bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Hydroxyapatite Nanoparticles on Biotransport Phenomena in Freezing HeLa Cells
Authors: Yi Jingru , Zhao Gang
Published: December 2014

The effect of nanoparticles on subzero biotransport phenomena of living cells is very rare in the literature, although the information is of great importance for the application of nanotechnology in the field of cryobiology. In this study, subzero water transport phenomena in freezing HeLa cells in 1 × phosphate buffered saline (PBS) containing 0%, 0.05%, and 0.1% (w/w) hydroxyapatite (HA) nanoparticles with and without pre-incubation at 37 °C was quantitatively investigated. The results reveal that the presence of HA nanoparticles slightly facilitates the subzero water transport of HeLa cells.
Online Identification of Power Required for Self-Sustainability of the Battery in Hybrid Electric Vehicles
Authors: Malikopoulos Andreas A.
Published: December 2014

Hybrid electric vehicles have shown great potential for enhancing fuel economy and reducing emissions. Deriving a power management control policy to distribute the power demanded by the driver optimally to the available subsystems (e.g., the internal combustion engine, motor, generator, and battery) has been a challenging control problem. One of the main aspects of the power management control algorithms is concerned with the self-sustainability of the electrical path, which must be guaranteed for the entire driving cycle. This paper considers the problem of identifying online the power required by the battery to maintain the state of charge within a range of the target value. An algorithm is presented that realizes how much power the engine needs to provide to the battery so that self-sustainability of the electrical path is maintained.
Enhancing Low Temperature Combustion With Biodiesel Blending in a Diesel Engine at a Medium Load Condition
Authors: Lee Sunyoup , Oh Seungmook , Kim Junghwan , Kim Duksang
Published: December 2014

The present study investigated the effects of biodiesel blending under a wide range of intake oxygen concentration levels in a diesel engine. This study attempted to identify the lowest biodiesel blending rate that achieves acceptable levels of nitric oxides (NOx), soot, and coefficient of variation in the indicated mean effective pressure (COVIMEP). Biodiesel blending was to be minimized in order to reduce the fuel penalty associated with the biodiesels lower caloric value. Engine experiments were performed in a 1-liter single-cylinder diesel engine at an engine speed of 1400 rev/min under a medium load condition. The blend rate and intake oxygen concentration were varied independently of each other at a constant intake pressure of 200 kPa. The biodiesel blend rate varied from 0% (B000) to 100% biodiesel (B100) at a 20% increment. The intake oxygen level was adjusted from 8 to 19% by volume (vol %) in order to embrace both conventional and low-temperature combustion (LTC) operations. A fixed injection duration of 788 μs at a fuel rail pressure of 160 MPa exhibited a gross indicated mean effective pressure (IMEP) between 750 kPa and 910 kPa, depending on the intake oxygen concentration.

The experimental results indicated that the intake oxygen level had to be below 10 vol% to achieve the indicated specific NOx (ISNOx) below 0.2g/kWhr with the B000 fuel. However, a substantial soot increase was exhibited at such a low intake oxygen level. Biodiesel blending reduced NOx until the blending rate reached 60% with reduced in-cylinder temperature due to lower total energy release. As a result, 60%-biodiesel blended diesel (B060) achieved NOx, soot, and COVIMEP of 0.2 g/kWhr, 0.37 filter smoke number (FSN), and 0.5, respectively, at an intake oxygen concentration of 14 vol%. The corresponding indicated thermal efficiency was 43.2%.
Effects of Multi-Grade Oils in Modeling Non-Newtonian Rheology Between Piston and Cylinder Surfaces in Engine Initial Start Up Conditions
Authors: Chaudhri Usman , Aung Kendrick
Published: December 2014

This paper presents the results of a transient analysis of hydrodynamic lubrication between piston and cylinder surfaces in engine Initial startup conditions with a Non Newtonian lubricant under oscillatory motion. Effects of different multi-grade oil viscosities are also investigated in the simulation. The time dependent Reynolds equations use a Maxwell type model to analyze fluid rheology. A perturbation scheme is used to derive coupled non linear partial differential equations to obtain the fluid velocity. The oil film profile is predicted by solving the two-dimensional Reynolds equations using the finite difference computational method. The piston velocities in engine secondary motion are adjusted by using fourth order Runge-Kutta technique. Using different oil viscosities, the effect of viscoelasticity on lubricant velocity and pressure fields is examined and the influence of film thickness on lubricant characteristics is investigated. Numerical simulations show that piston eccentricities and film thickness profiles vary under different multi grade oils at engine start up conditions.
Future Diesel Fuel Requirements and Fuel Quality Impacts on Tier 2-4 High Horsepower Offroad Engines With Common Rail Fuel Systems
Authors: Blizard Norman C.
Published: December 2014

Off highway Tier 2-4 emissions requirements for high speed, high horsepower diesel engines (>750 h.p.) have driven substantial engine, after-treatment and fuel system design improvements. Modern high pressure common rail (HPCR) fuel systems are being applied by engine manufacturers through use of increased injection pressure, precision injection timing, and multiple injection events to achieve emissions targets. In the field, careful attention to diesel fuel quality is now required by the end user to avoid problems with performance, reliability and durability of the fuel systems and after-treatment. Ultra-fine filtration and complete water separation are essential to maintain the fuel clean and dry. Internal Diesel Injector Deposit (IDID) formation due to degradation of the fuel and unintended consequences of additives must also be avoided. This is a voice of a fuel consumer and fuel system integrator to fuel suppliers and end customers on challenges encountered and countermeasures developed to achieve better fuel filtration, water separation, fuel cleanliness practices and end user education.
Fundamental Explorations of Spring-Varied, Free Piston Linear Engine Devices
Authors: Robinson Matthew C. , Clark Nigel N.
Published: December 2014

The conventional crank-based internal combustion engine faces many challenges to remain a viable option for electric power generation. Limitations in mechanical, thermal, and combustion efficiencies must be overcome by innovations in existing technologies and progress towards new ones. The free piston linear engine (FPLE) is a device with the potential to meet these challenges. Friction losses are reduced by avoiding rotational motion and linkages. Instead, electrical power is generated by the oscillation of the translator through a stator. Meanwhile, naturally variable compression ratio provides a unique platform to employ advanced combustion regimes. Possibly high variations in stroke length also result in unknown dead center piston positions and greater difficulties in compression control as compared to conventional engines. Without control, adverse occurrences such as misfire, stall, over-fueling, and rapid load changes pose greater complications for stable system operation. Based on previous research, it is believed that incorporating springs will advance former designs by both increasing system frequency and providing a restoring force to improve cycle-to-cycle stability.

Despite growing interest in the FPLE, current literature does not address the use of springs within a dual, opposed piston design. This investigation is an extension of recent efforts in the fundamental analysis of such a device. Previous work by the authors combined the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions to produce a closed-form non-dimensional model. Simulations of this model were used to describe ideal Otto cycle as the equilibrium operating point. The present work demonstrates more realistic modelling of the device in three distinct areas. In the previous model, the work term was a constant coefficient over the length of the stroke, instantaneous heat addition (representing combustion) was only seen at top dead center positions, and the use of the Otto cycle included no mechanism for heat transfer except at dead center positions. Instead, a position based sinusoid is employed for the work coefficient causing changes to the velocity and acceleration profiles. Instantaneous heat addition prior to top dead center is allowed causing the compression ratio to decrease towards stable, Otto operation. And, a simple heat transfer scheme is used to permit cylinder gas heat exchange throughout the stroke resulting in deviation from Otto operation. Regardless, simulations show that natural system stability arises under the right conditions. Highest efficiencies are achieved at a high compression ratio with minimal heat transfer and near-TDC combustion.
CFD Analysis of the Scavenging Process in Marine Two-Stroke Diesel Engines
Authors: Andersen Fredrik H. , Hult Johan , Nogenmyr Karl-Johan , Mayer Stefan
Published: December 2014

The scavenging process is an integral part of any two-stroke internal combustion engine regardless of being spark ignited (SI) or compression ignited (CI). The scavenging process is responsible for replacing the burned gas from the combustion process from the previous working stroke with fresh air/charge before the subsequent compression stroke. This implies that the scavenging process is integral to engine performance as it influence the initial condition for the combustion process, thus affecting the fuel economy, power output and emission of hazardous gases.

Two-stroke diesel engines for marine propulsion normally operates by the uniflow scavenging method, where the scavenge air enters the cylinder via inlet ports located near the bottom dead center and exits through one or several exhaust valves located in the cylinder head. This arrangement concentrates the airflow in one direction through the cylinder thus giving the method its name. The inlet ports are angled with respect to the local radius which will introduce a tangential velocity component to the air flow. The air moves axially through the cylinder in a swirling motion that favors mixing of fuel and air as the injected fuel is transported with the swirling air in the combustion chamber during fuel injection.

A known characteristic of swirling flows is an adverse pressure gradient in the center of the rotating flow which might lead to a local deficit in axial velocity and the formation of central recirculation zones, known as vortex breakdown. Optimal scavenging is achieved when the gas exchange is done by displacement, the local deficit in axial velocity will increase the mixing of burned gas and scavenge air thus decreasing the amount of pure displacement.
Gas and Particle Emissions From a Diesel Engine Operating in a Dual-Fuel Mode Using High Water Content Hydrous Ethanol
Authors: Hwang Jeffrey T. , Northrop William F.
Published: December 2014

Diesel engines running in a dual-fuel fumigation mode using injection of a high volatility fuel into the intake air and direct injection of diesel fuel can reduce NOX and particulate matter emissions. Fuels such as methanol, hydrogen, gasoline, and anhydrous ethanol have been studied as fumigants; however there has been less published regarding the use of high water content hydrous ethanol. Current production of ethanol yields anhydrous (200 proof) ethanol with no water content. The distillation and dehydration processes used to remove excess water from fermented starches during production require large amounts of input energy, reducing the renewability of the resulting fuel. This paper describes an experimental investigation of an aftermarket fumigation system provided by CleanFlex Power Systems, LLC. Experiments to measure gaseous and particulate emissions were conducted using 120 proof hydrous ethanol and non-oxygenated ultra-low sulfur diesel fuel. A John Deere 4045HF475 Tier 2 engine was modified to incorporate the fumigation system in the intake plumbing downstream of the charge-air cooler, just prior to the intake manifold. Data was collected for dual fuel fumigation combustion and compared to diesel only combustion. This study shows that the fumigation system achieved lower levels of NOX and soot proportional to the fumigant energy fraction (FEF), but increased CO and hydrocarbon levels as compared to diesel-only combustion modes. The results suggest that increasing the FEF by using lower water content or better mixing through port-injection may increase the emissions reduction potential of hydrous ethanol fumigation.
Effect of Renewable Diesel and Jet Blending Components on Combustion and Emissions Performance of a HCCI Engine
Authors: Guo Hongsheng , Neill W. Stuart , Chippior Wally , Gieleciak Rafal
Published: December 2014

Renewable diesel and jet blending components may be produced by hydrotreating waste fats and vegetable oils. The resulting hydrocarbon components are paraffinic in nature and free of sulfur and aromatics. An isomerization process may follow to improve the cold weather properties. The main differences between renewable diesel and jet blending components is that the jet blending components are more volatile, have a lower cetane number and a much lower cloud point. In this study, different percentages of hydrotreated renewable diesel and jet components were blended into an ultra-low sulfur diesel (ULSD) fuel and their effect on homogeneous charge compression ignition (HCCI) combustion and emissions performance was investigated.

The experiments were conducted using a Co-operative Fuel Research (CFR) engine coupled to an eddy-current dynamometer. The percentage of renewable blending components was varied from 0 to 100%. HCCI combustion and emissions data was collected at a single relative air/fuel ratio (λ) = 1.2 and engine speeds of 900 and 1200 rpm for each fuel blend. The experimental results indicate that the renewable diesel and jet blending components increased the heat release during low temperature stage and reduced the auto-ignition temperature compared to the ULSD fuel, which tended to advance the combustion phasing at a fixed compression ratio. The thermal efficiency was not significantly affected by renewable jet and diesel blends up to 10% by volume, but the renewable jet improved the thermal efficiency while the renewable diesel blends deteriorated thermal efficiency for higher percentage blends. The renewable jet fuel component improved unburned hydrocarbon (HC) emissions, but the renewable diesel component did not have a significant effect on HC emissions. Both renewable fuel components reduced CO emissions at a fixed compression ratio, but there was not a clear trend for CO emissions at the optimal thermal efficiency condition when renewable components were blended with the ULSD fuel. The NOx emissions were extremely low and did not show a clear trend as the percentage of renewable blending components increased.
Diesel and Compressed Natural Gas Dual Fuel Engine Operating Envelope for Heavy Duty Application
Authors: de Tablan Andrew
Published: December 2014

The abundance of natural gas in the United States and low price relative to diesel fuel has generated interest in dual fuel engines where natural gas is substituted for diesel fuel. The factors limiting the natural gas (NG) substitution rates are: minimum diesel injector pulse width, cycle-to-cycle variation in net indicated mean effective pressure (NIMEP), engine knock, peak cylinder pressure, compression ratio, boost pressure and lean air/fuel limits leading to misfire among others.

The objective of this study was to explore the highest natural gas substitution for a commercially available heavy duty diesel engine for several of the 13 Mode European Stationary Cycle (ESC) and US EPA Supplementary Emissions Tests (SET) speeds and loads while maintaining acceptable engine performance levels. A heavy duty 2012 Navistar MaxxForce 13® engine was retrofitted to accommodate dual-fuel operation. The engine was operated over several different speeds and loads to determine the possible NG substitution rates at different diesel injection timings, diesel injection pressures and equivalence ratios, while maintaining combustion phasing.

The data showed that dual fuel operation at high NG percentages was stable over several speeds and loads with brake thermal efficiencies comparable to 100% diesel operation. The introduction of NG generally demonstrated reductions in peak cylinder pressure and cylinder pressure rise rate at a given speed and load point. Increases in hydrocarbon and greenhouse gas emissions and a decrease in nitrogen oxides were observed during dual-fuel operation.
Measurements of n-Heptane Liquid Length and Spray Cone Angle for Low-Temperature, Low-Density Conditions in an Optically Accessible Flow Vessel
Authors: Wang Jin , James Kemar C. , Maynard Michael C. , Fisher Brian T.
Published: December 2014

The purpose of this study was to measure global properties of n-heptane sprays using high-speed spray visualization in a newly developed constant-pressure flow vessel. Liquid-phase fuel penetration distance and cone angle were determined for low-density and low-temperature ambient conditions, which are increasingly relevant due to the advent of early direct-injection low-temperature combustion. Results indicated that fuel sprays under these conditions do not behave as predicted by established models. Penetration distances increased steadily throughout and after injection, and liquid-phase fuel persisted long after end of injection. Results suggest that these sprays vaporize extremely slowly and could cause wall-wetting issues.
A Novel Fuel Performance Index for LTC Engines Based on Operating Envelopes in Light-Duty Driving Cycle Simulations
Authors: Niemeyer Kyle E. , Daly Shane R. , Cannella William J. , Hagen Christopher L.
Published: December 2014

Low-temperature combustion (LTC) engine concepts such as homogeneous charge compression ignition (HCCI) offer the potential of improved efficiency and reduced emissions of NOx and particulates. However, engines can only successfully operate in HCCI mode for limited operating ranges that vary depending on the fuel composition. Unfortunately, traditional ratings such as octane number poorly predict the autoignition behavior of fuels in such engine modes, and metrics recently proposed for HCCI engines have areas of improvement when wide ranges of fuels are considered. In this study, a new index for ranking fuel suitability for LTC engines was defined, based on the fraction of potential fuel savings achieved in the FTP-75 light-duty vehicle driving cycle. Driving cycle simulations were performed using a typical light-duty passenger vehicle, providing pairs of engine speed and load points. Separately, single-zone naturally aspirated HCCI engine simulations were performed for a variety of fuels in order to determine the operating envelopes for each. These results were combined to determine the varying improvement in fuel economy offered by fuels, forming the basis for a fuel performance index. Results showed that, in general, lower octane fuels performed better, resulting in higher LTC fuel index values; however, octane number alone did not predict fuel performance.
Case Studies on the Use of Two and Three Degree of Freedom Models to Understand Fundamental Vibration Behavior of Complex Systems
Authors: Hodge Ryan D. , Demirdogen Caner
Published: December 2014

Mathematical models of simple two and three degree of freedom vibrating systems are beneficial to ease understanding of a complex system by providing an opportunity to readily identify the effect of one degree of freedom on another. When dealing with short timelines in industry, simple models provide the opportunity to quickly develop potential solutions to excessive vibration issues or understand unexpected results. Simple models are not always appropriate and may have significant uncertainties but such an option may still add value when compared to the time and effort required to develop larger, detailed models. This paper presents two cases regarding the use of simple models to develop understanding of a complex system. In each case, the focus is on the insights that can be gained from a simple model rather than the detailed calculations and calibrations necessary to ensure its complete accuracy. Case 1 employs a two degree of freedom system to relate how an experimental modal test of an engine component can be affected by the base structure on which it is mounted. This study directly relates to the experimental modal testing of large engine components which are tested both in laboratories and on engines. Two charts are presented to evaluate the error of a measured natural frequency as a function of both the mass and natural frequency of the component to be tested and the base structure. Case 2 utilizes a three degree of freedom system built in a commercial finite element analysis (FEA) code and solved via a multi-disciplinary optimizer to determine the ideal parameters of a vibration absorber to effect the greatest possible reduction in vibration levels of a component. The lessons learned from this study are applicable to developing a vibration absorber to be installed on an engine component that is being excited by global modes of a generator set. Both cases display the significant lessons that can be learned from extremely simple systems.
Modeling Fuel Spray Vapor Distribution With Large Eddy Simulation of Multiple Realizations
Authors: Senecal P. K. , Mitra S. , Pomraning E. , Xue Q. , Som S. , Banerjee S. , Hu B. , Liu K. , Rajamohan D. , Deur J. M.
Published: December 2014

A state-of-the-art spray modeling methodology, recently presented by Senecal et al. [1, 2, 3], is applied to Large Eddy Simulations (LES) of vaporizing sprays. Simulations of non-combusting Spray H (n-heptane fuel) from the Engine Combustion Network are performed. Adaptive Mesh Refinement (AMR) cell sizes of 0.03125 mm to 0.25 mm are utilized to further demonstrate grid convergence of the Dynamic Structure LES model for diesel sprays.

Twenty-eight different realizations are simulated by changing the random number seed used in the spray submodels. Multi-realization (ensemble) averaging, which has been shown to be necessary when comparing to local spray measurements, is performed. Global quantities such as liquid and vapor penetration are compared, as well as local mean mixture fraction and mixture fraction standard deviation. The results suggest that the current model does a reasonable job predicting the major features of the n-heptane spray when appropriate grid resolution is utilized.
In-Cylinder NOx Reduction Using Different Camshaft Timings on Diesel Engines
Authors: Comitre Lucas , Lehmann Flavio G.
Published: December 2014

Over time, environmental protection standards have become more strict and complex. Nitrogen oxides (NOx) are regulated pollutants produced by combustion in a diesel engine. In this project, camshaft timing modifications were studied as a way of reducing NOx emission levels while using low cost hardware. Different valve timing strategies were proposed and modelled using engine simulation. This project was based on two concepts. The first was to open the intake valve during the exhaust stroke, thus expelling burnt gases from the cylinder into the intake manifold and then later re-admitting these gases into the cylinder during the intake stroke of the next cycle. The second was to open the exhaust valve during the intake stroke, allowing burnt gases from the exhaust manifold to enter the cylinder at the same time as the fresh charge enters. Both technologies studied were able to recirculate the exhaust gases without an external EGR system. The EGR amount was controlled by either an intake throttle or an exhaust throttle. The amount of EGR was predicted using engine simulation. The brake-specific fuel consumption (BSFC) and brake-specific NOx (BSNOx) trade off was the main criterion used to select the best technology, although other features such as predicted manifold pressures and engine-out soot were also considered.

The results indicate that, by using increased amounts of EGR while varying the intake or exhaust throttle position, NOx emissions can be reduced with a slight BSFC penalty. These methods are thus a low cost means of reducing engine-out NOx emissions.
Partial Flow DPF System for Large Bore or High Power Applications
Authors: Hedrick John C. , Fritz Steven G.
Published: December 2014

A number of technical challenges are faced when applying wall flow Diesel Particulate Filter (DPF) systems to large high horsepower off-highway applications, locomotives, and marine diesel engine applications due to the size of the DPF system required and the space constraints associated with these applications. Experimental results show that a new approach of adding an exhaust bypass valve, creating a partial-flow DPF system, can greatly reduce the DPF package size while continuing to offer significant PM emission reductions. The exhaust bypass valve is configured to open proportionally to maintain a pre-set maximum engine backpressure as the exhaust flow increases.

Proof-of-concept testing of an experimental partial flow DPF system was conducted on a 3MW, 4-stroke locomotive engine, following U.S. EPA locomotive certification test protocols. These tests showed that the experimental DPF system, which was approximately 40 percent smaller than what would be expected for this application, provided an 84 percent PM reduction over the US-EPA Switcher Cycle and 59 percent reduction over the Line-Haul Cycle. It was calculated that the system could provide a 91 percent PM reduction over the Switcher Cycle and 76 percent PM reduction over the Line-Haul Cycle with addition of a DOC in the bypass exhaust flow.
The Evolution of Diesel Engine Performance Prediction
Authors: Primus Roy J.
Published: December 2014

Thermodynamic system performance modeling has become an integral part of the engine development process. The modeling tools used for this type of analysis have evolved from fairly simple calculations of limited scope into detailed simulations with ever-increasing complexity. These analytical tools are based on the combination of basic concepts, physical phenomena and experimental correlations. As with other categories of analysis, their evolution has also been closely coupled with the advances in computer technology.

This document provides a historic view of thermodynamic system simulation and revisits some of the developments in modeling techniques, engine measurements, data acquisition systems and computer hardware that have contributed to the understanding of engine performance prediction.
Combustion Characteristics of Lean Burn and Stoichiometric With EGR Spark Ignited Natural Gas Engines
Authors: Xu Hui , LaPointe Leon A.
Published: December 2014

Natural gas has been widely used in reciprocating engines for various applications such as automobile, electricity generation, and gas compression. It is in the public interest to burn fuels more efficiently and at lower exhaust emissions. Natural gas is very suitable to serve this purpose due to its clean combustion, small carbon footprint, and, with recent breakthroughs in drilling technologies, increased availability and low cost. Natural gas can be used in lean burn spark ignited (LBSI) or stoichiometric EGR spark ignited (SESI) engines. Selection of either LBSI or SESI requires accommodation of requirements such as power output/density, engine efficiency, emissions, knock margin, and cost. The work described in this paper investigated the feasibility of operating an engine originally built as an LBSI under SESI conditions.

Analytical tools and workflow developed by Cummins, Inc. are used in this study. The tools require fundamental combustion properties as inputs, including laminar flame speed (LFS), adiabatic flame temperature (AFT) and autoignition interval (AI). These parameters provide critical information about combustion duration, engine out NOx, and relative knock propensity. An existing LBSI engine operating at its as released lambda was selected as baseline. The amount of EGR for the SESI configuration was selected so that it would have the same combustion duration as that of the LBSI at its reference lambda. One dimensional (1D) cycle simulations were conducted under both SESI and LBSI conditions assuming constant output power, compression ratio, volumetric efficiency, heat release centroid and brake mean effective pressure (BMEP). The 1D cycle simulations provide peak cylinder pressure (PCP) and peak unburned zone temperature (PUZT) under LBSI and SESI conditions. The results show that the SESI configuration has lower PCP but higher peak unburned zone temperature than that of the LBSI for the same output power. Also, for the same combustion duration, SESI has higher AFT than that of LBSI, resulting in higher engine out NOx emissions. The SESI configuration has shorter AI than that of LBSI engine, or smaller relative knock margin. Reduction of output power and emissions aftertreatment in the form of a three way catalyst (TWC) is required to operate under SESI engine conditions.
Comparison of Representative Interactive Flamelet and Detailed Chemistry Based Combustion Models for Internal Combustion Engines
Authors: Wang M. , Raju M. , Pomraning E. , Kundu P. , Pei Y. , Som S.
Published: December 2014

Representative Interactive Flamelet (RIF) and Detailed Chemistry based combustion models are two commonly used combustion models for non-premixed diesel engine simulations. RIF performs transient chemistry calculations on a one-dimensional grid based on the mixture fraction coordinate. Hence, the chemistry calculations are essentially decoupled from the computational fluid dynamics (CFD) grid. The detailed chemistry model, on the other hand, solves transient chemistry in the 3D CFD domain. An efficient parallelization strategy is used for the computation of the multiple flamelets RIF model. The multiple flamelets RIF and detailed chemistry combustion models are applied for modeling a constant volume spray combustion case and a diesel engine case, with a view to compare the differences between the two models. Results for ignition delay, flame lift-off length, cylinder pressure, and emissions are compared with experimental data. The effect of number of flamelets is evaluated. Finally, the effect of spray cooling is investigated based on the results from the RIF model and the detailed chemistry based combustion model.
A New Numerical Method for Developing the Lumped Dynamic Model of Valve Train
Authors: Guo J. , Cao Y. P. , Zhang W. P. , Zhang X. Y.
Published: December 2014

The dynamics of valve train is influenced by stiffness, size and mass distribution of its components and initial valve clearance and so on. All the factors should be taken into consideration correctly by dynamic model and described qualitatively and quantitatively through mathematical variables. This paper proposes a new simplified method for valve train components, namely mode matching method (MMM) for camshaft, pushrod, rocker arm, valve and valve spring. In this method the amount of lumped masses for each flexible component is determined based on its natural frequencies and the considered frequency range. As a result, the dynamic model of each component is required to match its low order modes within the considered frequency range. The basis of this method is that the contributions of each component to valve train vibration are mainly in the low order modes. The numerical model of valve train is verified by an experiment conducted on a motor driven valve train system.
Use of Early Exhaust Valve Opening to Improve Combustion Efficiency and Catalyst Effectiveness in a Multi-Cylinder RCCI Engine System: A Simulation Study
Authors: Bharath Anand Nageswaran , Kalva Nitya , Reitz Rolf D. , Rutland Christopher J.
Published: December 2014

Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI) can result in significant improvements of fuel economy and emissions reduction. However, they can produce significant carbon monoxide and unburnt hydrocarbon emissions at low load operating conditions due to poor combustion efficiencies at these operating points, which is a consequence of the low combustion temperatures that cause the oxidation rates of these species to slow down. The exhaust gas temperature is also not high enough at low loads for effective performance of turbocharger systems and diesel oxidation catalysts (DOC). The DOC is extremely sensitive to exhaust gas temperature changes and lights off only when a certain temperature is reached, depending on the catalyst specifications. Uncooled EGR can increase combustion temperatures, thereby improving combustion efficiency, but high EGR concentrations of 50% or more are required, thereby increasing pumping work and reducing volumetric efficiency. However, with early exhaust valve opening, the exhaust gas temperature can be much higher, allowing lower EGR flow rates, and enabling activation of the DOC for more effective oxidization of unburnt hydrocarbons and CO in the exhaust.

In this paper, a multi-cylinder engine system simulation of RCCI at low load operation with early exhaust valve opening is presented, along with consideration of the exhaust aftertreatment system. The combustion process is modeled using the 3D CFD code, KIVA, and the heat release rates obtained from this combustion are used in a GT-Power model of a turbocharged, multi-cylinder light-duty RCCI engine for a full system simulation. The post-turbine exhaust gas is fed into GT-Power’s aftertreatment model of the engine’s DOC to determine the catalyst response. It is confirmed that opening the exhaust valve earlier increases the exhaust gas temperature, and hence lower EGR flow rates are needed to improve combustion efficiency. It was also found that exhaust temperatures of around 457 K are required to light off the catalyst and oxidize the unburnt hydrocarbons and CO effectively. Performance of the DOC was drastically improved and higher amounts of unburnt hydrocarbons were oxidized by increasing the exhaust gas temperature.
A Numerical Study on Combustion and Emissions in a Dual Fuel Directly Injected Engine Using Biogas and Diesel
Authors: Dewan Akshit , Ramadan Bassem H. , Hoff Craig
Published: December 2014

A numerical study on the use of biogas and diesel in a dual-fueled directly-injected engine has been conducted. The objective of this study is to determine the effect of using biogas on engine performance, combustion, and emissions. The main fuel is biogas which is premixed with air in order to form a homogeneous mixture. The mixture is then compressed and ignited by injecting diesel fuel before TDC. The pilot fuel is expected to lead to multiple ignition points in the cylinder in order to achieve uniform combustion in the cylinder. The expected benefits are lower nitrogen oxides and soot compared to pure diesel combustion. Numerical simulations using CFD software were used to simulate fuel-air mixture, compression, fuel injection, combustion, and emissions. Different quantities of biogas and diesel were investigated to determine the optimum mixture ratio. Since biogas, which is natural gas produced from human waste, contains large quantities of carbon dioxide, the effect of carbon dioxide content in the fuel was investigated. The results of this study agree very well with results from other studies found in the literature.
Conrod Bearings With an Optimized Narrow Circumferential Oil Groove: Simulated Durability Improvement for Heavy-Duty Applications
Authors: Kalogiannis Konstantinos , Merritt David , Mian Omar , Gibson Hugh
Published: December 2014

Under normal operating conditions, engine crankshaft bearings experience variations in oil film temperature due to shearing of the oil film. This can have a negative impact on the bearing operating life since the viscosity of the lubricant is temperature dependent.

In the current study, a thermo-elastohydrodynamic lubrication (TEHL) analysis has been conducted using an in-house specialized simulation package called SABRE-TEHL. This advanced simulation tool has been used to optimize a new bearing design feature leading to a significant temperature reduction, which in turns increases the robustness of the system.
Effect of Premixed Fuel Preparation for Partially Premixed Combustion With a Low Octane Gasoline on a Light-Duty Multi-Cylinder Compression Ignition Engine
Authors: Dempsey Adam , Curran Scott , Wagner Robert , Cannella William
Published: December 2014

Gasoline compression ignition concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multi-cylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies has been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection strategy to create a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from −91° to −324° ATDC, which is just after the exhaust valve closes for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 L diesel engine with a variable geometry turbocharger, high pressure common rail injection system, wide included angle injectors, and variable swirl actuation was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).
Dynamic Identification of Thermodynamic Parameters for Turbocharger Compressor Models
Authors: Burke Richard , Olmeda Pablo , Serrano José Ramón
Published: December 2014

A novel experimental procedure is presented which allows simultaneous identification of heat and work transfer parameters for turbocharger compressor models. The method introduces a thermally transient condition and uses temperature measurements to extract the adiabatic efficiency and internal convective heat transfer coefficient simultaneously, thus capturing the aerodynamic and thermal performance. The procedure has been implemented both in simulation and experimentally on a typical turbocharger gas stand facility.

Under ideal conditions, the new identification predicted adiabatic efficiency to within 1%point and heat transfer coefficient to within 1%. A sensitivity study subsequently showed that the method is particularly sensitive to the assumptions of heat transfer distribution pre and post compression. If 20% of the internal area of the compressor housing is exposed to the low pressure intake gas, and this is not correctly assumed in the identification process, errors of 7–15%points were observed for compressor efficiency. This distribution in heat transfer also affected the accuracy of heat transfer coefficient which increased to 20%. Thermocouple sensors affect the transient temperature measurements and in order to maintain efficiency errors below 1%, probes with diameter of less than 1.5mm should be used.

Experimentally, the method was shown to reduce the adiabatic efficiency error at 90krpm and 110krpm compared to industry standard approach from 6% to 3%. However at low speeds, where temperature differences during the identification are small, the method showed much larger errors.
Diesel Spray Rate-of-Momentum Measurement Uncertainties and Diagnostic Considerations
Authors: Knox Benjamin W. , Franze Michael J. , Genzale Caroline L.
Published: December 2014

Interpretation of combustion and emissions outcomes in diesel engines is often enhanced by accurate knowledge of the transient fuel delivery rate and flow characteristics of the injector nozzle. Important physical characteristics of these flows, including velocity profile and flow separation or cavitation effects, are difficult to measure directly, but can be characterized from a flow-averaged perspective through the measurement of nozzle flow coefficients, namely the discharge, velocity, and area contraction coefficients. Both the transient fuel mass flow rate and the flow-averaged nozzle coefficients can be found by measuring the mass and momentum flux of the fuel stream leaving the nozzle during injection through the application of an impingement technique, where fuel is sprayed onto the face of a transducer calibrated for force measurement in close proximity to the nozzle. While several published experiments have employed the spray impingement method to quantify rate-of-injection, the experimental setup and equipment selections vary widely and may contribute to disagreements in measured rate-of-injection. This paper identifies and provides estimates of measurement uncertainties that can arise when employing different experimental setups using the impingement method. It was observed that the impingement technique was sensitive to the design of the strike cap, specifically the contact area between the cap and transducer diaphragm, in addition to fuel temperature. Conversely, we observed that the impingement technique was relatively insensitive to angular and vertical misalignment, where the uncertainty can be estimated using control volume analysis. Transducer selection, specifically those with low acceleration sensitivity, high resonant frequency, and integrated electronics piezoelectric circuitry substantially reduce the noise in the measurement.
Lean HCCI/Rich SACI Gasoline Combustion Cycling and Three-Way Catalyst for Fuel Efficiency and NOx Reduction
Authors: Chen Yi , Šíma Vojtěch , Lin Weiyang , Sterniak Jeff , Bohac Stanislav V.
Published: December 2014

Multi-mode combustion (MMC) concepts using homogeneous charge compression ignition (HCCI) gasoline combustion at low loads and spark assisted compression ignition (SACI) gasoline combustion at medium loads have the potential for improved fuel efficiency relative to spark ignition (SI) gasoline combustion. Two MMC concepts are compared in this paper with respect to fuel efficiency and tailpipe NOx emissions. The first concept uses stoichiometric HCCI and SACI to allow standard three-way catalyst (TWC) operation. The second concept also uses HCCI and SACI, but cycles between lean and rich combustion and uses a TWC with increased oxygen storage capacity (OSC) for potentially even greater fuel efficiency improvement.

This paper performs a preliminary comparison of the two MMC concepts by analyzing two scenarios: 1) cycling between stoichiometric HCCI at 2 bar BMEP (brake mean effective pressure) and stoichiometric SACI at 3 bar BMEP, and 2) cycling between lean HCCI at 2 bar BMEP and rich SACI at 3 bar BMEP. The effects of excess oxygen ratio during HCCI operation and the frequency of oxygen depletion events on TWC performance and fuel efficiency are investigated.

Results show that MMC lean/rich cycling can achieve better fuel efficiency than stoichiometric HCCI/SACI cycling. NOx emissions are moderately higher, but may still be low enough to meet current and future emission regulations.
Ethanol Optimized Powertrain for Medium Duty Trucks
Authors: Perfetto Anthony , Kameshwaran Karthik , Geckler Samuel C. , Zope Rohit , Lana Carlos , Kothandaraman Govindarajan
Published: December 2014

This paper includes a detailed description of an optimized E85 concept engine developed for medium duty applications (Class 4-6 trucks) targeting ultra-low carbon emissions while maintaining power and delivering competitive cost of ownership. The engine is a light weight, downsized and boosted in-line 4 cylinder with air handling, fuel, and combustion systems designed specifically for E85 capability, producing high brake mean effective pressure (BMEP) at high thermal efficiency. It is integrated with a 12V start/stop system including a smart alternator for improved energy management.

The present work demonstrates that even with the relative difference in the cost per heating value of fuel, using E85 can be upwards of 20% lower in cost while running middle to high loads. Combining high BMEP capability and a highly downsized engine displacement can ensure operation at high specific load where engine thermal efficiency is very good even in pickup-and-delivery type drive cycles.

The performance characteristics of this engine were mapped using stoichiometric combustion and a three way catalyst for emissions control. The ability to perform at or close to Maximum Brake Torque (MBT) spark timing throughout the torque curve has been facilitated by an optimized combustion system design along with direct injection. The high engine thermal efficiency and knock tolerance of this combustion system eliminates the need for fuel enrichment anywhere in the engine map.