Face Clearance on Gear Pump Flow
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

46

During the ensuing months, work will continue 

to resolve issues and further develop the individual 

components. Final single-cylinder engine testing will 

then be conducted. 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

47

C. Variable Compression Ratio Engine Technology 

Charles Roehm

Argonne National Laboratory

9700 S. Cass Avenue 

Argonne , IL 60439

(630) 252-9375, fax: (630) 252-3443, e-mail: croehm@anl.gov

Charles Mendler

Envera LLC

7 Millside Lane

Mill Valley, California 94941

(415) 380-5067, fax: (415) 380-5067, e-mail: mendler@earthlink.net

DOE Program Manager: Roland Gravel 

(202) 586-9263, fax: (202) 586-6109, e-mail: Roland.Gravel@ee.doe.gov

Objectives

• Develop a variable compression ratio (VCR) engine having a comparable cost to today’s production 

engines, capable of achieving U.S. Tier 2 and California LEV-II emissions certifications, and having 

an efficiency great enough to achieve a passenger car fuel economy of 80 mpg.

Approach

• Begin with a small displacement engine to achieve high energy conversion efficiency at low power 

levels.

• Supercharge and intercool the engine to achieve high specific power levels and to attain Partnership 

for a New Generation of Vehicles (PNGV) performance targets.

• Use variable compression ratio to prevent engine knock at high power levels and to substantially 

improve engine efficiency at low power levels.

• Use variable valve control to further improve efficiency and power.

• Use proven 3-way catalytic converter technology to achieve US Tier 2 and California LEV-II 

emissions certification.

Accomplishments

• Computer modeling at Ricardo, Inc. showed that the projected efficiency of the VCR engine should 

meet propulsion system requirements needed to reach the goal of 80 miles per gallon set by the PNGV.

• Dynamometer tests at AVL Powertrain validated the burn rates, compression ratio limits, and engine 

efficiencies predicted by the computer model. Engine-out emission levels were also shown to be 

similar to that of conventional engines. 

• Envera LLC built a 2-cylinder VCR engine and demonstrated operability and durability of the VCR 

mechanism with dynamometer testing. Compression ratio was varied while the engine was running 

from 8.5:1 to 17.5:1.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

48

Future Directions

• Build an optimized cylinder head for the 2-cylinder engine, and validate concurrently efficiency, 

emissions, and hardware. 

• Optimize engine variables for efficiency, emissions, and minimization of parasitic losses. Project 

vehicle mileage with optimized test data.

Introduction

The Partnership for a New Generation of 

Vehicles (PNGV) targeted compression-ignition 

direct-injection (CIDI) engines, an advanced version 

of the diesel engine, as one of the promising 

technologies for achieving its fuel economy goal of 

80 miles per gallon in a lightweight hybrid vehicle. 

However, due to increasingly stringent emission 

standards, development of a fall-back to the CIDI 

diesel engine was considered prudent. OAAT is 

sponsoring research to exploit the potential of using 

variable-compression-ratio (VCR) technology with 

supercharging to significantly improve spark-ignition 

engine efficiency while achieving low emissions 

using proven 3-way catalyst emission control 

technology. 

A fuel economy of 81 mpg was projected for a 

PNGV-intent vehicle powered by a simulated sparkignition gasoline VCR engine. The computer model 

was validated with single-cylinder dynamometer 

tests. A 2-cylinder VCR engine was built, validating 

operability, durability, and precision control of the 

VCR mechanism.

High Fuel Economy and Low Emissions 

Conventional gasoline engines operate at a fixed 

compression ratio, which is set low enough to 

prevent premature ignition of the fuel, or "knock," at 

high power levels under fast acceleration, high 

speeds, or heavy loads. Most of the time, however, 

gasoline engines operate at relatively low power 

levels under slow acceleration, lower speed, or light 

loads. If the compression ratio were increased at 

low-power operation, gasoline engines could achieve 

higher fuel efficiency. 

At the low power levels (0-20 kW), typical of 

most vehicle operating conditions, the VCR engine 

can achieve efficiency comparable to that of a diesel 

engine, a significant improvement over conventional 

port fuel-injected gasoline engines (see Figure 1). At 

the same time, because it is a gasoline engine, the 

VCR engine can achieve Federal Tier 2 and 

California LEV-II emission standards. 

Approach

Step 1: Modeling

By using WAVE (the Ricardo one-dimensional 

gas dynamics and engine simulation model), inhouse data on engine friction levels, and estimates of 

burn rate drawn from estimates of swirl and tumble 

within the combustion chamber and historical data 

for high compression ratio combustion, Ricardo was 

able to project the efficiency of the VCR engine. 

Ricardo then used their cycle simulation computer 

code to project vehicle mileage. Selected projections 

were validated by the National Renewable Energy 

Laboratory (NREL) using their ADVISOR cyle 

simulation computer code. 

The simulated vehicle was assumed to have a 6-

speed automated manual transmission and an 

Figure 1. Variable compression ratio engine 

promises high efficiency at low engine 

power levels.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

49

alternator that captures braking energy for powering 

accessory loads (electric forward drive not used). 

Vehicle weight and aerodynamic drag were 

comparable to an optimized PNGV-intent vehicle 

body.

Step 2: Engine Efficiency Validated

The projected engine efficiency depended on 

combustion burn rate assumptions for high 

compression ratio conditions that were based on 

relatively limited historical data. As a result, a 

development engine was built and tested at AVL 

powertrain to validate the efficiency values projected 

by the computer model and to quantify engine-out 

emission levels. Compression ratio was adjusted by 

shims in the test engine (Figure 2).

Step 3: VCR Mechanism Validated

A VCR 2-cylinder PNGV-intent prototype 

engine was built to evaluate its durability, reliability, 

precision control, response, and full variability 

within a range of 8.5:1 to 17.5:1. A donor cylinder 

head (cylinder head from an existing commercially 

available vehicle) was used to minimize program 

cost. All new components were designed and built 

from the head gasket down.

Results

Step 1: Modeling

A combined Environmental Protection Agency 

(EPA) city/highway fuel consumption of 81 mpg was 

projected for a PNGV-intent vehicle with a small 

displacement port-fuel-injected VCR engine 

equipped with on-demand supercharging, an 

automated manual 6-speed transmission, and 

accessory loads powered largely by regenerative 

braking.

The engine operated with a stoichiometric air/

fuel ratio throughout the Federal Test Procedure 

(FTP) city and highway driving cycles, providing a 

high probability of meeting Federal Tier 2 and 

California LEV II emission standards using threeway catalyst-based emission control systems.

All vehicle gradeability, acceleration, and 

maximum speed targets were met.

Step 2: Engine Efficiency Validated

Development engine test results validated 

Ricardo’s efficiency projections to within 98.5 

percent accuracy. Light-load efficiency results are 

shown in Table 1. (Slightly higher efficiency values 

were projected at other engine speeds.)

Step 3: VCR Mechanism Validated

The VCR engine operated for about 20 hours 

with no abnormal bearing or engine wear detected. 

The engine ran full throttle for several hours with 

noise and vibration characteristics within acceptable 

limits. The compression ratio was varied from 8.5:1 

to 17.5:1 during both part and full engine load, with 

high precision and responsiveness observed. 

Program expectations were surpassed. 

Future Work

A compact combustion chamber is necessary for 

achieving high efficiency and low emissions from 

the VCR engine at high compression ratio settings. 

The compact combustion chamber shape is best 

facilitated by using a bore/stroke ratio of about 0.9 

and a narrow valve included angle, preferably under 

25 degrees. A VCR-intent cylinder head for the 2-

cylinder prototype engine will be built and tested. 

Engine variables will be adjusted to provide 

optimum efficiency. Vehicle fuel economy 

projections will be made using the optimized engine 

efficiency test results. Projections will then be 

validated by conducting dynamometer tests of the 

Figure 2. Efficiency testing at AVL in Graz, Austria
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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VCR engine. Vehicle fuel economy modeling and 

engine tests are intended to validate the potential for 

achieving the PNGV 80 mpg goal and to validate the 

practicality of attaining high efficiency and low 

emissions with the VCR engine as a complete 

system.

Conclusion

VCR technology exhibits potential for providing 

a step-change improvement in spark-ignition engine 

efficiency, while retaining proven 3-way emission 

control technology. Planned cylinder head and VCR 

engine testing is intended to validate commercial 

practicality of a PNGV-intent engine. 

References

1. N. Miura, T. Raisen, G. Lu and N. Yamazoe, 

Sensors and Actuators B 47 (1998) 84-91.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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D. Performance of Plasmatron-Enhanced Lean-Burn SI Engine

Daniel R. Cohn (Primary Contact), PlasmaScience and Fusion Center, John B. Heywood, Andreas 

Lengwiler, Edward J. Tully, Sloan Automotive Laboratory

Massachusetts Institute of Technology

77 Massachusetts Avenue, NW16-106

Cambridge, MA 02139

(617) 253-5524, fax: (617) 253-0700, e-mail: cohn@psfc.mit.edu

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Map out a lean engine operating regime of a standard spark-ignition (SI) engine with different 

fractions of the gasoline fuel going to the engine via the plasmatron fuel to hydrogen converter.

• Determine the plasmatron-enhanced engine combustion characteristics, emissions levels, and 

efficiency at selected speed and load conditions.

• Develop a phenomenological model that predicts the lean plasmatron-enhanced SI engine behavior.

• Define the engine’s operating requirements (fraction of fuel energy in plasmatron gas) required for 

high efficiency and low NOx emissions operation with acceptable combustion stability.

Approach

• Develop phenomenological model that predicts engine torque, given the engine’s operating conditions, 

for use in planning the experimental matrix and achieving desired test conditions.

• Use single-cylinder research engine and bottled gas mixture (H2, CO, CO2, N2) to simulate plasmatron 

exit gas for initial mapping of the lean engine regime.

• Enhance engine combustion characteristics using swirl and/or tumble to assess minimum plasmatron 

gas requirements with a modern SI engine combustion system.

• At the appropriate stage in the development of this engine mapping program, confirm results in a 

multi-cylinder engine test.

Accomplishments

• A model for predicting plasmatron-enhanced lean engine performance has been developed and tested 

(Lengwiler, 2001).

• Preliminary data confirm that very lean engine operation with low emissions is feasible. More 

extensive tests have expanded the data set to leaner mixtures.

Future Work

• More complete mapping of the lean engine operating regime can expand the required database to 

leaner mixtures, with engine test conditions controlled more accurately.

• Engine modifications can be used to increase the burn rate of the single-cylinder test engine to enhance 

its lean limit capability.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Introduction

Hydrogen-enhanced lean gasoline operation 

using onboard conversion of gasoline to hydrogen 

could be a cost effective way to achieve significantly 

higher vehicle efficiency and lower emissions. The 

plasmatron, a discharge boosted fuel conversion 

device, can be used to provide a hydrogen-rich gas 

stream from gasoline when combined with a standard 

engine enable very lean engine operation. Such lean 

operation improves engine efficiency and lowers 

NOx emissions substantially.

To develop this engine concept, the fraction of 

the gasoline that needs to be converted to a mixture 

of H2, CO, and N2 must be quantified. This project 

addresses this issue. The objective is to define the 

plasmatron exit gas flow required to achieve the 

efficiency and low emissions objectives while 

maintaining sufficiently fast and stable combustion.

Approach

The data which will define the required 

plasmatron gas flow as a function of engine 

operating conditions is being generated on a singlecylinder research spark-ignition engine. The 

efficiency, combustion and emissions characteristics 

of the engine will be mapped out over a range of 

plasmatron exhaust gas/gasoline mixtures, engine 

loads, engine speeds and relative air/fuel ratios. This 

is being done with bottled gas to simulate the 

plasmatron exit gas. A phenomenological model of 

this engine concept has also been developed to assist 

in selecting test conditions for the experiments and in 

interpreting the results (Lengwiler, 2001)

 Results

The results obtained to date are preliminary; 

however, they show the expected trends. The 

addition of plasmatron gas to the gasoline vapor air 

mixture in the cylinder speeds up combustion and 

improves engine stability. The larger the relative 

amount of plasmatron gas, the greater the 

improvement. Figure 1 shows the coefficient of 

variation of indicated mean effective pressure, a 

common measure of combustion stability, versus the 

relative air/fuel ratio. Addition of plasmatron gas 

corresponding to 18% of the gasoline going directly 

to the plasmatron (where an 80% energy out/energy 

in ratio is assumed) extends the lean limit 

significantly.

The low emissions potential of the lean 

plasmatron enhanced engine is illustrated by the NOx

emissions data in Figure 2. At fixed engine load and 

speed, NOx emissions decrease steadily from the high 

values of close to stoichiometric mixture operation. 

The plasmatron engine example shown has lower 

emissions at a given Lambda due to the additional N2

in the plasmatron gas, and can operate leaner before 

combustion stability limits are reached. (Lambda is 

the actual air/fuel ratio divided by the stoichiometric 

air/fuel ratio.) This latter is the bigger effect and the 

primary objective. Hydrocarbon emissions are 

reduced by 10-20% with plasmatron enhanced lean 

operation due to better combustion.

Figure 1. Combustion stability, defined by coefficient of 

variation in indicated mean effective pressure, 

as a function of relative air/fuel ratio (Lambda) 

for operation with gasoline and with 18 

percent of the gasoline flow going to 

plasmatron. Net imep = 3.1 bar, 1500 rev/min.

Figure 2. Engine-out NOx emissions as a function of 

relative air/fuel ratio (Lambda) plotted up to 

stable lean operating limit; same conditions as 

Figure 1.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

53

The efficiency of the engine steadily improves as 

leaner operation is achieved. With the plasmatronenhanced lean operating engine, net indicated 

efficiencies of about 37% have been achieved to 

date. Upon converting these to brake efficiencies 

(based on the power delivered by the engine 

driveshaft), using values of friction mean effective 

pressure typical of multi-cylinder engines, one 

obtains a brake efficiency of about 30%. This is 

substantially higher than typical current part-load SI 

engine efficiencies.

More extensive mapping of the engine’s 

performance when enhanced by varying amounts of 

plasmatron H2, CO, N2 gas mixtures is in progress.

Conclusions

Preliminary results from single-cylinder engine 

tests, using appropriate synthesized gas mixtures to 

simulate plasmatron exhaust gases, show that faster 

and more stable combustion processes can be 

achieved. This extends the lean operating limit of the 

engine. Engine test results indicate the low NOx

emissions and high efficiency potential under these 

plasmatron-enabled lean operating conditions.

Publications

1. Lengwiler, A., "SI Engine Combustion and 

Enhancement Using Hydrogen from a 

Plasmatron Fuel Converter" Diploma Thesis 

ETH Zurich, winter semester 2000/2001; Sloan 

Automotive Laboratory, MIT, April 2001.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

54

E. On-Board Distillation of Gasoline 

Ron Matthews (Primary Contact) and Tom Kiehne 

Engines Research Program

The University of Texas 

Mail Code C2200

Austin, TX 78712

(512) 471-3108, fax: (512) 471-1045, e-mail: rdmatt@mail.utexas.edu

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Develop a model to explore the issues that might impact the implementation of the on-board 

distillation concept, and acquire the experimental data necessary for the model.

• Quantify the effects of the on-board distillation system on emissions; cold startability; cold 

driveability; and the Octane Ratings of the main fuel (the less volatile of the two fuels generated), 

including preliminary assessment of how this characteristic might be used to improve fuel economy. 

• Demonstrate that on-board distillation is a practical and cost-effective technology for decreasing 

emissions of hydrocarbons.

Approach

• Modify a 2001 Lincoln Navigator to incorporate a gasoline on-board distillation system (OBDS). 

Perform tests to optimize the design and calibration of the OBDS.

• Develop a model to examine the issues of "too many hot starts" and "too many cold starts". Use the 

model to aid design and calibration of the OBDS.

• Perform tests to demonstrate that on-board gasoline distillation decreases emissions of hydrocarbons.

• Perform tests to demonstrate that the driveability is improved.

• Perform tests to demonstrate that the startability in cold weather is improved.

• Perform tests to quantify the Octane Rating of the main fuel. Analyze how this shift in Octane Rating 

can be used to improve fuel economy.

Accomplishments

• The OBDS has been fabricated and installed on the 2001 Lincoln Navigator. We are finalizing the 

OBDS control system and waiting for hardware and software from Ford that will allow us to reprogram the Navigator’s on-board computer.

• We have begun developing the model.

Future Directions

Once the OBDS control system is complete, and we receive the Ford RCON re-programming unit, we will:

• Optimize the design and calibration of the OBDS via a combination of experiments and modeling.

• Send the 2001 Navigator to Southwest Research Institute for tests of emissions, cold startability, and 

cold driveability.

• Send fuel samples to Ford for analysis of the Octane Rating. 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Introduction

The first 1-2 minutes of vehicle operation 

contribute inordinately to tailpipe emissions of 

hydrocarbons (HCs), which are of concern because 

HCs contribute to ground level ozone formation. 

Typically, 60-80% of HCs are emitted during starting 

and warm-up for conventional gasoline engines, and 

~40% for direct injection gasoline engines 

(References 1-4).

The primary goals of this project are to develop 

and demonstrate a new technique for decreasing 

hydrocarbon emissions from gasoline vehicles and to 

transfer this technology to the automotive industry. 

The new concept is on-board distillation. This 

allows the consumer to refill the fuel tank with a 

single fuel (gasoline), from which two fuels are 

generated on-board the vehicle. Specifically, the 

more volatile fractions of the gasoline are separated 

from the less volatile portion. The volatile fraction is 

used for starting the engine and during a portion of 

the warm-up transient. Because the "start-up fuel" is 

very volatile, the normal need for start-up overfueling is minimized or eliminated. In turn, this 

significantly reduces emissions of hydrocarbons and 

"exhaust toxics". The high volatility of the start-up 

fuel also promises improved startability and 

driveability in cold weather. Furthermore, because 

on-board distillation changes the composition of the 

fuel that is used during the majority of driving, it is 

possible that an indirect fuel economy benefit will 

also be realized. 

Approach

Ford has provided a 2001 Lincoln Navigator to 

use as a test platform. A gasoline on-board 

distillation system will be installed on this vehicle. 

The operation of the OBDS is illustrated in Figures 1 

and 2. The OBDS hardware has been designed and 

fabricated and installed in the Navigator. We are 

near completion of the OBDS control system, which 

controls when and how long we generate start-up 

fuel, purging of the fuel rail with start-up fuel 

between starts, and how long the start-up fuel is used 

after each start. These are all functions that can be 

handled by the powertrain control module (PCM, the 

on-board computer) if this concept is incorporated 

into production vehicles. Additionally, we must 

minimize or eliminate the start-up over-fueling that 

the Navigator’s PCM is programmed to command. 

We have been working with Ford to secure an 

RCON, which they use to re-program their PCMs. 

Once we have this unit, we will use a combination of 

experiments and modeling to optimize the calibration 

of both controllers. 

Southwest Research Institute will perform 

standard emissions, cold-start, and driveability tests 

on the Navigator. Additionally, we will send fuel 

samples to Ford for Octane Ratings tests. We will 

use these results to explore the potential of a fuel 

economy benefit. 

Results

Because this project is only in its fourth month, 

we do not yet have any results to report.

Figure 1. On-board Distillation System, Illustrating 

Generation of Start-up Fuel

Figure 2. Fuel path during starting. Because the supply 

line and fuel rail are purged with start-up fuel 

following every engine shut down, start-up 

fuel is sitting on the injectors prior to starting.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

56

References

1. Crane, M.E., R.H. Thring, D.J. Podnar, and L.G. 

Dodge (1997), "Reduced cold-start emissions 

using rapid exhaust port oxidation in a sparkignition engine", SAE Paper 970264. 

2. Guillemot, P., B. Gatellier, and P. Rouveirolles 

(1994), "The influence of coolant temperature on 

unburned hydrocarbon emissions from SI 

engines", SAE Paper 941962.

3. Witze, P.O., and R.M. Green (1997), "LIF and 

flame-emission imaging of liquid fuel films and 

pool fires in an SI engine during a simulated cold 

start", SAE Paper 970866.

4. Stovell, C., R.D. Matthews, B.E. Johnson, , H. 

Ng, and B. Larsen (1999), "Emissions and fuel 

economy of 1998 Toyota with a direct injection 

spark ignition engine", SAE Paper 1999-01-

1527; also in Journal of Fuels and Lubricants

Vol. 108.

Awards/Patents

1. Matthews, R.D.,R. Stanglmaier, G.C. Davis, and 

W. Dai, "On-Board Gasoline Distillation for 

Reduced Hydrocarbon Emissions at Start-Up", 

U.S. Patent No. 6,119,637, issued Sept. 19, 2000.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

57

IV. EMISSION SENSOR DEVELOPMENT

A. Exhaust Gas Sensors CRADA (HC)

Ai Quoc Pham (Primary Contact)

Lawrence Livermore National Laboratory

P.O. Box 808, L-644

Livermore, CA 94550

(925) 423-7140, fax: (925) 423-3394, e-mail: pham2@llnl.gov

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• Identify factors influencing sensor response time.

• Develop new electrodes for faster sensor response time.

• Incorporate a hydrocarbon (HC) sensor to a self-heated device.

Approach

• Determine effect of electrode microstructure and electrode materials on sensor response.

• Investigate the response of composite electrodes having two or more different materials.

• Incorporate HC sensor on HEGO (Heated Exhaust Gas Oxygen) sensors provided by Ford.

Accomplishments

• Demonstrated a correlation between electrode thickness and sensor signal amplitude.

• Developed three new electrode formulations with response time faster than 1s.

• Developed self-heated sensors. 

Future directions

• Improve sensor packaging.

• Evaluate long-term stability.

Introduction

Due to increasing environmental concerns, in 

1994 the California Air Resources Board (CARB) 

and the U.S. Environmental Protection Agency 

(EPA) began implementing regulations that require 

automakers to incorporate comprehensive on-board 

diagnostics into new vehicles. The purpose is to 

monitor emissions, which will allow early detection 

of any malfunctioning of the engine and/or emission 

control system. Currently, monitoring of 

hydrocarbon (HCs) and NOx emissions is regarded as 

being critical for evaluating car emissions. This 

report describes the progress we have made on the 

development of the HC sensors during FY01. 

Approach

One of the major issues with HC sensing is the 

potential cross-sensitivity with CO, which has 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

58

similar chemical characteristics. Our approach has 

been to find chemical sensing reactions that will 

differentiate HCs from CO. One of the reactions 

considered was the dehydrogenation, which affects 

HCs only. The sensor itself can be either a hydrogen 

sensor or an oxygen sensor with a dehydrogenation 

catalyst covering one electrode only. The HCs will 

undergo the dehydrogenation reaction on the 

electrode having the catalyst layer, thus generating a 

hydrogen concentration difference across the sensor. 

This hydrogen concentration difference will generate 

a voltage across the hydrogen sensor, and the signal 

amplitude will be directly related to the gas phase 

concentration of HCs. If an oxygen ion conducting 

electrolyte is used instead of a proton conductor, and 

if oxygen is present, the hydrogen generated from the 

dehydrogenation will undergo a reaction with 

oxygen, causing an oxygen concentration difference 

across the sensor, thus providing similar sensing 

mechanism. Sensors based on the above approaches 

have been developed and characterized extensively. 

While a number of issues have been resolved, the 

sensor was still not suitable for real exhaust gas 

sensing because of the slow response time (from 10 

seconds up to 1 minute). Thus, effort this year was 

focused on decreasing sensor response time to less 

than 1 s.

Results

Our effort was first to determine the various 

factors that could influence the sensor response, both 

in terms of signal amplitude and response time. For 

the same electrode/catalyst material, we found that 

the sensor signal decreased with increasing electrode 

thickness (Figure 1). On the other hand, the sintering 

temperature of the electrode, and thus the particle 

size, was found to have direct influence on the sensor 

response time: the lower the sintering temperature, 

the faster is the sensor response. However, the factor 

that had the strongest influence on sensor response 

time was the catalyst material itself. Iron oxide had a 

much faster response than zinc oxide, for instance. 

Based on the above observations, we designed 

four different approaches to improve sensor response 

time. Three of the approaches involved the 

preparation of composite electrodes and/or 

multilayer structures. All sensors having composite 

or multilayer electrodes were found to exhibit 

extremely fast response to HCs. Figure 2 shows an 

example of the sensor response to butane. The 

measured response time of 2 s was limited by the gas 

phase exchange within the experimental chamber. 

Measurements performed at Ford Research 

Laboratory indicated an actual response time below 

0.5 s. The sensors are thus fast enough for real 

exhaust gas monitoring.

The operating temperature of the present sensors 

is in the range of 600-750°C. The heating, currently 

provided by an external furnace, is not convenient for 

exhaust gas monitoring. The sensor has thus been 

miniaturized and mounted directly on a HEGO 

sensor provided by Ford (Figure 3). The HEGO 

sensor provided the necessary heating and could be 

used for monitoring the oxygen concentration in 

exhaust gas as well. Extensive characterization of 

the heated sensor is underway.

Figure 1: Effect of Electrode/Catalyst Thickness on 

Sensor Signal

Figure 2: Sensor response to 194 ppm butane. The gas 

is switched on and off between each step. 

Time between two data points is 1 s.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

59

Conclusion

We have investigated the various factors that 

could influence sensor response time. The 

investigation has resulted in the development of three 

successful approaches to reduce sensor response 

time. The improved sensors exhibit a response time 

less than 0.5 s and are thus suitable for use in exhaust 

gas sensing. Efforts to package the sensor on a 

heater are underway.

Figure 3: Photograph of LLNL HC Sensor Mounted on 

a HEGO Sensor
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

60

B. Advanced Ion-Mobility NOx Sensor

A. C. Raptis (Primary Contact) and S. H. Sheen

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

(630) 252-5930, fax: (630) 252-3250, e-mail:raptis@anl.gov

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• The objective of this project is to develop a non-radioactive ion-mobility NOx sensor that can be used 

in an engine exhaust emission environment to provide real-time measurements of NOx emissions.

Approach

• Stage 1. Design and evaluation of a corona discharge ionization source.

• Stage 2. Design and evaluation of a laboratory prototype ion-mobility spectrometer (IMS).

• Stage 3. Parametric study of the non-radioactive IMS for detecting NOx.

• Stage 4. Development of a field prototype that applies to a typical exhaust emission environment.

• Stage 5. Field testing of the IMS.

Accomplishments

• Developed a spark-discharge ionization source.

• Developed a method to reduce the water-vapor effects on IMS.

• Designed and evaluated a laboratory prototype IMS.

• Analyzed laboratory test data to determine the sensor performance.

Future Directions 

• Design and fabricate a field prototype of IMS including control electronics.

• Conduct field tests.

Introduction

Future low-emission and high-fuel-efficiency 

vehicles need a sensor to monitor NOx emissions for 

optimizing the performance of exhaust emission 

control systems. Such a NOx sensor must have high 

sensitivity, fast response time (<1 sec), and be able to 

survive the hostile environment of an engine exhaust 

system. An ion-mobility spectrometer has been 

demonstrated as a low-cost gas sensor [1] that may 

meet the requirements of an exhaust gas application. 

Based on ion-molecule chemistry, the basic energy 

requirement for forming a negative molecular ion is 

determined by the electron affinity (EA) of the 

molecule. The EAs for the negative NO and NO2 

ions are about 0.02 eV and 2.3 eV, respectively [2]. 

Therefore, it is possible to measure the total NOx

emissions by simply measuring negative NOx ions 

produced in IMS. The feasibility of using 63Ni-IMS 

to detect negative NOx ions has been successfully 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

61

demonstrated [3]. Because a radioactive source is 

unacceptable for an automotive application, 

alternative ionization sources such as corona 

discharge need to be developed. Tabrizchi,et.al. [4] 

described a design of such a pulsed corona-discharge 

ionization source which uses a point-to-point 

geometry. In FY 2001, we focused on development 

of a pulsed corona discharge ionization source with a 

needle-to-cylinder geometry. Preliminary results of 

such a non-radioactive IMS in detecting negative 

NOx ions are presented.

Approach

The primary effort in FY 2001 was to develop a 

plasma-type ionization source to replace the 63Ni βemission source. Figure 1 shows the basic design of 

the laboratory prototype IMS sensor. It consists of a 

pulsed corona discharge ionization source, an ion 

drift tube, and a Faraday plate. The ion source 

assembly has a needle/metal-cylinder geometry. 

During operation the metal cylinder is biased with a 

negative voltage so that negative ions will be 

confined in the cell until the shutter grid opens. The 

drift tube of the IMS is a glass tube embraced by a 

series of steel-guard rings separated by Teflon rings, 

which establishes a uniform electrical field for 

detecting negative ions. Table 1 lists the specific 

design parameters and typical operating conditions 

of the IMS sensor.

Laboratory tests were conducted to evaluate the 

IMS sensor performance. The tests used a carrier gas 

typical of exhaust-gas composition mixed with NOx/

N2. Both ion drift time and current output were 

measured and correlated with NOx concentration. 

Water-vapor effect on the IMS spectrum was also 

examined, and a method to reduce the vapor 

concentration in the gas stream was developed. 

Results

Figure 2 shows the spectra of a gas mixture with 

97 ppm of NO2 in the carrier gas obtained under 

corona and spark discharge modes. The spark 

discharge (0.8 mA in-current) produces a better 

developed peak than does the corona discharge mode 

(0.1 mA in-current). The spark-discharge mode was 

chosen for IMS evaluation. Figure 3 shows 

dependence of peak amplitude on NO2 concentration 

up to 500 ppm for NO2/carrier-gas mixtures. 

Quantitatively, the NO2/carrier-gas mixture produces 

more ions than NO2/N2 gas mixture, and the carrier 

gas mixture alone also produces an ion peak of 

significant magnitude with a delay time in the region 

where the NO2 ions appear (14.5 — 16 ms). This 

suggests that NO2 may be produced in the plasma 

during the spark-discharge process if the buffer gas 

has the carrier-gas composition. It is possible that 

the presence of oxygen (8.1%) in the carrier gas 

induces the reactions leading to NO2 ion production. 

The presence of water vapor in IMS tends to 

degrade the ion spectrum. In most cases, we found 

Figure 1. Basic Design of Ion-Mobility Spectrometer

Ion Source Needle-surface 

gap

0.25 cm

Applied voltage -3.0/-4.0 kV

Shutter grid

Pulse width 2 ms

Pulse voltage 140 V

Frequency 12.5 Hz

Drift-tube electrical field 220 V/cm

Detection 

electronics

Filter (LP) 3 kHz

Sensitivity 2 nA/V

Table 1. Design Parameters and Operating Conditions of 

the IMS Sensor

Figure 2. Negative NO2 Ion Sprectra Produced by 

Corona and Spark Discharges
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

62

that the ion spectrum was completely masked by 

noise when the vapor content exceeded 1%. 

Therefore, a method to reduce the noise is necessary 

for practical applications. We investigated a cooling 

method using a thermoelectric cold plate that 

condenses water vapor before the gas enters the IMS. 

Figure 4 shows three ion spectra taken with vaporsaturated gas passing a cooling bath adjusted at the 

shown temperatures. The spectra show that as 

temperature decreases, the signal-to-noise ratio 

improves and the delay time of the peak decreases. 

The changes in delay time suggest that the size of 

water cluster may be reduced as the temperature 

decreases. 

Conclusions

Preliminary results show that the spark-discharge 

mode of operation can be used to quantify the NO2

concentration. The water-vapor effect has been 

examined. Without any pretreatment of the gas, the 

ion spectrum is completely masked by the noise 

when water content exceeds 1%. A thermoelectric 

cold plate was used to condense water from the gas 

stream before entering the IMS. Positive results to 

reduce the water effect were obtained. However, 

there are a few technical hurdles that need to be 

overcome before the IMS sensor can be used in an 

engine exhaust environment. These include (a) 

effects due to high-concentration water vapor, (b) 

drift time ambiguity, and (c) complexity of the ionmolecule chemistry due to variations of the exhaustgas composition.

List of References

1. G. A. Eiceman and Z. Karpas, "Ion mobility 

spectrometry," CRC Press, 1994.

2. B. M. Smirnov, "Negative ions," McGraw-Hill 

Inc., pp. 27-31, 1982.

3. J. A. Jendrzejczyk, S. L. Dieckman, S. Slaughter, 

and A. C. Raptis, "Response of a prototype 

vehicle exhaust gas sensor to various 

hydrocarbons and other constituents," Argonne 

National Laboratory publication, ANL-99/5, 

1999.

4. M. Tabrizchi, T. Khayamian, and N. Taj, "Design 

and operation of a corona discharge ionization 

source for ion mobility spectrometry," Rev. Sci. 

Inst. Vol. 71 (6), pp. 2321-2328, 2000.

Figure 3. Peak Amplitude Versus NO2 Concentration 

Measured with Carrier Gas and 5nA/V in 

Sensitivity

Figure 4. Negative NO2 Ion Peaks Detected by 

Controlling the Carrier Gas Temperature
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

63

C. Exhaust Gas Sensor Development

Fernando Garzon (Primary Contact)

MS D429, MST-11 Group

Los Alamos National Laboratory

Los Alamos, New Mexico, 87544

(505) 667-6643, fax (505) 665-4292, email: garzon@lanl.gov

DOE Program Manager, Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@lanl.gov

DOE Contractor: Los Alamos National Laboratory, Los Alamos, NM 87544

Objectives

• The goal is the development of low-cost solid-state electrochemical sensors that measure the nonmethane hydrocarbon emissions of internal combustion engines.

Approach

• Develop solid-state electrocatalytic sensors based on zirconia ceramic electrolyte materials that 

produce a voltage output that is proportional to the non-methane hydrocarbon emissions 

concentrations in automotive exhausts. 

• Novel thin-film metal oxide catalytic electrodes are used to sense the pollutants via electrode surfaceelectrochemical oxidation reactions. 

• Modern electronic device fabrication methods are used to make the sensors.

• Electrochemical theory and modeling are used to optimize the device performance.

Accomplishments

• We have developed low-cost sensor prototypes that measure 10 - 2000 ppm concentrations of nonmethane hydrocarbon gases (propylene and propane) under simulated high-temperature exhaust gas 

environments and engine dynamometer tests.

• We have reduced the cross interference of carbon monoxide to a ratio of better than 25 to 1.

• The devices exhibit almost no cross sensitivity for nitrogen oxides, water vapor or carbon dioxide 

gases.

• Our sensors exhibit excellent device-to-device response uniformity — less than 5% variability.

• We have improved the response times of our sensors from a minute to less than 3 seconds. 

• Our hydrocarbon sensor technology has been combined with Ford Laboratory flat plate oxygen sensor 

technology to produce standalone sensors.

Future directions

• The program will not be funded in FY2002. Future directions include negotiations between sensor 

suppliers and the CRADA partners for technology commercialization.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

64

Introduction

 Internal combustion engines do not operate at a 

high enough efficiency to completely combust their 

fuel to carbon dioxide and water vapor. All internal 

combustion engines used in transportation require 

control and diagnostic sensor systems to reduce 

unwanted hydrocarbons, carbon monoxide and 

nitrogen oxide tailpipe emissions. Currently used 

automotive sensor systems are not performing 

adequately in this role and are responsible for a high 

maintanence workload for the manufacturers and the 

vehicle owners. Our goal is the development of lowcost solid-state electrochemical sensors that measure 

non-methane organic gas (NMOG) emissions 

(hydrocarbons) of internal combustion engines. The 

sensors need sufficient sensitivity to measure the 

performance of the automobile’s emission control 

system to satisfy Federal On-Board Diagnostic 

requirements—typically, concentration levels of 10-

500 parts per million of the regulated species. 

Ideally, the sensors should operate in-situ in hot 

exhaust gas streams. We have developed low-cost 

sensors to meet the needs of future on-board 

diagostic requirements.

Approach

 Electrochemical sensors of the mixed potential 

class, operating at exhaust gas temperatures, offer a 

promising method of on-board emissions monitoring. 

The devices typically are comprised of two different 

catalytic electrodes deposited on an yttria-doped 

zirconium oxide solid electrolyte. Multiple charge 

transfer reactions occurring between the gas phase 

and the electrodes cause potentials of differing 

magnitude to develop at the dissimilar electrodes. 

The differences in heterogeneous kinetics, 

electrokinetics and the equilibrium potentials for 

these reactions all influence the device response to 

varying concentrations of analyte gas. 

Miura and co-workers using electrochemical 

theory that invokes Butler-Volmer kinetics at high 

over-potentials have described the response behavior 

of mixed potential sensors. While this model does 

accurately describe the response behavior of many 

types of mixed potential sensors, the current model is 

inadequate for describing mixed potential sensors 

whose electro-kinetic reactions are mass transport 

limited or occurring at low over-potentials. For low 

concentrations of analyte gas, mass transport 

limitations must also be considered. Also, under 

some conditions, one of the electrodes may be 

operating at low over-potentials in the linear current 

voltage regime. We have developed models 

describing the behavior under non-Tafel response 

conditions. These models successfully predict the 

response behavior of the hydrocarbon sensors and 

provide insight on optimization of sensor design.

Our devices are based on thin-film transition 

metal oxides catalyst/noble metal composites 

deposited on oxygen ion conducting solid-state 

electrolytes. The metal oxide electrodes are central 

to the operation of the devices: they are 

electronically conducting and act as the electrodes 

for our sensors; they are catalytically active and can 

provide selective catalyzation under appropriate 

conditions; and finally, they conduct oxygen atoms 

and act as the source of oxygen for oxidizing 

reactions. Materials such as electron conducting 

perovskite oxides—lanthanum manganese oxide, 

lanthanum chromium oxide or fluorite structure 

oxides such as terbium zirconium oxide—have been 

successfully used to produce HC sensors. Sensors 

have been fabricated using bulk ceramic processing 

methods such as isostatic pressing and also by using 

physical vapor deposition technology. Figure 1 

illustrates oxide electrode devices fabricated by 

Figure 1. LANL hydrocarbon sensors fabricated on Ford 

self-heated ceramic substrates, top and bottom 

views. The small dark square on the left side 

of the top sensor is the electrochemical gas 

sensing element.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

65

LANL on sensor substrates developed by Ford 

Research Laboratory. The devices respond well to 

common hydrocarbon exhaust gases blended into 

nitrogen, carbon dioxide and water vapor mixturessurrogate exhaust gas. Figure 2 displays the sensor’s 

excellent response to propylene gas. Our sensors are 

proving to be robust devices that can reproducibly 

measure hydrocarbon emissions under laboratory 

conditions for long time periods. Our automotive 

CRADA partners have also extensively tested these 

devices under laboratory and engine exhaust 

conditions. A number of automotive sensor suppliers 

have expressed interest in the possible testing and 

subsequent commercialization of our devices.

References

1. N. Miura, T. Raisen, G. Lu and N. Yamazoe, 

Sensors and Actuators B 47, (1998) 84-91.

Publications

1. Fernando H. Garzon, R. Mukundan, and Eric L. 

Brosha, "Modeling the Response of Mixed 

Potential Electrochemical Sensors," Solid State 

Ionic Devices II , Vol. 2000-32 Electrochemical 

Society, 2000.

2. Fernando H. Garzon, Rangachary Mukundan, 

and Eric L. Brosha, "Solid State Mixed Potential 

Gas Sensors: Theory, Experiments and 

Challenges," Solid State Ionics 136-137 (2000) 

633-638.

3. R. Mukundan, E.L. Brosha, F.H. Garzon, "SolidState Electrochemical Sensors for Automotive 

Applications," submitted to proceedings of the 

American Ceramics Society, Indianapolis, IN, 

2001.

4. E. L. Brosha, R. Mukundan, D.R. Brown, and 

F.H. Garzon, "Zirconia-based Mixed Potential 

CO/HC Sensors with LaMnO3 and Tb-doped 

YSZ Electrodes," Solid State Ionic Devices II 

Vol. 2000-32 Electrochemical Society, 2000.

5. E.L. Brosha, R Mukundan, D.R. Brown, F.H. 

Garzon, J.H. Visser, M. Zanini, Z. Zhou, and 

E.M. Logothetis, "CO/HC Sensors Based on 

Thin Films of LaCoO3 and La0.8Sr0.2CoO3."

Presentations

Invited Speaker

1. Rangachary Mukundan, Eric Brosha, Fernando 

Garzon, "Solid-State Electrochemical Sensors 

for Automotive Applications," presented at the 

Amercian Ceramics Society Conference, 

Indianapolis, Indiana, April 22-25, 2001.

Other Presentations

1. Fernando H. Garzon, R. Mukundan, Eric L. 

Brosha, "Modeling the Response of Mixed 

Potential Sensors," presented at the 198th

meeting of the Electrochemical Society, Phoenix, 

Arizona, 2000.

2. Eric L. Brosha, Rangachary Mukundan, David 

R. Brown, Fernando H. Garzon, "Sensing 

System for Closed Loop Combustion Control," 

presented at the national conference of the 

American Society of Gas Engineers, Las Vegas, 

Nevada, June 11, 2001. 

3. Eric L. Brosha, Rangachary Mukundan, David 

R. Brown, Fernando H. Garzon, J. H. Visser, 

David J. Thompson, D. H. Schonberg, and E.M. 

Logothetis, "Zirconia Based Mixed Potential 

CO/HC Sensors with LaMnO3 and Tb-doped 

YSZ Electrodes," presented at the 198th meeting 

of the Electrochemical Society, Phoenix, 

Arizona, October 23-27, 2000.

Figure 2. Hydrocarbon sensor response to part per 

million level changes of propylene gas 

concentration for six different runs.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

66

Patents

1. "Mixed potential hydrocarbon sensor with low 

sensitivity to methane and carbon monoxide" R. 

Mukundan, E.L. Brosha, F.H. Garzon inventors. 

patent applied for- case #94675

2. "Enhanced Electrodes for Solid State Gas 

Sensors" F.H. Garzon and E.L. Brosha inventors. 

US Patent Granted 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

67

D. NOx Sensor for Monitoring Vehicle Emissions

L. Peter Martin (Primary Contact), Ai-Quoc Pham

Lawrence Livermore National Laboratory

P.O. Box 808, MS L-333

Livermore, CA 94551-0808

(925) 423-9831, fax: (925) 424-3215, e-mail: martin89@llnl.gov

DOE Program Manager: Rogelio Sullivan

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov 

Objectives

• Evaluate suitable electrolyte/electrode combinations for NOx detection in vehicle exhaust. 

• Investigate the effects of processing parameters on sensor response. 

• Evaluate different sensor configurations.

Approach

• Utilize colloidal spray deposition to fabricate electrodes from ceramic powder precursors.

• Investigate mixed potential response of candidate electrode materials on an yttria-stabilized-zirconia 

(YSZ) electrolyte.

• Select most promising candidate electrode materials.

• Evaluate the effects of processing parameters on electrode response, including calcining temperature, 

particle size, and electrode thickness.

Accomplishments

• Identified two systems (Cr2O3, NiCr2O4) with mixed potential response of 40-60 mV.

• Evaluated the effects of calcining temperature and powder (precursor) particle size on response.

• Observed the effect of precious metal (catalyst) addition to metal oxide electrodes.

Future Directions

• Identify rate-limiting mechanisms in sensor response.

• Enhance sensor response time by engineering electrodes to minimize rate-limiting reactions. 

• Investigate and minimize cross sensitivity with other potential exhaust gases.

Introduction

Recent regulations require automobile 

manufacturers to incorporate a comprehensive onboard diagnostic system for exhaust gas monitoring. 

The regulated pollutants include hydrocarbons, 

carbon monoxide, and oxides of nitrogen (NOx). 

Increasingly more stringent emissions limits are 

being placed on each of these gases by both federal 

and state agencies. Because the need for a NOx

sensor is fairly recent, very few sensors of any kind 

are available, and most are still in the developmental 

phase. The most advanced NOx sensing technology 

to date is based on solid state electrochemical 

devices. These devices typically consist of a solid 

(ceramic) electrolyte attached with two or more 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

68

metal or metal-oxide electrodes. Two electrodes 

having different sensitivity to the test gas can both be 

exposed to the exhaust stream, or one electrode may 

be isolated from the exhaust and exposed to a 

reference gas (air). These devices can be operated in 

either the amperometric mode, which measures the 

current-voltage response, or the potentiometric 

mode, which monitors the open circuit voltage. 

Potentiometric sensors are currently being 

investigated as a relatively simple, cost effective 

method for NOx detection in vehicle exhaust.

In the potentiometric device, the open circuit 

potential difference between two electrodes is used to 

directly monitor the exhaust gas composition. This is 

the simplest mode of operation for these devices, 

with the measured (mixed) potential being directly 

related to the exhaust gas composition (p(O2), p(NO), 

etc.). During the FY 01 effort, the effects of electrode 

processing conditions upon the mixed potential NO 

sensitivity and response were evaluated for a number 

of material systems (Mn2O3, Cr2O3, NiCr2O4, CeO2). 

Approach

While there exist in the literature numerous 

reports of the mixed potential NOx response of 

various metal oxides, these reports are often 

contradictory as to the measured response of the 

various oxides investigated [1,2,3]. The 

contradictory nature of the measured responses, 

sometimes reported by the same groups, are 

attributable to the potentially strong dependence of 

the mixed potential response upon the electrode 

morphology. That is, identical electrode materials 

deposited by, for example, sputtering and screen 

printing, may exhibit very different NOx response 

characteristics. For these reasons, a logical starting 

point for this effort is to survey the NOx response of 

potentially attractive metal oxide electrode materials 

as determined by the target environment and by the 

processing technique used in our laboratory 

(colloidal spray deposition). The spray deposition 

technique is a potentially ideal technique for 

application of the metal oxide electrodes because it 

allows close control of particle size and morphology, 

electrode thickness and porosity, and thermal history 

(i.e. calcining temperature). In this investigation, 

these processing parameters were evaluated for their 

effect on the NOx sensitivity of selected metal oxide 

electrodes on yttria-stabilized-zirconia (YSZ) for the 

purpose of identifying the processing conditions 

providing optimal response characteristics. 

Results

Data obtained during FY 01 demonstrate mixed 

potential responses in excess of 40 - 60 mV for 

certain metal oxide (Cr2O3, NiCr2O4) electrodes 

exposed to 500 ppm NO at 500-600 o

C and 10% O2

(balance N2). Figure 1 shows a schematic of the test 

configuration, where the sensor response is the open 

circuit voltage measured between the Pt leads a’ and 

a". Other metal oxides were deemed too reactive 

(Mn2O3/Mn3O4) or refractory (CeO2) to provide 

useful results by the processing techniques used here. 

The data also demonstrate clearly that the processing 

conditions of the sensor may significantly affect the 

sensor response. Figure 2 shows the open circuit 

potential of Cr2O3 on YSZ versus a Pt counter 

electrode at 500 o

C. Data are shown for two different 

particle sizes and for a composite electrode including 

a precious metal catalyst. For the "coarse" powder 

data, the electrode was applied using the powder in 

its "as received" state, while for the "fine" data the 

powder was milled in ethanol for 48 hours prior to 

deposition. It is apparent that refinement of the 

Figure 1: Schematic of the experimental test set-up 

showing: a’, a") Pt wire leads, b) YSZ 

electrolyte, c) metal oxide electrode, d) Pt 

counter electrode, and e) test gas flow.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

69

powder particle size leads to a slight increase in the 

response amplitude (46 vs. 40 mV) with 

approximately the same response time. Incorporation 

of the precious metal catalyst into the porous Cr2O3

electrode provides a further increase in signal 

amplitude (46 vs. 57 mV). Analysis of the 

electrochemical mechanisms responsible for the 

observed behavior is ongoing. 

It is interesting to note that the specific effects of, 

for example, particle size refinement or metal 

catalyst addition may be very different for different 

material systems. For example, in Figure 3, the open 

circuit potential at 550 o

C of NiCr2O4 on YSZ with a 

Pt counter electrode is shown for two different 

particle sizes and for a composite electrode including 

a precious metal catalyst. Again, the "coarse" and 

"fine" designations indicate "as received" and after 

milling in ethanol for 48 hours. Note that in this case, 

the refinement of particle size leads to a very 

significant increase in both signal amplitude (12 vs. 

>43 mV) and response time. This is in contrast to the 

approximately constant response time observed in 

the Cr2O3 system, indicating that the surface-related 

mechanisms/kinetics dominating the responses in the 

two systems may be very different. Also, in contrast 

to the Cr2O3 results, both the amplitude and response 

time decrease with the incorporation of the precious 

metal catalyst. Quantitative data are not currently 

available for the relative reduction in particle sizes 

for the two sets of data shown. However, these data 

indicate that the contributions of the various 

electrochemical mechanisms involved in the NO 

response may be different for the Cr2O3 and the 

NiCr2O4 electrodes. 

Determination of the effects of processing 

parameters such as particle size (surface area) or 

electrode thickness upon the mixed potential 

response can provide a means for evaluation, and 

comparison of, the dominant mechanisms involved 

in the NOx sensor response. In addition, a strong 

understanding of processing effects is required to 

insure optimal sensor performance. The data 

presented here demonstrate that the effects of, for 

example, particle size can be isolated and quantified 

with respect to the NOx sensor response. This will 

facilitate the further development of mixed potential 

sensors for vehicle exhaust monitoring. 

Conclusions

To date, a number of metal oxide electrode 

materials have been evaluated for mixed potential 

electrochemical response. The most promising 

candidates, based upon response amplitude, have 

been Cr2O3 and NiCr2O4. These materials both show 

mixed potential responses in excess of 40 mV to 500 

ppm NO under test conditions determined to be 

relevant to vehicle exhaust monitoring. A careful 

investigation of the effects of processing parameters 

Figure 2: Open circuit potential of Cr2O3 on YSZ with Pt 

counter at 500°C in 10% O2, balance N2, with 

500 ppm NO. Performance is shown for two 

different particle sizes and for a composite 

electrode including a precious metal catalyst.

Figure 3: Open circuit potential of NiCr2O4 on YSZ with 

Pt counter at 550°C in 10% O2, balance N2, 

with 500 ppm NO. Performance is shown for 

two different particle sizes and for a 

composite electrode including a precious 

metal catalyst.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

70

upon the response characteristics of these electrode 

materials indicate that electrode powder precursor 

characteristics and calcining temperature play a 

significant role in the measured mixed potential 

response. 

References

1. V. Bruser, U. Lawrenz, S. Jakobs , H. -H. Mobius, 

and U. Schronauer, Solid State Phenomena, 39-

40 (1994), 269-272. 

2. G. Lu, N. Muira and N. Yamazoe, Sensors and 

Actuators, B65 (2000), 125-127.

3. N. Muira H. Kurosawa, M. Hasei, G. Lu and N. 

Yamazoe, Solid State Ionics, 86-88 (1996), 1069-

1073.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

71

E. Improved Exhaust Emissions and Fuel Economy through the Use of an 

Advanced NOx Sensor

G. Coffey, D. Rector, X. Li, L-Q. Wang, C. Habeger and Suresh Baskaran (Primary Contact)

Pacific Northwest National Laboratory

P.O. Box 999/MS K2-44

Richland, WA 99352

(509) 375-6483, fax: (509) 375-2186, e-mail: suresh.baskaran@pnl.gov

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax: (292) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

CRADA Partner: Delphi Energy and Chassis Systems

Subcontractor: SRI International, Menlo Park, CA

Objectives

• Define the fundamental chemical reactions and the associated reaction rates on the current electrode 

systems of electrochemical NOx sensors.

• Refine materials set and processing for the oxygen pump to improve sensor performance and 

durability.

• Optimize sensor structure for improved response time.

• Develop new materials for use as NOx electrodes.

Approach

• Determine the optimum microstructure for sensor electrodes through analysis of electrode and other 

sensor subcomponents and electrochemical testing.

• Obtain fundamental electrochemical activity of electrode/electrolyte microstructures for O2 and NO 

dissociation and transport.

• Develop models to correlate sensor performance to electrode and electrolyte performance and to 

physical parameters of sensor sub-components.

• Recommend sensor configuration based on the optimum structure derived from the models.

• Optimize the materials set and processing for improved durability and response. 

• Determine potential for NOx detection using alternative differential pulse voltametry method.

Accomplishments

• Sensor analysis has provided directions for design of optimal electrode microstructures and diffusion 

channels to and from the oxygen pump.

• Electrode performance was correlated to microstructural characteristics in current noble metal 

electrodes used in the oxygen pump, leading to identification of key parameters governing durability.

• Alternative oxide electrode compositions for the oxygen pump electrode were prepared and 

characterized.

• A computational model was constructed in order to relate the different geometrical parameters to an 

oxygen pump outlet PO2 and, ultimately, response characteristics of devices.

• The differential pulse voltametry method showed potential for high NO sensitivity.
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

72

Future Directions

• Complete electrochemical characterization of oxygen pump and NOx electrode materials, and provide 

recommendations for optimal materials, synthesis and microstructural design. 

• Complete and test models relating sensor performance to physical parameters of the device and basic 

electrochemical performance of the electrode/electrolyte systems; provide recommendations on sensor 

design.

Introduction

Direct injection gasoline powertrains are being 

developed to effectively meet new emissions 

regulations while improving fuel economy. This 

technology allows for engine operation from rich 

conditions (9/1 Air/Fuel under loads) to very lean 

conditions (40/1 to 50/1 Air/Fuel) in economy mode. 

Because there are significantly higher NOx emissions 

while operating in the lean mode, these systems 

require an emission control device to convert the 

NOx. Typically a NOx absorber is used; however, a 

NOx sensor is necessary to control the regeneration 

cycle. 

A NOx sensor behind the NOx absorber will 

enable closed-loop control over the regeneration 

cycle as well as provide the diagnostics that indicate 

that the absorber is functioning properly. The 

increase in fuel economy that is directly related to the 

use of a NOx sensor device for closed-loop control 

(versus a model-based approach) is estimated to be 

between 0.5 to 1%. This is significant in that it is 

about 7-15% of the total estimated fuel economy 

benefit provided by a Direct Injection Gasoline 

System (conservatively, about a 7% increase in total 

fuel economy). Therefore, this sensor is an enabling 

technology for the emission control devices and 

system to effectively meet the legislated emissions.

Most of the current NOx sensor technology is 

built on the technology base used for today’s exhaust 

oxygen sensors, but are much more complex. The 

complexity requires both sophisticated construction 

techniques and electronics processing on the sensor. 

The design of a prototypical NOx sensor is shown in 

Figure 1. The sensor device contains many layers of 

dissimilar materials, gas diffusion channels, internal 

heaters, and multiple electrodes using different 

electrode materials. 

While considerable progress has been made with 

zirconia electrolyte-based sensor technology, these 

products still suffer from poor durability, sensitivity 

to exhaust species, long response and recovery times 

after an extended rich operation, and measurement 

drift over time. In this project, the fundamental 

material and device parameters that govern these 

issues are addressed.

Approach

The project work focused on four areas:

1. Analysis of Sensor Devices

Microstructure and chemical analysis of several 

sensor designs was performed to understand the 

range of materials and microstructure in prototypical 

sensors. This effort provided guidance in design and 

development of optimal materials and 

microstructures for the various sensor subcomponents.

2. Electrode Materials and Design

This task investigated the composition, 

processing and design parameters for existing noble 

metal electrodes and potential oxide electrodes in 

oxygen pumps within NOx sensors. These 

Figure 1. A Schematic Diagram Illustrating the Basic 

NOx Sensor Function Model
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

73

parameters control the physical and chemical 

mechanisms that determine sensor response. Both 

materials’ design and fabrication are being optimized 

through improved fundamental understanding of the 

materials’ surface chemistry, electrode reactions, 

morphological effects and electrode aging. 

3. Device Modeling 

Refined sensor models were constructed in order 

to predict the optimal design, geometry, size and 

configuration of the complete sensor structure. 

4. Alternative Differential Pulse Voltametry Method 

of Detection

Current prototype sensors are based on 

amperometric measurements. This project also 

looked at using the differential pulse voltametry 

method applied to a zirconia-based sensor to detect a 

small quantity of NOx in the mixture of O2 and N2. 

The potential for this approach was investigated by 

SRI. 

Results and Conclusions

1. Analysis of Sensors

Several variations of two-stage zirconiamembrane based prototype NOx sensors were 

compared. The diffusion channels to and from the 

oxygen pump cavity were compared for total length, 

area, grain size, and pore diameter/distribution. 

Sensor samples were flow tested, and compositions 

of the electrodes in each sensor were also compared. 

The electrode morphology showed some clear 

differences between various samples. These 

differences suggested some potential directions for 

optimal electrode design. The important parameters 

investigated were electrode thickness, triple phase 

boundary lengths, pore size/distribution, and primary 

grain size/distribution. The analysis of NOx sensors 

provided insight in two designs areas for obtaining 

improved sensors. Optimal design and fabrication of 

diffusion channels to control gas flow to the oxygen 

pump cavity is critical for developing an accurate 

and sensitive sensor element. Second, carefully 

optimized grain morphology and pore structure in the 

electrode is required to obtain the desired 

electrocatalytic reduction behavior from electrode 

structures.

2. Electrode Materials and Design

2.1 Noble metal electrodes

The noble metal system is the baseline electrode 

material for oxygen pumps in NOx sensors. The 

material shows promise for high selectivity of 

oxygen over NO adsorption using model surfaces, 

but key challenges with this material set are the lack 

of adequately high O2 differentiation over NO in 

fabricated sensor devices, durability, and reliable 

performance. 

The electrochemical dissociation/reduction 

behavior was correlated with microstructure for a set 

of prototypical noble metal Au/Pt electrodes. 

Microchemical analysis of the electrode materials 

indicated that this electrochemical behavior could be 

correlated to microchemical instabilities and 

variations in local composition between samples. 

Variations in Au/Pt concentration and distribution 

were observed after controlled high temperature 

processing. Gold migration is likely a key factor 

affecting reliability and aging response for some of 

the candidate Au/Pt O2 pump electrodes studied, 

where high oxygen selectivity as well as high NO 

"de-selectivity" is needed. These investigations have 

directed material design and fabrication for 

imparting microstructural stability and providing 

improved, repeatable electrode characteristics.

2.2 Oxide electrodes

Oxide-based materials can also function as 

electrocatalysts for reduction of oxygen and are 

consequently used as state-of-the-art electrode 

materials in solid oxide fuel cells, electrochemical 

sensors and electrochemical oxygen pumps. To begin 

assessing the potential for oxide electrodes in oxygen 

pumps in the presence of NO, preliminary work was 

carried out in synthesis and microstructural 

development of porous perovskite materials. The 

baseline perovskite materials exhibited uniform 

porous microstructures with micron-scale grain sizes 

at the required processing temperatures. Preliminary 

electrochemical tests for the first baseline 

compositions showed electrocatalytic reduction 

activity for both O2 and NO. These oxides and 

similar classes of oxides used in other similar high 

temperature electrolytic applications offer the 

potential for improving the relative dissociation/
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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adsorption/reduction behavior for oxygen over NO 

through careful doping and/or alloying. 

3. Device Modeling

Using an experimentally measured diffusion 

channel resistance and pump parameters, a model 

was constructed to relate the different geometrical 

parameters to an oxygen pump outlet PO2. This 

model was derived for a single geometry, a typical 

diffusion channel, and typical pump parameters. The 

model needs to be refined for multiple geometries 

with alternative dimensions and various 

modifications to diffusion channels, and the model’s 

predictions will be correlated to experimental 

observations related to the effects of flow, geometry, 

and size on the sensitivity and response time of the 

sensor element.

4. Differential Pulse Voltametry Method of 

Detection

The DPV method can produce a useful detection 

limit for NO measurement. However, this approach 

requires development of stable sensor materials and 

sensor structure, in order to demonstrate sensing 

repeatability and fast response time in a practical 

sensor. 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

75

F. Fuel Vapor Sensor

S. H. Sheen (Primary Contact), H. T. Chien, and A. C. Raptis

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

(630) 252-7502, fax: (630) 252-3250, e-mail: sheen@anl.gov

DOE Program Manager: Rogelio Sullivan 

(202) 586-8042, fax: (202) 586-1600, e-mail: Rogelio.Sullivan@ee.doe.gov

Objectives

• The objective of this project is to develop low-cost, fast-response, acoustic-based fuel-vapor sensors 

that can be used in an automotive environment to measure or monitor fuel-vapor mass flow rate and to 

detect variations in fuel-vapor composition.

Approach

• Stage 1. Design and test a laboratory prototype.

• Stage 2. Establish fuel-vapor acoustic relaxation spectra.

• Stage 3. Develop a fuel-vapor flow sensor.

• Stage 4. Develop field prototype sensors and conduct field tests.

Accomplishments

• Designed and fabricated a laboratory prototype for measuring acoustic properties of methane/nitrogen 

mixtures.

• Designed a signal processing and control system.

Future Directions

• Conduct tests to obtain acoustic properties of different fuel-vapor (ethane, propane and butane) 

compositions.

• Develop a prototype fuel-vapor sensor.

• Develop a prototype fuel-vapor mass-flow sensor.

• Conduct field tests. 

Introduction

Vehicles sold in the U.S. have a carbon canister 

to trap fuel vapors from the fuel tank, greatly 

reducing hydrocarbon emissions. The fuel vapors 

are purged from the canister into the engine, where 

they are combusted during normal operation. The 

present engine control system strategy uses the 

oxygen sensor (in the exhaust gas manifold) to 

correct for rich shifts in the air-to-fuel ratio caused 

by the additional fuel vapors added to the engine 

during purge of the canister. A new requirement 

being phased in is to also trap all fuel vapors during 

refueling (on-board refueling vapor recovery). This 

increases the amount of fuel vapors to be purged into 

the engine during a drive cycle. The resulting large 

canister purge flow rates make it more difficult to 

reduce/eliminate driveability and stall problems and 
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

76

to minimize disturbances in air-to-fuel ratio that may 

create an even bigger challenge to meet the 

increasingly stringent tailpipe emissions 

requirements. A feed forward system, in which a 

fuel vapor sensor located in the canister purge line 

would measure the mass of fuel vapors, is expected 

to result in a much more refined canister purge 

system. The system will also result in lower tailpipe 

emissions, less driveability problems, and a modest 

improvement in fuel economy by better controlling 

the air-to-fuel ratio. Unfortunately, such an 

automotive fuel vapor sensor currently is 

unavailable. Such a fuel-vapor sensor may have 

other related applications, including, for example, (1) 

a system that uses fuel vapor for vapor cold-start, and 

(2) a feedback system that improves combustion by 

monitoring hydrocarbon emissions.

This project is to conduct research and 

development leading to practical fuel-vapor sensors 

as specified in the objective, with the primary focus 

on development of a sensor that can speciate the fuel 

vapor and determine the vapor composition for 

engine combustion control. A fuel-vapor mass 

flowmeter will also be developed so that the fuel 

vapor can be quantified. 

Approach

This program is a collaborative effort between 

Argonne National Laboratory (ANL), Ford Motor 

Company and Northwestern University (NU). ANL 

will primarily conduct the sensor development. The 

ANL speed-of-sound (SOS) sensor will be applied to 

measurements of acoustic properties of fuel vapors. 

The sensor will use SOS to predict the fuel-vapor 

concentration and determine the fuel-vapor 

composition by measuring the acoustic relaxation 

spectra. In FY 2001 we developed a laboratory 

prototype for measuring SOS and acoustic spectra of 

the fuel vapors. To study the acoustic relaxation 

phenomenon [1,2], the laboratory prototype uses a 

pair of transducers and measures the acoustic 

attenuation over a range of gas pressures. However, 

an array of transducers is proposed for the fieldsensor design. A method to measure the vapor flow 

rate will also be developed and integrated with the 

composition and concentration measurements to 

form a fuel-vapor sensor. The sensor will then be 

tested at Ford. 

Results and Conclusions

Figure 1 shows a schematic diagram of the 

laboratory prototype developed at ANL. It consists 

of two 0.5 MHz transducers operating in a pitchcatch mode. Gated sine waves of a fixed frequency 

(0.5 MHz or its harmonics) are propagated in a 

narrow flow channel, and their reflections are 

analyzed for variations in amplitude and time-offlight, from which attenuation and speed-of-sound 

are measured. The prototype uses a high-pressure 

vessel to house the transducers and the flow cavity. 

To obtain the acoustic relaxation spectra, we vary the 

gas pressure because the attenuation in a gas depends 

on the ratio of acoustic frequency over the gas 

pressure. 

Figure 2 shows the SOS in methane/nitrogen 

mixtures. The solid line represents the calculated 

values based on isentropic modeling. Although the 

measured SOS are higher than the calculated values, 

it is clearly shown that the SOS can be used to 

Figure 1. Schematic Diagram of the Laboratory 

Prototype Fuel-Vapor Sensor

Figure 2. Speed of Sound in Methane/Nitrogen Mixtures 

(solid line is the calculated values using 

isentropic modeling)
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

77

predict the methane concentration in nitrogen gas. 

This is true as long as the carrier gas mixture has a 

fixed composition so that the mixture of methane and 

carrier gas can be considered as a binary gas mixture. 

In Figure 3, the dimensionless attenuation 

(attenuation times wavelength, αλ) is plotted against 

the frequency/pressure ratio (f/P) for 50% methane in 

nitrogen. The solid line represents the best-fit curve 

to the data. It is clearly shown that there exists a 

relaxation peak around f/P = 0.07; that is, under 

ambient conditions the relaxation peak appears at 70 

kHz, which is much lower than model prediction [3]. 

In FY 2001, we have demonstrated that (1) SOS 

in a fuel-gas/air mixture can be used to measure the 

percent concentration of the fuel gas, and (2) it is 

feasible to use acoustic relaxation spectra to predict 

the fuel-gas composition. 

References

1. H. J. Bauer, "Phenomenological theory of the 

relaxation phenomena in gases," Physical 

Acoustics vol. II part A, pp.48-132, 1965.

2. H. O. Kneser, "Phenomenological theory of the 

relaxation phenomena in gases," Physical 

Acoustics vol. II part A, pp.133-202, 1965.

3. Y. Dain and R. M. Lueptow, "Acoustic 

attenuation in a three-gas mixture: results," 

Submitted to J. of Acoustic Society of America. 

Figure 3. Dimensionless Attenuation Versus Frequency/

Pressure in 50% Methane in Nitrogen
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

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Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

79

2-DTwo-dimensional

3-DThree-dimensional

ANL Argonne National Laboratory

APS Advanced Photon Source

ATDC After top dead center

Au Gold

BOTDBall-On-Three-Disc

CADCrank angle degrees

CARB California Air Resources Board

cc Cubic centimeter

CFDComputational Fluid Dynamics

CHADComputational Hydrodynamics for 

Advanced Design

CHESS Cornell High Energy Synchrotron 

Source

CIDI Compression Ignition Direct Injection

cm Centimeter

CO Carbon monoxide

CO2 Carbon dioxide

COV Coefficient of variation

CRADA Cooperative Research and Development 

Agreement

DI Direct Injection

DOE Department of Energy

DPV Differential pulse voltametry

EA Electron affinity

EDAX Energy Dispersive Analysis of X-rays

EGR Exhaust gas recirculation

EPA Environmental Protection Agency

eV Volts electric

FTP Federal Test Procedure

FY Fiscal year

g Gram

GDI Gasoline Direct Injection

GM General Motors

H2 Diatomic hydrogen

HC Hydrocarbon

HEGO Heated exhaust gas oxygen

HP Horsepower

Hz Hertz

IMEP Indicated mean effective pressure

IMS Ion-mobility spectrometer

keV Kilovolt electric

kHz Kilohertz

kPa Kilopascal

kV Kilovolt

kW Kilowatt

kWh Kilowatt-hour

L Liter

LANL Los Alamos National Laboratory

LEP Low Emission Partnership

LEV Low Emission Vehicle

LIF Laser-induced fluorescence

mA Milliamps

mJ Millijoule

mm Millimeter

mm3

/N*m Cubic millimeter per Newton-meter

MPa Megapascal

mpg Miles per gallon

MTV Molecular tagging velocimetry

mV Millivolt

N2 Diatomic nitrogen

NFC Near-Frictionless Carbon

nm Nanometer

NMOG Non-methane organic gas

NO Nitric oxide

NO2 Nitrogen dioxide

NOx Oxides of nitrogen

NREL National Renewable Energy Laboratory

O2 Diatomic oxygen

OAAT Office of Advanced Automotive 

Technologies

OBDS On-board distillation system

°C Degrees Celsius

OE Optical engine

OH Hydroxyl radical

OTT Office of Transportation Technologies

PADPixel Array Detector

PCM Powertrain control module

PFI Port fuel injected

PIV Particle Image Velocimetry

PLIF Planar laser-induced fluorescence

PM Particulate matter

PNGV Partnership for a New Generation 

Vehicle

PNNL Pacific Northwest National Laboratory

ppm Parts per million

Pt Platinum

Q1 First fiscal quarter

R&DResearch and Development

rms Root mean square

TDC Top dead center

rpm Rotations per minute

s Second

SC Stratified charge

SCE Single-cylinder engine

ACRONYMS
Spark Ignition Direct Injection R&D Program FY 2001 Progress Report

80

SEM Scanning Electron Microscopy

SI Spark Ignition

SIDI Spark Ignition Direct Injection

SNL Sandia National Laboratory

SOS Speed-of-sound

TEM Transmission Electron Microscopy

TKE Turbulent kinetic energy

ULEV Ultra low emission vehicles

UV Ultraviolet

V Volt

VCR Variable compression ratio

vol% Percent by volume

W Watt

YSZ Yttria-stabilized-zirconia

μg/mm3 Micrograms per cubic millimeter

μm Micrometer

μs Microsecond
This document highlights work sponsored by agencies of the U.S. Government. Neither the U.S.

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or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately

owned rights. Reference herein to any specific commercial product, process, or service by trade name,

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expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.

Printed on recycled paper
www.cartech.doe.gov

DOE/EERE/OTT/OAAT - 2001/006

Office of Transportation Technologies

Series of 2001 Annual Progress Reports

• Office of Advanced Automotive 

Technologies FY 2001 Program Highlights

• Vehicle Propulsion and Ancillary Subsystems

• Automotive Lightweighting Materials

• Automotive Propulsion Materials

• Fuels for Advanced CIDI Engines and Fuel Cells

• Spark Ignition, Direct Injection Engine R&D 

• Combustion and Emission Control for 

Advanced CIDI Engines

• Fuel Cells for Transportation

• Advanced Technology Development 

(High-Power Battery) 

• Batteries for Advanced Transportation 

Technologies (High-Energy Battery) 

• Vehicle Power Electronics and Electric Machines

• Vehicle High-Power Energy Storage

• Electric Vehicle Batteries R&D