凝胶的撞击射流雾化DNS研究

To better understand the breakup mechanism of non-Newtonian gelled propellants with a strong unsteady feature, it is necessary to accurately describe the spatial and temporal change of the liquid internal viscosity. However, the current experimental setups do not possess the ability to measure the non-Newtonian viscosity after the impingement. Numerical methods like RANS, LES or DES cannot describe the flow details in a decent way. Therefore, our proposal is exactly to solve this problem. We will investigate the property change of gelled propellants after impingement with our own-developed DNS tool, and analyze the influence of this property change on breakup mechanism. In detail, we will first develop the numerical tool, and validate it with classical cases from literature. A few parameters will be varied to examine their influence on the non-Newtonian viscosity and the impinging jet breakup. Meanwhile, the correlation among the shear-thinning viscosity, the flow state, the shear behavior and the breakup feature will be discussed. Finally, based on the non-Newtonian viscosity, a new method to determine the breakup mode of gelled propellants with impinging jet injectors will be proposed. The results of the current proposal will definitely promote the application of gelled propellants in liquid rockets.

凝胶的撞击射流雾化极具非定常特征，要深入理解其雾化机理就必须精确捕捉流体内部各处异性非牛顿粘性的时空域变化，但目前的实验诊断方法仍无法捕捉凝胶离开喷嘴后的粘性特征，RANS、LES、DES等常规数值手段也无法对两相精细流动进行准确描述。因此，本项目将发展精细化直接数值模拟DNS工具，专门针对凝胶的撞击射流雾化问题分析其非牛顿粘性特征，并进而研究凝胶撞击雾化的物理机制及雾化模态。具体包括：发展直接数值模拟DNS工具，并基于文献实验结果开展典型算例对比验证；改变喷注参数分析凝胶的非牛顿粘性在流变及撞击雾化过程中的变化，以及非牛顿粘性与流态转变、剪切稀化特征和喷注破碎品质之间的关联，并深入分析其撞击雾化机理；定义基于凝胶非牛顿粘性的本地无量纲参数，提出评判凝胶撞击雾化模态的新定量准则。本项目的顺利开展，将有望为凝胶推进剂在液体火箭发动机中的工程应用提供坚实的理论指导与技术支撑。