Aerodynamic Gas Turbine Compressor Design for an Oxy-fuel Combined Cycle

A number of different CCS-technologies are currently being developed to reduce CO, emissions from thermal power stations. One of these technologies is based on the oxy-fuel combined cycle process, the basics of which have been described in several publications. The key difference in this cycle is the working fluid, which requires further investigation. The working fluid in the topping gas turbine cycle of an OCC mainly consists of CO2 (80-95 wt%) and steam (5-15 wt%), with a few percentage of enriched N-2 and Ar. The gas properties of this working fluid differ significantly from those of a conventional air-breathing gas turbine; hence, the gas turbine has to be designed accordingly. The isentropic exponent is lower, for example, with the result that a higher pressure ratio is required in an oxy-fuel combined cycle gas turbine than in a conventional combined cycle to achieve exhaust gas conditions that fit the design of a conventional bottoming steam cycle. This higher pressure ratio results in additional challenges in the design of the aerodynamic compressor. The amount of information in the public domain about designing an oxy-fuel gas turbine is sparse and is mainly limited to the cycle design. The main objective of this work is therefore to demonstrate the feasibility of achieving the aerodynamic compression in a single-spool compressor design, suitable for an oxy-fuel combined cycle application, with the aim of bringing the technology closer to commercialization. The aerodynamic compressor design includes 1D mid-span and 2D through-flow design calculations, and a steady-state 3D analysis calculation for validation. The compressor's design suits an oxy-fuel combined cycle with a net plant power of 115 MWel.