Investigation of CO recombination in the boundary layer of CH4/O2 rocket engines

Abstract

In this work, the combustion and thermal recombination in the boundary layer of a single-element methane/oxygen rocket combustor is investigated using large-eddy simulations. The experimental configuration consists of a coaxial injector and an operating point with a nominal pressure of 20 bar and gaseous injection of both propellants are considered. A non-adiabatic flamelet model is utilized with the purpose of examining its capability to predict the wall heat transfer. Good agreement of the simulation results with measurements of heat flux and pressure profiles is obtained using the non-adiabatic model. By comparing results with a frozen flamelet model, the importance of the recombination reactions in the cold boundary layer is investigated. The species profiles of CO and CO2 are examined and the reaction pathways leading to the recombination reactions at the wall were analyzed. Results from this analysis show that the reaction of OH with CO forming CO2 is the main contributor to the additional heat release in the boundary layer.