直升机中减三相流金属屑末可达性

Accessibility of metal particles in three-phase flow of helicopter intermediate gearbox

直升机中间减速器(简称“中减”)在飞溅润滑下运转,轴承会因润滑不充分或磨损产生金属屑末,若油池底部的金属屑末信号器无法及时吸附报警则会导致直升机出现故障。为此,基于CFD理论,应用Fluent18.2软件建立中减固-液-气三相流模型,应用RNG k-ε湍流模型及动网格技术,基于欧拉-拉格朗日耦合计算方法,采用VOF-DPM耦合模型仿真计算并分析金属屑末的可达性程度,且与试验获得了良好的一致性。结果表明,金属屑末在刚射入机匣内部时以其自身的运动状态为主导,在齿轮将润滑油完全搅动后以齿轮的运动状态为主导,并且运动的随机性与无序性极大,碰到机匣壁面反弹后会发生轨迹突变;所有金属屑末在机匣内均围绕齿轮有离心运动的趋势,且金属屑末的平均速度与距齿轮的距离呈非线性负相关;金属屑末在机匣内的可达性较弱,会在导油管的凹槽与回油孔口沉积,导致直升机无法达到实时报警监测,需对金属屑末易沉积的机匣结构进行改进。

The helicopter intermediate gearbox operates under splash lubrication,and the bearing will produce metal particles due to insufficient lubrication or wear.If the metal particles signal at the bottom of the gearbox fails to absorb and alarm in time,it will lead to the helicopter failure.Therefore,based on Computational Fluid Dynamics(CFD)theory,this paper established the solid-liquid-gas three-phase flow model of the intermediate gearbox,using Fluent 18.2 software.Based on the Euler-Lagrange coupling calculation method,the accessibility of metal particles was cal⁃culated and analyzed by applying the RNG k-ɛturbulence model and dynamic grids and the VOF-DPM coupling model simulation,which achieved good consistency with tests.The results show that the motion of the metal particles is mainly dominated by their own state upon initial entry into casing.After the gear completely stirs the lubricating oil,the motion state of the gear dominates,and the randomness and disorder of the movement are fairly great.The trajectory will abruptly change after bouncing off the casing wall.All metal particles in the gearbox tend to move centrifugally around the gear,and the average velocity of the metal particles shows a nonlinear negative correlation with the dis⁃tance from the gear.The accessibility of metal particles in the gearbox is weak,and the metal particles will deposit in the grooves and return holes of the oil guide pipe,which prevents the helicopter from achieving real-time alarm moni⁃toring.The gearbox structure,where the metal particles are easy to deposit,should be improved.