Flame propagation into lean region in stratified mixture

In diesel engines, most of the fuel is burned in a diffusion combustion phase, leading to the formation of excessive amount of soot and NO_x emissions. To decrease soot and NO_x emissions simultaneously, the concept of lean homogeneous charge compression ignition (HCCI) engine was proposed. The onset of the combustion of the HCCI engine depended on the autoignition of the fuel, thus, it was quite difficult to control the start of combustion. In contrast, Pulsed Flame Jet (PFJ) showed a great potential to enhance ignition reliability and burning rate in lean mixtures within the lean flammability limit. A compact rapid compression machine (RCM) was used in the experiments, and the fuels used were lean n-butane/air mixtures. The compression ratio of RCM was adjusted to 14.7, and the cavity volume of PFJ used was 500 cu mm and two orifice diameters (4 and 2.5 mm) were used. Thus, the start of combustion of lean n-butane/air mixtures changed appropriately with varying the ignition timing of PFJ. PFJ shoed a potential for ignition timing control of homogeneous charge compression ignition combustion. Original is an abstract.