Improving Off-Design Nozzle Performance Using Fluidic Injection

Use of fluidic injection of high-pressure air is proposed to improve nozzle performance and reduce the off-axis component of thrust at off-design flight conditions, generally at low Mach number and low pressure ratio. Hypersonic flight vehicles are typically designed with a high expansion ratio single expansion ramp nozzle (SERN) with a design point at high Mach number flight conditions. However, at low Mach number flight, lower nozzle expansion ratios are required for optimum performance. Thus, these vehicles suffer from poor performance throughout much of the low-speed flight regime. In addition, the long SERN ramp creates a significant off-axis thrust at off-design, which must be overcome by shifting the vehicle center-of-gravity or by using the vehicle?s control surfaces. This concept manages the engine and freestream flows to alleviate these problems and improve the overall vehicle performance. The Phase I effort will focus on employing 1-D and CFD analyses to prove concept feasibility and to define the injectant pressure and flow requirements. The Phase II program will focus on a preliminary design, including integration issues, design of the secondary valve and injection features, and component testing to verify overall performance gains.