Effects of bleed hole size on supersonic boundary layer bleed mass flow rate

Abstract

The bleed hole diameter, depth, and boundary layer thickness are key design parameters of a supersonic bleed system. The evolution trend of single-hole bleed flow coefficient with the ratio of boundary layer thickness to bleed hole diameter and the ratio of bleed hole depth to diameter is investigated by numerical simulations under choking and non-choking conditions. The results show that the subsonic leading edge of the circular hole and the subsonic part of the boundary layer are the main factors causing lateral flow of the bleed hole. The effect of diameter on bleed mass flow rate is due to the viscous effect which reduces the effective diameter. The larger the ratio of displacement thickness to bleed hole diameter, the more obvious the viscous effect is. The depth affects bleed flow rate by changing the opening and closing states of the separation zone. When a certain depth is reached, the development of the boundary layer reduces the effective captured stream tube and thus reduces the bleed mass flow rate. The main objective of the study is to obtain the physical mechanism of the bleed hole size parameters affecting the bleed mass flow rate, and to provide theoretical guidance for the selection of the size of bleed holes in the design of a porous arrays bleed system in hypersonic inlets.

概要

目的

在超声速来流条件下, 探索影响抽吸流量的关键 参数, 为高超声速进气道抽吸系统的设计提供 参考.

方法

1. 从抽吸系统提取出边界层厚度、抽吸孔径和深 度三个尺度, 并采用单变量原则, 通过数值模拟 分别研究三个尺度对抽吸流量的影响; 2. 采用普 朗特-迈耶膨胀波理论, 根据抽吸流动是由压差驱 动的物理机制, 建立超声速抽吸壅塞模型.

结论

1. 超声速圆孔抽吸包括超声速前缘、亚声速前缘 和边界层中的亚声速部分三种抽吸物理机制; 2. 在非壅塞与壅塞条件下, 随着孔径与深度比值 的变化, 流量系数具有不同的演化规律; 3. 深度 是影响抽吸流量的主要因素, 孔径是次要因素; 4. 在一定的孔径深度比值下, 抽吸在非壅塞条件 下具有回流现象, 而在壅塞条件下不具有回流 现象.