Supersonic Combustion - A Shock Tunnel and Vitiation-heated Slowdown Tunnel Comparison

TLDR: In this paper, a comparison between supersonic combustion in two commonly used, but fundamentally different, facilities for scramjet research - a vitiation-heated blowdown tunnel and a free piston shock tunnel -was made.

Abstract: A comparison has been made between supersonic combustion in two commonly used, but fundamentally different, facilities for scramjet research - a vitiation-heated blowdown tunnel and a free piston shock tunnel. By passing the shock tunnel freestream flow through a normal shock and then expanding it to Mach 2.5, combustor inlet conditions were nominally replicated between the two facilities, as were the combustor geometries. A straight rectangular duct and a diverging duct, both employing central strut hydrogen injection, were used. Boundary layer growth and separation in the straight duct limited meaningful comparisons to a fuel equivalence ratio Φ of the order of 0.20. With the diverging duct, comparisons were made up to Φ = 1.05. Reasonably good agreement between the two facilities was found, with differences attributable to differences in the flow parameters between the two facilities, particularly the total enthalpy and static temperature, and to the large water content of the vitiation-heated flow.