Study on the influence of electronic injector nozzle geometry on the injection rate

The experimental study was carried out to analyze the influence of nozzle geometries on the injection rate of common rail injector in test bench by using EFS instantaneous fuel mass instrument, and the internal flow field and cavitation in nozzle holes with different geometries were researched with CFD code FIRE using two-phase flow model. The nozzle geometric parameters including the hole number, the hole diameter, the length-to-hole diameter (L/D) ratio and the spray cone angle. The results showed that the nozzle geometry parameters have different effects on the peak value of the injection rate and the prophase injection rate under different injection pressures and injection pulse widths, especially the L/D ratio had great influence on the cycle to cycle fuel mass of larger cross area injectors under small pulse width. The CFD analysis showed that the cavitations originating at the entrance of the nozzle holes due to the local pressure drop which diminish the cross area result in the difference of injection rates and increase the hole to hole variations of fuel mass, and the cavitation had strong effect on the injection rate characteristics at the initial stage of needle lifting process for small L/D ratio.