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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.

This paper evaluates how the fuel consumption of the average new U.S. passenger car will be penalized if engine and vehicle improvements continue to be focused on developing bigger, heavier and more powerful automobiles. We quantify a parameter called the Emphasis on Reducing Fuel Consumption (ERFC) and find that there has been little focus on improving fuel consumption in the U.S. over the past twenty years. In contrast, Europe has seen significantly higher ERFC. By raising the ERFC over the next few decades, we can reduce the average U.S. new car's fuel consumption by up to some 40 percent and cut the light-duty vehicle fleet's fuel use by about a quarter. Achieving substantial fuel use reduction will remain a major challenge if automobile size, weight and power continue to dominate.

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.

Two aspects of the dispersion of pollutants from aircraft are reviewed. The first is the dispersal of aircraft exhaust emissions in the vicinity of airports; the second is the dispersal of exhaust trails in the upper atmosphere. Techniques available for modeling this dispersal and how they might be applied to the airport problem are discussed. Field studies of airport pollution are then reviewed to assess current pollutant levels around airports and the aircraft's contribution to those levels. The possibility of contrail formation from jet emissions at high altitude is then considered and the effect of uncertainties in the trail mixing processes evaluated.

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.

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.

Experiments were carried out to collect in-cylinder pressure data and microphone signals from a single-cylinder test engine using spark timingsbefore, at, and after knock onset for toluene reference fuels. The objective was to gain insight into the phenomena that determine knock onset, detected by an external microphone. In particular, the study examines how the end-gas autoignition process changes as the engine's spark timing is advanced through the borderline knock limit into the engine's knocking regime. Fast Fourier transforms (FFT) and bandpass filtering techniques were used to process the recorded cylinder pressure data to determine knock intensities for each cycle. Two characteristic pressure oscillation frequencies were detected: a peak just above 6 kHz and a range of peaks in the 15-22 kHz range. The microphone data shows that the audible knock signal has the same 6 kHz peak.

This study examines the scaling between engine performance, engine configuration, and engine size and geometry, for modern spark-ignition engines. It focuses especially on design features that impact engine breathing. We also analyze historical trends to illustrate how changes in technology have improved engine performance. Different geometric parameters such as cylinder displacement, piston area, number of cylinders, number of valves per cylinder, bore to stroke ratio, and compression ratio, in appropriate combinations, are correlated to engine performance parameters, namely maximum torque, power and brake mean effective pressure, to determine the relationships or scaling laws that best fit the data. Engine specifications from 1999 model year vehicles sold in the United States were compiled into a database and separated into two-, three-, and four-valves-per-cylinder engine categories.

The fate of hydrocarbon species in the exhaust systems of spark-ignition engines is an important part of the overall hydrocarbon emissions problem. In this investigation models were developed for the instantaneous heat transfer, fluid mixing, and hydrocarbon oxidation in an engine exhaust port. Experimental measurements were obtained for the instantaneous cylinder pressure and instantaneous gas temperature at the exhaust port exit for a range of engine operating conditions. These measurements were used to validate the heat transfer model and to provide data on the instantaneous cylinder gas state for a series of illustrative exhaust port hydrocarbon oxidation computations as a function of engine operating and design variables. During much of the exhaust process, the exhaust port heat transfer was dominated by large-scale fluid motion generated by the jet-like flow at the exhaust valve.

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.

The in-cylinder hydrocarbon (HC) mole fraction was measured on a cycle-resolved basis during simulated starting and warm-up of a port-injected single-cylinder SI research engine on a dynamometer. The measurements were made with a fast-response flame ionization detector with a heated sample line. The primary parameters that influence how rapidly a combustible mixture builds up in the cylinder are the inlet pressure and the amount of fuel injected; engine speed and fuel injection schedule have smaller effects. When a significant amount of liquid fuel is present at the intake port in the starting process, the first substantial firing cycle is often preceded by a cycle with abnormally high in-cylinder HC and low compression pressure. An energy balance analysis suggests that a large amount of liquid vaporization occurs within the cylinder in this cycle.

The liquid fuel entry into the cylinder and its subsequent behavior through the combustion cycle were observed by a high speed CCD camera in a transparent engine. The videos were taken with the engine firing under cold conditions in a simulated start-up process, at 1,000 RPM and intake manifold pressure of 0.5 bar. The variables examined were the injector geometry, injector type (normal and air-assisted), injection timing (open- and closed-valve injection), and injected air-to-fuel ratios. The visualization results show several important and unexpected features of the in-cylinder fuel behavior: 1) strip-atomization of the fuel film by the intake flow; 2) squeezing of fuel film between the intake valve and valve seat at valve closing to form large droplets; 3)deposition of liquid fuel as films distributed on the intake valve and head region. Some of the liquid fuel survives combustion into the next cycle.

The occurrence of liquid fuel in the cylinder of automotive internal combustion engines is believed to be an important source of exhaust hydrocarbon (HC) emissions, especially during the warm-up process following an engine start up. In this study a Phase Doppler Particle Analyzer (PDPA) has been used in a transparent flow visualization combustion engine in order to investigate the phenomena which govern the transport of liquid fuel into the cylinder during a simulated engine start up process. Using indolene fuel, the engine was started up from room temperature and run for 90 sec on each start up simulation. The size and velocity of the liquid fuel droplets entering the cylinder were measured as a function of time and crank angle position during these start up processes. The square-piston transparent engine used gave full optical access to the cylinder head region, so that these droplet characteristics could be measured in the immediate vicinity of the intake valve.

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 residual gas fraction prior to ignition at the vicinity of the spark plug in a single cylinder, two-valve spark ignition engine was measured with a fast-response flame ionization hydrocarbon detector. The technique in using such an instrument is reported. The measurements were made as a function of the intake manifold pressure, engine speed and intake/exhaust valve-overlap duration. Both the mean level of the residual fraction and the statistics of the cycle-to-cycle variations were obtained.

An experimental study was performed to determine the fraction of unburned hydrocarbon emissions which are oxidized in the exhaust port of a spark ignition engine. The technique used was injection of a CO2 quench gas into the exhaust port, at various planes along the port centerline, to cool the exhaust gas and “freeze” the hydrocarbon oxidation reactions. By quenching the reaction of hydrocarbons at the cylinder exit plane, cylinder exit hydrocarbon emissions levels were determined. By differencing the concentration of hydrocarbons observed during quenching and nonquenching operation, the fraction of hydrocarbons reacting in each section of the exhaust was determined. Experiments were carried out to define the effects of engine operating conditions on the fraction of hydrocarbons oxidized. The variables studied were fuel-air equivalence ratio, speed, load, spark advance and compression ratio.

A conventional spark plug and a spark plug with smaller electrodes were studied in M.I.T.'s transparent square piston engine. The purpose was to learn more about how the electrode geometry affects the heat losses to the electrodes and the electrical performance of the ignition system, and how this affects the flame development process in an engine. A schlieren system which provides two orthogonal views of the developing flame was used to define the initial flame growth process, for as many as 100 consecutive cycles. Voltage and current waveforms were recorded to characterize the spark discharge, and cylinder pressure data were used to characterize the engine performance. The spark plug with the smaller electrodes was shown to reduce the heat losses to the electrodes, and thereby extend the stable operating regime of the engine. At conditions close to the stable operating limit, cycle-by-cycle variations in heat losses cause significant cyclic variations in flame development.

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.

The transportation sector in the United States is a major contributor to global energy consumption and carbon dioxide emission. To assess the future potentials of different technologies in addressing these two issues, we used a family of simulation programs to predict fuel consumption for passenger cars in 2020. The selected technology combinations that have good market potential and could be in mass production include: advanced gasoline and diesel internal combustion engine vehicles with automatically-shifting clutched transmissions, gasoline, diesel, and compressed natural gas hybrid electric vehicles with continuously variable transmissions, direct hydrogen, gasoline and methanol reformer fuel cell hybrid electric vehicles with direct ratio drive, and battery electric vehicle with direct ratio drive.