AFRL Enhances Reactive Conformal NLET Technology Published Dec. 13, 2006 By Plans and Programs Directorate AFRL/XP WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- As part of its Reactive Conformal Inlet Technology Enhancement program, AFRL is examining conformal inlet technology. Conformal engine air inlets are flush to an air vehicle's fuselage, causing less drag and increasing survivability compared to other inlet designs. AFRL is examining technology to take full advantage of the benefits associated with conformal inlets while minimizing a common drawback--airflow distortion that negatively affects engine performance. AFRL investigated a conformal inlet that incorporated active flow control with an injection slot near the leading edge of the conformal inlet ramp in order to keep flow attached to the ramp. AFRL evaluated two flow control slots. The first flow control slot was larger, with a slot height equal to 20% of the inlet height. The second flow control slot was smaller, with a slot height equal to 5% of the inlet height. In addition, engineers evaluated the effectiveness of the ramp's sidewalls, since the shape of these sidewalls passively influences air quality. AFRL engineers evaluated the effectiveness of these active and passive flow control variations during a wind tunnel test involving various tunnel Mach numbers, inlet mass flow rates, and flow control mass flow rates. Test results showed that the smaller flow control slot performed as desired and was most effective at lower wind tunnel Mach numbers and at higher active flow control mass flow rates. While the ramp sidewalls did not significantly influence air quality, they proved a good starting point for further research. AFRL engineers are working to incorporate this valuable data into future conformal inlet designs that require smaller amounts of active flow control air and have improved passive flow control methods.