Control of Flame-Holding in Supersonic Airflow by Secondary Air Injection

Active control tests were performed to improve e ame-holding in a e xed-geometry rectangular scramjet combustor at an off-design point and to improve self-ignition in the combustor. With a e xed-geometry combustor, the pressure oscillation originated from unstable e ame-holding, and/or blowoff were measured at an off-design point. Eight air injectors were installed in the combustor wall, and secondary air was injected into the boundary layer, which developed downstream of a step that controlled the effective cross-sectional area of the combustor. Signals from pressure transducers on the combustor wall were used as feedback signals for the control. This control system was simple to install in a e xed-geometry combustor. The control system was effective in improving combustion oscillation and/or blowoff at an off-design point and was responsive to a rapid condition change. It was also valid for improving the selfignition limit.