Direct fired oxy-fuel combustion as a heat source for supercritical carbon dioxide (sCO2) power cycles is a promising method for providing the needed thermal energy input. The method of combustion has the potential to provide efficient power generation with integrated carbon capture at up to 99% of generated CO2. One of the highest efficiency power cycles being considered for sCO2 cycles in the recompression cycle. In the recompression sCO2 power cycle, the amount of energy recovered from the recuperation is roughly five times the energy added via the combustor. Because of this high degree of recuperation in sCO2 power cycles, the inlet temperature of the combustor is much higher than a more traditional combustor design. This elevated combustor temperature leads to some unique design challenges and approaches which are quite different from a traditional combustion system. A combustor designed for these conditions has never been built, and thus the design of the combustor discussed in this paper started from a clean slate.
This necessitates a large degree of fundamental research which might not be necessary for a more well understood traditional combustor design process. Building on previous thermodynamic and chemical kinetics studies, a reduced order reaction kinetics model was used with ANSYS CFX software to explore various auto-ignition type combustor geometries. A discussion of some geometries and the modelling techniques used is presented. Various injector configurations were examined and metrics were used to compare the various configurations. By utilizing the CFD flow field results, a preliminary design for a 1MW-class oxy-fuel combustor was developed.
In the past, little experimental research has been conducted on combustion within carbon dioxide at pressures above 200 bar. In order to confirm the validity of the auto-ignition style combustor a small bench top test rig was constructed to test the oxy-fuel combustion at the full pressure and temperature. This system was designed to validate some of the fundamental properties of the combustion. This includes a gas sampling system and a measurement of auto-ignition delay. Preliminary, data from a bench top scale, sCO2 oxy-fuel combustor experiment will be presented.
The results from this work will enable future development of sCO2 power cycles which enable 99% carbon capture, while maintaining overall cycle efficiency which is competitive with natural gas combined cycle power plants.
