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A scramjet engine operates in a “started” state by capturing and maintaining supersonic air through the entire inlet. In comparison, there also exists an “unstarted” state, where the flow does not remain supersonic through the entire inlet. By over-contracting to the point where the flow chokes at the inlet throat, the inlet unstarts and becomes inoperable. Unstart can cause the vehicle to lose control due to the reduced thrust and increased forces from undesired shock structures. One method to prevent unstart is by applying a bleed system in the inlet/isolator region This study used computational fluid dynamics (CFD) to model the scramjet inlet with a bleed system. A variety of bleed slot placements and turbulence models were investigated, and the boundary layer flow type was analyzed. The optimal bleed configuration was evaluated based on the systems’ operability and inlet parameters at different flight Mach numbers and angles of attack. From the data, it is shown that by placing bleed slots near the inlet throat, the operability of the engine can be increased for different mission trajectories. The success of this project will provide a better understanding on the impact of boundary layer bleed and improve our design for scramjet inlets. |
