Experimental investigation on two stream mixing of adaptive cycle engine afterburner

This study investigated two-stream mixing flow in a simplified Adaptive Cycle Engine (ACE) afterburner under different bypass ratios, splitter plate angles, and center cone types. Based on Particle Image Velocimetry (PIV), the boundaries of main stream were extracted. The expanding main stream influences the flow in center cone and bypass injector. The recirculation region downstream of center cone is enlarged with increasing bypass ratio and splitter plate angle. By constraining the flow deflection with center cone structure, the mixing intensity downstream of the splitter plate is enhanced. These effects are defined as the splitter plate-center cone coupling mechanism. Under high baseline mixing conditions, this mechanism allows the enhancement methods to contribute a further increase in mixing intensity, reaching up to 18.99%. Turbulent kinetic energy decomposition confirms the streamwise shear is the primary contributor to mixing intensity, while the vertical mixing intensity is promoted by the density gradients caused by large temperature differences. Based on Instantaneous Vorticity Interface (IVI) orientation analysis, the multi-scale mixing enhancement mechanisms were summarized. The large-scale structures enhance the mixing intensity by enlarging the mixing region, while small-scale structures by strengthening two-stream attachment. These small-scale structures were primarily responsible for the downstream mixing intensity.