Experimental study on the combustion characteristics of impinging diesel spray at low temperature environment

Highlights: • Diesel spray combustion flame interaction with wall under cold start conditions was experimental studied. • The critical temperature of the actual in-cylinder ignition is 430 °C. • Increasing the wall distance shortens the distance from the initial flame to the impingement point. • Increasing the velocity component perpendicular to the wall can promote the combustion process of the impinging spray. • Flame development of the impinging spray is more sensitive to lower wall temperature. -- Abstract: Impingement is a typical phenomenon occurring in diesel engine under cold start conditions. In this paper, the ignition and combustion characteristics of wall-impinging diesel spray under different wall conditions were investigated by using the high-speed photography, Mie scattering and Schlieren method on a constant volume chamber. It is found that the small wall distance and high wall temperature can accelerate the vaporization and mixing process of the spray, which shorten the ignition delay and accelerate the development of the flame. The wall angle has an obvious influence on the ignition position. The initial flame often appears first in the front of the downward spray. With the increase of wall angle, the promoting effect of the wall to the atomization and ignition is weakened, and the ignition delay increases. It is also found that the promotion of the wall on the combustion process mainly depends on the velocity component perpendicular to the wall. The research results of this paper will provide the basis of the control strategy for the cold start process of diesel engine.