A simulation study on the pilot injection in electronic unit pump

The technology of pilot injection is studied on a high-pressure fuel injection system with electronic unit pump (EUP). A model for EUP is established in AMESim and with the model both simulation and verification test are conducted. The results indicate that the pilot injection produces pressure fluctuations in high-pressure line and exerts significant effects on main injection. The more the pilot injection quantity, the severer the pressure fluctuations of the main injection, and the smaller the average pressure of main injection, leading to the reduction in fuel quantity of main injection under same injection purse width. Though the pressure fluctuations caused by pilot injection weakens with the increase in engine speed, its effects at low and medium speed cannot be ignored. So if the pilot injection is adopted the purse width MAP of main injection should be recalibrated.