CONTROL OF FLAME-HOLDING SUPERSONIC AIR-FLOW BY SECONDARY AIR INJECTION

Active control tests were performed to improve flame-holding in a fixe d-geometry rectangular scramjet combustor at an off-design point and t o improve self-ignition In the combustor. With a fixed-geometry combus tor, the pressure oscillation originated from unstable flame-holding, and/or blowoff were measured at an off-design point. Eight air injecto rs were installed in the combustor wall, and secondary air was injecte d into the boundary layer, which developed downstream of a step that c ontrolled 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 fixed-geometry combustor. The control system was effective in impro ving combustion oscillation and/or blowoff at an off-design point and was responsive to a rapid condition change. It was also valid for impr oving the self-ignition limit.