柴油温度对喷孔内流动特性影响的仿真分析

Numerical study on internal nozzle flow characteristic of diesel under hot fuel conditions

为研究柴油温度对真实喷孔内流动特性的影响,对柴油在喷油嘴喷孔内部的流动进行三维数值仿真.利用计算流体动力学(CFD)软件模拟得到不同燃油温度和背压条件下燃油的质量流量、有效喷射速度、空穴断面分布与无量纲流动参数,并进行分析.结果表明:温度越高,背压越低,更容易进入临界超空穴状态;在进入超空穴状态之后,喷孔内的超空穴现象加剧有效喷射速度的升高,并且随着燃油温度上升,有效速度增加了6%;雷诺数随温度上升而上升,空穴数随着雷诺数的增加而呈指数下降,而流量系数在空穴发展阶段维持不变.

The study was conducted to investigate the change of real internal nozzle flow parameters under hot fuel conditions. According to a model of the conventional six-hole, valve-covered orifice （VCO） diesel injector, three-dimensional numerical simulation of cavitation flow in the nozzle was studied. The mass flow, effective velocity at the outlet, cavitation distribution and non-dimensional flow coefficients under different temperature and pressure conditions were considered in the analysis. The result showed that criti- cal super cavitation conditions are achieved easier when fuel temperature rises or back pressure drops. Af- fected by internal nozzle super cavitation flow, effective velocity increases rapidly after critical super cavita- tion, besides, it shows positive correlation to temperature（increased by 6%）; Reynolds number rises with the temperature rising, the cavitation number decreases exponentially with increases in the Reynolds numbers, besides, discharge coefficient remain stable without super cavitation flow.