bluuebunny/crossref_metadata_2025 huggingface dataset:
Oil Ring Design Influence on Lube Oil Consumption of SI Engines
Authors: Ferrarese Andre´ , Rovai Fernando F.
Published: December 2008

2-piece and 3-piece oil ring designs were tested in dynamometer and vehicles in order to evaluate the ring type influence on lube oil consumption of spark ignited (SI) engines. The dynamometer tests were executed according a typical durability cycle of SI engines. This cycle is predominantly in full load conditions. Under these conditions, 2-piece oil ring design showed lower lube oil consumption than 3-piece. Two different vehicle tests were also run: urban and mountain circuits. The purpose of the urban circuit test was to simulate the actual use of the engine. The mountain circuit was selected to verify the rings behavior under motoring conditions. In vehicle tests, 3-piece showed lower or equivalent oil consumption than 2 piece, which disagreed with the dynamometer tests. This difference can be explained by the better side sealing capacity of the 3-piece oil ring. On the other hand, 2-piece oil rings present better conformability, important for applications with larger bore distortion. So, the most appropriate application of oil ring type depends on the load and speed conditions, in which the engine would predominantly operate. Ring wear and thermal stability are compared using bench and vehicle tests.
Analysis of Compression-Ignition Engine Design Concerning Engine Structural Loading Capacity
Authors: Chen Gong
Published: December 2008

Present-day high-power compression-ignition engines are required in design not only to achieve a targeted high fuel efficiency, but also to meet regulated exhaust emissions standards. This paper investigates the effects of the in-cylinder combustion related design parameters, including cylinder compression ratio, fuel injection-start timing, and the amount of cylinder air charge, on engine performances and emissions as the engine structure-loading allowance is specified. Thereby the determination of those parameters to optimize the engine overall performances without exceeding the allowances in engine mechanical and thermal loading can be achieved. An enhanced understanding of those design parameters associated with the engine structural loading parameters, such as the cylinder peak firing pressure and exhaust temperature, is studied. The analytical prediction of the trade-off between those parameters with peak firing pressure contained is modeled and developed.
Lean NOx Trap Catalysis for NOx Reduction in Natural Gas Engine Applications
Authors: Parks James E. , Ferguson H. Douglas , Williams Aaron M. , Storey John M. E.
Published: December 2008

Reliable power generation and distribution is a critical infrastructure for the public and industry. Large-bore spark-ignited natural gas reciprocating engines are a reliable source of power generation. Lean operation enables efficient operation, and engines can conveniently be placed wherever natural gas resources are located. However, stricter emission regulations may limit the installation and use of more natural gas reciprocating engines if emissions cannot be reduced. Natural gas engine emissions of concern are generally methane, carbon monoxide, and oxides of nitrogen (NOx). Methane and carbon monoxide can be controlled by oxidation catalysts; however NOx emissions are difficult to control in lean exhaust conditions. One method of reducing NOx in lean exhaust conditions is lean NOx trap catalysis. Lean NOx trap technologies (also known as NOx adsorber catalysts, NOx storage and reduction catalysts, etc.) have demonstrated >90% NOx reduction for diesel reciprocating engines and natural gas turbines. In the work presented here, the feasibility of a lean NOx trap catalyst for lean burn natural gas reciprocating engines will be studied. Tests were conducted on a Cummins 8.3-liter engine on a dynamometer. The lean Nox trap catalyst was controlled in a valved exhaust system that utilized natural gas as the catalyst reductant. Oxidation and reformer catalysts were used to enhance utilization of methane for catalyst regeneration. The feasibility of this approach will be discussed based on the observed NOx reduction and associated fuel penalties.
Optical Diagnostics of Laser Ignition for Future Advanced Engines
Authors: Lackner Maximilian , Winter Franz , Charareh Soren , Iskra Kurt , Neger Theo , Kopecek Herbert , Wintner Ernst , Klausner Johann , Herdin Gu¨nther
Published: December 2008

A laser-based system should be advantageous to a spark-plug based ignition system. Free choice of the ignition spot and precise timing constitute two major advantages. Multi point laser ignition could lead to higher efficiencies, and laser ignition as such is capable of igniting leaner mixtures than a spark plug, thereby decreasing thermal NOx and soot emissions. This paper is devoted to advances in optical diagnostics of laser ignition for future internal combustion engines. The focus of this paper is on diagnostics at high pressures, that is engine-like conditions. Laser ignition tests were performed with the fuels methane, hydrogen and biogas in static combustion cells with dimensions comparable to stationary engines. A Nd:YAG laser (5 ns pulse duration, wavelength 1064 nm, 1–20 mJ pulse energy) was used to ignite gaseous fuel/air mixtures at initial pressures of 1–3 MPa. Schlieren photography and laser-induced fluorescence (LIF) were used for optical diagnostics (flame kernel development, shock wave propagation). The lean burn characteristics were investigated. Schlieren photography was used to determine the velocity of the shock wave and to study the influence of the shock wave on temperature rise and energy loss. Using planar laser-induced fluorescence (PLIF), the spatial distribution of the combustion intermediates OH and formaldehyde were recorded. The temporally resolved imaging shows that the initial stages of the flame front evolution closely follows the turbulence and density fluctuations caused by the shock and pressure wave induced by the laser spark. In this paper, results from LIF spectroscopy and Schlieren photography are compared. Depending on the laser pulse energy and focus size, at later stages after the ignition the flame front propagation approaches the laminar burning regime and flame front speed decrease. Flame front break up at lean conditions indicates the limit of the ignitable mixture fraction when the speed due to spark-induced convection exceeds the flame propagation rate.
Simulation of Timing Chain Drives Using Ketsim
Authors: Engelhardt Thomas , Hoesl Andreas , Lebrecht Wolfram , Ulbrich Heinz , Pfeiffer Friedrich
Published: December 2008

In modern combustion engines timing chains are used to actuate camshafts, balance shafts, diesel injection pumps, oil pumps and auxiliaries. Optimizing the engine design with respect to operation reliability, efficiency, noise and acoustics requires a profound knowledge of the vibrational behavior of all chain drive components. The amount of expensive experiments can be significantly reduced by analyzing and studying such systems using computer simulation. At the Institute of Applied Mechanics at the Technical University of Munich, Germany, a multi body simulation program has been developed to compute the dynamical behavior of complex timing chain drives. It is used by several members of the German FVV (Forschungsvereinigung fuer Verbrennungskraftmaschinen), e.g. Porsche, Audi, BMW, DaimlerChrysler and others. This paper describes how the components and the effects of timing chain drives are modelled within the simulation tool. the underlying models are to be explained but also a comparison between simulation and experiment will be presented for a DaimlerChrysler 8-cylinder diesel engine (OM628) which drives the Mercedes-Benz S-Class (S 400 CDI).
Friction Reduction via Piston and Ring Design for an Advanced Natural-Gas Reciprocating Engine
Authors: Smedley Grant , Mansouri S. H. , Tian Tian , Wong Victor W.
Published: December 2008

Friction from the power cylinder represents a significant contribution to the total mechanical losses in internal combustion engines. A reduction in piston ring friction would therefore result in higher efficiency, lower fuel consumption, and reduced emissions. In this study, models incorporating piston ring dynamics and piston secondary motion with elastic skirt deformation were applied to a Waukesha natural gas power generation engine to identify the main contributors to friction within the piston and ring pack system. Based on model predictions, specific areas for friction reduction were targeted and low-friction design strategies were devised. The most significant contributors to friction were identified as the top ring, the oil control ring, and the piston skirt. Model predictions indicated that the top ring friction could be reduced by implementing a skewed barrel profile design or an upward piston groove tilt design, and oil control ring friction could be reduced by decreasing ring tension. Piston design parameters such as skirt profile, piston-to-liner clearance, and piston surface characteristics were found to have significant potential for the reduction of piston skirt friction. Designs were also developed to mitigate any adverse effects that were predicted to occur as a result of implementation of the low-friction design strategies. Specifically, an increase in wear was predicted to occur with the upward piston groove tilt design, which was eliminated by the introduction of a positive static twist on the top ring. The increase in oil consumption resulting form the reduction in the oil control ring tension was mitigated by the introduction of a negative static twist on the second ring. Overall, the low-friction design strategies were predicted to have potential to reduce piston ring friction by 35% and piston friction by up to 50%. This would translate to an improvement in brake thermal efficiency of up to 2%, which would result in a significant improvement in fuel economy and a substantial reduction in emissions over the life of the engine.
A Numerical Study of Spark Ignition
Authors: Ekici O. , Bokka V. K. , Ezekoye O. A. , Matthews R. D.
Published: December 2008

We present theoretical models to simulate spark discharge and ignition. Two models are presented. The first model considers simplified fluid mechanics with chemistry effects. The second model utilizes more sophisticated flow with no chemistry. The simplified model incorporates physical models of breakdown and chemical kinetics of combustion with species and energy equations solved using a control volume method. A three-step mechanism is used to simulate chemical kinetics for fuel combustion and nitrogen chemistry. Dissociation and ionization in the plasma are included by assuming local thermal equilibrium. The second model simulates a spark discharge in air with more complete physics of flow using a high order numerical method, which shows the evolution of the shock wave and a torus-like plasma kernel.
The Influence of High Cetane Blending Components on Emissions From a Heavy-Duty Diesel Engine With EGR
Authors: Neill W. Stuart , Chippior Wallace L. , Mitchell Ken , Faibridge Craig , Pigeon Rene´ , McCormick Robert L. , Van Heyst John
Published: December 2008

The exhaust emissions form a single-cylinder version of a heavy-duty diesel engine with exhaust gas recirculation (EGR) were measured with eight high-cetane components blended into an ultra-low sulphur diesel base fuel. the blending components evaluated were conventional nitrate and peroxide cetane improver additives, paraffins from two sources, three ethers, and soy methyl ester. The blending components were used to increase the cetane number of a base fuel by ten numbers, from 44 to 54. Exhaust emissions were measured using the AVL eight-mode steady-state test procedure. PM and NOx emissions from the engine were fairly insensitive to ignition quality improvement by nitrate and peroxide cetane improvers. Soy methyl ester and two of the ethers, 1,4 diethoxybutane and 2-ethoxyethyl ether, significantly reduced PM emissions, but increased ONx emissions. The two paraffinic blending components reduced both PM and NOx emissions.
Preliminary Thermal Analyses on Diesel Converter Overheating
Authors: Zuo Jun , Wang Meiping , Reader Graham T. , Zheng Ming
Published: December 2008

The use of oxidation catalytic converters (OCC) in Diesel engines has proved to be an effective method to reduce emissions of total hydrocarbons (THC), carbon monoxide (CO), and the soluble organic fractions (SOF) of particulate matter (PM). However, the exothermal reaction effected by the oxidation of THC, CO, and especially the soot accumulated in the converters impose a risk of catalytic flow bed overheating that subsequently results in catalyst failure and may cause safety concerns. This paper presents a one-dimensional transient model that uses an energy balance method to analyze the overheating scenario when considering combustible gas reaction, clogged soot burning, and active flow control for a number of Diesel aftertreatment devices. The monolith temperature profiles were simulated by varying the exhaust gas temperature, oxygen concentration, and flow rate. Simulation results indicated that the potential of overheating elevates with increases in combustible gas concentration, soot loading, oxygen concentration, and engine exhaust temperature. The impacts of active control, such as flow reversal control, on converter overheating have also been investigated therein.
Corona Discharge Ingnition for Internal Combustion Engines
Authors: Theiss Nathan , Ronney Paul , Liu Jian-Bang , Gundersen Martin
Published: December 2008

The use of Corona (Transient Plasma) discharge as an ignition source alternative to spark ignition (SI) for a Natural Gas fired engine presents an opportunity for increased efficiency and reduced NOx emissions. The multiple ignition sites created by a Corona discharge produce a faster and more complete burn than conventional SI. Bench tests show a faster combustion rise time (∼3×) and higher peak combustion pressures with corona discharge compared to SI. There are challenges encountered in retrofitting a corona discharge ignition system onto an IC engine. Electrode design and placement are critical in preventing arc formation and engine knock.
Two-Stage Catalytic NOx Reduction With Hydrocarbons for Lean Burn Gas Fired Reciprocating Engines
Authors: Holmgreen Erik M. , Yung Matthew M. , Ozkan Umit S.
Published: December 2008

A two-stage NOx reduction system has been proposed to address the challenges associated with exhaust treatment from high efficiency lean burn natural gas engines. This concept is based on oxidation of NO to NO2 followed by the subsequent reduction of NO2 to N2 with a hydrocarbon reducing agent. Titania supported cobalt catalysts prepared by both incipient wetness and modified sol-gel techniques are effective for the oxidation of NO to NO2, being capable of reaching equilibrium conversions at or below 300°C. Screening of several formulations of NO2 reduction catalysts are presented, with silver supported on alumina being the most promising. Kinetic experiments are monitored by gas chromatography and chemiluminescent NOx analysis. Characterization of the catalysts is performed by BET surface area measurements, thermogravimetric analysis, and in-situ X-ray diffraction.
Development of an Interface Method for Implementing Road Grade in Chassis Dynamometer Testing
Authors: Thompson Gregory J. , Clark Nigel N. , Atkinson Richard J. , Luzader Zac , VanScoy Frances L. , Baker Vic , Chandler Jesse
Published: December 2008

Mobile source emissions inventory data from heavy-duty on-road vehicles are traditionally obtained using three methods: engine dynamometer, chassis dynamometer, or in-use vehicle driving. Engine dynamometer testing provides for the greatest control and highest accuracy but requires the most time and can be cost prohibitive when obtaining emissions from many in-use engines. In-use emissions collection is a relatively inexpensive and rapid method of obtaining real-world data, but this method is relatively new and is not regulated by any Federal or international regulations as of yet and accuracy of the data from these devices has not been established. Chassis dynamometer-based testing provides for the means of obtaining a large sample of data from in-use vehicles in a controlled environment. However, existing chassis dynamometer cycles assume a level road surface with no grade. In a chassis dynamometer test cycle, a simple line trace is used to represent the desired vehicle speed on a video monitor for the driver to follow. A second line trace is overlaid on the first to indicate the actual vehicle speed on the dynamometer and the drive adjusts the vehicle speed to match the scheduled speed as closely as he is able. Experienced chassis dynamometer test drivers are able to look at the desired speed and anticipate the required gearshifts during the testing. However, to account for road grade in a chassis dynamometer test schedule, the driver of the vehicle will require additional cues. Also, drivers may not drive a vehicle while following a trace in the same way that they drive on the road. To implement grade and inject a sense of the real world in a chassis dynamometer test cycle, a virtual reality interface has been developed to employ images of a roadway with feedback between the driver’s performance and the image. As a first step to implementing grade, a level road surface using a virtual reality interface was emulated using an in-house developed software package to present images of roadways, including traffic control signals and constraints due to traffic congestion. In the virtual reality execution, the driver perceives the position of the vehicle relative to traffic signals and other traffic cues. An initial investigation into the effect of road grade using the conventional line trace method is shown and then use of the virtual reality approach is compared with the conventional line trace. The results from the study shows that an experienced driver can use the virtual reality interface with similar emission results as the conventional line trace method.
Comparison Between Steady and Unsteady CFD Simulations of Two Different Port Designs in a Four Valve HSDI Diesel Engine: Swirl Intensity and Engine Permeability
Authors: Cantore Giuseppe , Fontanesi Stefano , Montorsi Luca , Ortolani Paolo
Published: December 2008

Swirl control strategies are useful methods for controlling mixture formation in HSDI Diesel engines. Test rigs allows only steady state measurements of the Swirl number, and give only a rough estimation of the charge motion during the actual compression stroke within the engine. On the contrary, CFD simulations are powerful tools to characterize the air flow drawn into the cylinder, since they allow not only steady state operations, but also full dynamic modeling of the intake and compression strokes. This paper studies an application of computational fluid dynamics for predicting intake swirl intensity in an automotive 4 valve per cylinder C.I. Diesel engine. Two different intake ports are compared and the best trade off between engine permeability and swirl intensity is assessed. Both steady state and dynamic simulations of the induction process are carried out, and results demonstrate that steady state analysis is a reliable tool for predicting the port permeability, while the same capability is not proved in investigating the organized charge motion within the chamber.
Numerical-Experimental Comparison of the Performance of a Partially Stratified Charge Natural Gas Fuelled Engine
Authors: Andreassi Luca , Cordiner Stefano , Mulone Vincenzo , Reynolds C. , Evans R. L.
Published: December 2008

Compressed natural gas (CNG) has great potential as an alternative fuel for vehicle engines, and can reduce emissions and improve fuel economy. A single cylinder research engine has been modified to enable direct injection of a small quantity of fuel near the spark plug, independently of an overall lean homogeneous charge. Thus a partially stratified charge is formed within the chamber, which allows significant extension of the lean limit of combustion. This results in an improvement in specific fuel consumption. Numerical simulation also plays an important role in the development of such technological solutions. 3D simulations, in particular, are desirable to provide complete information about thermal and fluid dynamical fields within the chamber. In particular, among the developed numerical tools linked to the KIVA-3V code, special attention was dedicated to the formulation of the combustion model (CFM) turbulent combustion model based on the flamelet hypothesis), to adequately model non-homogeneities and lean mixture compositions. In this paper an optimization procedure is assessed, with the ultimate goal of designing combustion chambers properly devoted to be operated under lean (homogeneous and PSC) mixture conditions. The results related to the procedure definition and to its experimental validation are presented. Experimental and numerical data have been compared in terms of pressure cycles and heat release rate profiles. The overall results are encouraging, taking into special account the difficulty to reliably predict the key performance parameters without any “tuning interventions”, even when mixture richness and homogeneity were varied.
Stable Fuel Confinement in Stratified Charge GDI Engines
Authors: Zanforlin S. , Gentili R.
Published: December 2008

Direct fuel injection combined with charge stratification represents a must for two-stroke S.I. engines, since it prevents fuel loss from the exhaust port and incomplete combustion or misfire at light loads. The most difficult aims are keeping stable stratification when engine operating conditions change and, at very light loads, avoiding excessive dilution and spreading of fuel vapour in consequence of burned gas expansion. Two new-concept engine designs are proposed in this paper. In both cases shapes of piston and head, together with scavenging-duct orientation have been optimised to obtain stable in-cylinder flow field features (independently of engine speed) and proper fuel distribution at ignition time. Computational Fluid Dynamics (CFD) predictions at different loads and speeds are reported and discussed.
Study of Pulse Spray, Heat Release, Emissions and Efficiencies in a Compound Diesel HCCI Combustion Engine
Authors: Su Wanhua , Zhang Xiaoyu , Lin Tiejian , Pei Yiqiang , Zhao Hua
Published: December 2008

A compound diesel HCCI combustion technology has been developed based on the combustion strategies of combination of controlled premixed charge compression ignition (CPCCI) through multi-injections and lean diffusion combustion (LDC) organized by a mixing enhanced combustion chamber. The purpose of this paper is to investigate the fuel spray evolution during multi-injections, heat release mode, thermo-efficiency and exhaust emissions from the compound combustion. In this work, the STAR-CD based, multidimensional modeling is employed to improve the understanding and assist the optimization of the multiple injection process. The parameters explored include the effects of injection timing, dwell time, and the pulse width. Insight generated from these studies provides guidelines on designing an injection profile for optimization of fuel-air mixing. By comparison of different heat release modes of conventional diesel combustion, the pure HCCI combustion and the compound HCCI combustion, the engine heat release can be summarized as forward concentrated mode (FC mode), post concentrated mode (PC mode) and dispersed mode (DS mode). The FC mode gives the highest thermo-efficiency but with highest NOx emissions. The PC mode gets lower NOx emissions but with the drawback of lower thermo-efficiency and higher soot emissions. The DS mode is a flexible heat release mode created by the compound HCCI combustion. A typical DS mode reveals two equivalent peaks of heat release. The first peak represents the CPCCI combustion and the later peak represents the lean diffusion combustion. The thermo-efficiency in a DS mode can reach approximately as high as that in FC mode, while NOx and soot emission can be reduced simultaneously and remarkably. The combustion efficiency and the heat loss in different combustion mode are also discussed.
Stochastic Model for the Investigation of the Effect of Inhomogeneities on Engine Knock
Authors: Gogan Adina , Sunde´n Bengt , Lehtiniemi Harry , Mauss Fabian
Published: December 2008

A stochastic model based on a probability density function (PDF) approach was developed for the investigation of spark ignition (SI) engine knock conditions. The model is based on a two zone model, where the burned and unburned gases are described as stochastic reactors, and the movement of the turbulent flame front is expressed with a Wiebe function. Using a stochastic particle ensemble to represent the PDF of the scalar variables associated with the burned and unburned gases, allows the consideration of inhomogeneities in gas composition and temperature, as well as turbulence mixing effects. The turbulent mixing is described with the interaction by exchange with the mean model. A stochastic jump process is used for modeling the heat transfer, hence accounting for the temperature fluctuations and the fluid wall interaction. Detailed chemistry is used in the calculations. A parameter study investigates the effects of end gas inhomogeneities related to residual gas composition and temperature, on the autoignition process.
The Effects of Intake Flow Swirl on the Combustion Characteristics of Hydrogen Fueled HCCI Engines
Authors: Liu Chengke , Karim Ghazi A.
Published: December 2008

This paper describes the effects of the initial intake flow swirl on the combustion process of hydrogen-air homogeneous mixtures in HCCI engines. CFD KIVA3 code incorporated with detailed chemical kinetics was employed. The effects on the development and extent of non-uniformities in velocity, pressure, and temperature within the cylinder charge were investigated. Moreover, the effects of the initial flow swirl ratio values on the onset of autoignition and its timing, combustion duration, NOx emissions, and the onset of knock were evaluated. It is shown that an increase in the initial flow swirl ratio or speed lengthens the delay period for autoignition and extends the combustion period while reducing NOx emissions. There are optimum values of the initial swirl ratio and engine speed for a certain set of engine operating conditions that can achieve high thermal efficiencies and low NOx emissions while reducing the tendency to knock.
Fuel Economy Improvement Potential of a PFI Gasoline Engine Using VVT/VCR
Authors: Washko Frank M. , Lai Ming-Chia
Published: December 2008

It is desired to optimize a spark ignition PFI (port fuel injected) engine for various regimes within the operating ranges of a vehicle. The goal of this work is to identify the set of technologies that complement each other and offer the optimum performance and fuel economy. For an ideal powertrain system, the engine should be optimized for best fuel economy during the typical drive cycles and best performance during high load acceleration. A typical PFI 1.8L four-cylinder engine is baselined at cycle representative speed/load points. The engine is supercharged and intercooled to later quantify the efficiency benefits from replacing a larger engine with a smaller boosted engine that offers similar performance. Then the effects of different operating regimes and the effect of different proposed technologies are studied. The fuel economy enablers considered include variable valve timing (VVT) and variable compression ratios (VCR). The effects of VVT was studied to see which valve event scenarios afford the best operating efficiency and fuel economy during part load operation. VVT can also be a source of performance improvement if implemented appropriately. VCR operation is studied to see if the efficiency gains from VCR are additive with VVT or if they overlap to some degree. Typically, the fuel efficiency potential of a production engine is limited by spark knock. The engine studied here uses the geometrical and virtual compression ratio reductions offered by the VVT and VCR systems to give knock limit relief and allows the knock-limited BMEP curve to be pushed up. The results showed that the fuel economy gain with the above mentioned technologies is somewhat additive throughout the typical driving cycle but is highly dependent on proper optimization of the many system variables.
Effect of Combustion Chamber Design on the Performance and Emission Characteristics of a Direct Injection (DI) Diesel Engine Fuelled With Refined Rice Bran Oil Blends
Authors: Samuel Raja A. , Lakshmi Narayana Rao G. , Nallusamy N. , Selva Ganesh Kumar M.
Published: December 2008

The present work deals with the experimental investigations on the effect of refined rice bran oil and its blends with diesel on performance and emission characteristics of diesel engine with different combustion chamber geometry. The engine was tested with various neat vegetable oils and it was found that with refined rice bran oil the performance and emission characteristics were comparable with that of neat diesel. The K- factor of the combustion chamber geometry (ratio of the piston bowl volume to the clearance volume) was maintained at 0.74. The D/d ratio (ratio of piston crown diameter to piston bowl diameter) was altered to achieve re-entrant and torroidal shapes from spherical shape. Tests were carried out for each blend, with particular geometry of combustion chamber. Results with different combustion chamber geometry and different blends have been compared.
The Effects of Cylinder Liner Finish on Piston Ring-Pack Friction
Authors: Jocsak Jeffrey , Wong Victor W. , Tian Tian
Published: December 2008

This paper presents enhancements to a previously developed mixed-lubrication ring-pack model that has been used extensively in the automotive industry in predicting piston-ring/liner oil film thickness, friction and oil-transport processes along the liner. The previous model considers three lubrication regimes, shear thinning of the lubricant, and the unsteady wetting conditions of the rings at the leading and trailing edges. The model incorporates the effects of surface roughness by using Patir and Cheng’s average flow model and the Greenwood and Tripp statistical asperity contact model, assuming a Gaussian distribution of surface roughness. However, as a result of the methods used to machine a cylinder liner and the wear-in process observed in engines, the cylinder liner finish is highly non-Gaussian. The purpose of this current study is to understand the effects of additional surface parameters other than Gaussian root-mean-square surface roughness on piston ring-pack friction in the context of a natural gas reciprocating engine ring/liner interface. In general, the surface roughness of a cylinder liner is negatively skewed. Applying similar methodology published in the literature, a wide variety of non-Gaussian probability density functions were generated in terms of the skewness of the cylinder liner surface. These probability density functions were implemented into the Greenwood and Tripp asperity contact model, and subsequently into the traditional MIT ring-pack friction model. The effects of surface skewness on flow were approximated using Gaussian flow factors and a simple truncation method. The enhanced model was studied in conjunction with results from an existing ring-pack dynamic model that provided the dynamic twists of the rings relative to the liner and inter-ring pressures. In this manner, a detailed analysis of the effects of engineered cylinder liner finish on reducing friction losses was performed.
Investigation Into the Deteriorated Performance of Diesel Engine After Prolonged Use of Vegetable Oil
Authors: Bari Saiful
Published: December 2008

The use of vegetable oil in its original from in diesel engines poses a few challenges especially after prolonged use. In this study, it was found that after 500 hours of cumulative running with crude palm oil (CPO), the maximum power was reduced by about 20% and the minimum brake specific fuel consumption (bsfc) increased by about 26%. Examination of the different parts revealed heavy carbon deposits in the combustion chamber, traces of wear on the piston rings, the plunger and the delivery valve of the injection pump; slight scuffing of the cylinder liner, and uneven spray from the nozzles. The affected parts were installed in a new identical engine one by one to evaluate the performance of each respectively. Tests revealed that the main reason for engine performance deterioration was ‘valve sticking’ contributing about 18% and 23% to the deterioration of maximum power and minimum bsfc respectively.
Residual Gas Fraction Estimation for Model-Based Variable Valve Timing and Spark Advance Control
Authors: Cavina Nicolo` , Ponti Fabrizio , Siviero Carlo , Suglia Rosanna
Published: December 2008

As it is well known, the combustion process in Spark Ignition (SI) engines is strongly affected by the quality and quantity of the fluid within the cylinder at Intake Valve Closing (IVC). Residual gas affects the engine combustion processes (and therefore emissions and performance) through its influence on charge mass, temperature and dilution. Moreover, in Gasoline Direct Injection (GDI) engines, the amount of oxygen in the residual gas may be significant if the engine is operated in stratified charge mode (low loads and speeds), while almost no oxygen may be found in the residual gas during homogeneous-charge operation. In this paper, different approaches to residual gas fraction estimation are analyzed and compared. The main objective is to obtain a simple and reliable model also in presence of Variable Valve Timing (VVT, both on intake and exhaust valves) and External Gas Recirculation (EGR) systems, that could be used to control combustion duration and position. In fact, the two main contributions to residual gas fraction (backflow of the burned gas during the valve overlap period, and amount of gas trapped within the cylinder) are strongly affected by intake and exhaust valves timing, and EGR flow should be taken into account in order to determine the total exhaust gas mass within the cylinder at IVC. Therefore, estimation of residual gas mass and composition is crucial for designing VVT and EGR management strategies, integrated with optimal control of Spark Advance (and therefore of the combustion process). Experimental data have been acquired on a 3.2 liter V6 GDI engine, equipped with intake and exhaust VVT systems. Tests were performed throughout the engine operating range for different combinations of intake and exhaust valve timings, while varying EGR flow.
Microphones and Knock Sensors for Feedback Control of HCCI Engines
Authors: Souder Jason S. , Mack J. Hunter , Hedrick J. Karl , Dibble Robert W.
Published: December 2008

Homogeneous charge compression ignition (HCCI) engines lack direct in-cylinder mechanisms, such as spark plugs or direct fuel injection, for controlling the combustion timing. Many indirect methods have been used to control the combustion timing in a HCCI engine. With any indirect method, it is important to have a measure of the combustion timing so the control inputs can be adjusted for the next cycle. In this paper, it is shown that microphones and knock sensors can be used to detect combustion in HCCI engines. The output from various microphones and a knock sensor on an HCCI engine are measured at light and high loads. The combustion timing data obtained from the sensors are compared to the combustion timing data obtained from a piezoelectric cylinder pressure transducer. One of these sensors is selected and used for closed-loop control of the combustion timing in a single cylinder HCCI engine.
The Friction Reduction With a New Two-Piece Spring Retainer Design and Light Weight Valve Train Components in SI Engines
Authors: Brinkmann Thomas , Gaertner Jens , Gebauer Klaus
Published: December 2008

The reduction of friction in the valve train of four-stroke combustion engines is a promising opportunity to decrease fuel consumption and to improve pollutant emissions. The possibilities are reviewed by comparing light weight and newly developed components. The friction in the valve train causes a loss from the BMEP by about 0.2 to 0.4 bar. To measure friction forces in this range requires constant and well maintained environmental conditions. The viscosity as well as the pressure and temperature of the lubricating oil have a big influence on the friction. Due to the valve spring forces a strong fluctuation of the cam torque appears. This makes it very demanding to set up the measurement equipment in a correct way. Measurement equipment which is able to gauge with sufficient accuracy may be overloaded by the effects caused by the spring forces. Based on this special care is necessary during the first ramp up of the cylinder head. It has to be modified to avoid overloading the measurement equipment. One possibility to achieve lower friction between the valve stem and the valve guide is the reduction of the lateral forces which are caused by the asymmetry of the valve spring. Using recently new developed components these detrimental forces within a valve train can be reduced which leads to lower friction losses. In addition the wear between the valve train components can be reduced. In detail this can be accomplished by using two-piece spring retainer which allows a tilted position of the spring end during the valve lift and by this only allow axial forces to act onto the valve. The friction in a valve train using a direct acting mechanical tappet is mainly caused by the sliding contact of the cam on the tappet face. To lower the friction in this area the spring forces have to be reduced. This requires valve train components with lower masses and weaker springs. Therefore valves, spring retainers and tappets made from light weight alloys where developed. The mass of these light weight components could be reduced by more than 50%. Detailed measurements are performed and the results will be presented. As a conclusion it can be seen, what light weight components in the valve train of four stroke engines can contribute to a torque reduction in innovative valve trains.
Numerical Analysis of the Flow Within a Clark Turbocharger Compressor
Authors: Chapman K. S. , Dey Sudip , Keshavarz Ali
Published: December 2008

The flow field within a Clark turbocharger compressor has been thoroughly analyzed by numerical simulation. The numerical simulation was validated with experimental data collected from field test sites. The numerical results are found to closely match the experimental data. Once validated, the numerical simulation was used to investigate the flow field within the turbocharger compressor under a variety of operating conditions. Several regions of flow recirculation were identified that restrict flow through the turbocharger.
Regulated and Unregulated Emissions From a Stoichiometric 250kW Natural Gas Engine
Authors: Storey J. M. , Lewis S. A. , Dam T. , Kahl K. W. , Theiss T. J.
Published: December 2008

The emissions profile from a natural gas (NG) stationary power, stoichiometric, engine have been measured. Of particular interest are the unregulated emissions (especially formaldehyde) from this engine class. A relatively small 250 kW Caterpillar G3406 engine without a catalyst was used as the test platform with the emissions being characterized as a function of applied load and external conditions. In addition, multiple formaldehyde measurement techniques have been used and are compared. This paper presents the formaldehyde results, comparison of formaldehyde with various other parameters, a comparison of the different measurement techniques, and measurement of other toxic emissions from this engine.
Particulate Deposition Modeling in Diesel Filter
Authors: Chiatti Giancarlo , Chiavola Ornella
Published: December 2008

The objective of this work is to evaluate the possibility of extracting information about the filter loading status from the running history of the engine and to assess the interaction between spatial deposition of soot inside the porous wall and the engine operating conditions. The attention is drawn to the non-uniform particles distribution on the channels which may compromise the filter safety as during the thermal regeneration process, the evolution of particulate oxidation results in temperature differences in the soot layer and critical overheating phenomena may originate. CFD simulations are performed by means of a multi dimensional approach in which a two-step stationary calculation is used to simulate the soot loading; results concerning the correlation between the engine operative conditions and the deposition of particulate are presented.
Fuel Quality: An Essential Element in Vehicle Emission Control
Authors: Colucci Joseph M.
Published: December 2008

Enormous progress has been made in the past 40 years in reducing vehicle emissions in the United States and around the world. Emission control technology has progressed from rudimentary engine controls to sophisticated computer-controlled catalyst systems. Another major factor in reducing emissions, whose contribution is not as well known as that of the hardware, is the fuel. This paper will review three significant fuel changes; unleaded gasoline, deposit control additives, and reformulated gasoline. In will provide the background for these changes and the technical data to substantiate the changes. It will also delve into the people and the strategies involved for implementing the changes, and some of the major aftereffects of the changes.
Performance Analysis of a Natural Gas Generator Using Laser Ignition
Authors: Biruduganti Munidhar S. , Gupta Sreenath B. , Bihari Bipin , Klett Gregory , Sekar Raj
Published: December 2008

A single cylinder spark ignited gasoline engine was modified to operate with natural gas. In such an engine, laser ignition was successfully demonstrated while transmitting the high-power laser pulses via solid core optical fibers. Subsequently, ignition studies were performed while using laser ignition (LI) and conventional spark ignition (SI). However, due to limitations imposed by the engine hardware the adverse conditions for ignition could not be simulated, i.e., of lean operation and high-pressures. As a result, the scope of the study was limited to comparing LI and SI ignition characteristics at various ignition timings. It was observed that both LI and SI resulted in reliable combustion over all ignition timings. Furthermore, LI resulted in higher rates of pressure rise and higher peak cylinder pressures. However, the higher NOx emissions resulting from such conditions might not be representative as the final performance of an engine as it is determined by optimizing ignition timing and other operating parameters.
Repowering an Existing Power Generating Plant
Authors: Shahnazari Mohammad R. , Abbassi Abbas
Published: December 2008

A common repowering option is converting a fossil-fired steam unit to a gas-fired combined-cycle plant by addition of a combustion turbine and a Heat Recovery Steam Generator. In this approach the existing steam turbine and related auxiliaries are typically retained and some plant modification is applied. This paper intends to study this option for two old power plants. In this study the HRSGs are modeled, designed and their costs are estimated. Total generating cost for both plants are calculated in order to show whether or not the final cost is competitive with the cost of a new combined cycle unit.
Case Study Heat Capacity for an Industrial Plant Facility in a Complex
Authors: Seyedan Babak , Hynes Rory , Bhan Satish K.
Published: December 2008

Cogeneration systems are typically used for supplying heat and electricity generation. The main advantages of such systems are energy savings and reduced operational costs. Plants that use cogeneration systems are often equipped with parallel components feeding various internal energy vector networks. The energy consumption of the plant can be improved by selecting suitable operating levels of the various parallel machines and components connected to the cogeneration system. Recently, cogeneration systems have been equipped with comprehensive monitoring systems. With the availability of these monitoring systems, the concept of a computerized procedure capable of recognizing the status of the equipment from the monitoring data to optimize the plant operation has been established. This can lead to significant economic and energy consumption improvements. In this paper, heat capacity of a typical installation is presented and a procedure to optimize energy utilization is developed. The procedure is presented for a cogeneration system based on natural gas engines, hot water boilers and other heat sources. Plant existing condition is taken as a reference condition. To improve system heat capacity, two alternate methods have been proposed and compared with plant existing condition. First option is the use of system available heat sources as a prime heat source and the second option is adding new gas boilers to improve complex heat production and also as a back up heat source to meet peak complex heat demand requirements. General block diagram of the system is presented and discussed. Installation heat load allocation is analyzed.
Cathodic Protection for Underground Piping in Power Plants
Authors: Huck Ted
Published: December 2008

Cathodic protection systems are often used to protect critical underground piping systems. This paper discusses the various anode systems used for power plant underground piping applications. It is intended for engineers responsible for the underground piping systems for new power plant design — this could include owner’s engineers, EPCs, and construction contractors responsible for these systems. The paper begins with an overview of cathodic protection and when it is needed. The paper provides an overview of how cathodic protection works and discusses key piping issues that impact the design and operation of the system. After providing a framework for establishing the need for cathodic protection, this paper provides detailed comparisons of the various available types of anode systems. Each anode system is described in detail and then the advantages and disadvantages of each system are examined. The first anode system discussed is the galvanic distributed bed system. This is followed by three impressed current anode systems; linear anodes, distributed bed, and deep well systems. The paper concludes with a summary of each of these systems. An appendix is included which provides typical design calculations for galvanic, linear and deep well systems.