Strut Injectors for Scramjets: Total Pressure Losses in Two Streamwise Vortex Interactions

Abstract

Pressure losses and mixing effectiveness are key parameters in the performance of an injection system suitable for scramjet engines. This work thus focuses on the characterization of the total pressure losses associated with two selected vortex interaction processes in a Mach 2.5 flow in order to better understand the role of vortex dynamics in the operation of scramjet combustors. Specifically, the interaction modes are targeted to obtain merging of two corotating vortices in one case while preventing it in the second. The streamwise vortices are shed from ramps placed on the surface of a strut mounted in a cold-flow supersonic wind tunnel. In-stream pitot and total temperature measurements are conducted at two downstream streamwise stations located within a shock-free region. Stereoscopic particle image velocimetry is used in conjunction with the intrusive measurement techniques to retrieve the local Mach numbers and the total pressure in the flows of interest. The losses are quantified through the pressure loss parameter. It is found that the main contribution to the momentum deficit in the wake is given by the shocks departing from the strut rather than by the vortices, with the merging case yielding slightly higher losses.