DNS analysis of the effects of combustion on turbulence in a supersonic H2/air jet flow

Abstract

In this paper, the effects of combustion on turbulence features are investigated by direct numerical simulation (DNS) of supersonic round turbulent hydrogen jet flows. Two DNS cases are conducted: the one is combustion hydrogen/air jet and the other is non-combustion jet with the same components as a comparison case. In the DNS, the supersonic jet consists of 85% hydrogen and 15% nitrogen in volume with temperature of 305 K and jet velocity of 900 m/s. The ambient air velocity is 20 m/s and temperature is 1150 K. The Reynolds numbers based the jet exit diameter and hydrogen jet velocity both are 22000 and the jet Mach numbers both are 1.2. The DNS results show that occurrence of combustion significantly delays the transition of the jet flow, and results in a 38% decrease in the peak of turbulent kinetic energy, compared with the non-combustion jet flow. The decreasing of the Reynolds number due to the heat release is considered as the main reason. Compared with the non-combustion jet flow, the combustion jet flow has more complete coherent vortex rings in the early stage. In addition, the positive and minus energy fluxes of combustion jet flow are always larger than that of non-combustion jet flow.