NUMERICAL INVESTIGATION OF SUPERSONIC INLET WITH REALISTIC BLEED AND BYPASS SYSTEMS

A supersonic mixed-compression inlet was designed for Mach 2.5 and aerodynamically analyzed using a CFD approach. Its ramp bleed and throat bypass systems were simulated in order to examine the physical nature of flow in the system. From the calculation, two types of unstart were predicted. One is a shock/boundary-layer interaction induced unstart. The other is usual unstart due to failure of pressure balance. A ramp bleed was found to play an important role for avoiding the former unstart. For avoiding or delaying the latter unstart, a throat bypass system plays an important role. Shock-capturing and stabilizing effects by the throat bypass were also confirmed numerically. Furthermore, the mechanism of improving pressure recovery in a shock-capturing mode, a critical mode, was examined in detail and the important role of a throat slot was revealed numerically for the first time. A streamline passing over the slot automatically constructs an optimum equivalent wall boundary in accordance with the flow conditions around the system. On the high-back-pressure-shock-capturing mode, the equivalent wall boundary reduces mainstream throat area, because of high pressure in the throat plenum chamber, and weakens the terminal shock. As a result, the total pressure recovery improves. This noteworthy result could be obtained owing to the great advantage of the CFD approach.