Investigation into the deformation of injector components in a common rail system based on numerical simulation 2020-01-1398
The deformation of fuel injection system components cannot be disregarded as the pressure of the system increases. In particular, the control plunger and the needle of the solenoid injector tend to deform under high working pressure. Their deformation directly affects the volume of the control plunger chamber and the cross-section area of the fuel that enters the sac. A change in chamber volume influences the characteristics of needle movement, whereas a change in cross-section area influences needle movement and injection quantity. Consequently, the deformation of the injector bring difficulties to the precise control of the fuel injection system.
In this study, a ADINA (a finite-element software) model of a BOSCH solenoid injector is established to calculate the structural deformation of the nozzle, the needle and the control plunger under different pressures. The accuracy of the model is validated using experimental data published in prior studies. The validated model is used to calculate the structural deformations of the injector components when the solenoid valve is non-energized and energized. Corresponding results indicate that the maximum deformation location of the injector components is at the upper end of the control plunger when the solenoid valve is non-energized, whereas the maximum deformation location is at the lower end of the needle when the solenoid valve is energized. Moreover, the location with maximum deformation is fixed in space under each working status (i.e. energized or non-energized) of the solenoid valve regardless of the working pressure. The value of the maximum deformation, however, does change as a function of the working pressure. Specifically, the maximum deformation of the control plunger and the needle reaches 0.238 mm and 0.0544 mm, respectively, under the highest pressure in the simulation (i.e. 250 MPa). Furthermore, under the same pressure, the deformation of the control plunger increases the control chamber volume by 24.5%, while the deformation of the needle increases the cross-section area between the needle and the needle seat by 20%.
A MATLAB model is established to investigate the influence of structural deformation of the solenoid injector components on needle movement characteristics and injection quantity. The results show that the deformations of the control plunger and the needle change the needle movement process and injection quantity significantly. In particular, the characteristic points of needle movement are delayed and injection quantity increases due to the deformation. Specifically, the needle opening timing delays by 14% and the injection quantity increases by 0.48 mg under 240 MPa. Furthermore, the degree of the two effects increases with pressure. In conclusion, the deformation location and value of the injector are calculated through ADINA model, and the effects of deformation on needle movement characteristics and injection quantity are investigated through the MATLAB model. Therefore, this paper completes the numerical calculation model of the injector and provides guidance for accurate injection under high pressure.
Dan Xu, Baigang Sun, Qing Yang, Dongwei Wu