Large-Eddy Simulation of Traversing Jet Re-Ignition in a Wave-Rotor Constant-Volume Combustor

Abstract A three-dimensional turbulent-flow simulation with detailed chemistry is conducted to investigate re-ignition in a wave-rotor combustor when a traversing jet from a fixed prechamber torch ignition source crosses one end of a combustion channel. The formation of multiple vortices that mix hot gas with fuel-air mixture mediates the initiation of a turbulent premixed flame. Two configurations of prechamber geometries are considered in this study to deliver hot reactive gas into the constant-volume combustor with premixed ethylene and air reactants. The fluid dynamics and combustion are simulated in one wave rotor channel and the pre-combustion chamber using large-eddy simulation (LES). The role of the prechamber nozzles on the ignition delay time are investigated, with results showing substantial increase in ignition delay time with jet having inclined-converging exit orifice compared to jet of converging-diverging nozzle. The effects of the vortex structure including head vortex rings, pinch-off separation process and Kelvin-Helmholtz vortices on the onset of heat release are investigated along the axial and radial stream components. The sensitivity of near-field entrainment on turbulent mixing properties and ignition are evaluated. Normalized turbulent intensity measured along radial component of the combustor reveals increasing intensity from the channel axis and growing radially outward toward the shear layer.