The Study Of Cavitation In Steady State Condition In Diesel Injector Nozzle

Diesel engine nozzles, as the terminal system of injection, influences the quality of the fuel atomization combustion, oil and cooperate, spray duration length, and directly influences the quality of cylinder combustion. The spray nozzle quality is an important factor of the performance of diesel. Good atomization effect can improve the dynamic performance in diesel engines and reduce the harmful emissions, improve fuel economy. There is many factors that Influences fuel spray mixing, and the cavitation phenomenon of injector is particularly obvious. The liquid spray disorder caused by cavitations plays a more import part in atomization than the friction caused by the surrounding air .But so far, cavitation is still not fully study thoroughly, mainly because the actual diesel spray nozzle is small, the injection pressure is huge and the existence time of cavitation is short.This article studied how dimensionless Numbers (Reynolds number and cavitation number), actual jet parameters (the inlet pressure, the outlet pressure, needle valve lift ) and the structure parameters(spray hole inclination, nozzle diameter, length-diameter ratio and entrance chamfer) affect the cavitation occurrence, development and breaking using high-resolution camera on large scales orifices, through the adjustment of the inlet and outlet pressure. Experimental results show that the effect of cavitation number is obvious,and the cavitational effect increases with the . The cavitational effect also increases with the Reynolds number,but it is not as obvious as the cavitation number. All parameters of increasing cavitation number and inhibitting the flow in actual jet parameters and structure parameters will make the cavitational effect increased. So it will make cavitation appear in advance when increasing inlet pressure and length-diameter ratio,reducing outlet pressure and needle valve lift,decreasing spray hole inclination and nozzle diameter, existence of entrance chamfer .And then compared that and the spray of a real scale nozzle and analyzed the spray particle size and the results of CFD simulation. Experimental results show that spray is getting better with the increase of the inlet pressure and cavitation number and spray cone Angle and distance are getting large. Diameter of particles is getting smaller with the increase of the inlet pressure and cavitation number. The measurement results and simulation experiment results are coincide.In-depth study of cavitation in the diesel nozzle flow has important practical significance for diesel engine fuel injection spray mechanism, and the improvement of diesel combustion and emission reduction. And controlling the cavitation flowing has important significance for many other mechanical industry.