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A prior study (Chon and Heywood, [1]) examined how the design and performance of spark-ignition engines evolved in the United States during the 1980s and 1990s. This paper carries out a similar analysis of trends in basic engine design and performance characteristics over the past decade. Available databases on engine specifications in the U.S., Europe, and Japan were used as the sources of information. Parameters analyzed were maximum torque, power, and speed; number of cylinders and engine configuration, cylinder displacement, bore, stroke, compression ratio; valvetrain configuration, number of valves and their control; port or direct fuel injection; naturally-aspirated or turbocharged engine concepts; spark-ignition and diesel engines. Design features are correlated with these engine’s performance parameters, normalized by engine and cylinder displacement.

The flow and heat transfer phenomena in the intake port of a spark ignition engine with port fuel injection play a significant role in the mixture preparation process, especially at part load. The backflow of the hot burned gas from the cylinder into the intake port when the intake valve is opened breaks up any liquid film around the inlet valve, influences gas and wall temperatures, and has a major effect on the fuel vaporization process. The backflow of in-cylinder mixture with its residual component during the compression stroke prior to inlet valve closing fills part of the port with gas at higher than fresh mixture temperature. To quantify these phenomena, time-resolved measurements of the hydrocarbon concentration profile along the center-line of the intake port were made with a fast-response flame ionization detector, and of the gas temperature with a fine wire resistance thermometer, in a single-cylinder engine running with premixed propane/air mixture.

Spark Ignited Direct Injection (SI DI) of fuel extends engine knock limits compared to Port Fuel Injection (PFI) by utilizing the large in-cylinder charge cooling effect due to fuel evaporation. The use of gasoline/ethanol blends in direct injection (DI) is therefore especially advantageous due to the high heat of vaporization of ethanol. In addition to the thermal benefit due to charge cooling, ethanol blends also display superior chemical resistance to autoignition, therefore allowing the further extension of knock limits. Unlike the charge cooling benefit which is realized mostly in SI DI engines, the chemical benefit of ethanol blends exists in Port Fuel Injected (PFI) engines as well. The aim of this study is to separate and quantify the effect of fuel chemistry and charge cooling on knock. Using a turbocharged SI engine with both PFI and DI, knock limits were measured for both injection types and five gasoline-ethanol blends.

The effects of injection variability, low velocity fuel injection, and injector orifice size on unburned hydrocarbon emissions were studied in a direct-injection stratified-charge (DISC) engine. The engine incorporated a combustion process similar to the Texaco Controlled Combustion System (TCCS) and was operated with gasoline. The variability in the amount of fuel injected per cycle was found to have a negligible effect on HC emissions. Changing the amount of fuel injected at low velocity at the end of injection impacted the HC emissions by up to 50%. A positive pressure differential between the injection line and the combustion chamber when the injector needle closed resulted in more fuel injected at low velocity and increased HC emissions. High speed single frame photography was used to observe the end of injection. Injectors with smaller orifices had substantially lower HC emissions than the baseline injector.

Liquid fuel flow into the cylinder an important source of hydrocarbon (HC) emissions of an SI engine. This is an especially important HC source during engine warm up. This paper examines the phenomena that determine the inflow of liquid fuel through the intake valve during a simulated start-up procedure. A Phase Doppler Particle Analyzer (PDPA) was used to measure the size and velocity of liquid fuel droplets in the vicinity of the intake valve in a firing transparent flow-visualization engine. These characteristics were measured as a function of engine running time and crank angle position during four stroke cycle. Droplet characteristics were measured at 7 angular positions in 5 planes around the circumference of the intake valve for both open and closed-valve injection. Additionally the cone shaped geometry of the entering liquid fuel spray was visualized using a Planar Laser Induced Fluorescence (PLIF) setup on the same engine.

The oil control ring is the most critical component for oil consumption and friction from the piston system in internal combustion engines. Three-piece oil control rings are widely used in Spark Ignition (SI) engines. However, the dynamics and lubrication of three piece oil control rings have not been thoroughly studied from the theoretical point of view. In this work, a model was developed to predict side sealing, bore sealing, friction, and asperity contact between rails and groove as well as between rails and the liner in a Three Piece Oil Control Ring (TPOCR). The model couples the axial and twist dynamics of the two rails of TPOCR and the lubrication between two rails and the cylinder bore. Detailed rail/groove and rail/liner interactions were considered. The pressure distribution from oil squeezing and asperity contact between the flanks of the rails and the groove were both considered for rail/groove interaction.

Experiments were performed to identify the knock trends of lean hydrocarbon-air mixtures, and such mixtures enhanced with hydrogen (H2) and carbon monoxide (CO). These enhanced mixtures simulated 15% and 30% of the engine's gasoline being reformed in a plasmatron fuel reformer [1]. Knock trends were determined by measuring the octane number (ON) of the primary reference fuel (mixture of isooctane and n-heptane) supplied to the engine that just produced audible knock. Experimental results show that leaner operation does not decrease the knock tendency of an engine under conditions where a fixed output torque is maintained; rather it slightly increases the octane requirement. The knock tendency does decrease with lean operation when the intake pressure is held constant, but engine torque is then reduced.

A gasoline direct injection fuel spray was observed using a fired, optical access, square cross-section single cylinder research engine and high-speed video imaging. Spray interaction with the piston is described qualitatively, and the results are compared with Computational Fluid Dynamics (CFD) simulation results using KIVA-3V version 2. CFD simulations predicted that within the operating window for stratified charge operation, between 1% and 4% of the injected fuel would remain on the piston as a liquid film, dependent primarily on piston temperature. The experimental results support the CFD simulations qualitatively, but the amount of fuel film remaining on the piston appears to be under-predicted. High-speed video footage shows a vigorous spray impingement on the piston crown, resulting in vapor production.

An experimental study was performed to investigate the effects of various intake charge motion control valves (CMCVs) on mixture preparation, combustion, and hydrocarbon (HC) emissions during the cold start-up process of a port fuel injected spark ignition (SI) engine. Different charge motions were produced by three differently shaped plates in the CMCV device, each of which blocked off 75% of the engine's intake ports. Time-resolved HC, CO and CO2 concentrations were measured at the exhaust port exit in order to achieve cycle-by-cycle engine-out HC mass and in-cylinder air/fuel ratio. Combustion characteristics were examined through a thermodynamic burn rate analysis. Cold-fluid steady state experiments were carried out with the CMCV open and closed. Enhanced charge motion with the CMCV closed was found to shorten the combustion duration, which caused the location of 50% mass fraction burned (MFB) to occur up to 5° CA earlier for the same spark timing.

Gasoline/ethanol fuel blends have significant synergies with Spark Ignited Direct Injected (SI DI) engines. The higher latent heat of vaporization of ethanol increases charge cooling due to fuel evaporation and thus improves knock onset limits and efficiency. Realizing these benefits, however, can be challenging due to the finite time available for fuel evaporation and mixing. A methodology was developed to quantify how much in-cylinder charge cooling takes place in an engine for different gasoline/ethanol blends. Using a turbocharged SI engine with both Port Fuel Injection (PFI) and Direct Injection (DI), knock onset limits were measured for different intake air temperatures for both types of injection and five gasoline/ethanol blends. The superior charge cooling in DI compared to PFI for the same fuel resulted in pushing knock onset limits to higher in-cylinder maximum pressures. Knock onset is used as a diagnostic of charge cooling.

A single-zone burn-rate analysis based on measured cylinder pressure data proposed by Gatowski et al. in 1984 was evaluated over the full load and speed range of a spark-ignition engine. The analysis, which determines the fuel mass burning rate based on the First Law of Thermodynamics, includes sub-models for the effects of residual fraction, heat transfer, and crevices. Each of these sub-models was assessed and calibrated. Cylinder pressure data over the full engine operating range obtained from two different engines were used to examine the robustness of the analysis. The sensitivity of predictions to the parameters wall temperature, heat transfer model coefficients and exponent, swirl ratio, motoring polytropic constant, in-cylinder mass, and to uncertainty in pressure data was evaluated.

An improved theoretical model that predicts the nitric oxide concentration in the exhaust of a spark-ignition engine has been evaluated over a wide range of fuel-air ratios, percentage of exhaust gas recycled, and engine speed. Experiments were carried out in a standard CFR single-cylinder engine. Comparison of the measured and calculated exhaust nitric oxide concentrations shows good agreement over all operating conditions. It is shown that in lean mixtures, nitric oxide concentrations freeze early in the expansion stroke. For rich mixtures, freezing occurs later after all the charge has been burned and substantial nitric oxide decomposition takes place. In addition, effects of exhaust gas recirculation on flame speed, ignition delay, and cycle-to-cycle pressure variations were evaluated. A simple model relating cycle-to-cycle variations with changes in ignition delay is presented.

Photographic and performance studies with a Rapid Compression Machine at the Massachusetts Institute of Technology have been used to develop insight into the role of mixing in diesel engine combustion. Combustion photographs and performance data were analyzed. The experiments simulate a single fuel spray in an open chamber diesel engine with direct injection. The effects of droplet formation and evaporation on mixing are examined. It is concluded that mixing is controlled by the rate of entrainment of air by the fuel spray rather than the dynamics of single droplets. Experimental data on the geometry of a jet in a quiescent combustion chamber were compared with a two-phase jet model; a jet model based on empirical turbulent entrainment coefficients was developed to predict the motion of a fuel jet in a combustion chamber with swirl. Good agreement between theory and experiment was obtained.

A performance model of a Wankel engine is developed which performs a leakage mass balance, accounts for heat transfer and flame quenching, and predicts the mass fraction burned as a function of chamber pressure. Experiments were performed on a production Wankel engine to obtain chamber pressure-time diagrams, and engine performance and emissions data. Model predictions of mass burned, global heat transfer, and hydrocarbon emission gave good agreement with measurements. Predictions of oxides of nitrogen are higher than measurements, especially at low loads. This is thought to be due to the adiabatic core gas assumption in the model. The need for a Wankel boundary layer study is identified.

This paper describes the results of experimental and computer simulation studies of the combustion process in the prechamber three-valve stratified-charge engine. Prechamber and main-chamber pressure data and matched computer simulation calculations are used to determine the effects of variations in overall air/fuel ratio, engine speed and load, and prechamber volume and orifice diameter on the parameters which define the combustion process (spark advance for optimum torque, ignition delay, combustion duration), on cylinder pressure diagrams (mean main-chamber pressure, mean pressure difference across the orifice, and cycle-by-cycle pressure fluctuations) and on exhaust emissions. General correlations are derived from the data for the shape of the combustion rate profile and the extent of the combustion duration.

In analyzing the processes inside the cylinder of an internal combustion engine, the principal diagnostic at the experimenter's disposal is a measured time history of the cylinder pressure. This paper develops, tests, and applies a heat release analysis procedure that maintains simplicity while including the effects of heat transfer, crevice flows and fuel injection. The heat release model uses a one zone description of the cylinder contents with thermodynamic properties represented by a linear approximation for γ(T). Applications of the analysis to a single-cylinder spark-ignition engine, a special square cross-section visualization spark-ignition engine, and a direct-injection stratified charge engine are presented.

High levels of hydrocarbon emissions during light load operation keep the direct injection stratified charge engine from commercial application. Previous analytical work has identified several possible hydrocarbon emissions mechanisms which can result from poor in-cylinder fuel distribution. Poor fuel distribution can be caused by erratic fuel injection. Experiments conducted on a single cylinder DISC engine show a dramatic increase in the cycle to cycle variation in injection characteristics as engine load decreases. This is accompanied by an increase in cycle to cycle variation in combustion behavior suggesting that degradation in combustion results from the degradation in the quality of the injection event. Examination of combustion and injection characteristics on a cycle by cycle basis shows that, at light load, IMEP and heat release do not correlate with the amount of fuel injected into the cylinder.

The effects of two commonly used methods for altering the combustion process in a spark-ignition engine are examined using pressure measurements and high-speed schlieren photography. A square cross-section visualization engine with two quartz sidewalls was used to allow optical access over the entire four-stroke operating cycle. Engine operation with a shrouded intake valve, which changed the intake-generated flow, and with a stepped piston, which changed the compression-generated flow, are compared to a base condition. In addition, cyclic variations in burning are examined for all cases.

The influence of charge motion and fuel injection characteristics on diesel combustion was studied in a rapid compression machine (RCM), a research apparatus that simulates the direct-injection diesel in-cylinder environment. An experimental data base was generated in which inlet air flow conditions (temperature, velocity, swirl level) and fuel injection pressure were independently varied. High-speed movies using both direct and shadowgraph photography were taken at selected operating conditions. Cylinder pressure data were analyzed using a one-zone heat release model to calculate ignition delay times, premixed and diffusion burning rates, and cumulative heat release profiles. The photographic analysis provided data on the liquid and vapor penetration rates, fuel-air mixing, ignition characteristics, and flame spreading rates.

This paper describes two types of computer models which have been developed to analyze the performance of both premixed-charge and direct-injection stratified-charge Wankel engines. The models are based on a thermodynamic analysis of the contents of the engine's chambers. In the first type of model, the rate of combustion is predicted from measured chamber pressure by use of a heat release analysis. The analysis includes heat transfer to the chamber walls, work transfer to the rotor, enthalpy loss due to flows into crevices and due to leakage flows into adjacent chambers, and enthalpy gain due to fuel injection. The second type of computer model may be used to predict the chamber pressure during a complete engine cycle. From the predicted chamber pressure, the overall engine performance parameters are calculated. The rate of fuel burning as an algebraic function of crank angle is specified.