Abstract
The stratified charge combustion system has been widely studied due to the significant potentials for low fuel consumption and low exhaust gas emissions. The mixture formation process for a direct-injection stratified charge engine is influenced by various parameters such as the atomization, the fuel evaporation, and the in-cylinder gas motion at high temperature and high pressure conditions. It is difficult to observe the in-cylinder phenomena in such conditions and also challenging to analyze the following stratified charge combustion. Therefore, the combustion phenomena in idealized stratified charge conditions aiming to analyze the fundamental stratified charge combustion are examined. That is, an experimental apparatus which can control the mixture distribution and the gas motion at ignition timing was developed, and the effects of turbulence intensity, mixture concentration distribution, and mixture composition on stratified charge combustion were examined. The schematic of experimental setup is shown in Fig. 1. Three volumes separated by two partitions were evacuated and then three premixtures were charged simultaneously through pressure regulators. After the charging was completed, the gas motion generator was operated to control turbulence at spark timing. After partitions were removed, ignition was made. As a result, it was found that in stratified charge combustion using propane-air mixture, when the overall equivalence ratio, φo, is unity, no advantages by charge stratification is found, but when φo is set at 0.8 combustion is enhanced by additive effects combining turbulence with charge stratification, and that combustion is enhanced by strong turbulence in slightly stratified charge fields using methane-air mixture, but extending stratification brings unfavorable results compared with the homogeneous condition.
