Flowfield of a helicopter submerged inlet with power output shaft

• 作者: He-Xia Huang Hui-Jun Tan Zheng-Kang Lin Zi-Jie Li Shu Sun Hao Chen Zhi-Xiang Xiao
• 来源期刊: 力学学报（英文版）
• 年，卷（期）: 2021,（1）
• 所属期刊栏目: DISTINGUISHED YOUNG SCHOLARS
• 页码范围: 156-168
• 页数: 13页
• 语种: 英文

摘要

The submerged inlet is an attractive configuration for advanced helicopters due to its high stealth performance and low external drag.In this paper,a submerged inlet,integrated with a ROBIN helicopter fuselage and a simplified power output shaft,is experimentally and numerically investigated to obtain the basic flow characteristics under a freestream velocity of 23.6 m/s.The results indicate that the pylon ahead of the inlet induces a horseshoe vortex.Though the vortex is ingested into the inlet,it has little effect on the internal flows and can be neglected.When the airflow enters into the inlet,it inter-acts with the shaft with a large incidence angle,yielding a vortex pair.At the leeside of the shaft,the two side flows of the shaft impinge at the center plane,generating a local high-pressure region at the azimuthal angle of 180°,which forces the boundary layer to roll up a counter-rotating vortex pair.In addition,the airflow adjacent to the cowl lip accelerates rapidly,resulting in a local low-pressure region at the azimuthal angle of 0°.Therefore,the inlet duct has a strong circumferential pressure gradient,which originates from an azimuthal angle of 180° to 0° and induces a vortex pair at the azimuthal angle of 0°.The three vortex pairs are the main origins of the distortion at the duct exit plane,among which the one near the cowl lip with the azimuthal angle of 0° plays the dominant role.Additionally,as the velocity ratio increases from 3.9 to 5.5,the circumferential pressure gradient and the cowl lip vortex get intensified,which causes that the total-pressure recovery coef-ficient drops by 0.5％and the distortion index increases by 28％.