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A model which converts flame arrival times at a head gasket ionization probe, used in a spark-ignition engine, into flame contours has been developed. The head gasket was manufactured at MIT using printed circuit board techniques. It has eight electrodes symmetrically spaced around the circumference (top of cylinder liner) and it replaces the conventional head gasket. The model is based on engine flame propagation rate data taken from the literature. Data from optical studies of S.I. engine combustion or studies utilizing optical fiber or ionization probe diagnostics were analyzed in terms of the apparent flame speed and the entrainment speed (flame speed relative to the fluid ahead of the flame). This gives a scaling relationship between the flame speed and the mass fraction burned which is generic and independent of the chamber shape.

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.

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]

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.

An analysis method for characterizing fuel behavior during spark-ignition engine starting has been developed and applied to several sets of start-up data. The data sets were acquired from modern production vehicles during room temperature engine start-up. Two different engines, two control schemes, and two engine temperatures (cold and hot) were investigated. A cycle-by-cycle mass balance for the fuel was used to compare the amount of fuel injected with the amount burned or exhausted as unburned hydrocarbons. The difference was measured as “fuel unaccounted for”. The calculation for the amount of fuel burned used an energy release analysis of the cylinder pressure data. The results include an overview of starting behavior and a fuel accounting for each data set Overall, starting occurred quickly with combustion quality, manifold pressure, and engine speed beginning to stabilize by the seventh cycle, on average.

Today's diesel PM reduction systems are mainly based on catalyzed particulate filter(CPF) systems. However, most of their reaction kinetics remain unresolved. Among others, the soot oxidation rate over catalyst is particularly important in the evaluation of the performance of the catalysts and the efficient control of CPF regeneration. This study, therefore, investigated the oxidation rate of carbon black (Printex-U) over various Pt supported catalysts using a flow reactor setup simulating diesel exhaust conditions. Compared to non-catalyzed soot oxidation, the oxidation rate of carbon black over Pt catalysts was to an extent shifted towards low temperatures. This activity enhancement of soot oxidation over a catalyst can be attributed principally to NO to NO2 conversion because NO2 oxidizes soot with much lower activation energy (Ea=60kJ/mol) than O2 (Ea=177kJ/mol).

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.

An experimental study was conducted on a direct-injection stratified-charge (DISC) engine incorporating a combustion process similar to the Texaco Controlled Combustion System and operated with gasoline. Analysis of the injected fuel flow and the heat release showed that the combustion process was characterized by three distinct phases: fuel injection and distribution around the piston bowl, flame propagation through the stratified fuel-air mixture, and mixing-controlled burn-out with the heat-release rate proportional to the amount of unburned fuel in the combustion chamber. This characterization was consistent with previous visualization studies conducted on rapid-compression machines with similar configurations. Experiments with varied injection timing, spark plug location, and spark timing showed that the combustion timing relative to injection was critical to the hydrocarbon emissions from the engine.

This paper describes two types of computer models which have been developed to analyze the performance of both premixed-charge and direct-injection stratified-charge Wankel engines. The models are based on a thermodynamic analysis of the contents of the engine's chambers. In the first type of model, the rate of combustion is predicted from measured chamber pressure by use of a heat release analysis. The analysis includes heat transfer to the chamber walls, work transfer to the rotor, enthalpy loss due to flows into crevices and due to leakage flows into adjacent chambers, and enthalpy gain due to fuel injection. The second type of computer model may be used to predict the chamber pressure during a complete engine cycle. From the predicted chamber pressure, the overall engine performance parameters are calculated. The rate of fuel burning as an algebraic function of crank angle is specified.

The purpose of this work was to develop an understanding of how liquid fuel transported into the cylinder of a port-fuel-injected gasoline-fueled SI engine contributes to hydrocarbon (HC) emissions. To simulate the liquid fuel flow from the valve seat region into the cylinder, a specially designed fuel probe was developed and used to inject controlled amounts of liquid fuel onto the port wall close to the valve seat. By operating the engine on pre-vaporized Indolene, and injecting a small amount of liquid fuel close to the valve seat while the intake valve was open, we examined the effects of liquid fuel entering the cylinder at different circumferential locations around the valve seat. Similar experiments were also carried out with closed valve injection of liquid fuel at the valve seat to assess the effects of residual blowback, and of evaporation from the intake valve and port surfaces.

An experimental study was performed to investigate the effects of various intake charge motion control valves (CMCVs) on mixture preparation, combustion, and hydrocarbon (HC) emissions during the cold start-up process of a port fuel injected spark ignition (SI) engine. Different charge motions were produced by three differently shaped plates in the CMCV device, each of which blocked off 75% of the engine's intake ports. Time-resolved HC, CO and CO2 concentrations were measured at the exhaust port exit in order to achieve cycle-by-cycle engine-out HC mass and in-cylinder air/fuel ratio. Combustion characteristics were examined through a thermodynamic burn rate analysis. Cold-fluid steady state experiments were carried out with the CMCV open and closed. Enhanced charge motion with the CMCV closed was found to shorten the combustion duration, which caused the location of 50% mass fraction burned (MFB) to occur up to 5° CA earlier for the same spark timing.

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.

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.

Plasma-catalyst (Ag, Au/Al2O3) systems were applied to NOx reduction in a model lean-burn engine exhaust gas. Also, DeNOx test of real diesel exhaust gas was performed by plasma-Ag/Al2O3 system. In the case of model exhaust gas, the catalytic activity for NOx reduction was enhanced by the assistance of plasma in the wide temperature range. The NOx conversion efficiency of plasma-Ag/Al2O3 was 40∼90% under the condition of C3 H6 3200ppm (C1/NOx = 5.96) and 10% O2 over the temperature range of 250∼400°C. The plasma-Au/Al2 O3 system showed remarkable low temperature NOx reduction activity at 100∼250°C. The real engine full flow test was performed for 70% of the full load and at engine speed of 1500rpm. NOx removal of 46% from the diesel exhaust gas was achieved by the plasma-Ag/Al2O3 catalyst system at 364°C(C1/NOx = 6). In the case of higher C1/NOx = 10, the NOx conversion increased up to 73% at 381°C. Also, DeNOx engine tests were performed for full load of 1500, 2000 and 2500rpm.

The oxidation of soot (carbon black) which is assisted by Pt/CeO2 catalyst is studied using a flow reactor system simulating the condition of diesel exhaust. In this study, the temperature programmed oxidation (TPO) scheme is mainly used for different NO and O2 concentrations and soot oxidation rate is evaluated by monitoring both CO and CO2 concentrations. Pt/CeO2 catalyst lowers the temperature of the peak CO/CO2 concentrations significantly when there is either NO or O2. Oxidation starts at 200°C and the peak CO2 concentration is observed at 360°C, which depends on the amount of catalyst and NO concentration. The effect of catalyst on NO2 recycling is also investigated. For this purpose, two different types of sample have been prepared. For the mixed case, 10mg of carbon black is mixed with 50mg of Pt/CeO2 catalyst under conditions of loose contact. For the unmixed case, the catalyst layer is placed on top of soot layer without mixing.

Two features to facilitate chemical reactions at low temperature, non-thermal plasma and the weak dependency of photocatalyst on temperature, have been exploited by many researchers to effectively decompose hydrocarbon emissions emitted until the light-off of a three-way catalyst in spark ignition engines. To develop a realizable emissions reduction reactor, as part of such effort, this study investigates for the three model gases, propylene, n-butane and acetylene: 1) the conversion efficiency of the emissions reduction reactor, which utilizes the effect of dissociation, ionization-by-collision of the non-thermal plasma and the photocatalytic effect of TiO2, and 2) the concentrations of the products such as acetaldehyde, acetic acid, polymerized hydrocarbons and NO2. The operating parameters to obtain the plasma energy density ranging from 7.8 to 908 J/L were varied.

In this research, an optical system for the detection of the flame propagation under the non-knocking and knocking conditions is developed and applied to a mass produced four cylinder SI engine. The normal flames are measured and analyzed under the steady state operating conditions at various engine speeds. For knocking cycles, the flame front propagations before and after knock occurrence are simultaneously taken with cylinder pressure data. In non-knocking and knocking cycles, flame propagation shows cycle-by-cycle variations, which are quite severe especially in the knocking cycles. The normal flame propagations are analyzed at various engine speeds, and show that the flame front on the exhaust valve side becomes faster as the engine speed increases. According to the statistical analysis, knock occurence location and flame propagation process after knock can be categorized into five different types.

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.

This vehicle simulation study estimates the fuel economy benefits of an HCCI engine system and assesses the NOx, HC and CO aftertreatment performance required for compliance with emissions regulations on U.S. and European regulatory driving cycles. The four driving cycles considered are the New European Driving Cycle, EPA City Driving Cycle, EPA Highway Driving Cycle, and US06 Driving Cycle. For each driving cycle, the following influences on vehicle fuel economy were examined: power-to-weight ratio, HCCI combustion mode operating range, driving cycle characteristics, requirements for transitions out of HCCI mode when engine speeds and loads are within the HCCI operating range, fuel consumption and emissions penalties for transitions into and out of HCCI mode, aftertreatment system performance and tailpipe emissions regulations.