微乳化生物质燃油在喷嘴内部的空化流动特性

Cavitation Flow Properties of Micro-emulsified Biomass Fuel in Injector Nozzle

运用混合均相流模型加完全空化模型对微乳化生物质燃油在喷嘴内部的空化流动特性进行数值模拟研究,并结合WINKLHOFER的试验验证所选模型的合理性。研究尖角入口和圆角入口两种喷嘴反应入口形状对微乳化生物质燃油在喷嘴内部空化流动特性的影响,同时将结果与0号柴油进行对比。引入量纲一参数雷诺数(Re),空化参数(K),韦伯数(We),流量系数(Cd)等分析喷嘴的内部流动特性。结果表明,空化发生后,燃油的出流质量流量,量纲一参数的变化规律和出口截面的速度分布均与空化前不同;相比于柴油,微乳化生物质燃油开始空化和达到超空化需要较高的喷射压力;喷嘴入口圆角的存在削弱了空化,不利于出口燃油的喷雾。此外,所选模型预测的结果也与Nurick理论关系式吻合较好。

The cavitation flow inside injector nozzle of microemulsificated biomass fuel is numerically simulated by using homogeneous mixture flow model plus full cavitation model.The rationality of the models is verified by WINKLHOFER＇s test case.Two different nozzles with sharp and round inlets are selected to describe the influence of orifice inlet on the cavitation flow,and the results are compared with those of 0# diesel fuel.The dimensionless numbers such as the Reynolds number（Re）,cavitation number（K）,Weber parameter（We）,and discharge coefficient（Cd） are introduced to analyze the internal flow characteristics.The results show that the change pattern of injection mass flow rate,dimensionless numbers and velocity distribution on the outlet section are different before and after cavitation.Compared with diesel fuel,the microemulsificated bio-fuel needs higher injection pressure to start cavitatation and come up to supercavitaion.The existence of round inlet weakens cavitation and is unfavorable to the fuel spray.Besides,the predicted result by the model agrees well with Nurick＇s equation.