Recent advances in supercritical CO2 combustion for zero-emission direct-fired power cycles

Oxy-fuel combustion in supercritical carbon dioxide (sCO 2 ) cycles can increase plant efficiencies up to 52% and reduce pollutants such as NOx while enabling 100% CO 2 capture. The supercritical CO 2 power cycle is a revolutionary concept and has demonstrated electricity costs, which are competitive compared to the world's widely implemented conventional coal and natural gas power plants. This increase in efficiency is mainly driven by the near-liquid density of the working fluid (sCO 2 ) in the supercritical regime before entering the turbine for energy extraction while converting to the high-pressure high-density sCO 2 gas. In addition, direct supercritical CO 2 combustion engine cycles produce zero CO 2 emissions to the atmosphere since CO 2 , a combustion product, is the system's working fluid which can be regenerated to the combustor medium or captured at high pressures for storage/transportation. Although trace-level NOx and SOx emissions may arise from fuel and oxidizer impurities, the cycle is designed for zero greenhouse gas emissions with inherent CO 2 capture. This novel concept is of great interest to various government agencies, the energy industry, and researchers across the globe. However, such devices operate at extreme pressures up to 300 bar and significantly higher CO 2 dilution levels (∼95%) than current combustors; hence knowledge of combustion mostly falls outside of well-documented literature. There have been worldwide efforts in developing and validating a combustion chemical kinetic mechanism for sCO 2 oxy-methane/syngas combustion, modeling thermal and transport properties, and fundamental non-premixed sCO2 flame characteristics useful in computational fluid dynamic code (CFD) simulations for sCO 2 oxy-combustor development. This review paper will present a summary and examples from recent efforts in understanding sCO 2 diluted combustion physics, chemistry, and thermal properties.