剪切气流中无黏液体横向射流破碎机理

航空发动机燃烧室中，液体燃料的雾化过程、特别是初始雾化过程非常复杂，至今无法建立准确的初始雾化模型。忽略液体射流黏性，采用线性不稳定性分析法对无黏液体（工质为水）在二维剪切横向气流中的破碎机理进行研究。通过建立射流的色散方程，根据其表面波的增长率及波数的发展情况对射流破碎进行预测。当气体韦伯数或液体韦伯数增大时，射流表面波增长率显著增加，最佳波长明显减小。液气动量比大于临界值时，Kelvin-Helmholtz （K-H）不稳定性占主导作用；反之，Rayleigh-Taylor （R-T）不稳定性占主导作用。二维剪切气流在射流方向上具有速度梯度，只改变横向气动力对射流表面波的作用。气体韦伯数与液体韦伯数对射流破碎的作用与均匀气流相似；保持气流流量相同时，负梯度剪切气流可以加速射流的破碎。

Breakup mechanism of inviscid liquid transverse jet in shear airflow

The complicated atomization process of liquid fuels, in particular, the initial atomization process, in the aero-engine combustor hinders the establishment of accurate primary atomization models. We apply the linear instability analysis to the study on the breakup mechanism of inviscid liquid (water) without considering the jet viscosity. The jet breakup is predicted according to the growth rate of the surface wave and the unstable wave number range by establishing the dispersion equation. When the Weber number of the air or the liquid increases, the growth rate of the jet surface wave increases significantly, while the optimal wavelength decreases significantly. When the liquid to air momentum ratio is larger than the critical value, K-H instability is dominant; otherwise, R-T instability is dominant. The two-dimensional shear airflow has a velocity gradient in the jet direction, changing only the effect of transverse aerodynamic force on the jet surface wave. When the jet flow rate is constant, the negative gradient shear airflow can accelerate the jet breaking.