Hypersonic Mixing Enhancement by Compression at a High Convective Mach Number

Abstract

The effect of an oblique shock and of a Prandtl‐Meyer compression fan on the characteristics of the turbulent mixing of a square-cross-section hydrogen jet in hypervelocity air is presented. The air properties before the compression process are set to those found after the first shock of a two-shock external compression shcramjet inlet at a flight Mach number of 11 and an altitude of 34.5 km. The hydrogen properties are such that the convective Mach number is 1.2, the global equivalence ratio is 0.68, and the pressure of the hydrogen matches the pressure of the air at injection. Also presented is an algebraic expression approximating increase in mixing efficiency growth through compression. The algebraic expression is based on available empirical correlations for the turbulent mixing layer and is simplified for the special case of a high-convective-Mach-number mixing layer in which the Mach numbers of both streams are high. The numerical results are obtained by using the WARP code to solve the Favre-averaged Navier‐Stokes equations closed by the Wilcox kω turbulence model and the Wilcox dilatational dissipation correction, discretized by the Yee‐Roe flux-limited scheme. Results obtained indicate increase in the mixing efficiency growth by 5.7 and 6.3 times through the oblique shock and the compression fan, respectively. Despite generating weaker axial vortices, the compression fan results into a greater increase mixing efficiency growth because of a higher density increase.