Study on Self-Starting Characteristics of an Inward Turning Inlet

Aiming at a detailed investigation on the self-starting characteristics of an inward turning inlet, and the influence of bleeding at the down-wall, studies using both numerical simulations and wind tunnel experiments were carried out. The numerical simulations are conducted using quasi-steady methods. In the experiments, the surface tuft flow visualization technique is used to detect the starting state of the inlet, combined with shadowgraph images. Both numerical and experimental results show that the inlet can not self-start at Ma5, attack angle 0°, and there are large-scale flow separations at the down-wall, leading to severe flow loss. In order to enhance the self-starting capability of the inlet, a porous region composed of a large amount of bleeding holes whose diameters are 3mm is used at 400mm downstream of the leading edge of the down-wall. The area of the region is 100mm×40mm and the bleeding porosity is 0.2. Results show that with the help of the bleeding holes, the inlet self-starts successfully and the total pressure recovery coefficient increases by 0.25, the flux loss due to the bleeding holes is only 1% of the captured mass flow rate. Further numerical simulations show that the self-starting Mach number of the inlet with bleeding holes is between Ma4.3 and Ma4.4 at attack angle 0°, indicating that appropriate bleeding is able to broaden the working range of the inlet. © 2019, Editorial Department of Journal of Propulsion Technology. All right reserved.