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We present the effect of EGR, at a set fuel flow rate and intake temperature, on the operating parameters of timing of combustion, duration of combustion, power output, thermal efficiency, and NOx emission; which is remarkably low. We find that addition of EGR at constant inlet temperature and constant fuel flow rate has little effect on HCCI parameter of start of combustion (SOC). However, burn duration is highly dependent on the amount of EGR inducted. The experimental setup at UC Berkeley uses a 1.9-liter 4-cylinder diesel engine with a compression ratio of 18.8:1 (offered on a 1995 VW Passat TDI). The engine was converted to run in HCCI mode by addition of an 18kW air pre-heater installed in the intake system. Pressure traces were obtained using four water-cooled quartz pressure transducers, which replaced the Diesel fuel injectors. Gaseous fuel (propane or butane) flowed steadily into the intake manifold.

An experimental fuel surrogate validation approach is proposed for a compression ignition application, and applied to validate a Jet-A POSF 4658 fuel surrogate. The approach examines the agreement of both physical and chemical properties of surrogate and target fuels during validation within a real compression-ignition engine environment during four sequential but distinct combustion phases. In-cylinder Mie Scattering measurements are applied to evaporating sprays to compare the behavior of the surrogate, its target fuel, and for reference, n-heptane. Early mixture formation and low temperature reaction behavior were investigated using 2-D broadband chemiluminescence imaging, while high temperature ignition and combustion chemistry were studied using OH chemiluminescence imaging. The optical measurements were combined with cylinder pressure-based combustion analysis, including ignition delay and premixed burn duration, to validate the global behavior of the surrogate.

A new formulation is developed for the ignition delay (ID) in diesel engines to account for the effect of piston motion on the global autoignition reaction rates. A differentiation is made between the IDe measured in engines and IDv, measured in constant volume vessels. In addition, a method is presented to determine the coefficients of the IDe correlation from actual engine experimental data. The new formulation for IDe is applied to predict the misfiring cycles during the cold starting of diesel engines at different low ambient temperatures. The predictions are compared with experimental results obtained on a multi-cylinder heavy-duty diesel engine.

Traditional Lagrangian spray modeling approaches for internal combustion engines are highly grid-dependent due to insufficient resolution in the near nozzle region. This is primarily because of inherent restrictions of volume fraction with the Lagrangian assumption together with high computational costs associated with small grid sizes. A state-of-the-art grid-convergent spray modeling approach was recently developed and implemented by Senecal et al., (ASME-ICEF2012-92043) in the CONVERGE software. The key features of the methodology include Adaptive Mesh Refinement (AMR), advanced liquid-gas momentum coupling, and improved distribution of the liquid phase, which enables use of cell sizes smaller than the nozzle diameter. This modeling approach was rigorously validated against non-evaporating, evaporating, and reacting data from the literature.

In this paper, a wall-modified interactive flamelet model is developed for improving the modeling of Diesel combustion. The objective is to include the effects of wall heat loss on the transient flame structure. The essential idea is to compute several flamelets with several representative enthalpy defects which account for wall heat loss. Then, the averaged flamelet profile can be obtained through a linear fit between the flamelets according to the enthalpy defect of the local gas which results from the wall heat loss. The enthalpy defect is estimated as the difference between the enthalpy in a flamelet without wall heat loss, which would correspond to the enthalpy in the gas without wall heat loss, and the gas with wall heat loss. The improved model is applied to model combustion in a Diesel engine. In the application, two flamelets, one without wall heat loss and one with wall heat loss, are considered.

Detailed chemical kinetics, although preferred due to increased accuracy, can significantly slow down CFD combustion simulations. Chemistry solutions are typically the most computationally costly step in engine simulations. The calculation time can be significantly accelerated using a multi-zone combustion model. The multi-zone model is integrated into the CONVERGE CFD code. At each time-step, the CFD cells are grouped into zones based on the cell temperature and equivalence ratio. The chemistry solver is invoked only on each zone. The zonal temperature and mass fractions are remapped onto the CFD cells, such that the temperature and composition non-uniformities are preserved. Two remapping techniques published in the literature are compared for their relative performance. The accuracy and speed-up of the multi-zone model is improved by using variable bin sizes at different temperature and equivalence ratios.

In an effort of providing better understanding of regeneration mechanisms of diesel particulate matter (PM), this experimental investigation focused on evaluating the amount of heat release generated during the thermal reaction of diesel PM and the concentrations of soluble organic compounds (SOCs) dissolved in PM emissions. Differences in oxidation behaviors were observed for two different diesel PM samples: a SOC-containing PM sample and a dry soot sample with no SOCs. Both samples were collected from a cordierite particulate filter membrane in a thermal reactor connected to the exhaust pipe of a light-duty diesel engine. A differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA) were used to measure the amount of heat release during oxidation, along with subsequent oxidation rates and the concentrations of SOCs dissolved in particulate samples, respectively.

A supercritical organic Rankine cycle (ORC) system for recovery of waste heat from heavy-duty diesel engines is proposed. In this system, an organic, medium-boiling-point fluid is selected as the working fluid, which also serves as the coolant for the charge air cooler and the EGR coolers. Because the exhaust temperature can be as high as 650 °C during the DPF regeneration, an exhaust cooler is included in the system to recover some of the high level exhaust energy. In the present ORC system, the expansion work is conducted by a uniflow reciprocating expander, which simplifies the waste-heat-recovery (WHR) system significantly. This reciprocating Rankine engine is more appropriate for on-road-vehicle applications where the condition for waste heat is variable. The energy level of waste heat from a heavy-duty diesel engine is evaluated by the analyses of the first and second law of thermodynamics.

For several years there has been a great deal of effort made in researching ways to run a compression ignition engine with simultaneously high efficiency and low emissions. Recently much of this focus has been dedicated to using gasoline-like fuels that are more volatile and less reactive than conventional diesel fuel to allow the combustion to be more premixed. One of the key challenges to using fuels with such properties in a compression ignition engine is stable engine operation at low loads. This paper provides an analysis of how stable gasoline compression ignition (GCI) engine operation was achieved down to idle speed and load on a multi-cylinder compression ignition engine using only 87 anti-knock index (AKI) gasoline. The variables explored to extend stable engine operation to idle included: uncooled exhaust gas recirculation (EGR), injection timing, injection pressure, and injector nozzle geometry.

The objective of this work is to develop a strategy to reduce the penalties in the diesel engine performance, fuel economy and HC and CO emissions, associated with the operation in the low temperature combustion regime. Experiments were conducted on a research high speed, single cylinder, 4-valve, small-bore direct injection diesel engine equipped with a common rail injection system under simulated turbocharged conditions, at IMEP = 3 bar and engine speed = 1500 rpm. EGR rates were varied over a wide range to cover engine operation from the conventional to the LTC regime, up to the misfiring point. The injection pressure was varied from 600 bar to 1200 bar. Injection timing was adjusted to cover three different LPPCs (Location of the Peak rate of heat release due to the Premixed Combustion fraction) at 10.5° aTDC, 5 aTDC and 2 aTDC. The swirl ratio was varied from 1.44 to 7.12. Four steps are taken to move from LTC to ALTC.

The standard model for predicting the outcome of drop-drop collisions in sprays is one developed based on measurements in rain drops under atmospheric pressure conditions. This model includes the possible outcomes of grazing collisions and coalescence. Recent measurements with hydrocarbon drops and at higher pressure (up to 12 bar) indicate the possibility of additional outcomes: bounce, reflexive separation and drop shattering. The measurements also indicate that the Weber number range over which bounce occurs is dependent on the gas pressure. The probability of a drop-drop collision resulting in bounce increases with gas pressure. A composite model that includes all these outcomes as possibilities is employed to carry out computations in a constant volume chamber and in a Diesel engine. A sub-model for bounce that includes the pressure effects is also part of the composite model.

Simultaneous measurements of the radial and the tangential components of velocity are obtained in a high-speed, direct-injection diesel engine typical of automotive applications. Results are presented for engine operation with fuel injection, but without combustion, for three different swirl ratios and four injection pressures. With the mean and fluctuating velocities, the r-θ plane shear stress and the mean flow gradients are obtained. Longitudinal and transverse length scales are also estimated via Taylor's hypothesis. The flow is shown to be sufficiently homogeneous and stationary to obtain meaningful length scale estimates. Concurrently, the flow and injection processes are simulated with KIVA-3V employing a RNG k-ε turbulence model. The measured turbulent kinetic energy k, r-θ plane mean strain rates ( 〈Srθ〉, 〈Srr〉, and 〈Sθθ〉 ), deviatoric turbulent stresses , and the r-θ plane turbulence production terms are compared directly to the simulated results.

The particulate matter (PM) produced from a diesel engine-simulating combustor was characterized in its morphology, microstructure, and fractal geometry by using a unique thermophoretic sampling and Transmission Electron Microscopy (TEM) system. These results revealed that diesel PM produced from the laboratory-scale burner showed similar morphological characteristics to the particulates produced from diesel engines. The flame air/fuel ratio and the particulate temperature history have significant influences on both particle size and fractal geometry. The primary particle sizes were measured to be 14.7 nm and 14.8 nm under stoichiometric and fuel-rich flame conditions, respectively. These primary particle sizes are smaller than those produced from diesel engines. The radii of gyration for the aggregate particles were 83.8 nm and 47.5 nm under these two flame conditions.

This research work has focused on measuring the effect of fuel/air mixing on performance and emissions for a homogeneous charge compression ignition engine running on propane. A laser instrument with a high-velocity extractive probe was used to obtain time-resolved measurements of the fuel concentration both at the intake manifold and from the cylinder for different levels of fuel-air mixing. Cylinder pressure and emissions measurements have been performed at these mixing levels. From the cylinder pressure measurements, the IMEP and peak cylinder pressure were found. The fuel-air mixing level was changed by adding the fuel into the intake system at different distances from the intake valve (40 cm and 120 cm away). It was found that at the intake manifold, the fuel and air were better mixed for the 120 cm fuel addition location than for the 40 cm location.

Cavitation induced cylinder liner erosion can be a significant durability problem in high power density diesel engines. It is typically discovered in the field, thus causing costly redesigns. The application of a predictive simulation to analyze the liner cavitation process upfront could identify the problem early on and enable significant savings. Hence, this work investigates the ability of the computational fluid dynamics (CFD) multiphase flow simulation tool to handle vibration induced cavitation. A flow of liquid through a U-shaped duct is analyzed, where a middle segment of the duct is set to vibrate in a manner resembling vibration of the cooling jacket walls in an internal combustion engine. Velocity, pressure and vapor concentration fields are tracked for two cases, distinguished by different frequencies of duct wall vibration.

The current paper describes a methodology for combustion bowl assessment for diesel engines. The methodology is based on the application of Computational Fluid Dynamics (CFD) following a Design of Experiments (DoE) procedure. In this work the 3D CFD simulation was performed by the commercial CFD code AVL-FIRE for different combustion bowls from intake valve closing (IVC) to exhaust valve opening (EVO). The initial conditions (at IVC) and boundary conditions were obtained from 1D simulation. Since the work was concentrated on the spray injection, mixing, combustion as well as bowl aerodynamics only a sector mesh was employed for the calculations. A DoE procedure was also used for this simulation work in order to minimize the number of simulation runs and at the same time maintaining the accuracy required assessing the influences of different bowl geometry, spray and intake air motion parameters.

Cold starting problems of diesel engines are caused mainly by the failure of the auto-ignition process or the subsequent combustion of the rest of the charge. The problems include long cranking periods and combustion instability leading to an increase in fuel consumption in addition to the emission of undesirable unburned hydrocarbons which appear in the exhaust as white smoke. The major cause of these problems is the low temperature and pressure of the charge near the end of the compression stroke and/or the poor ignition quality of the fuel. This paper presents the results of an experimental investigation of cold starting of a high speed diesel engine with ULSD (Ultra Low Sulphur Diesel) and JP8 (Jet Propulsion) fuels at ambient temperature (25°C). A detailed analysis is made of the autoignition and combustion of the two fuels in the first few cycles in the cold start transient. In addition, a comparison is made between these processes for the two fuels during idle operation.

A computational fluid dynamics (CFD) guided combustion system optimization was conducted for a heavy-duty diesel engine running with a gasoline fuel that has a research octane number (RON) of 80. The goal was to optimize the gasoline compression ignition (GCI) combustion recipe (piston bowl geometry, injector spray pattern, in-cylinder swirl motion, and thermal boundary conditions) for improved fuel efficiency while maintaining engine-out NOx within a 1-1.5 g/kW-hr window. The numerical model was developed using the multi-dimensional CFD software CONVERGE. A two-stage design of experiments (DoE) approach was employed with the first stage focusing on the piston bowl shape optimization and the second addressing refinement of the combustion recipe. For optimizing the piston bowl geometry, a software tool, CAESES, was utilized to automatically perturb key bowl design parameters. This led to the generation of 256 combustion chamber designs evaluated at several engine operating conditions.

A computational fluid dynamics (CFD) guided combustion system optimization was conducted for a heavy-duty compression-ignition engine with a gasoline-like fuel that has an anti-knock index (AKI) of 58. The primary goal was to design an optimized combustion system utilizing the high volatility and low sooting tendency of the fuel for improved fuel efficiency with minimal hardware modifications to the engine. The CFD model predictions were first validated against experimental results generated using the stock engine hardware. A comprehensive design of experiments (DoE) study was performed at different operating conditions on a world-leading supercomputer, MIRA at Argonne National Laboratory, to accelerate the development of an optimized fuel-efficiency focused design while maintaining the engine-out NOx and soot emissions levels of the baseline production engine.

Experiments were conducted to investigate the characteristics of a common rail fuel injection system using a flow rate test rig and a single cylinder research diesel engine. Experiments covered speeds and loads typical to engine conditions under Hybrid Electric Vehicle operation. Different injection modes were investigated including main injection, main-post injection and pilot-main injection. The analysis indicated that the common rail fuel pressure affects all the injection parameters including the start of fuel delivery, its duration and amount under all modes of injection. Also, the pressure waves produced in the system have an impact on the operation of the nozzle-needle and fuel delivery particularly in the main-post injection mode.