Abstract In order to reduce the axial size of the supercritical carbon dioxide (SCO 2 ) Brayton cycle system and enhance its power-weight ratio, this paper proposes a counter-rotating design approach for SCO 2 turbines. The design process primarily involves 1D aerodynamic design based on theoretical analysis of velocity triangles and blade geometry modeling. A three-stage 10 MW SCO 2 axial turbine is selected as a test case and redesigned as a 1 + 1/2-stage counter-rotating turbine (CRT) configuration. Compared with the three-stage turbine, the axial length of the CRT is reduced by 63.5%. Subsequently, the performance of the designed counter-rotating SCO 2 turbine is validated through detailed numerical analysis utilizing the three-dimensional computational dynamics method, considering real gas effects of CO 2 by employing a physical property database for property calculations. The computational fluid dynamics results demonstrate that under design conditions, the isentropic efficiency is 92.4%, which represents a 12.4 percentage points improvement over the design target and satisfactorily meets the design objectives. Further analysis on the flow field was conducted, and it was found that the turbine streamlines are uniform, the entropy increase is concentrated at the trailing edge of the blades, and the average absolute outlet flow angle is 0° approaching the axial direction. The behavior of the CRT under off-design conditions is also discussed.
Wu et al. (Wed,) studied this question.
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