Investigation On The Movement Characteristics Of The Needle In The Common Rail Injector For Diesel Engines

With the emergence of energy crisis,Human beings paied more and more attention to environmental pollution in recent years.Increasingly stringent diesel emissions regulations.High-efficiency,low-emission diesel engine has become the focus of research.It is necessary to control the efficiency of the injection,the time of injection and the injection pressure to improve the combustion efficiency of the diesel engine,and to reduce the emission of diesel engine.However in the high pressure common rail injector is the most critical parts and it's working process of the direct decision efficiency of fuel injector and injection pressure,and the injector needle valve movement finally decided jet injector opening and closing.Therefore,the needle valve movement of injector has a great influence on the efficiency of diesel engine.Therefore,it is very practical to study the motion characteristics of injector needle valve.In high pressure common rail test bench test needle valve movement test,found an interesting phenomenon: in the process of needle valve open,you can clearly see the different before and after the opening paragraph,open the front is very slow,back-end open faster,namely the process of needle valve open a turning point.Through theoretical analysis,based on the test findings and found that the direct cause of needle valve open two paragraphs due to the fuel injector control indoor pressure process effective mass flow.So,in order to verify the theoretical analysis,this paper uses the MATLAB/Simulink simulation software,through the injector model,the control room of the discharge coefficient and pressure relationship between in and out of the oil hole programming,in order to obtain a better simulation studio control room fuel injector flow rate changes.By comparing the test results with the simulation results,the curve of the motion of the needle valve,the oil injection volume and the oil injection pressure curve are compared,and the error is within 5%,which verifies the correctness of the simulation model.At the same time,the theoretical analysis is verified by the simulation model,and the following conclusions are obtained through simulation and theoretical analysis.(1)Cause of needle valve open two paragraphs is to control the indoor effective flow change,the effective flow is the effective cross-sectional area changes,namely when the ball valve open to a certain extent,the minimum flow area by ball valve and valve seat area into the oil orifice clearance;The transformation of the minimum flow area(i.e.,the effective area)will result in two stages of the needle valve opening.(2)The close process of the needle is only a stage,because when the needle valve is closed,the effective flow cross-sectional area is determined by the cross-sectional area between the ball valve's steel ball and the seat.(3)The change of rail pressure mainly affects the quick opening stage of the needle valve without affecting the initial opening segment of the needle valve;Moreover,with the increase of rail pressure,the time of rapid opening of the needle valve decreases.And the rail pressure increases to a certain value,no longer affects the needle valve movement.