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This paper quantifies the potential of electric propulsion systems to reduce petroleum use and greenhouse gas (GHG) emissions in the 2030 U.S. light-duty vehicle fleet. The propulsion systems under consideration include gasoline hybrid-electric vehicles (HEVs), plug-in hybrid vehicles (PHEVs), fuel-cell hybrid vehicles (FCVs), and battery-electric vehicles (BEVs). The performance and cost of key enabling technologies were extrapolated over a 25-30 year time horizon. These results were integrated with software simulations to model vehicle performance and tank-to-wheel energy consumption. Well-to-wheel energy and GHG emissions of future vehicle technologies were estimated by integrating the vehicle technology evaluation with assessments of different fuel pathways. The results show that, if vehicle size and performance remain constant at present-day levels, these electric propulsion systems can reduce or eliminate the transport sector's reliance on petroleum.

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.

Difficulties in the starting and operation of diesel engines at low temperatures are an important consideration in their design and operation, and in selection of the fuels for their use. Improvements in operation have been achieved primarily through external components of the engine and associated subsystems. A Rapid Compression Machine (RCM) has been modified to operate over a wide range of temperatures (−20°C to 100°C). It is used to isolate the combustion chamber in an environment in which all significant parameters are carefully defined and monitored. The influence of temperature and cetane number on the ignition and combustion processes are analyzed. Examination of the combustion characteristics show that temperature is by far the most influential factor affecting both ignition delay and heat release profiles. Cetane number (ASTM D-613) is not found to be a strong indicator of ignition delay for the conditions investigated.

Currently, states that are out of compliance with the National Ambient Air Quality Standards must, according to the Clean Air Act Amendments of 1990 (CAAA), develop and implement control strategies that demonstrate specific degrees of reduction in emissions-with the degree of reduction depending upon the severity of the problem. One tool that has been developed to aid regulators in both deciding an appropriate course of action and to demonstrate the desired reductions in mobile emissions is EPA's Mobile 5a emission estimation model. In our study, Mobile 5a has been used to examine the effects of regulatory strategies, as applied to the Northeast United States, on vehicle emissions under worst-case ozone-forming conditions.

Modern natural gas-to-liquids (GTL) conversion processes (Fischer-Tropsch liquid fuels (FTL)) offers an attractive means for making synthetic liquid fuels. Military diesel and jet fuels are procured under Commercial Item Description (CID) A-A-52557 (based on ASTM D 975) and MIL-DTL-83133/MIL-DTL-5624 (JP-8/JP-5), respectively. The Single Fuel Forward (single fuel in the battlefield) policy requires the use of JP-8 or JP-5 (JP-8/5). Fuel properties crucial to fuel system/engine performance/operation are identified for both old and new tactical/non-tactical vehicles. The 21st Century Truck program is developing technology for improved safety, reduced harmful exhaust emissions, improved fuel efficiency, and reduced cost of ownership of future military and civilian ground vehicles (in the heavy duty category having gross vehicle weights exceeding 8500 pounds).[1]

A set of experiments was performed to investigate the effects of relative air-fuel ratio, inlet boost pressure, and compression ratio on engine knock behavior. Selected operating conditions were also examined with simulated hydrogen rich fuel reformate added to the gasoline-air intake mixture. For each operating condition knock limited spark advance was found for a range of octane numbers (ON) for two fuel types: primary reference fuels (PRFs), and toluene reference fuels (TRFs). A smaller set of experiments was also performed with unleaded test gasolines. A combustion phasing parameter based on the timing of 50% mass fraction burned, termed “combustion retard”, was used as it correlates well to engine performance. The combustion retard required to just avoid knock increases with relative air-fuel ratio for PRFs and decreases with air-fuel ratio for TRFs.

This paper provides an overview of spark-ignition engine unburned hydrocarbon emissions mechanisms, and then uses this framework to relate measured engine-out hydrocarbon emission levels to the processes within the engine from which they result. Typically, spark-ignition engine-out HC levels are 1.5 to 2 percent of the gasoline fuel flow into the engine; about half this amount is unburned fuel and half is partially reacted fuel components. The different mechanisms by which hydrocarbons in the gasoline escape burning during the normal engine combustion process are described and approximately quantified. The in-cylinder oxidation of these HC during the expansion and exhaust processes, the fraction which exit the cylinder, and the fraction oxidized in the exhaust port and manifold are also estimated.

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.

Spark-ignition engine knock was characterized in terms of when during the engine cycle and combustion process knock occurred and its magnitude or intensity. Cylinder pressure data from a large number of successive individual cycles were generated from a single-cylinder engine of hemispherical chamber design over a range of operating conditions where knock occurred in some or all of these cycles. Mean values and distributions of following parameters were quantified: knock occurrence crank angle, knock intensity, combustion rate and the end-gas thermodynamic state. These parameters were determined from the cylinder pressure data on an individual cycle basis using a mass-burn-rate analysis. The effects of engine operating variables on these parameters were studied, and correlations between these parameters were examined.

Passenger cars in the United States continue to incorporate increasing levels of technology and features. However, deployment of technology requires substantial development and time in the automotive sector. Prior analyses indicate that deployment of technology in the automotive sector can be described by a logistic function. These analyses refer to maximum annual growth rates as high as 17% and with developmental times of 10-15 years. However, these technologies vary widely in complexity and function, and span decades in their implementation. This work applies regression with a logistic form to a wide variety of automotive features and technologies and, using secondary regression, identifies broader trends across categories and over time.

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.

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.

As part of ongoing research on hydrogen-enhanced lean burn SI engines, this paper details an experimental combustion system optimization program. Experiments focused on three key areas: the ignition system, in-cylinder charge motion produced by changes in the inlet ports, and uniformity of fuel-air mixture preparation. Hydrogen enhancement is obtained with a H2, CO, N2 mixture produced by a fuel reformer such as the plasmatron. The ignition system tests compared a standard inductive coil scheme against high-energy discharge systems. Charge motion experiments focused on the impact of different flow and turbulence patterns generated within the cylinder by restrictor plates at the intake port entrance, as well as novel inlet flow modification cones. The in-cylinder fluid motion generated by each configuration was characterized using swirl and tumble flow benches. Mixture preparation tests compared a standard single-hole pintle port fuel injector against a fine atomizing 12-hole injector.

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.

Diesel engines are the most commonly used power plant of freight and public transportations in the world. Also, the newly developed injection system, Common Rail system, increases the demands for both light and heavy duty diesel vehicles. On the other hand, stringent emission regulations are being proposed with growing concern on NOx and PM emissions from diesel engines. Future emission regulations require advanced emission control technologies, such as EGR and SCR. Exhaust gas recirculation (EGR) is a commonly used technique to reduce NOx emission. In this paper, a model-based investigation was conducted to compare the effect of high pressure loop (HPL) EGR and low pressure loop (LPL) EGR system on NOx level and BSFC of a heavy-duty diesel engine. A WAVE model was created to simulate EURO 3 engine and each component of the engine was modeled using CATIA and WaveMesher.

NO2 is an effective soot oxidizer operating at lower temperatures than O2. The effect of pure NO2 on soot oxidation was evaluated and compared with the gas treated by plasma, which initially consisted of NO, O2, and hydrocarbons. The cutout of a commercial DPF was used and the pressure difference across the DPF was monitored for an hour. The concentration of NO/NO2, CO, CO2 at the outlet of the DPF was measured as a function of time. CO and CO2 concentration was measured periodically by gas chromatography. The experiment was performed at 230, 250, 300, 350°C. When NO2 only was used as an oxidizing agent, there was a close relationship between the decrease of the pressure difference across the DPF, the CO and CO2 concentration at the outlet of the DPF, and the back conversion of NO2 to NO.

The goal of this paper is to quantitatively assess the implications of congressionally mandated biofuel targets on requirements for ethanol blending, distribution, and usage in spark ignition engines in the U.S. light-duty vehicle fleet. The “blend wall” is a term that refers to the maximum amount of ethanol that can be blended into the gasoline pool without exceeding the legal volumetric blend limit of 10%. Beyond the blend wall, the additional ethanol fuel must be used in higher blends of ethanol like E85. Once the blend wall is reached, the existing fleet of flex fuel vehicles (FFVs) will be required to use E85 for some percentage of vehicle miles traveled (VMT) in order to achieve the Renewable Fuel Standard (RFS) targets.

This paper reviews the major changes that have occurred in spark-ignition engine design and operation over the last two decades. The automobile air pollution problem, automobile emission standards, and automobile fuel economy standards -- the factors which have and are producing these changes -- are briefly described. The major components in spark-ignition engine emission control systems are outlined, and advances in carburetion, fuel injection, ignition systems, spark retard and exhaust gas recycle strategies, and catalytic converters, are reviewed. The impact of these emission controls on vehicle fuel economy is assessed. The potential for fuel economy improvements in conventional spark-ignition engines is examined, and promising developments in improved engine and vehicle matching are outlined.

A computer simulation of the four-stroke spark-ignition engine cycle has been developed for studies of the effects of variations in engine design and operating parameters on engine performance, efficiency and NO 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 NO emissions. Predictions made with the simulation have been compared with data from a single-cylinder CFR engine over a range of equivalence ratios, spark-timings and compression ratios.

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.