双腔室自激振荡脉冲喷嘴空化射流的数值模拟

Numerical simulation of cavitating jet in dual chamberself-oscillation pulse nozzle

为研究自激振荡脉冲喷嘴结构参数对内部空化射流流场的影响,以单腔室自激振荡脉冲喷嘴结构为基础,对采用前后串联方式建立的双腔室自激振荡脉冲喷嘴进行Fluent数值模拟.选用RNG k-ε湍流模型,分析来流雷诺数、前后腔室腔长比、腔径比的改变对空化射流的影响,并以腔室内的液相体积分数及喷嘴出口处的流速作为流场变化的评价指标.数值研究结果表明:当双腔室内部来流雷诺数由2.98×105变到4.31×105时,喷嘴腔室内的空化程度先增大后减小,与之相对应的液相体积分数先减小后增大;前后腔室腔长比为0.67时,腔室内空化气囊形状规则同时具有对称分布的涡环结构,有利于脉冲空化射流的发生;当腔室腔径比为1.20时,腔室内涡环结构与空化气囊均具有一定的对称性,同样可促进脉冲空化射流的发生,同时在出口处速度分布均匀且流速较大.

Based on the single chamber self-oscillation pulse nozzle,a dual chamber self-oscillation pulse nozzle was designed by adding an additional single chamber nozzle in series.The cavitating jet flow in the dual chamber nozzle was simulated by Fluent in terms of the RNG k-εturbulence model to clarify effects of the nozzle geometrical parameters on the cavitating jet flow field.The influences of Reynolds number,chamber length ratio and diameter ratio on the cavitating jet were analyzed with the liquid volume fraction in the chamber and the velocity at the nozzle exit.The numerical results show that when the Reynolds number rises to 4.31×10^5 from 2.98×10^5,the cavitation extent in the chamber increases first and then decreases,and the corresponding liquid volume fraction firstly decreases and then increases.When the chamber length ratio is 0.67,the airbag in the chamber presents a regular shape and is with symmetrical vortex ring structure,which facilitates the occurrence of pulse cavitating jets.When the chamber diameter ratio is 1.20,both the vortex ring structure and the airbag in the chamber are symmetrical and promote the onset of pulse cavitating jets,and the velocity at the nozzle exit is more uniform and higher.