Hybrid RANS/LES Simulation of Methane–LO_x Combustion

To have a better understanding of the liquid rocket engine combustion characteristics, numerical simulations of cryogenic combustion need to be carried out. Transcritical combustion involving methane and liquid oxygen propellant mixture is carried out in the 3D domain. Experimental works of Singla et al. in MASCOTTE test chamber are used for comparison with numerical results. Hybrid RANS/LES formulation is employed by carrying out Detached eddy simulations (DES) with a steady diffusion flamelet PDF approach to model the non-premixed combustion regime. Real gas effects are considered using Soave-Redlich-Kwong equations, and a reduced Jones–Linstedt chemkin mechanism is chosen to describe the chemistry. Further, the impact of chamber pressure is also studied by conducting simulations at a higher chamber pressure. The results obtained from the numerical study offer good agreement with experimental findings. The jet flame has thin flame front post injector inlet and gradually broadens downstream. The presence of shear layer and turbulent mixing at near-critical conditions causes large gradients of density and temperature to exist in the flow field while recirculation zones enable flame holding mechanism at Lo_x tip. At higher chamber pressure, the flame characteristics remain similar but the mixing process is subdued. DES poses certain discrepancies in simulating the rear part of flame, possibly due to the unsuccessful resolution of small, turbulent scales.