The Study Of Cavitation In Diesel Injector Nozzle

Diesel engine nozzles, as the terminal system of injection, influences the quality of the fuel atomization combustion, spray duration length, and directly influences the Diesel engine of cylinder combustion ,fuel economy and power performance.To learn more about diesel nozzle, Understand the flow state in the internal engine nozzle.In this paper, we study fuel Flow characteristics,learn the cavitation phenomenon in injector.cavitating flow in diesel injector affect diesel fuel spray and combustion characteristic, But Diesel fuel injection holes in nozzle is small, the injection pressure is very large,so the fuel speed is fast, the cavitation existence time is short,so far, computational fluid dynamics (CFD) has been widely performed, This article by using of the software FIRE from AVL simulate the multi-dimension numerical simulations in nozzle about cavitation.because of the theory of similarity, the large-scale nozzles are designed in case the similarity of structure, dynamics and boundary conditions. Cavitation phenomenon is investigated by a series of visualizing experiments by analyzing the effect factors such as Reynolds number and cavitation number, actual jet parameters (the inlet pressure, the outlet pressure, needle valve lift ) and the structure parameters affect the cavitation occurrence in nozzle.And then compared that the spray of a real scale nozzle and analyzed the spray particle size, Spray penetration and the results of CFD simulation in VCO type nozzle. By the fire software we kown when needle valve is moving.the results show that the cavitation appears initially at the nozzle hole inlet edge,and it is improving when the diesel fuel increase speed, Ultimately, nozzle hole was throughde by cavitation bubble and the flow field is divided into two-phase flow. Under unsteady(transient) conditions, needle valve moving results to pressure fluctuation near the inlet of nozzle hole,and it influences part of cavitation and supercavitation.