Large eddy simulations of supersonic combustion of mixture of H₂/CH₄/C₂H₄ based on skeletal chemical mechanism

Endothermic hydrocarbon fuels are used widely in cooling strategy because they can absorb additional heat through physical and chemical heat sinks. In this paper, supersonic combustion of pure hydrogen and pyrolytic products of hydrocarbon fuels (H₂/CH₄/C₂H₄ mixtures) based on DLR model scramjet combustor are investigated. A skeletal chemical mechanism with 39-species and 386-reactions for combustion of H₂/CH₄/C₂H₄ is achieved from Konnov Model using two-stage DRGEP method and validated on auto-ignition delays and laminar burning velocity. Large Eddy Simulation with Partially Stirred Reactor combustion model is performed based on OpenFOAM code. The total equivalence ratio is set to 0.034 for hydrogen-fuel and the mixture fuel. Simulation results show that with addition of methane and ethylene, the maximum flame temperature at chamber becomes lower, and the same trend can be found in OH mass fraction distributions. The mixtures show a weaken flame zone compared to the pure hydrogen, which may result from the larger ignition delays of mixture fuels. Mixture fraction is extracted to indicate the relationship between distributions of CO₂ and OH. Chemical reaction pathways of CO₂ generation using Rate-Of-Production analysis are performed at different locations for X=125mm. CO+OH=CO₂+H is the most important reaction in CO₂ generation for three locations.