Understanding Scramjet Combustion using LES of the HyShot II Combustor

Abstract

Experimental and flight data for hypersonic air-breathing engines are both difficult and expensive to obtain, motivating the use of computational models to enhance the understanding of the physics involved. Here, a numerical investigation has been carried out for the HyShot II scramjet combustor using Large Eddy Simulation (LES) models together with a skeletal reaction mechanism. Based on a survey of the experimental results available for the HyShot II combustor we focus on the High Enthalpy Shock Tunnel Göttingen (HEG) case XIII, emulating flight conditions at 28 km altitude. To account for the slightly different conditions of the different experimental runs, two simulations at different global equivalence values are performed. The skeletal reaction mechanism used is evaluated against several other reaction mechanisms in order to quantify its accuracy and appropriateness for this type of flows. The LES model is observed to capture the experimental wall-pressure and heat flux data well compared with the measurement data. The LES results are then used to analyze the combined flow, mixing and combustion processes involved. The tools used include conventional as well as recently developed methods such as Takeno Flame Index and Chemical Explosive Model Analysis. These methods give a concise description of the interactions between flow, fuel-air mixing and combustion and it is found that supersonic combustion is a combination of auto-ignition regions, non-premixed flame regions and self-igniting fronts.

Modeling Analysis of an Actively Cooled Scramjet Combustor Under Different Kerosene/Air Ratios

“…The downstream combustion region is composed of the non-premixed mode in the fuel jet core and the premixed mode in the surrounded jet wake. The premixed regions are helpful to stabilize the flame through acting as an igniter for the neighbor non-premixed regions [32]. In addition to the positive heat release rate, negative heat release rate can also be observed, for example, near the leading edge of the upstream cavity and in the jet wake of the downstream fuel jet.…”

Reactive Flow Dynamics of Low-Frequency Instability in a Scramjet Combustor

“…In addition, through simple numerical analysis, they illustrated that the control of upstream-traveling shock waves generated in the combustor is essential to prevent the inlet un-start and engine surging of the scramjet engine. Zettervall et al [14] conducted a numerical simulation of the University of Michigan dual-mode ramjet combustor to investigate combustion dynamics. The results showed the flame behavior, which is the repetitive moves between the fuel injector and the cavity close-out region with a 3.0~6.0 ms period.…”