自激扫掠喷嘴气液两相流场特性研究

Gas-liquid two-phase flow field characteristics based on self-excited sweeping nozzle

为研究自激扫掠喷嘴内、外流场结构,分析高频扫掠液柱的变形和破碎过程,首先采用高速阴影成像法,在0.1~4.0 MPa压降范围内,对喷嘴的扫掠频率及扫掠张角等基本工作特性进行了测量;其次,采用实验测量结果对气液两相数值模型进行了校核;最后,采用校核后的数值模型对喷嘴内、外气液两相流场结构开展了模拟研究。研究结果表明:喷嘴内部为单相流动,无气相介质的回流;液柱的高频扫掠使其在喷嘴出口形成了一个扇形液面;液柱的自旋增强了气相对液柱的剪切作用;在扇形液面两侧,液柱的反向偏转会导致其变形和破碎;在扇形液面中间,液柱的横向扫掠形成一个高速气相区,气相速度可达液相的3倍,提高了韦伯数,使得“液丝状”的液柱进一步破碎并扩散。

In order to study the internal and external flow field structures of self-excited sweeping nozzle,and to analyze the deformation and breakup process of the high frequency sweeping liquid column,firstly,the basic operating characteristics of the nozzle,such as the sweeping frequency and sweeping angle,were measured using high-speed shadowgraph within a pressure drop range of 0.1~4.0 MPa.Secondly,the experimental results were used to validate the numerical settings of gas-liquid two-phase model.Finally,the validated numerical model was employed to simulate the gas-liquid two-phase flow field structure inside and outside the nozzle.The results indicate that the internal flow of the nozzle is single-phase and there is no backflow of gas.The liquid column injected out of the nozzle sweeps at a high-frequency,forming a fan-shaped liquid surface.The self-swirling of the liquid column enhances the shear effect of gas on the liquid column.On both sides of the fan-shaped liquid surface,the reversed deflection of the liquid column will make itself deformed and broken.In the middle of the fan-shaped liquid surface,the transverse sweeping of the liquid column forms a high-speed gas phase area,and the gas phase velocity is three times as that of liquid phase,which increases the Weber number,making the filament shaped liquid column further broken and dispersed.