柴油机喷嘴内部空穴流动的三维瞬态数值模拟

3D numerical simulation of cavitation transient flow inside diesel injection nozzles

建立了柴油机喷嘴内部空穴两相流动的三维气液两相流模型,并针对多孔垂直喷嘴进行了喷孔内部空穴两相瞬态流动的数值模拟;研究了喷嘴内部的瞬态速度场、压力场和湍动能的分布特点.通过计算可知,湍动能主要集中在喷孔上部空穴区,随着针阀升程的增大,喷孔入口的环状压降愈加明显,入口上拐角处形成的涡流区范围不断扩大.同时分析了不同针阀升程下空穴流动特性,获得了空穴产生、发展过程的规律,为进一步准确模拟和分析喷雾特性提供依据.模拟计算结果与已有的实验结果吻合较好.

A three-dimensional two-phase model of cavitation flow in nozzle was developed, and the simu- lation on two-phase transient cavitating flow inside vertical multi-holes diesel injection nozzle was dealt with. With the model, the velocity field, pressure field and turbulent energy distribution inside injection nozzle were analyzed in detail. Simulation results showed that the distribution of turbulent energy was at the top of orifice where cavitation distributes, with the increase of nozzle lift, cyclic pressure drop at the intake of orifice was more remarkable, and the domain of eddy flow was bigger. Cavitating flow characteristics in different needle lift, its generation and developing process were pointed out, which provided basis for advanced simulation and analysis of fuel spray. The calculation results from the model had good agreement with the experimental graphics available in the literatures.