Deformation of nozzle, needle, and control plunger of solenoid fuel injector under high injection pressure

Abstract

Future diesel engines require the use of solenoid fuel injection system with the ultra-high pressure of more than 2000 bars. The nozzle, needle, and control plunger of the solenoid injector deform under high pressure. This deformation affects the movement characteristics of the needle, thereby influencing the precise control of fuel injection. A test rig is set up to investigate the structural deformation and influencing factors of the solenoid injector under high pressure. The structural deformation of nozzle, needle, and control plunger under different pressures can be obtained by measuring the displacement of the upper end of the control plunger in the axial direction. The experimental longitudinal deformation of nozzle, needle, and control plunger of the solenoid injector, which was selected for the study, reaches 0.109 mm under the pressure of 1600 bars. This value is close to 40% of the maximum needle lift, which is 0.3 mm. Thus, the deformation can no longer be ignored. In view of the solenoid injector deformation under high injection pressure, a three-dimensional calculation model is established. The calculated results are compared with the experimental data. The calculation total longitudinal deformation of nozzle, needle, control plunger, and contact surface reaches 0.238 mm under the pressure of 2500 bars. The structure deformation of solenoid injector with different materials or geometric parameters is calculated under the pressure of 100–2500 bars. The deformation with new materials is 0.198 mm and the deformation with new geometric parameters is 0.0333 mm under the pressure of 2500 bar. These calculations show that the use of shorter control plungers, shorter needles, and larger wall thickness nozzles can effectively reduce injector deformation under high pressure. The results of the study can provide guidance on injector design, which can work with high injection pressure and much accurate injection.