Mixing Characteristics of Active Microjet-Based Actuators in a Supersonic Backward-Facing-Step Flow

Mixing in self-ignited supersonic combustors continues to be an important process that influences the performance and limitations for propulsion applications. A common approach for current generation combustors involves the employment of fuel jet injection that enhances the shear layer mixing. Associated with these fuel jets issuing in a supersonic crossflow, a bow shock coupled with an oblique shock causing total pressure losses and consequently reducing scramjet combustor efficiency. Multiple microjet injection forming a virtual ramp at the trailing edge of backward-facing step will reduce the pressure losses due to a weak shock formed while enhancing mixing and increasing the shear layer thickness. Three microjet arrays supplied with different pressures were used to form the virtual ramp. Shadowgraph was used to visualize the flow features. The shear layer mixing was characterized using particle image velocimetry. Relative comparisons were made with and without the microjet actuation under non-reacting conditions.