A numerical study of the effect of spiral counter grooves on a needle on flow turbulence in a diesel injector

Abstract

In the paper, the necessity to improve the fuel injection process in diesel engines was shown. The purpose of the study is to quantitatively evaluate the increase of flow turbulence in a diesel injector caused by spiral counter grooves which are made on the injector needle and intend to improve fuel injection and atomization processes. Different parameters of the spiral counter grooves are considered from the point of view of the turbulization of fuel flow in the injector. The two-phase flow in such nozzles with different spiral grooves has been numerically investigated. Cavitation in the nozzle was modeled with using the Schnerr-Sauer equilibrium model and taking into account the influence of turbulence on the development of cavitation. The Realizable k-ε turbulence model along with Enhanced Wall Treatment for ε equation is used. The possibility of increasing the turbulence of fuel flow in the nozzle is demonstrated. It is noted that the existence of the spiral counter grooves leads to a reduction in flow velocity and improving the flow turbulence in the cylindrical space of the nozzle. The turbulence induced by the spiral grooves can lead to an increase in the cavitation intensity in the nozzle hole. The parameters of the spiral grooves which ensure the greatest flow turbulization in the nozzle have been determined. After replacing the standard nozzle with the modified nozzles No. 2 and 7, the effective turbulent kinetic energy at the nozzle hole outlet averaged over five nozzle holes increased from 2402 to 2464 and 2470 m2/s2, respectively.