Transient Analysis and Control of Scramjet Isolator Flowfields

This SBIR will investigate the use of bleed slots to control shock wave/turbulent-boundary-layer interactions within the isolator of a scramjet engine. A successful control strategy for shock wave motion can prevent inlet unstart and lead to the design ofa shorter isolator yielding reduced system drag and weight. The optimal location and size of the bleed slots will be determined using Computational Fluid Dynamics (CFD) employing Reynolds-averaged Navier Stokes (RANS) methods. The effectiveness of thebleed design will be demonstrated over a range of Mach numbers, boundary layer displacement thicknesses and effective back pressures. The bleed slot design will be tested experimentally and the required mass removal rate to achieve the desired performancewill be quantified. CFD will also be used to determine the time scale associated with the shock train movement due to changes in the back pressure. The information will assist the development of an active control system for shock stabilization that will bea major part of the Phase II effort. For the design of scramjet engines, the development of effective isolators to contain the pressure rise generated by heat release within the combustor is critical. The proposed Phase I control device employing bleedslots can be used to build innovative designs for reducing the risk of inlet unstart, while decreasing the overall system drag and weight associated with long isolators. In addition, CFD analysis can provide time-accurate prediction tools to facilitate thedesign of efficient isolators and guide the development of lower-order prediction tools that can be used for isolator design in a more cost-effective manner.The control devices and analytical tools to be developed in Phase II of the proposed research program will provide very attractive alternatives to those currently in use or being considered for military and commercial use. Moreover, the control device willbe applicable not only to scramjet engine isolators, but also to other parts of the engine such as over-contracted inlets. The commercial strategy is to market the design tool to both military and commercial aircraft customers. All major airframe andengine manufacturers, e.g., Boeing Company, Lockheed-Martin, GE Aircraft Engines, and Pratt-Whitney, should be potential customers.