同轴气流式液体射流的非线性演化规律和失稳机理研究

Jet stability, a key scientific problem, is focused in this project. The liquid jet in coaxial gas flow is studied as the research object, and theoretical analysis, numerical simulation and experimental research method are applied to carry out the research on the nonlinear evolution regularity and instability mechanism of liquid jet in coaxial gas flow. The research contents are as follows: (1) Based on the nonlinear stability theory, the disturbance wave development on jet surface and its effects on jet instability are studied; (2) DNS method is applied to carry out the research on the evolution regularity of liquid jet in coaxial gas flow at middle and low liquid Re number, and the space and time evolution of vortex structure with different scales are discussed; (3) experimental research on the shape and breakup pattern of liquid jet in coaxial gas flow, and corresponding SMD and their distribution law at different breakup patterns; (4) study on the instability mechanism of liquid jet in coaxial gas flow, to understand the causes and conditions of jet instability, and to build a new critical condition expression for the generation and shift of the different breakup patterns. By the research, the instability mechanism of liquid jet in coaxial gas flow can be understood more deeply, and the way how to control the breakup and atomization of liquid jet well will be known.

本课题将针对射流稳定性这一关键科学问题，以同轴气流式液体射流为研究对象，采用理论解析、数值模拟与实验研究相结合的方法，开展同轴气流式液体射流的非线性演化规律和失稳机理研究。研究内容为：(1) 基于非线性稳定性理论，进行同轴气流式液体射流表面扰动波发展及其对射流失稳的作用机制研究；(2) 采用直接数值模拟方法，研究中低液体Re数下同轴气流式液体射流的演化规律，明确气体引射作用下喷孔下游不同尺度涡结构的时空演变及剪切层界面的非线性演化；(3) 开展同轴气流式液体射流形态及破裂模式的实验研究，明确不同射流形态及其对应的破裂模式，各破裂模式对应的SMD及其分布规律；(4) 开展同轴气流式液体射流的失稳机理研究，明确射流失稳原因及条件，建立射流各破裂模式产生及转变的临界条件表达式，给出射流破裂模式图。通过本课题研究，可加深对同轴气流式液体射流失稳机理的理解，并为控制液体射流的分裂与雾化效果奠定基础。

本项目针对射流稳定性这一关键科学问题，以同轴气流式液体射流为研究对象，采用理论解析、数值模拟与实验研究相结合的方法，开展同轴气流式液体射流的非线性演化规律和失稳机理研究。主要研究内容及取得的重要成果包括：(1) 基于非线性稳定性理论，建立了描述射流失稳的数学模型，并进行了同轴气流式液体射流表面扰动波发展及其对射流失稳的作用机制研究；(2) 分别建立了有无考虑相变条件下，射流分裂液滴内气泡生长及溃灭的数值模型，采用直接数值模拟方法，进行了射流分裂液滴内气泡生长及溃灭的数值模拟研究；(3) 开展了同轴气流式液体射流形态及破裂模式的实验研究，明确了不同射流形态及其对应的破裂模式，并给出了索特平均粒径的解析表达式；(4) 开展了同轴气流式液体射流的失稳机理研究，明确了射流失稳原因及条件，建立了射流各破裂模式产生及转变的临界条件表达式，给出射流形态模式图。本项目研究可以加深对射流稳定性这一科学问题的理解，并为有效控制射流的分裂与雾化效果进而改善发动机的动力性、经济性以及排放特性提供依据，具有重要的理论意义和工程应用价值。