In practical gasoline engines it is necessary to achieve low emissions and low fuel consumptions with high load operation. Several techniques were developed for reducing the emissions and the fuel consumptions from gasoline engines, such as EGR (exhaust gas recirculation) and Ultra lean combustion [1, 2]. Especially, in automotive gasoline engines, low-particulate and low-NOx emissions are very much needed by using alcohol blend fuels and vegetable oil. Nevertheless, there are only few data available for reducing the emissions and fuel consumptions of small gasoline engines by using blended fuels. As the first step in this study, experiments have been carried out to examine the influence of alcohol-blended fuels on combustion characteristics for small gasoline engines. The fuels used in this study are gasoline, methanol, ethanol, propanol and butanol. The addition of alcohol ratio are changed by mixing the volume of alcohol in gasoline and the addition ratios are from 0 to 30 vol% in the fuel. The main conclusions are as follows: 1) The NOx emissions for all the alcohol blend fuels are smaller than that of gasoline. 2) The heat release rate increases with addition of alcohol fuel under higher load conditions for small gasoline engines.
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In practical gasoline engines it is necessary to achieve a low emissions and low fuel consumption with high load operation. Several techniques were developed for reducing the emissions and fuel consumption from gasoline engines, such as EGR (exhaust gas recirculation) and Ultra lean combustion. Nevertheless, there are only very few data available for reducing the fuel consumption in small gasoline engines (50-125cc). As the first step of this study, experiments have been carried out to examine the influence of oxygen concentration in intake air and fuel concentration on flame speed in small gasoline engine by using carburetor and EFI system. The flame front travel time was measured using ionization probes located at different point of cylinder head. The main conclusions are as follows: 1) the flame speed monotonically increases with increasing the engine rotation at any concentration in intake air; 2) Mean increasing rate of pressure is not affected by oxygen concentration in intake air and fuel concentration without load; 3) It is possible to improve the combustion behavior by using EFI system for small gasoline engine.
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