Understanding the total pressure losses nature in a Scramjet Combustor

The total pressure losses are of a twofold source: 1. due to high losses due to friction and shock waves as predicted by the Fanno model or 2. due to the release of heat in a supersonic stream, according to Rayleigh's law. Understanding the contribution of each of these terms is essential to improving engine performance. Several studies have been conducted to define the most efficient injection systems, flame anchoring techniques and combustor geometries. Most often, the techniques used to improve mixing, have the disadvantage of increasing the total pressure losses in the flow. For example, cross-flow injection, which on the one hand allows greater penetration and therefore good mixing, on the other hand allows too strong shocks. Shock waves also generate boundary layer separation regions on the wall, or subsonic zones downstream of the impact itself, which while generating high total pressure losses, allow for more efficient mixing. Therefore, the aim of this work is to study these two effects separately, by numerical simulations of the combustor flow field before fuel injection, and after fuel ignition. RANS numerical simulations of the Scramjet Hypersonic International Flight Research Experimentation (HiFIRE-2) combustor were performed. JP-7 was selected as a fuel for the experimental test work HiFiRE2, as it is well known for its good endothermic nature with low volatility and high thermal stability.