Combustion aspects in advanced internal combustion engines

Combustion characteristics in recently developing internal combustion engines can be different from those in conventional engines, where the combustion occurs predominantly as premixed and diffusion flame modes. In advanced engines including direct-injection (DI) gasoline engines and high speed direct injection (HSDI) diesel engines, mixtures are frequendy partially-premixed inhomogeneous conditions. The flame then could propagate through stratified fuel/air mixing layers ranging from fuel lean to fuel rich conditions. In such cases, the leading edge of propagating flame could be the structure of tribrachial (or triple) flames. In this paper, the propagation characteristics of tribrachial flames will be discussed together with their relevance to diesel spray combustion. A brief description of soot formation characteristics in partially premixed conditions will be also discussed.