Modeling of supercritical-pressure turbulent combustion of hydrocarbon fuels using a modified flamelet-progress-variable approach

•A modified flamelet-progress-variable model for supercritical combustion.•Model validations based on data from laminar flames and turbulent combustion.•Model validations and numerical studies conducted in RANS framework.•Pressure effect on coaxial injection and combustion of LOx/methane.•Pressure effect on swirling injection and combustion of LOx/kerosene. Non-premixed turbulent combustion at a supercritical pressure is an important physicochemical phenomenon in many propulsion and power-generation systems. In this paper, a modified flamelet-progress-variable model, in which a simple term is proposed to approximately account for the extra turbulent mixing related to large density difference between two fluid streams, has been developed and incorporated into a single-phase general fluid numerical scheme in RANS framework for solving supercritical-pressure turbulent combustion of hydrocarbon fuels. The model was validated and then applied for studying the coaxial injection and turbulent combustion of LOx/methane and the swirling injection and turbulent combustion of LOx/kerosene at various supercritical pressures. Results indicate that for the coaxial injection and combustion of LOx/methane at a mixture ratio of 3, flame length decreases as chamber pressure increases, dictated by the penetration capability of the injected LOx stream. For the swirling injection and combustion of LOx/kerosene at supercritical pressures, flame moves closer to the injector as chamber pressure increases. This phenomenon at a higher pressure is similar to that caused by an increased inlet-flow swirling number. It suggests that increasing chamber pressure may lead to a shorter combustor for the turbulent combustion of LOx and hydrocarbon fuels.