Combustion characteristics of stratified mixture formed by transient gas fuel jet

Combustion properties of a stratified mixture formed by transient gas fuel jet were studied to clarify the basic combustion process in the spark-ignited direct-injection stratified-charge engines. The stratified mixture was formed in the constant volume bomb by the injection of gaseous propane. The combustion process was visualized by schlieren photographs and images of CH emission. The ignition timing significantly affected the combustion pressure and the amount of the unburned fuel. An inverse proportional relationship was found between the combustion pressure and the amount of the unburned fuel throughout all the ignition timings. Ignition timing (before or after the completion of the fuel injection) significantly influenced flame propagation. Based on the schlieren images, flame seemed to propagate through the jet fuel. Intensity of the CH emission was weak after the flame reached the outer edge of the fuel jet. Strong CH images appeared again and continued over 50 msec. The CH images in the later stage of the combustion were markedly differently from those in the initial stage. The combustion pressure also increased slightly in the later period. After the completion of the injection, such an image was not detected and the flame propagation seemed to be completed when the flame had propagaged throughout the fuel jet. Original is an abstract.