This presentation will focus on technical issues and simulation challenges in modeling sCO2 oxy-combustors for direct fired cycles.  These combustors operate at high pressures (~300 bar) with large amounts of CO₂ recycled as diluent to achieve a low exit temperature (~1150K).  Thus, there is a large design space for splitting the CO2 between the injector and chamber wall for cooling.  These design parameters have a direct impact on combustor performance since oxygen concentration correlates with flame temperature and impacts CO produced which can reduce combustor performance. Furthermore, pipeline natural gas has significant amount of nitrogen (~1.6%) and can result in NO_x generation.  The modeling framework would need to address unique challenges in developing accurate models for issues including:  a) chemical kinetics and turbulence-chemistry interactions that are currently not well characterized in this regime, b) an efficient numerical framework that integrates kinetic models with large number of species (including NO_x/SO_x contaminants), and c) real fluid thermodynamic properties.  A comprehensive computationally efficient framework for high-fidelity design support is demonstrated on a conceptual oxy-combustor and the impact of various physics issues on flame stability and combustor performance identified.