Large Eddy Simulation of Ethylene-Air Combustion in High Speed Flow Environments

This paper characterizes the unsteady behavior of a bluff-body stabilized ethylene-air flame in a supersonic coflow using Large Eddy Simulation (LES). The geometry consists of a cylindrical centerbody that extends through a converging-diverging supersonic nozzle to form a coflow of air. Ethylene is injected axially through a single port centered at the tip of the centerbody. The centerbody diameter is much larger than the injector port diameter to create a large recirculation region for flameholding. Combustion is modeled using a well-established 22-species, 206-step finite-rate reaction mechanism with detailed thermodynamics and transport. The recirculation zone created in the centerbody wake promotes turbulent mixing and stabilizes the flame. Results provide a qualitative description of the unsteady flow-flame interactions, species mass fraction distributions, flame premixedness, and relevant time and length scales among other quantities of interest. Emphasis is placed on understanding the local character of the flame relative to the dynamics of the fuel injector and wake, as well as implications with respect to modeling these processes accurately.