| Cavitation inside the nozzle has an important influence on performance of the diesel engine.On the one hand,it can promote fuel atomization,make fuel efficiently and fully combust in engine,reduce the carbon deposition.On the other hand,it can cause erosion in the nozzle,and affect the performance and service life of nozzle.Because the size of orifice in engine nozzle is very small and the flow velocity of fuel in orifice is very high,it is difficult to research cavitation phenomenon in engine.In this paper,we use the aluminum foil and AlMg5 as the alternative materials to study cavitation erosion.We attached a thin aluminum foil to the surface of a transparent nozzle.This paper conducted the visualization experiments cavitation flow and erosion inside real-sized nozzles and enlarged transparent diesel nozzles.Moreover,the effect of fuel temperature on cavitation flow inside vertical multi-hole nozzles and spray characteristics with different nozzle geometries have been conducted.The main content and innovative research results are as flows:(1)A nozzle flow and spray visualization test rig equipped with a fuel heating system was designed and set up.The scaled-up nozzle tip was manufactured by an innovative use of the 3D printing and finish machining.Measurements show that the dimensional accuracy of the nozzle tip reached to 0.02 mm,which can assure the similarity of internal flow passage between the scaled-up nozzle tip and real nozzle.(2)Comparative study of flow with mini-sac,improved ? and improved ? were carried out.The results can provide the experimental basis for the optimum structure design of injector.(3)Taking the aluminum foil and AlMg5 as the alternative materials,the link between cavitation development and erosion in diesel injector nozzles were conducted.With the analysis on the cavitation,the mechanism of cavitation erosion inside the nozzle was revealed. |
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