收缩扩张喷管中稀疏颗粒加速运动及喉道优化

直升机、运输机在简易场地起降过程中,发动机可吸入的二氧化硅等微小颗粒,对叶片造成冲击磨损,冲击速度可达200m/s以上。冲蚀试验常采用直喷管加速固体颗粒,在入口总压为0.6 MPa时,颗粒速度难以达到200m/s。为更有效地加速颗粒,采用超音速收缩-扩张喷管,通过数值模拟研究了该喷管对稀疏二氧化硅颗粒的加速运动,并利用实验验证了数值模拟的准确性。在此基础上,对喉道尺寸进行优化以提高喷管对颗粒的加速性能。结果表明:收缩-扩张喷管对颗粒的加速主要发生在扩张段,管内激波不会引起颗粒速度的震荡,颗粒的加速度与气流、颗粒之间的相对速度以及气流的密度有关;在入口总压为0.6 MPa的条件下复现5级砂尘环境,喉道半径为0.001 6m的喷管加速效果最佳,可获得的颗粒速度达到218m/s。

A Research on Particles Motion and Throat Optimization for Accelerating Sparse Particles in Supersonic Convergent-divergent Nozzle

Small silica particles may be inhaled into the engine when helicopters and other aircraft are in the process of takeoff or landing on the gravel ground. The particles collide with engine blades at a relative speed more than 200 m/s, thus eroding the blades seriously. The particle velocity is hard to reach 200 m/s with straight-wall nozzle when total pressure is 0-6 MPa. So supersonic convergent divergent nozzle is designed to increase the particle velocity. Particles motion in and out of the nozzle and throat optimization are studied by two phase simulations. The research shows that particles are speeded up mainly in the divergent part of the nozzle, and the acceleration of particles not only depends on the relative speed of gas and particles, but also the gas density. The throat radius is optimized, and the particles can be accelerated to 218 m/s by the nozzle with 0-001 6 m throat radius.