Experimental investigation of ramp injection into supersonic crossflow using nanoparticle-based planar laser scattering

Nanoparticle-based Planar Laser Scattering (NPLS) method and other nonintrusive optical diagnostic techniques have been employed in an experimental investigation of the flowfield downstream of ramp injection system in a scramjet combustor. The high enthalpy supersonic air crossflow is at Mach 2.0, and the fuel is simulated by nitrogen injected at Mach 1.0. Mixing the injection nitrogen gas with nanoparticles, the fuel distribution and instantaneous displacement demonstrated by the nanoparticles are imaged with laser sheet scattering measurement. The NPLS method which gives clear identification of the jet/mainstream interface in each of the three visualized cross planes and in the side views has proved to be a successful flow visualization technique for three-dimensional supersonic flow. Mixing characteristics of ramps with different geometries are inferred from image analysis. The results indicate that the mixing process is dominated by the ramp-generated streamwise vortices. It is also found that the sweepback configuration strengthens the streamwise vortices greatly and the reflected oblique shock projecting onto the injection plume can intensify mixing effectively.