压气机叶栅冰晶撞击特性的数值模拟研究

航空发动机吸入冰晶会导致推力损失甚至叶片损坏,对飞行安全构成潜在威胁。为了研究冰晶在压气机叶栅中的撞击特性,建立了一种分别计算颗粒撞击叶片压力面和吸力面时运动轨迹的方法,该方法可以避免冰晶颗粒轨迹交叉。在此基础上,对颗粒等效直径和形状对冰晶撞击特性的影响进行了数值模拟研究。结果表明,总收集系数随颗粒等效直径和长宽比的增加而增加。对于相同形状的颗粒,当颗粒直径从20μm增加到50μm时,总收集系数增加了44.1%;对于相同等效直径的颗粒,当颗粒长宽比从0.1增加到10时,总收集系数增加了39%。叶片压力面收集系数的增加是总收集系数增加的主要原因。冰晶撞击叶片前缘时发生破碎现象,撞击叶片表面时发生反弹现象。在叶片表面的大部分区域,冰晶颗粒发生非弹性反弹。就粒径而言,二次撞击后收集系数的分布趋势与一次撞击近似,二次收集系数的最大值减少了约70%。然而,就颗粒长宽比而言,叶片前缘处二次撞击收集系数的分布趋势与一次撞击相反,细长型冰晶颗粒撞击叶片前缘的二次收集系数反而低于粗短型冰晶颗粒撞击叶片前缘的二次收集系数。

Numerical study on the morphology of a liquid-liquid pintle injector element primary breakup spray

Primary breakup in a liquid-liquid pintle injector element at different radial jet velocities is investigated to elucidate the impingement morphology,the formation of primary breakup spray half cone angle,the pressure distribution,the liquid diameter distribution,and the liquid velocity distribution.With a sufficient mesh resolution,the liquid morphology can be captured in a physically sound way.A mushroom tip is triggered by a larger radial jet velocity and breakup happens at the tip edge first.Different kinds of ligament breakup patterns due to aerodynamic force and surface tension are captured on the axial sheet.A high pressure core is spotted at the impinging point region.A larger radial jet velocity can feed more disturbances into the impinging point and the axial sheet,generate stronger vortices to promote the breakup process at a longer distance,and form a larger spray half cone angle.Because of the re-collision phenomenon the axial sheet diameter does not decrease monotonically.The inner rim on the axial sheet shows a larger diameter magnitude and a lower velocity magnitude due to surface tension.This paper is expected to provide a reference for the optimum design of a liquid-liquid pintle injector.