壁面粗糙度对喷油器内空化流动特性的影响

Numerical Simulation of Wall Roughness Effects on Cavitating Flow

水力空化对柴油机喷油器的性能及污染物的生成有重要的影响,它影响燃油的雾化和燃烧过程效率。运用混合均相流模型及完全空化模型对柴油器喷油器内部的空化流动特性进行数值模拟研究;并结合Nurick的试验验证所选模型的合理性,研究了壁面粗糙度对柴油机喷油器内部空化流动特性的影响。结果表明,在入口压力较低时,流量系数随着粗糙度的增加而减小;流量系数随着空化参数的增加而缓慢增加。当空化参数大于某一值后,流量系数则变化较小。在靠近尖角区域,空化产生的蒸汽气泡向中心轴方向迁移,使得在中心区域雾化增强。

Hydrodynamic cavitation has an important effect on the performance of Diesel injectors. It influences the nature of the fuel spray and the efficiency of the combustion process. The cavitation flow inside Diesel injector is numerically simulated by using homogeneous mixture flow model plus full cavitation model. The rationality of the models is verified by Nurick＇ s test case. The results show for small inlet pressure, the discharge coefficient Cd decreases as the roughness height increases ; The coefficient of discharge Cd increases slightly with the cavitation number K, and Cd does not depend on the roughness height when the cavitation number K is greater than certain value. The vapor bubbles migrate toward the axis. The atomization of the spray is enhanced in the central region.