To develop the combustion method with combination of PCCI and conventional diesel combustion, mixture formation process of early injection was investigated using an optically accessible single-cylinder diesel engine. Effects of injection pressure, injection timing, injection quantity, split injection, and the dwell between injections on spray penetration and mixture distribution were investigated. The penetration was measured by a high-speed photographic method, and the mixture distribution at TDC was observed by the LIF imaging method. When applying high injection pressure and split injection, relatively rich mixture spreads across wide area in the combustion chamber.
