The Use of Carbon Dioxide as Working Fluid for a Single-Stage Mixed-Flow Turbine

Abstract

The article considers the use of supercritical carbon dioxide (sCO₂) as working fluid in the turbine stage consisting of a vane row and a mixed-flow blade row. The operation of the existing turbine on natural gas combustion products and on supercritical carbon dioxide is analyzed by way of comparison. The numerical simulation results show that the use of supercritical carbon dioxide makes it possible to increase the turbine power output to 14.3 MW. This is more than a factor of 30 higher than the power output of the same turbine operating on natural gas combustion products. Such a significant increase of power output is achieved without changing the turbine stage design, which points to the possibility of modernizing the existing units without the need to make essential changes of the design. The turbine stage efficiency during its operation on supercritical carbon dioxide was estimated at 0.87, and that during operation on natural gas combustion products was 0.88. Despite an insignificant drop of the efficiency, the total increase of the power output results in that the use of sCO₂ is economically feasible. Based on the data obtained, a conclusion has been drawn that it is advisable to use the existing turbine stages for operation on supercritical carbon dioxide. This opens the prospects in achieving more efficient operation of power systems without the need to develop new types of turbines, decreasing capital outlays, and more rapidly introducing new technologies. The transition for using supercritical carbon dioxide as working fluid can result in obtaining a significantly higher output of turbine units while retaining high efficiency indicators and making minor changes in the equipment design.