Aerodynamic turbine design for an oxy-fuel combined cycle

The oxy-fuel combined cycle (OCC) is one of several carbon capture and sequestration (CCS) technologies being developed to reduce CO2 emissions from thermal power plants. The OCC consists of a semi-closed topping Bryton cycle, and a traditional bottoming Rankine cycle. The topping cycle operates with a working medium mixture of mainly CO2 and H2O. This CO2-rich working fluid has significantly different gas properties compared to a conventional open gas turbine cycle, which thereby affects the aerodynamic turbine design for the gas turbine units. The aerodynamic turbine design for oxyfuel gas turbines is an unexplored research field. The topic of this study was therefore to investigate the aerodynamic turbine design of turbines operating with a CO2-rich working fluid. The investigation was performed through a typical turbine aerodesign loop, which covered the 1D mid-span, 2D through-flow, 3D blade profiling design and the steady-state 3D analysis. The design was performed through the use of conventional design methods and criteria in order to investigate if any significant departures from conventional turbine design methods were required. The survey revealed some minor deviations in design considerations, yet it showed that the design is feasible with today's state-of-the-art technology by using conventional design practice and methods. The performance of the oxy-fuel combined cycle was revised based on the performance figures from the components design. The expected total performance figures for the oxy-fuel combined cycle were calculated to be a net electrical power of 119.9 MW and a net thermal efficiency of 48.2%. These figures include the parasitic consumption for the oxygen production required for the combustion and the CO2 compression of the CO2 bleed stream.