Showing papers on "Spark-ignition engine published in 1977"

A Turbulent Entrainment Model for Spark-Ignition Engine Combustion

Abstract: A turbulent entrainment model for the turbulent combustion process in spark-ignition engines is described The model uses the basic quantities of turbulent flow, ie, the integral length scale, micro length scale, and turbulent intensity The characteristic reaction time for a large eddy tau was calculated using the characteristic reaction time tau/sub c/ for the microscale, lambda/S/sub l/, where S/sub l/ is the laminar flame speed and propagation of ignition sites within a coherent turbulent structure Tau is related to the flame kernel development time and shows similar trends to the ignition delay time The combustion model is demonstrated by calculations showing the typical trend behavior of combustion duration with equivalence ratio, exhaust gas recirculation, spark timing and engine speed

Validation of a turbulent flame propagation model for a spark ignition engine

Abstract: An analytical and experimental investigation of the combustion process in a spark ignition engine has been performed The analysis is based on a flame propagation model developed which assumes that turbulent eddies are engulfed at an entrainment speed and burn in a characteristic time equal to the eddy radius divided by the laminar flame speed Measurements were made of burning intervals and ignition delays on a CFR engine The model could be adjusted to give correct trends in burning intervals for variations in equivalence ratio, EGR, compression ratio, spark timing, and level of turbulence However, the amount of variation was less than that observed in experiment Predicted burning intervals increased with RPM contrary to experimental data Predicted ignition delays were a factor of four less than experimentally observed The difficulties with the model are thought to be due to assumptions of constant time and entrainment speed It is recommended that future work on the 'eddy-entrainment' type of model be directed at removing this restriction and at understanding the behavior of these two variables during the engine cycle in terms of measureable turbulence scales, and ultimately in terms of engine operating variables such as RPM, spark timing and equivalence ratio

Performance and Emission Predictions for a Multi-Cylinder Spark Ignition Engine

Abstract: A comparison is made of experimental results and predictions of performance and emissions from a multi-cylinder spark ignition engine over a range of air-fuel ratios and two throttle settings The results showed that a simplified two zone combustion model, a seven reaction scheme for nitric oxide formation, a partial freezing model for carbon monoxide and the inclusion of chemical reactions and variable specific heat along the pathlines in the wave equations gave good agreement with the measurements at the common pipe junction and exhaust outlet, but due to cyclic dispersion and maldistribution of fuel between cylinders the predictions of the emissions in the exhaust manifold adjacent to the cylinder were not so goodThe predicted air flow and indicated power agreed well with experiment

A Variable-Displacement Spark-Ignition Engine

Abstract: A five-cylinder variable displacement research engine has been designed, built, and tested for over one year. Displacement is varied by changing the piston stroke using a four-bar linkage. By proper choice of the linkage dimensions, compression ratio can be held constant as the stroke changes, or it can be tailored to optimize economy and performance. Before the engine was built, its dynamics were thoroughly analyzed, and a five-cylinder configuration was selected to minimize vibration. Test data show that BSFC is, as expected, less dependent on load than in conventional engines, and averages less than 0.5 lb/bhp-hr over the load and speed range of ordinary automobile operation. Several methods for estimating urban fuel economy from dynamometer data predict a significant improvement compared with conventional engines. Emission controls have not yet been applied to this engine.

Multi-point spark ignition engine provided with exhaust recirculation circuit

Abstract: An internal combustion engine of the reciprocating piston type, which is provided with an exhaust gas recirculation circuit to suppress the formation of NOx and has two or three spark plugs for each combustion chamber. There is a substantial overlap of the opening periods of exhaust and intake valves, so that a portion of the combustion gas is left unexhausted. The combustion chamber has a simple shape such as hemisphere, and the spark gaps of the plural spark plugs are arranged distant from each other in each combustion chamber so as to respectively share approximately equally divided portions of each combustion chamber. The number of the spark plugs is two when the volume of the recirculated exhaust gas, including the unexhausted combustion gas, is about 50% at the maximum of the volume of air admitted into the combustion chamber but three when the recirculated exhaust gas amounts to about 60% of the air at the maximum.

Combustion and emissions characteristics of methanol, methanol-water, and gasoline-methanol blends in a spark ignition engine

Abstract: Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Voltage distributor for a spark ignition engine

Abstract: A voltage distributor for a spark ignition internal combustion engine. The distributor supplies voltage to spark plugs in a sequence corresponding to the firing order of the engine. The distributor is not driven by the camshaft of the engine in the conventional manner, but rather uses steering logic and a decoder in conjunction with a multiple position switch and trigger pulses to produce the voltage distribution. The steering logic and decoder may comprise a stepper motor and stepper motor decoder circuit operated by trigger pulses to produce rotation of a rotary switch or, alternatively, may comprise a binary counter and associated decoder for controlling relay switches.

Spark ignition engine

Abstract: A spark ignition engine has a crankshaft speed pulse generator and a plurality of cylinders each cylinder containing a spark plug. Each plug is connectable to a high voltage ignition winding by way of a reed relay. The relays are divided into two groups and, with a periodicity dependent on generator output, a selected relay in each group is closed immediately prior to generation of voltage in the winding and opened when the voltage has been dissipated. Although both plugs connected to the selected relays produce a spark only one of the cylinders contains fuel mixture and, consequently, one one power stroke occurs.

Rates of exhaust gas--air reactions

Abstract: The purpose of this work has been to determine rate expressions, kinetic rate coefficients, and constants, for the overall reactions of exhaust gas and air that take place under conditions existing in engine exhaust reactor systems. For this aim, actual exhaust gas was generated in situ by a spark ignition engine. The gas was then mixed and reacted with air in a tubular reactor, whose diameter, flow rates, and temperatures of operation were of the same order of magnitude as those found in experimental engine exhaust reactor systems designed to reduce exhaust gas emissions. Specifically, the reactions investigated were those of air with the carbon monoxide, hydrogen, and total hydrocarbons contained in the exhaust gas.

Control of Noxious Emissions from Internal Combustion Engines

Abstract: Automotive air pollution has been recognized as an environmental hazard for over 30 years. The nature of the problem has been investigated from almost every angle. The relationship between photochemical smog and the components of engine exhausts has been demonstrated. Methods of measuring exhausts and atmospheric pollutants have been developed. Consideration has been given to the effect of traffic density, driving mode, and vehicle maintenance. Solutions have been sought by changes in vehicle design, in the road system, and in the fuels used. Potential new methods of powering automobiles and new methods of public transport have been evaluated.

High compression spark ignition engine - has plug points set back from main combustion chamber in auxiliary one

Abstract: The combustion chamber is for a high-compression four-stroke engine with a sparking plug in the cylinder head. The electrodes (7, 8,) of the plug (6) are set back from the main combustion chamber (1), in an auxiliary chamber (11) directly connected to it. The lower portion of the tapped hole accommodating the plug can form the auxiliary chamber, and a distance piece (12) can be fitted between plug and head. Where the tapped hole for the plug is short, an intermediate sleeve can be screwed into it, into which the plug in turn screws. The design allows engines originally designed to run on high-lead-content fuel to be simply modified to take that of lower grade.

The Effect of Gasoline Additives on Fuel Economy

Abstract: Crude petroleum consists essentially of hydrocarbons of various kinds boiling over a wide temperature range. In the early days of the spark ignition engine it was possible to use some of the light fractions as fuel without modification. Similarly it was possible to use selected heavy fractions as the crankcase lubricant. However, advances in engine and petroleum technology over the last several decades have led to the development of more efficient and much more powerful engines which need more complex fuels and lubricants for their operation. The performance of oil products can be improved to a substantial extent by selection and modification of the hydrocarbon structures, but there are practical and economic limitations to the performance levels that can be reached by hydrocarbon processing alone.