外物损伤对民用飞机短舱内/外流气动特性的影响

根据民用飞机动力装置/机体适航验证研究需要,结合三维有限元碰撞冲击仿真,进行了外物损伤(FOD)条件下发动机短舱内/外流数值模拟分析,初步获得了外罩变形对短舱气动特性的影响。结果表明:结合三维有限元碰撞冲击仿真进行的民用飞机短舱气动特性数值模拟,可以较好地分析FOD对发动机短舱内/外流气动特性和安全性能的影响;在内流方面,外罩和唇口的变形导致了巡航状态和低速大流量等状态短舱内流品质降低,一定程度上影响了进气道流通能力并进一步降低了发动机效率;在外流方面,外物损伤变形导致的气流分离致使局部唇口的前缘吸力丧失,这使得FOD短舱的阻力系数始终比光滑短舱的大,但是当外罩流动均处于失速状态时,两者的阻力特性差异降低。通过对严重影响短舱气动特性或飞机安全性的FOD进行评估,表明该研究成果可以为短舱结构设计的优化和民用飞机安全性分析提供技术依据与建议。

Effects of foreign object damage on civil aircraft nacelle internal/external aerodynamic characteristics

The aerodynamic characteristic of a civil aircraft nacelle with foreign object damage (FOD) is numerically simulated which is motivated by the engine/airframe airworthiness validation. The effects of FOD on nacelle internal/external flow characteristics and their underlying flow physics are investigated. The results suggest that the influence of FOD on the nacelle aerodynamic characteristics and the safety performance can be preferably learned in the investigation which are based on the three-dimensional finite element simulation of collision impact conducted beforehand; the damage and deformation of the cowl result in a reduced outflow quality and affect the through flow capacity of the inlet and further reduce the engine efficiency, while results in a loss of suction at the lip which leads to even greater drag coefficient of nacelle with FOD than the smooth one. Although the drag coefficients in general are becoming similar between the two when the outflows are stalling at the cowl of nacelle. The study also indicates that the numerical simulation performed in this paper will provide a technical basis and some recommendations to the safety assessment of the civil aircraft and structural design of the engine nacelle.