| As an important power source for the automobile industry,the quality of fuel combustion determines the power,economy and emissions of automobiles.The combustion of fuel is inseparable from the good fuel injection characteristics of the injector.The realization of good fuel injection characteristics is related to the matching of various structural parameters of the injector.The electronically controlled injector is the most critical and complex component of the diesel high pressure common rail system,and it is also the precision component with the highest design and processing precision.Due to the different working environments(high temperature,high pressure)and the interaction between structures in the structure of the injector,it is often affected by factors such as wear and cavitation during the working process,resulting in changes in various structural parameters.The change of its structural parameters will directly cause changes in the fuel injection characteristics.In order to achieve energy saving,emission reduction and noise reduction for the diesel engine,the injector must have better fuel injection characteristics.In this paper,the effects of fuel injection characteristics(injection quantity characteristics,fuel injection consistency and spray characteristics)on the combustion performance of diesel engines are analyzed theoretically.Through the system analysis of fuel injection,atomization and combustion process,the requirements of the system for fuel injection characteristics of diesel injectors were obtained.From the mechanical characteristics,electromagnetic characteristics and hydraulic characteristics of injectors and by analyzing the specific movement pattern between the couples during the working process of the injector and the wear and leakage mechanism between the parts,the influence of various factors on the fuel injection characteristics is obtained,and then the actual working process of the injector is obtained.Vulnerable structures and the main factors affecting the fuel injection characteristics of these injectors.This paper is based on the theoretical study of the mechanical characteristics,electromagnetic characteristics,hydraulic characteristics and fuel atomization characteristics of the injector and the actual structure of the CRIN series injector and engine cylinder,AMESim and ANSYS WorKbench simulation software were used to establish the injector injection and atomization simulation models.The feasibility of the model was verified by establishing a test bench for fuel injection and atomization test,combined with single injection quantity and oil return,spray penetration distance,spray cone angle test data and simulation data.In this paper,by running the fuel injector AMESim fuel injection model and the ANSYS WorKbench atomization model,the influence law of the fuel injector related structural parameters on the fuel injection characteristics is obtained,and the injector-Vehken response surface method is used to carry out the injector damage.Representative structural parameters in the family of structures: the needle valve spacing,the plunger coupler clearance,the needle lift displacement,and the armature lift displacement parameter.The experimental study on the influence of variation on the characteristics of fuel injection characteristics,and the influence of various factors on the injection quantity and injection consistency.Through the multi-objective optimization method for fuel injection consistency: when the plunger coupler gap is 4.38 ?m,the needle valve coupler gap is 2.66 ?m,the armature lift stroke displacement is 0.05 mm,the needle valve When the lift displacement is 0.34 mm,the rate of change of injection quantity and response time are 1.70% and 2.27%,respectively,which achieves the best injection consistency.On this basis,through simulation test,it is concluded that when the plunger coupler gap is 3.05~5.93 ?m,the needle valve coupler gap is 1.50~3.95 ?m,the armature lift displacement is 0.045~0.053 mm,the needle valve lift displacement is 0.33~0.38 mm,fuel injection consistency indicators can meet national standards and engineering requirements.Fuel injection consistency indicators can meet national standards and engineering requirements.Through the single factor multi-index method,the influence of the structural parameters of the injector on the spray characteristics was obtained.It is concluded that the increase of the displacement of the plunger coupler and the lift of the needle valve will lead to the increase of the spray penetration distance and the spray cone angle.The average diameter of the fuel cable decreases,which is conducive to atomization;when the gap of the needle valve is increased,the spray penetration distance and the spray cone angle decrease,and the average diameter of the fuel cable is increased,which is not favorable for atomization.The displacement of the armature lift is increased,the spray penetration distance,the spray cone angle and the average diameter of the fuel gas are basically unchanged,and the atomization is basically unchanged.This study provides a reference for the design of injector structure for developing high fuel injection consistency and spray atomization characteristics.It also gives an important guidance for the matching,repair and calibration of injector structure. |
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