气液针栓式喷注器液膜破碎过程和结构的数值研究

Numerical simulation of liquid sheet breakup process and structures in gas-liquid pintle injector

为了更好地认识针栓式喷注器雾化场的结构,基于网格自适应加密技术以及VOF (volume of fraction)方法追踪气液的分界面,采用realizable k-ε湍流模型模拟整个流动过程,还原了不同时刻气/液撞击的初次破碎过程,数值模拟结果与高速摄影试验结果定性定量对比均吻合较好,验证了数值方法的准确性。进一步对针栓式喷注器气/液撞击的初次破碎过程、内部流场涡结构、速度场进行分析,研究了初次破碎雾化的动力学过程和机理。研究结果表明:液桥的形成主要是由液洞的扩展和拉伸、合并而形成,而液滴主要是由中心液膜拉伸、液丝断裂以及液桥断裂而形成,液膜破碎阶段形成的涡结构是造成液膜断裂的主要原因。

Numerical simulations of the primary atomization in the gas-liquid pintle injector were conducted,using the VOF(volume of fraction)method with the adaptive mesh refinement to capture the gas-liquid interface.The realizable k-εturbulence model was adopted for the turbulence modelling.The entire breakup process and the gas-liquid interaction at different instants were captured.The numerical results were qualitatively and quantitatively in good agreement with the high-speed photograph measurement results,which verified the accuracy of the numerical method.The breakup process and mechanism of the primary breakup and atomization were studied by analyzing the evolution of the gas-liquid interface,the vortex structure of the flow field and the velocity field in the pintle injector.The results showed that the formation of the liquid bridge was mainly caused by the expansion,stretching and coalescence of the liquid hole,while the droplet was mainly caused by the stretching of the central liquid sheet,the fractures of the liquid ligament and liquid bridge.The fracture and displacement of liquid sheet was mainly attributed to the vortex structure formed in the liquid sheet breaking stage.