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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.

In order to understand better the operation of spark-ignition engines during the warm-up period, a computer model had been developed which simulates the thermal processes of the engine. This model is based on lumped thermal capacitance methods for the major engine components, as well as the exhaust system. Coolant and oil flows, and their respective heat transfer rates are modeled, as well as friction heat generation relations. Piston-liner heat transfer is calculated based on a thermal resistance method, which includes the effects of piston and ring material and design, oil film thickness, and piston-liner crevice. Piston/liner crevice changes are calculated based on thermal expansion rates and are used in conjunction with a crevice-region unburned hydrocarbon model to predict the contribution to emissions from this source.

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.

A thermodynamic based cycle simulation which uses a thermal boundary layer, either, a fully mixed or layered adiabatic core, and a crevice combustion inefficiency routine has been used to explore the sensitivity of NO concentration predictions to critical physical modeling assumptions. An experimental database, which included measurements of residual gas fraction, was obtained from a 2.0 liter Nissan engine while firing on propane. A model calibration methodology was developed to ensure accurate predictions of in-cylinder pressure and burned gas temperature. Comparisons with experimental NO data then showed that accounting for temperature stratification during combustion with a layered adiabatic core and including a crevice/combustion inefficiency routine, improved the match of modeling predictions to data, in comparison to a fully mixed adiabatic core.

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.

Higher compression ratio and turbocharging, with engine downsizing can enable significant gains in fuel economy but require engine operating conditions that cause engine knock under high load. Engine knock can be avoided by supplying higher-octane fuel under such high load conditions. This study builds on previous MIT papers investigating Octane-On-Demand (OOD) to enable a higher efficiency, higher-boost higher compression-ratio engine. The high-octane fuel for OOD can be obtained through On-Board-Separation (OBS) of alcohol blended gasoline. Fuel from the primary fuel tank filled with commercially available gasoline that contains 10% by volume ethanol (E10) is separated by an organic membrane pervaporation process that produces a 30 to 90% ethanol fuel blend for use when high octane is needed. In addition to previous work, this paper combines modeling of the OBS system with passenger car and medium-duty truck fuel consumption and octane requirements for various driving cycles.

This paper explores the modeling of a lean boosted engine concept. Modeling provides a useful tool for investigating different parameters and comparing resultant emissions and fuel economy performance. An existing architectural concept has been tailored to a boosted hydrogen-enhanced lean-burn SI engine. The simulation consists of a set of Matlab models, part physical and part empirical, which has been developed to simulate a working engine. The model was calibrated with production engine data and experimental data taken at MIT. Combustion and emissions data come from a single cylinder research engine and include changes in air/fuel ratio, load and speed, and different fractions of the gasoline fuel reformed to H2 and CO. The outputs of the model are brake specific NOx emissions and brake specific fuel consumption maps along with cumulative NOx emissions and fuel economy for urban and highway drive cycles.

A model has been developed which predicts engine-out hydrocarbon (HC) emissions for spark-ignition engines. The model consists of a set of scaling laws that describe the individual processes that contribute to HC emissions. The model inputs are the critical engine design and operating variables. This set of individual process scaling relations was then calibrated using production spark-ignition engine data at a fixed light-load operating point. The data base consisted of engine-out HC emissions from two-valve and four-valve engine designs with variations in spark timing, valve timing, coolant temperature, crevice volume, and EGR, for five different engines. The model was calibrated separately for the three different engines to accommodate differences in engine design details and to determine the relative magnitudes of each of the major sources. A good fit to this database was obtained.

A computational fluid dynamics (CFD) prediction of the transient flow in the intake system of a spark ignition engine is compared to experimental data. The calculation was performed for a single cylinder version of a pre-1995 Ford two-valve production engine, while experiments were carried out on a single cylinder Ricardo Mark 3 research engine with similar overall geometric parameters. While the two engines have somewhat different geometries, this was not considered to be a significant problem for our study of flow features. Both set-ups employed gaseous fuel. The calculation was performed using the commercially available Star-CD code incorporating the complete intake manifold runner and cylinder into the mesh. Cylinder pressures were in good agreement with experiment indicating that wave dynamics were well captured. Comparison was also made to the measured instantaneous gas temperatures along the intake system.

This paper describes the use of a modified quasi-dimensional spark-ignition engine simulation code to predict the extent of cycle-to-cycle variations in combustion. The modifications primarily relate to the combustion model and include the following: 1. A flame kernel model was developed and implemented to avoid choosing the initial flame size and temperature arbitrarily. 2. Instead of the usual assumption of the flame being spherical, ellipsoidal flame shapes are permitted in the model when the gas velocity in the vicinity of the spark plug during kernel development is high. Changes in flame shape influence the flame front area and the interaction of the enflamed volume with the combustion chamber walls. 3. The flame center shifts due to convection by the gas flow in the cylinder. This influences the flame front area through the interaction between the enflamed volume and the combustion chamber walls. 4. Turbulence intensity is not uniform in cylinder, and varies cycle-to-cycle.

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 computer simulation of the four-stroke spark-ignition engine cycle has been used to examine the effects of turbocharging and reduced heat transfer on engine performance, efficiency and NOx emissions. The simulation computes the flows into and out of the engine, calculates the changes in thermodynamic properties and composition of the unburned and burned gas mixtures within the cylinder through the engine cycle due to work, heat and mass transfers, and follows the kinetics of NO formation and decomposition in the burned gas. The combustion process is specified as an input to the program through use of a normalized rate of mass burning profile. From this information, the simulation computes engine power, fuel consumption and NOx emissions. Wide-open-trottle predictions made with the simulation were compared with experimental data from a 5.7ℓ naturally-aspirated and a 3.8ℓ turbocharged production engine.

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 this study, a set of performance and emissions data, obtained from a single-cylinder divided-chamber automotive diesel engine over the normal engine operating range, is described and analyzed. The data are used to evaluate a computer simulation of the engine's operating cycle, described in a companion paper, which predicts the properties of gases inside the engine cylinder throughout the cycle, and engine efficiency, power and NOx emissions. Satisfactory agreement between predictions and measurements is obtained over most of the engine's operating range. The characteristics of the experimental pre- and main-chamber pressure versus crank angle data are then examined in detail. A heat release analysis appropriate for divided-chamber diesel engines is developed and used to obtain heat release rate profiles through the combustion process.