Detached Eddy Simulation Simulation of Asymmetrical Flow in a High Pressure Diesel Injector

Recent experiments have shown that the lateral motion of a high pressure injector needle can lead to significant asymmetrical flow in the sac and asymmetric spray pattern in the combustor, which in turn degrades the combustion efficiency and results in spray hole damage. However, the underlying cause of the lateral needle motion is not understood. In this paper, we numerically studied the complex transient flow in a high pressure diesel injector using the detached eddy simulation to understand the cause of the lateral needle motion. The flow field was described by solving the compressible Navier-Stokes equations. The mass transfer between the liquid and vapor phases of the fuel was modeled using the Zwart-Gerber-Belamri equations. Our study revealed that the vortical flow structures in the sac are responsible for the lateral needle motion and the hole-to-hole flow variation. The transient motion of the vortical structure also affected vapor formation variations in spray holes. Further analysis showed that the rotational speed of the vortical flow structure is proportional to the lateral force magnitude on the lower needle surfaces.