尾气颗粒对可变混流涡轮增压器喷嘴环冲蚀磨损特性的数值模拟

可变涡轮增压器在运行过程中其涡轮喷嘴环会受到尾气颗粒的冲蚀磨损,造成喷嘴环叶片失效和涡轮运行效果下降。借助CFD软件对可变混流涡轮内部的气固两相流进行数值模拟计算,分析喷嘴环开度的变化和颗粒粒径对喷嘴环磨损规律的影响。结果表明：喷嘴环处于不同开度下时,磨损率和磨损区域均有所不同,磨损区域主要集中在喷嘴环压力面的中后段区域,随着开度的增大,磨损率和磨损区域均减小,压力面的磨损程度明显大于吸力面;尾气中的小颗粒因惯性较小对气流的跟随性较好,主要撞击喷嘴环前缘,且开度对喷嘴环前缘的磨损影响较小;尾气中大颗粒的运动轨迹趋于直线,主要撞击喷嘴环压力面的中后段区域;由于涡轮进气涡壳结构的周向不对称性,使得涡轮内部流场沿周向分布不均匀,导致不同周向位置的喷嘴环磨损率和磨损区域有所不同,且随着开度的增大,各喷嘴环之间的磨损差异也增大。

Numerical simulation of erosion wear characteristics of nozzle ring of variable mixed flow turbocharger by exhaust particles

The turbine nozzle ring of the variable turbocharger will be eroded and worn by exhaust particles in the process of operation,resulting in the failure of nozzle ring blade and the decline of turbine operation effect.With the help of CFD software,the gas solid two phase flow in the variable mixed flow turbine was numerically simulated,and the influence of the change of nozzle ring opening degree and particle size on the wear rule of nozzle ring was analyzed.The results show that the wear rate and wear area are different when the nozzle ring is at different opening degrees,and the wear area is mainly concentrated in the middle and rear regions of the pressure surface of the nozzle ring.With the increase of opening degrees,the wear rate and wear area decrease,and the wear degree of the pressure surface is obviously greater than that of the suction surface.The small particles in the exhaust gas have a good following effect on the airflow due to small inertia and mainly impact the leading edge of the nozzle ring,and the opening degree has little influence on the wear at the leading edge of the nozzle ring.The movement trajectory of large particles in the exhaust gas tends to be straight line and mainly impacts the middle and rear regions of the pressure surface of the nozzle ring.Due to the circumferential asymmetry of the turbine inlet vortex shell structure,the flow field in the turbine is not evenly distributed along the circumferential direction,resulting in different wear rates and wear regions of nozzle rings at different circumferential positions.Moreover,with the increase of opening degree,the wear differences among nozzle rings also increase.