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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.

Experimental measurements of the instantaneous exhaust gas temperature, mass flowrate, and hydrocarbon concentration have been made in the exhaust of a single cylinder research engine. The temperature measurements were accomplished using an infrared optical technique and observing the radiation of the exhaust gas at the 4.4 μm band of CO2. Instantaneous exhaust gas mass flowrates were monitored by placing a restriction in the exhaust manifold and measuring the instantaneous pressures across the restriction. Time-resolved hydrocarbon concentrations were measured using a fast-acting sampling valve with an open time of 2 ms. From these measurements, the hydrocarbon mass flowrate is calculated as a function of crank angle.

In the jet-ignition prechamber stratified-charge spark-ignition engine, the fuel-air mixture at the time of combustion is non-uniform. Instantaneous exhaust mass flow rates and emission concentrations from this engine were measured and used to determine the degree to which this charge stratification persists in the products of combustion immediately downstream of the exhaust valve throughout the exhaust process. In all the cases studied no appreciable variations, during the exhaust process, were detected either in the air-fuel ratio of the exhaust gases as a function of time or in the instantaneous concentrations of CO2, O2 and NOx. The experimentally obtained instantaneous HC and CO concentrations in the exhaust, however, displayed large fluctuations and were used to study the sources of these two pollutants in this engine.

Measurements were made of exhaust histories of the following species: unburned hydrocarbons (HC), carbon monoxide, carbon dioxide, oxygen, and nitric oxide (NO). The measurements show that the exhaust flow can be divided into two distinct phases: a leading gas low in HC and high in NO followed by a trailing gas high in HC and low in NO. Calculations of time resolved equivalence ratio throughout the exhaust process show no evidence of a stratified combustion. The exhaust mass flow rate is time resolved by forcing the flow to be locally quasi-steady at an orifice placed in the exhaust pipe. The results with the quasi-steady assumption are shown to be consistent with the measurements. Predictions are made of time resolved mass flow rate which compare favorably to the experimental data base. The composition and flow histories provide sufficient information to calculate the time resolved flow rates of the individual species measured.

Since the advent of the spark ignition engine, the maximum engine efficiency has been knock limited. Knock is a phenomena caused by the rapid autoignition of fuel/air mixture (endgas) ahead of the flame front. The propensity of a fuel to autoignite corresponds to its autoignition chemistry at the local endgas temperature and pressure. Since a fuel blend consists of many components, its autoignition chemistry is very complex. The octane index (OI) simplifies this complex autoignition chemistry by comparing a fuel to a Primary Reference Fuel (PRF), a binary blend of iso-octane and n-heptane. As more iso-octane is added into the blend, the PRF is less likely to autoignite. The OI of a fuel is defined as the volumetric percentage of iso-octane in the PRF blend that exhibits similar knocking characteristics at the same engine conditions.

A study at MIT of the energy consumption and greenhouse gas emissions from advanced technology future automobiles has compared fuel cell powered vehicles with equivalent gasoline and diesel internal combustion engine (ICE) powered vehicles [1][2]. Current data regarding IC engine and fuel cell vehicle performance were extrapolated to 2020 to provide optimistic but plausible forecasts of how these technologies might compare. The energy consumed by the vehicle and its corresponding CO2 emissions, the fuel production and distribution energy and CO2 emissions, and the vehicle manufacturing process requirements were all evaluated and combined to give a well-to-wheels coupled with a cradle-to-grave assessment. The assessment results show that significant opportunities are available for improving the efficiency of mainstream gasoline and diesel engines and transmissions, and reducing vehicle resistances.

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.

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.

The initial flame kernel behavior in a SI engine was measured by a spark-plug-fiber-optics probe. From these measurements, the flame kernel may be characterized by an expansion speed and a convection velocity. These quantities were correlated with the bum rate on a cycle-to-cycle basis in an engine configurated with quiescent, swirl, and tumble in-cylinder motion. The expansion speed correlates well with the 0-2 percent mass burn duration for all the configurations. The flame convection velocity depends on the in-cylinder motion in the expected manner. There was, however, only a weak correlation between the 10-90 percent burn duration and the initial flame kernel behavior.

To understand the effects of crevices on the engine-out hydrocarbon emissions, a series of engine experiments was carried out with different piston crevice volumes and with simulated head gasket crevices. The engine-out HC level was found to be modestly sensitive to the piston crevice size in both the warmed-up and the cold engines, but more sensitive to the crevice volume in the head gasket region. A substantial decrease in HC in the cold-to-warm-up engine transition was observed and is attributed mostly to the change in port oxidation.

Light-load unburned hydrocarbon emissions were studied experimentally in a spark-ignited direct-injection engine burning gasoline where the piston temperature was varied. The test engine was a single-cylinder Direct Injection Stratified-Charge (DISC) engine incorporating a combustion process similar to the Texaco Controlled Combustion System. At a single low load operating condition, the piston temperature was varied by 50 K by controlling the cooling water and oil temperature. The effect of this change on unburned hydrocarbon emissions and heat release profiles was studied. It was found that by carefully controlling the intake air temperature and pressure to maintain constant in-cylinder conditions at the time of injection, the change in piston temperature did not have a significant effect on the unburned hydrocarbon emissions from the engine.

An experimental study was conducted on a spark-ignited direct-injection engine burning fuels with different evaporation and autoignition characteristics. The test engine was a single-cylinder Direct-Injection Stratified-Charge (DISC) engine incorporating a combustion process similar to the Texaco Controlled Combustion System. Two fuels were tested and compared with a baseline gasoline fuel: diesel fuel, and gasoline mixed with an ignition improver. The tests were done at low to medium engine loads. Diesel fuel was found to have similar levels of hydrocarbon (HC) emissions as gasoline but had different characteristics. The optimum timing for diesel fuel was retarded from that for gasoline and combustion variability was much less with diesel than with gasoline. Gasoline with a commercial ignition improver normally used to increase the cetane number of diesel fuel was also tested. The effect of changing the autoignition quality of the fuel depended on the injector used.

The way In which combustion chamber geometry affects combustion in SI engines was studied using a quasi-diraensional cycle simulation. Calculations were performed to investigate the following questions: (i) the sensitivity of geometric effects on combustion to engine operating conditions; (ii) the differences in burn duration between ten chamber geometries and spark plug locations; and (iii) the relative merits of improved chamber design and amplified turbulence as means to reduce burn duration. The results from these studies are presented and discussed.

As a part of the effort to comply with increasingly stringent emission standards, engine manufacturers strive to minimize engine oil consumption. This requires the advancement of the understanding of the characteristics, sources, and driving mechanisms of oil consumption. This paper presents a combined theoretical and experimental approach to separate and quantify different oil consumption sources in a production spark ignition engine at different speed and load conditions. A sulfur tracer method was used to measure the dependence of oil consumption on engine operating speed and load. Liquid oil distribution on the piston was studied using a Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder parameters for oil transport and oil consumption, such as liner temperatures and land pressures, were measured.

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.

The design and operating characteristics of a single-cylinder transparent spark-ignition engine for Schlieren flow visualization are described. The engine is built on a CFR engine crankcase using the CFR piston and cylinder as a crosshead for the square cross-section piston and cylinder assembly. The square cross-section assembly has two parallel steel walls and two parallel quartz glass walls to permit optical access to the entire cylinder volume over the complete engine operating cycle. The CFR head and valve mechanism completes the assembly. It is shown that the engine operates satisfactorily with propane fuel under typical engine operating conditions. Schlieren short time-exposure photographs and high speed movies were taken to define details of the flow and density fields through the engine cycle. Photographs which illustrate key features of these fields are presented and described.

The prediction of knock onset in spark-ignition engines requires a chemical model for the autoignition of the hydrocarbon fuel-air mixture, and a description of the unburned end-gas thermal state. Previous studies have shown that a reduced chemistry model developed by Keck et al. adequately predicts the initiation of autoignition. However, the combined effects of heat transfer and compression on the state of the end gas have not been thoroughly investigated. The importance of end-gas heat transfer was studied with the objective of improving the ability of our knock model to predict knock onset over a wide range of engine conditions. This was achieved through changing the thermal environment of the end gas by either varying the inlet air temperature or the coolant temperature. Results show that there is significant heating of the in-cylinder charge during intake and a substantial part of the compression process.

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.

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.

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.