CH4/O2 4 /O 2 supercritical flame structure and simulation

The oxi-combustion of methane is studied by high-fidelity simulations in the context of liquid rocket engines. The pressure thus exceeds the critical pressure of incoming fluids but stays below the critical pressure of water. Methane and oxygen are injected at cryogenic temperatures in a splitter plate configuration that mimics a small part of a co-axial injector. Simulations are performed with a reduced chemistry containing 17 species and 44 reactions, along with a specific treatment for thermodynamics and transport properties to address real-gas effects. The resulting flame is stuck between two dense flows that locally modify the turbulent kinetic energy. As a consequence, the flame can split and experience different regimes of combustion: non-premixed, lean, and rich premixed. Accordingly, species concentration varies with the flame regime and OH is only found in regions poor in methane, contrary to H2O. 2 O. For the latter, depending on the local temperature, a part of it should be in liquid or even solid phase meaning that additional modeling effort should be performed in the future. Large-eddy simulations are conducted with a no-model assumption or using the TFLES approach for the subgrid species source term. The global flame characteristics are recovered but coarsening the mesh makes the rich regime disappear.