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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.

Transport policy research seeks to predict and substantially reduce the future transport-related greenhouse gas emissions and fuel consumption to prevent negative climate change impacts and protect the environment. However, making such predictions is made difficult due to the uncertainties associated with the anticipated developments of the technology and fuel situation in road transportation, which determine the total fuel use and emissions of the future light-duty vehicle fleet. These include uncertainties in the performance of future vehicles, fuels' emissions, availability of alternative fuels, demand, as well as market deployment of new technologies and fuels. This paper develops a methodology that quantifies the impact of uncertainty on the U.S. transport-related fuel use and emissions by introducing a stochastic technology and fleet assessment model that takes detailed technological and demand inputs.

This paper assesses the potential improvement of automotive powertrain technologies 25 years into the future. The powertrain types assessed include naturally-aspirated gasoline engines, turbocharged gasoline engines, diesel engines, gasoline-electric hybrids, and various advanced transmissions. Advancements in aerodynamics, vehicle weight reduction and tire rolling friction are also taken into account. The objective of the comparison is the potential of anticipated improvements in these powertrain technologies for reducing petroleum consumption and greenhouse gas emissions at the same level of performance as current vehicles in the U.S.A. The fuel consumption and performance of future vehicles was estimated using a combination of scaling laws and detailed vehicle simulations. The results indicate that there is significant potential for reduction of fuel consumption for all the powertrains examined.

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 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.

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.

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.

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.

A method for determining the flame contour based on the flame arrival time at the fiber optic (FO) spark plug and at the head gasket ionization probe (IP) locations has been developed. The experimental data were generated in a single-cylinder Ricardo Hydra spark-ignition engine. The head gasket IP, constructed from a double-sided copper-clad circuit board, detects the flame arrival time at eight equally spaced locations at the top of the cylinder liner. Three other IP's were also installed in the cylinder head to provide additional intermediate data on flame location and arrival time. The FO spark plug consists of a standard spark plug with eight symmetrically spaced optical fibers located in the ground casing of the plug. The cylinder pressure was recorded simultaneously with the eleven IP signals and the eight optical signals using a high-speed PC-based data acquisition system.

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.

An experimental study was carried out that qualitatively examined the mixture preparation process in port fuel injected engines. The primary variables in this study were intake valve lift, intake valve timing, injector spray quality, and injection timing. A special visualization engine was used to obtain high-speed videos of the fuel-air mixture flowing through the intake valve, as well as the wetting of the intake valve and head in the combustion chamber. Additionally, videos were taken from within the intake port using a borescope to examine liquid fuel distribution in the port. Finally, a simulation study was carried out in order to understand how the various combinations of intake valve lifts and timings affect the flow velocity through the intake valve gap to aid in the interpretation of the videos.

A methodology is presented with which aggregate emissions from the in-use automobile population can be calculated for any given calendar year. The data base needed for such a calculation is discussed, and areas in which further research is needed are pointed out. Results of a series of calculations are then presented showing the effect on aggregate emissions of various control strategies. The effects of an inspection/maintenance and retrofit program, different vehicle population growth rates, catalyst deterioration in use, and various schedules of new car emission standards for post-1975 vehicles are presented. It is shown that the rate at which old, higher-polluting vehicles are retired from the in-use vehicle population is the major factor in determining the rate at which aggregate emissions will decrease in the 1970s, with the precise level of post-1975 standards only becoming important in the 1980s.

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.

A model for predicting the performance and emissions characteristics of Wankel engines has been developed and tested. Each chamber is treated as an open thermodynamic system and the effects of turbulent flame propagation, quench layer formation, gas motion, heat transfer and seal leakage are included. The experimental tests were carried out on a Toyo Kogyo 12B engine under both motoring and firing conditions and values for the effective seal leakage area and turbulent heat transfer coefficient were deduced. The agreement between the predicted and measured performances was reasonable. Parametric studies of the effects of reductions in seal leakage and heat transfer were carried out and the results are presented.

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.

A conventional coil ignition system and two breakdown ignition systems with different electrode configurations were compared in M.I.T.'s transparent square piston engine. The purpose was to gain a deeper understanding of how the breakdown and glow discharge phases affect flame development and engine performance. The engine was operated with a standard intake valve and with a shrouded intake valve to vary the characteristic burning rate of the engine. Cylinder pressure data were used to characterize the ignition-system performance. A newly developed schlieren system which provides two orthogonal views of the developing flame was used to define the initial flame growth process. The study shows that ignition systems with higher breakdown energy achieve a faster flame growth during the first 0.5 ms after spark onset for all conditions studied.

This paper explores the benefits that would be achieved if gasoline marketers produced and offered a higher-octane gasoline to the U.S. consumer market as the standard grade. By raising octane, engine knock constraints are reduced, so that new spark-ignition engines can be designed with higher compression ratios and boost levels. Consequently, engine and vehicle efficiencies are improved thus reducing fuel consumption and greenhouse gas (GHG) emissions for the light-duty vehicle (LDV) fleet over time. The main objective of this paper is to quantify the reduction in fuel consumption and GHG emissions that would result for a given increase in octane number if new vehicles designed to use this higher-octane gasoline are deployed. GT-Power simulations and a literature review are used to determine the relative brake efficiency gain that is possible as compression ratio is increased.

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.