Combustion modes of the lean methane-air mixture in a U-shaped burner

Base on the model of a flowing reactor with an inert internal body, a numerical study of a lean methane-air mixture burning in a U-tube is carried out in the case of initiation of the combustion process by a preliminarily heated internal wall of the tube. The calculations were carried out for two values of a tube extent for revealing qualitative distinctions between established operating regimes. It is shown that, depending on the dimensionless parameter of heat exchange intensity in the reaction mixture on an external wall of the tube and dimensionless parameter of the mixture current, a high-temperature or low-temperature stationary regime, or an oscillatory operating mode can be implemented in the system. It is determined that the high-temperature stationary state is established at some distance from the input of the tube, and oscillatory modes are implemented in the top part of the tube; at the same time, the mixture in the bottom part of the tube has a decreasing temperature profile. It is shown that the parameter of heat exchange intensity of the mixture at the external wall of the tube determines the depth of establishing the high-temperature steady state.