Abstract
Interaction of fuel spray and surrounding air plays an important role on mixture formation, ignition and combustion processes in diesel combustion. Effects of ambient gas density and temperature on development, ignition and combustion processes of diesel spray were investigaed by using free piston type rapid compression machine and high-speed video camera. The obtained images at ignition and combustion process were analyzed using their color information. Two types of flame including dark and bright one are found in all cases except low temperature cases. Dark flame fragment is always found ahead of appearance of bright flame fragment. Dark flame is found at relatively well-mixed region. Bright flame is found only at fuel rich retion, such as nearby spray axis and spray stagnating region in high-density condition.
