Aerodynamic characteristics analysis of quadrangle inlet and exhaust grille for embedded ventilation cooling system of aircraft

飞行器内埋式通风冷却系统四边形进排气口格栅气动特性分析研究

¹ AVIC the First Aircraft Institute, Xi'an, 710089, China
² School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China

Received: 27 January 2021

Abstract

Adding grilles at the inlet and exhaust of the aircraft ventilation cooling system helps to improve the aerodynamic characteristics and electromagnetic shielding characteristics of the whole system. Taking the X-47B aircraft as the research object, the quadrilateral open inlet and exhaust ducts and their grilles of the ventilation and cooling system embedded in the fuselage are designed. Based on CFD method, the influence of four design parameters of intake and exhaust grille: diversion angle, grille thickness, aperture shape and aperture size on flow resistance characteristics of the pipeline system is analyzed. The results show that the flow resistance characteristics are better when the grille diversion angle of inlet and outlet is smaller and closer to the conventional inlet and outlet. For the inlet, the rectifier effect is better when the grille thickness is larger, and the outlet of the exhaust duct needs a suitable thickness of the grille to balance the rectification and exhaust resistance. Besides, the circular hole grille shows good effect in the inlet and exhaust port. The small flow rate of inlet needs to use small aperture grilles to increase the rectification effect and suppress the internal and external flow interference, while the small flow rate of exhaust channel uses large aperture grilles, and the large flow rate uses small aperture grilles to improve the mixing rectification efficiency of internal flow to external flow.

摘要

飞行器通风冷却系统的进排气口加设格栅有助于提高整个系统的气动特性和电磁屏蔽特性。以X-47B飞行器为研究对象，设计了内埋于机身的通风冷却系统四边形开口进气道和排气道及其格栅，基于CFD方法深入分析了进/排气口格栅的4个设计参数：导流角、格栅厚度、孔径形状和孔径大小，对管道系统流阻特性的影响。结果表明，进排气道的格栅导流角越小，越接近常规进排气道，表现出更好的流阻特性；而对于进气道，格栅厚度越大，整流效果越佳，而排气道的出口需要适宜厚度的格栅兼顾整流和排气阻力；圆形孔格栅在进排气道口都表现出了较好的作用效果；进气道小流量需要使用较小孔径的格栅增加整流效果，抑制内外流干扰而排气道则小流量采用大孔径格栅，大流量使用小孔径格栅提高内流向外流的掺混整流效率。