三维流场数值模拟在柴油机喷油嘴中的应用

Application of Three Dimensional Flow Simulation in Diesel Engine Injector Nozzle

由于喷油嘴内的流动状态以及燃油喷射情况在很大程度上影响柴油机的排放和经济性能,对喷油嘴进行流场分析就显得越来越重要了。鉴于试验和测量受种种条件限制,可以采用CFD模型来预测柴油机喷油嘴内的流场状态,并与试验相结合,提高喷油嘴的选配和设计水平。采用Fluent软件进行模拟计算。主要研究喷油嘴的压力室、喷孔以及针阀的前端结构,并考虑燃油的可压缩性及黏度随压力、温度的变化。通过研究可以预测喷油嘴内流场的分布,分析喷油嘴设计的合理性,指出改进方向。

The investigation of the flow characteristics inside the nozzle becomes more and more important because the flow status in the nozzle and fuel injection significantly influence the emission and economy of diesel engines. Due to limited experimental conditions, CFD models can be used to predict the flow pattern inside the injectors and promote the level of selection and design of injectors. In this investigation, the CFD model is calculated by FLUENT software and the emphases concentrate in the sac volume, inject hole and structure of needle top, considering the compressibility of fuel and viscosity changing with the variety of the pressure and temperature. By means of analysis, it is possible to predict real situation of the flow field in the nozzle and analyze whether the design of an injector is reasonable, as well as indicate the direction of improvement.