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An experimental study was performed to develop a more fundamental understanding of the effects of secondary air injection (SAI) on exhaust gas emissions and catalyst light-off characteristics during cold start of a modern SI engine. The effects of engine operating parameters and various secondary air injection strategies such as spark retardation, fuel enrichment, secondary air injection location and air flow rate were investigated to understand the mixing, heat loss, and thermal and catalytic oxidation processes associated with SAI. Time-resolved HC, CO and CO₂ concentrations were tracked from the cylinder exit to the catalytic converter outlet and converted to time-resolved mass emissions by applying an instantaneous exhaust mass flow rate model. A phenomenological model of exhaust heat transfer combined with the gas composition analysis was also developed to define the thermal and chemical energy state of the exhaust gas with SAI.

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.

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.

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.

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.

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.

In the study of internal combustion engines, gas temperatures within the system are of significant importance. The adverse conditions under firing operation, however, make measurements by any means very difficult. This current study seems to have gone the farthest to date for velocity of sound gas temperature measurements in internal combustion engine applications. An ultrasound signal is sent by a transmitting transducer, through the gas medium, and into the receiving transducer. The received signal is recorded, and the gas temperature determined from the time of flight. In-cylinder and exhaust manifold gas temperatures under fired conditions are presented, and are all consistent. Impacts of operating parameters like mixture equivalence ratio and coolant temperature are investigated.

A dynamometer-mounted four-cylinder Saturn engine was used to accumulate combustion chamber deposits (CCD), using an additized fuel. During each deposit accumulation test, the HC emissions were continuously measured. The deposit thickness at the center of the piston was measured at the beginning of each day. After the 50 and 35-hour tests, HC emissions were measured with isooctane, benzene, toluene, and xylene, with the deposited engine, and again after the deposits had been cleaned from the engine. The HC emissions showed a rapid rise in the first 10 to 15 hours and stabilization after about 25 hours of deposit accumulation. The HC increase due to CCD accumulation accounted for 10 to 20% of the total engine-out HC emissions from the deposit build-up fuel and 10 to 30% from benzene, isooctane, toluene, and xylene, making CCDs a significant HC emissions source from this engine. The HC emissions stabilized long before the deposit thickness.

Previous research has shown the potential benefits of running an engine with excess air. The challenges of running lean have also been identified, but not all of them have been fundamentally explained. Under high dilution levels, a lean limit is reached where combustion becomes unstable, significantly deteriorating drivability and engine efficiency, thus limiting the full potential of lean combustion. This paper expands the understanding of lean combustion by explaining the fundamentals behind this rapid rise in combustion variability and how this instability can be reduced. A flame entrainment combustion model was used to explain the fundamentals behind the observed combustion behavior in a comprehensive set of lean gasoline and hydrogen-enhanced cylinder pressure data in an SI engine. The data covered a wide range of operating conditions including different compression ratios, loads, types of dilution, fuels including levels of hydrogen enhancement, and levels of turbulence.

For some time, spatial nonuniformities in the unburned mixture within a spark ignition engine have been suspected of contributing to cycle-by-cycle variations in combustion. In this work, an experimental structure was developed that allowed the effects of fuel/air nonuniformity and residual gas/fresh charge nonuniformity to be separately addressed, with special regard given to their impact on the flame development process and combustion rate. Under the conditions of light loads and low speed, it was found that a decrease in fuel-air nonuniformity caused a slight reduction in the variation of the early flame development angle but had no significant impact on the statistics of the main combustion phase or IMEP. Eliminating residual gas nonuniformity by skip firing the engine and adding equivalent residual to the fresh mixture prior to entry to the cylinder had no detectable impact on the flame development process.

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.

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.

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.

Experiments were conducted to determine the effects of substantial spark retard on combustion, hydrocarbon (HC) emissions, and exhaust temperature, under cold engine conditions. A single-cylinder research engine was operated at 20° C fluid temperatures for various spark timings and relative air/fuel ratios. Combustion stability was observed to decrease as the phasing of the 50% mass fraction burned (MFB) occurred later in the expansion stroke. A thermodynamic burn rate analysis indicated combustion was complete at exhaust valve opening with -20° before top dead center (BTDC) spark timings. Chemical and thermal energy of the exhaust gas was tracked from cylinder-exit to the exhaust runner. Time-resolved HC concentrations measured in the port and runner were mass weighted to obtain an exhaust HC mass flow rate. Results were compared to time averaged well downstream HC levels.

Experiments were performed to identify the knock trends of lean hydrocarbon-air mixtures, and such mixtures enhanced with hydrogen (H2) and carbon monoxide (CO). These enhanced mixtures simulated 15% and 30% of the engine's gasoline being reformed in a plasmatron fuel reformer [1]. Knock trends were determined by measuring the octane number (ON) of the primary reference fuel (mixture of isooctane and n-heptane) supplied to the engine that just produced audible knock. Experimental results show that leaner operation does not decrease the knock tendency of an engine under conditions where a fixed output torque is maintained; rather it slightly increases the octane requirement. The knock tendency does decrease with lean operation when the intake pressure is held constant, but engine torque is then reduced.

Experiments to study the effects of oxygenated fuels on emissions and combustion were performed in a single-cylinder direct-injection (DI) diesel engine. A matrix of oxygen containing fuels assessed the impact of weight percent oxygen content, oxygenate chemical structure, and oxygenate volatility on emissions. Several oxygenated chemicals were blended with an ultra-low sulfur diesel fuel and evaluated at an equivalent energy release and combustion phasing. Additional experiments investigated the effectiveness of oxygenated fuels at a different engine load, a matched fuel/air equivalence ratio, and blended with a diesel fuel from the Fischer-Tropsch process. Interactions between emissions and critical engine operating parameters were also quantified. A scanning mobility particle sizer (SMPS) was used to evaluate particle size distributions, in addition to particulate matter (PM) filter and oxides of nitrogen (NOx) measurements.

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.

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.

Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contributes directly to hydrocarbon and particulate emissions. In addition, chemical compounds present in oil additives poison catalytic converters and reduce their conversion efficiency. Oil consumption can increase significantly during critical non-steady operating conditions. This study analyzes the oil consumption behavior during ramp transients in load by combining oil consumption measurements, in-cylinder measurements, and computer-based modeling. A sulfur based oil consumption method was used to measure real-time oil consumption during ramp transients in load at constant speed in a production spark ignition engine. Additionally in-cylinder liquid oil behavior along the piston was studied using a one-point Laser-Induced-Fluorescence (LIF) technique.

When hydrogen is added to a gasoline fueled spark ignition engine the lean limit of the engine can be extended. Lean running engines are inherently more efficient and have the potential for significantly lower NOx emissions. In the engine concept examined here, supplemental hydrogen is generated on-board the vehicle by diverting a fraction of the gasoline to a plasmatron where a partial oxidation reaction is initiated with an electrical discharge, producing a plasmatron gas containing primarily hydrogen, carbon monoxide, and nitrogen. Two different gas mixtures were used to simulate the plasmatron output. An ideal plasmatron gas (H2, CO, and N2) was used to represent the output of the theoretically best plasmatron. A typical plasmatron gas (H2, CO, N2, and CO2) was used to represent the current output of the plasmatron. A series of hydrogen addition experiments were also performed to quantify the impact of the non-hydrogen components in the plasmatron gas.