Numerical Investigation of the Effect of Needle Lift and Seat Design on Steady and Transient Flow in Diesel Injector Nozzle

Abstract

In this study, the flow of fluid in the fuel injector nozzle of a Diesel engine was simulated under steady-state and transient conditions using ANSYS Fluent. At first, a nozzle for which experimental results were available was simulated. Then, validating the results, the $$ k - \varepsilon $$ turbulence model and the Schnerr–Sauer cavitation model were selected for the numerical simulation of a real four-hole fuel injector nozzle. In order to reduce the computational costs, only a quarter of the nozzle was modeled and the flow rate and discharge coefficient were obtained for different pressure differences. Three different seats with various needle lifts were analyzed in the steady-state case. Next, the problem was addressed under transient conditions and the results were compared with the steady-state case. Transient analysis has been performed by using ANSYS Fluent layering dynamic mesh with using UDF code for the needle lift. Ultimately, the impact of the needle lift frequency was investigated on the formation of vapors in the nozzle under transient conditions. The results of the numerical simulation show that, in addition to the discharge coefficient, needle lift, the seat design, and the frequency of the needle lift also affect the location and the size of the cavitation.