Effects of Supercritical Carbon Dioxide Dilution on Oxy-Methane Combustion Using a DNS Approach

Supercritical oxy-combustion cycles use supercritical CO2 (sCO2) as a working fluid and diluent with pure oxygen as the oxidizer, providing high efficiency and reduced emissions for power generation with carbon capture. Designing direct-fired oxy-fuel combustors is challenging due to the lack of understanding of combustion at supercritical pressures (~200 bar) influenced by sCO2 dilution. A Direct Numerical Simulation (DNS) framework, incorporating a one-step chemistry mechanism and multispecies real-fluid properties, reveals supercritical mixing and combustion under the operating conditions of Southwest Research Institute's (SWRI) sCO2 oxy-combustor. The results show that CO2 dilution significantly impacts heat release rate, temperature, and flame edge thickness. Optimal heat release rate and lowest CO production occur at 75%-80% CO2 dilution, with a maximum temperature of 2000 K. These findings provide essential insights for designing sCO2 oxy-combustors.