The Analysis Of Structural Improvement And Cavitation Of Diesel Injector

With the lack of energy and the deterioration of the environment in the world,people have put forward higher requirements for the comprehensive performance of diesel engines.As an important part of the fuel injection system,the fuel flow inside fuel injector directly affects the atomization effect of the fuel,and is one of the important components that affect the performance and reliability of the diesel engine.Increasing the injection pressure has become the development direction of injectors.Higher injection pressure will not only improve the atomization effect of fuel,but also reduce fuel consumption and harmful product emissions.The existence of cavitation inside the injector improves the atomization quality of the fuel,but also erodes the needle valve and the needle seat,which reduces the life of the injector.Therefore,it is necessary to analyze the cavitation inside the injector.In order to reduce the fuel pressure loss and improve the atomization quality of fuel injector,based on the original 16V280ZJ diesel injector,two improved schemes were put forward:scheme 1 is a longitudinal fuel injector structure;scheme 2 is to cancel the two annular grooves between the injector body and the support plate,the support plate and the needle valve body.Instead,they are respectively positioned with two pins.The injector assemblies and fuel ducts before and after the improvement were modeled,and the Ansys Workbench was used to perform the fluid-structure coupling analysis of the injectors before and after the improvement.Analysis of the influence of the improved two types of fuel injector structure on fuel pressure and compared with the injector before improvement.The results show that the two improvement schemes can reduce the loss of fuel pressure to a certain extent.Since the structure of the support plate and the needle valve body of the improved fuel injector has been greatly changed,strength analysis is required to determine whether the support plate and the needle valve body before and after the improvement satisfy the strength requirements.Combining the simulation results of the fluid model simulated in Fluent with the solid parts,and constraining and applying loads to the solid parts,the results of the stress and deformation before and after the improvement are obtained.The effect of structural improvement on stress and deformation of the support plate and needle valve body is analyzed.The results show that both the support plate and the needle valve body can meet the requirements of strength.Taking internal fuel duct of the original 16V280ZJ diesel engine injector as an object,the transient cavitation phenomenon in the injector is studied by using the dynamic grid technology in Fluent.First,the cavitation phenomenon of the original fuel duct model was simulated,and the law of cavitation formation was described.Then the effects of some structural parameters of the injector(the diameter and entrance round angle of the nozzle)on the cavitation are also studied.It is found that the cavitation intensity increases with thediameter of the nozzle;the cavitation intensity is weakened after add round angle at the inlet of the nozzle,and the cavitation degree decreases with the increase of the radius of the round angle.