The Experiment And Simulation Investigation On Characteristics Of Diesel Spray Wall Impingement

Diesel spray impingement is inevitable in DI diesel engines.Diesel accumulation caused by spray impingement will influence the gas mixture and combustion,which result in the high emission of hydrocarbon and soot.As for some combustion system,spray impingement will enhance the mixture of gas and oil.Rational utilization of spray impingement is in favor of optimization design of combustion system.It will also help control the oil evaporation rate and gas mixture,achieving the aims of improving the engine performance and reducing emissions.A constant volume experiment system was established and directly photography and shadow method were used in this paper.Diesel spray impingement was investigated under the condition of different injection pressures and constant oil mass.The results showed that,with the injection pressure increasing: spray penetration velocity increased,the spray hit the wall earlier;radius,height and area of both gaseous phase and liquid phase increased;injection duration and evaporation time were shorter;diffusion rates of horizontal and vertical direction increased linearly and they were higher before injection stopped;at injection ending time,radius of liquid phase and radius,height and area of gaseous phase did not change basically,height of liquid phase increased slightly and areas of liquid phase increased first then decreases.Diesel spray impingement was investigated under the condition of different nozzle diameters and constant oil mass.The results showed that,with the nozzle diameter increasing: spray penetration velocity increased slightly;before injection stopped,radius,height and area of both gaseous phase and liquid phase increased;diffusion rates of horizontal and vertical direction increased linearly and they changed faster with injection pressures;at injection ending time,radius of liquid and gaseous phase did not change basically,height and area of liquid phase increased,height and area of gaseous phase slightly decreased;injection duration was shorter and evaporation time after injection stopped was shorter.Diesel spray impingement was investigated under the condition of different wall temperatures by both testing and simulation.The results showed that,with the wall temperature increasing: height and area of liquid phase decreased and they changed faster above 150?;radius of liquid phase and radius,height,area of gaseous phase did not change basically;evaporated oil film mass increased,oil film mass decreased,gas mass increased and gas concentration near the wall increased;average film thickness decreased and it changed faster when the wall temperature is low;oil film area increased first then decreases and the velocity of the oil film became faster.