类X-47狭缝式进气道的流动特征与工作性能

对一种背部安装的狭缝式进气道进行了设计和仿真研究,获得了该类进气道的流动特征和工作特性.结果表明,由于存在剧烈的通道弯曲和宽度收缩,进气道的内部流动较为恶劣,边界层气流在通道的上方和下方两侧堆积,并在扩压器后段的上部出现了分离.当自由流马赫数为0.70、迎角为0.时,进气道出口截面的总压恢复系数为0.975,总压畸变指数则达0.484.另外,进气道前方的大鼓包未能起到有效排除前体边界层气流的效果,而正迎角下前体侧棱产生的前缘涡则能将前体边界层扫向机体的两侧,有效减少了进入内通道的低能气流,对出口截面下方两侧的低总压区起着抑制作用.本文的工作还为狭缝式进气道的改进设计提供了依据.

Flow Structure and Performance Characteristics of X-47-like Slot-shaped Inlet

A top-mounted slot-shaped inlet similar to that of an X-47 vehicle is designed and numerically studied to obtain its flow structure and performance characteristics. Results indicate that due to rapid changes in duct width and longitudinal curvature the internal flow of the slot-shaped inlet is unsatisfactory. The boundary layer accumulates near the top and bottom sides of the diffuser and even reverses at the top region of the duct aft part. When the free stream Mach number is 0.7 and the angle of attack is 0°, the total pressure recovery coefficient of the inlet is 0.975, and the total-pressure-distortion index reaches 0.484. In addition, the huge bump in the front of the duct fails to push the fuselage boundary layer away from the entrance of the inlet, whereas at positive angles of attack the leading-edge vortices on the upper surface of the forebody sweep aside part of the fuselage boundary layer, thus improving the quality of the entering flow and finally restraining the low total pressure regions at the bottom side of the exit plane. The results obtained may serve to provide direction for performance enhancement of this type of inlet.