Large eddy simulation of flame and thermal-acoustic characteristics in a strut-based scramjet with dynamic thickened flame model

Abstract

Supersonic combustion is a complex phenomenon with multi-physical coupling, and the thermal-acoustic coupling under supersonic inflow is also a matter of concern. In this work, Large Eddy Simulation of a strut-stabilized model scramjet is performed with dynamic thickened flame combustion model, and an efficiency function accounting for both, wrinkling loss due to flame thickening and turbulence/flame interaction. The finite-rate chemistry model and a skeletal hydrogen reaction mechanism with 9 species and 27 reactions are adopted. The method allows to predict the complex physical in supersonic reactive flow efficiently and the results are in good agreement with experimental. A comprehensive analysis of the Damköhler number, modified flame index and heat release rate is conducted to investigate the flame structure under shock-waves condition, and the difference between heat release rate and reaction rate distributions in Mach number space is also observed. The oscillation characteristics in the strut-based scramjet is discussed mode by mode using the Proper Orthogonal Decomposition approach, and the results identify a mode at 4.997 kHz, in which the thermal-acoustic coupling found, while the stronger modes are the results of multiple factors, including auto-ignition, vortexes shedding and the resulting shock-waves oscillation.

Keywords

• Supersonic combustion
• Thermal-acoustic coupling
• Large eddy simulation
• Dynamic thickened flame model
• Proper orthogonal decomposition