Exploration of Combustor Design for Direct Fired Oxy-fuel Application in a sCO2 Power Cycle

Significant interest has developed over the past several years in direct fired oxy-fuel combustion as a heat source for supercritical carbon dioxide (sCO2) power cycles. This is a promising method for providing the needed thermal energy input while integrating carbon capture directly into the sCO2power cycle. This innovative method of energy addition into the sCO2has the potential to provide highly efficient power generation while maintaining extremely environmentally friendly emissions. sCO2power cycles rely on a very high degree of recuperation when compared to a traditional Rankine or open Brayton cycle. This large amount of recuperation results in a high combustor inlet temperature. This high inlet temperature makes design of the combustor challenging for a variety of reasons. Additionally, since the amount of oxygen is precisely controlled, proportions of CO2, O2, and fuel in the primary burning zone can all be controlled independently. This adds considerable flexibility to the design process, which is not typically found in a combustion system using air as the oxidizer. Another major challenge and difference between this combustion system and more typical gas turbine combustion systems in the vast variation in density of the inflowing CO2that occurs between the startup state and the design point condition.

The current work focuses on the design of a 1MW thermal sized combustor. This work lays out some of the basic design sizing and cases which should be studied as part of the design effort. The exploration of some of the major geometry features and dimensions are discussed. This design will need to be capable of startup, part load, and full load operation. The maximum exit temperature of this design will approach ~1200°C. Past cycle analysis has shown this temperature to be the maximum temperature the current state of the art recuperators will permit a closed sCO2 cycle to operate. Simplified combustor geometry is described in detail so that researchers interested in simulating oxy-fuel combustion for sCO2 environments will have a starting point on which to base their work. The results of this work will be useful for others considering some of the design challenges of a direct fired oxy-fuel combustor for sCO2 application.