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An experimental study was conducted to determine if an organic fuel additive could reduce engine out hydrocarbon and NOx emissions. A production four cylinder spark ignited engine with throttle body fuel injection was used for the study. A full boiling range base fuel, an additized base fuel, a base fuel with methyl tertiary butyl ether (MTBE) and a base fuel with MTBE and additive were used in the engine tests. Additive concentration was 1/2% by mass. Hydrocarbon and NOx measurements were recorded for 11 load/speed conditions. Hydrocarbon speciation data was taken at two of these conditions. The data from the experiments was analyzed in a pair-wise fashion for the fuels with and without the additive to determine whether statistically significant changes occurred.

Experiments have been conducted in a laminar flow system and in a research engine to investigate the effect of additives on the combustion of gasoline-like fuels. The purpose of the laminar system is to enable rapid screening of additives to determine which, if any, have an enhancing effect on the early stages of combustion, especially under conditions of poor fuel vaporization which exist during cold-start in a spark ignited engine and which make flame propagation difficult to start and sustain. The base fuel used in the laminar and engine systems was a 9 component mixture formulated to simulate those components of gasoline expected to be present in the vapor phase in the intake system of an engine under cold-start conditions. In the laminar system, the pre-mixed, pre-vaporized fuel-air mixture is ignited and a time history of the combustion generated, hydroxyl radical chemiluminescence is recorded.

Results are presented from an experimental study of the effects of engine speed and injection pressure transients on the cold start performance of a gasoline direct injection engine operating on iso-octane. The experiments are performed in an optically-accessible single-cylinder research engine modified for gasoline direct injection operation. In order to isolate the effects of the engine speed and injection pressure transients, three different cold start simulations are used. In the first cold start simulation the engine speed and injection pressure are constant. In the second cold start simulation the injection pressure is constant while the engine speed transient of an actual cold start is simulated. In the third cold start simulation both the engine speed and the injection pressure transients of an actual cold start are simulated.

The gas-phase exhaust emissions which resulted when a variably timed, variable mass of water was injected directly into the cylinder of a spark-ignition engine are reported. The experimental setup and the procedure used in the investigation are also described. Conclusions are drawn with regard to the optimum injection timing and amount of water introduced. Generally, direct-cylinder injection of water reduces NO, increases unburned HC, and does not effect CO and CO2. For a fixed-ignition timing, power also deteriorates. Another finding of this investigation is that direct-cylinder injection does result in NO reductions of better than 85% while using about one-third the mass of water required by manifold injection to effect a similar reduction.

The lean misfire limit air-fuel ratio of a spark ignition engine was extended by various modifications of the intake and ignition systems. The effects of long duration spark, extended spark plug gap projections and gap widths, and a vaned collar intake valve are reported. These modifications allowed for reliable operation up to air-fuel ratios of 24:1. The experimental apparatus and procedure used in this study are described. Conclusions are drawn concerning the optimization of the various modifications to extend the lean misfire limit and reduce the exhaust emissions. In general, all modifications extended the lean misfire limit, but increased gap width had the most profound effect. In all cases, the exhaust emissions were reduced by extension of the lean misfire limit.

A nondimensional representation for a four stroke spark ignition engine was obtained that included the transient charging and exhaust effects. Two basic advantages accrued from this approach; the design and operating parameters that evolved from the nondimensional approach are truly basic in nature, which makes the computer solution more universally applicable to all engines. The inclusion of the transient effects made the representation more realistic and of particular value in the study of engine breathing problems. The effect of valve timing, cam design, valve dimensions, and inlet temperature on engine performance were studied with the computer model.

The cycle-by-cycle variations of the combustion process of a spark ignition engine result in cycle-by-cycle (CBC) variations of the cylinder pressure development histories. Many investigators have postulated that these pressure variations are due to CBC variations of the gas motion near the spark plug at the time of ignition. This investigation was undertaken to determine if such a correlation does in fact exist. The CBC combustion variations of a CFR-RDH engine were examined in terms of the CBC pressure development histories. A constant-temperature hot-film probe was used to determine the velocity variations from cycle to cycle of the motored engine in the vicinity of the spark plug at the crank angles at which ignition would take place under firing conditions. The standard deviations of the gas velocity near the spark plug were correlated to the standard deviations of the crank angle at which maximum pressure occurred for different operating variables.

The ignition of single fuel droplets in air is modeled according to the time-varying conditions within the droplet and the boundary layer around the droplet. Ignition is hypothesized when some point in the boundary layer has experienced a sufficiently severe history in terms of pressure, temperature, equivalence ratio, and time to auto ignite. Experiments were conducted with a wide variety of fuels to validate the model. A critical size concept for ignition was predicted by the model and substantiated by the experiments.

Cycle-to-cycle variations of the combustion process of spark ignition engines, usually observed as peak pressure variations, are a phenomenon whose causes have not yet been identified with certainty. For investigating whether or not there is a relationship between physical cycle characteristics, such as peak pressure, and exhaust gas composition, a sampling system was developed which collects bag samples from specified cycles only. It consists of an analog portion for obtaining pressure and rate-of-pressure change signals, a digital logic portion for discriminating between signals according to selected criteria, and an electrically actuated sampling valve in the engine exhaust system. Since signal analysis and discrimination are instantaneous, gas sampling is done during the exhaust stroke of the same cycle for which the logic generated the command to sample. The system is described in detail and its use is illustrated with an example.

Current methods for reducing emission of oxides of nitrogen (NOx) from the spark ignition (SI) engine employ dilution of intake charge with relatively inert gases which tends to limit peak combustion temperatures and pressures. Employment of intake charge dilution has led to reduction in engine power output and increased combustion cycle-by-cycle (CBC) irregularity. This investigation sought to determine the degree of increased CBC combustion variations experienced as increased amounts of charge dilution reduced emission of NOx. Emission of unburned hydrocarbons (HC) was also documented. It was found that increased CBC variations result from employing intake charge dilution as a tool to reduce NOx emissions. The significant aspects of the increased CBC variations were an observed increase in maximum cyclic pressure dispersion, a slower flame speed as reflected by an increased angle of occurrence of peak cyclic pressure, and increased variations in the crank angle of peak pressure.

The paper presents a composite picture of current knowledge concerning characteristics and causes of friction between tire and road. The mechanisms that control development of friction forces in the contact area of a tire in rolling, driving, braking, and cornering, are related to sliding of a simple rubber block. In both cases, friction is due to a combination of adhesion and hysteresis. On dry, smooth surfaces adhesion predominates while hysteresis is principal factor on wavy, lubricated surfaces. Influence of normal pressure, sliding velocity, temperature, deformation frequency, and contamination on both friction components are dealt with. Conditions in contact area are analyzed and maximum coefficients obtainable in the several modes of operation are derived. Measures to improve frictional coupling between tire and pavement are outlined.

The effect of turbulence on flame kernel growth in lean propane-air mixtures has been studied in a flow reactor at atmospheric pressure and 300 K using laser ignition. The flame kernel growth rate was measured using laser shadowgraphy. Measurements were made under two different turbulent flow conditions, with two different ignition energies and over a range of fuel to air ratios. The effects of these parameters on flame kernel growth through changes in the mass burning rate and the expansion velocity are discussed. A comparison of the effect of turbulence on ignition probability and flame kernel growth rate variation is also presented.

Engine and vehicle tailpipe emissions can be measured in laboratories equipped with engine dynamometers and chassis dynamometers, respectively. In addition to laboratory testing, there is an increase in interest to measure on-road vehicle emissions using portable emissions measurement systems in order to determine real-driving emissions. Current methods to quantify engine, vehicle tailpipe, and real-driving emissions include the raw continuous, dilute continuous, and dilute bag measurement methods. Although the dilute bag measurement method is robust, recent improvements to the raw and dilute continuous measurement methods can account for the time delay between the probe tip and analyzer in addition to gas transport dynamics in order to reliably recover the tailpipe concentration signals. These improvements significantly increase the reliability of results using the raw and dilute continuous measurement methods, making them possible alternatives to the bag method.