City Research Online

Abstract

The application of supercritical carbon dioxide (sCO2) mixtures in power generation cycles could improve power block efficiency for concentrated solar power applications. Mixing CO2 with titanium tetrachloride (TiCl4), hexafluoro-benzene (C6F6), sulphur dioxide (SO2) or others increases the critical temperature of the working fluid, allowing it to condense at ambient temperatures in dry solar field locations. Therefore, transcritical power cycles, which have lower compression work and higher thermal efficiency compared to supercritical cycles, become feasible. This paper presents the flow path design of a utility-scale axial turbine operating with an 80-20% molar mix of CO2 and sulphur dioxide (SO2). A preliminary turbine design has been developed for the selected mixture using an in-house mean-line design code considering both mechanical and rotor dynamic criteria. Furthermore, 3D blades have been generated and blade shape optimisation has been carried out for the first and last turbine stages of the multi-stage design. It has been found that increasing the number of stages from 4 to 14 stages increase the total-to-total efficiency by 6.3%. The final turbine design has a total-to-total efficiency of 92.9% as predicted by the 3D numerical results with maximum stress less than 260 MPa and a mass flow rate within 1% of the intended cycle mass-flow rate. Optimum aerodynamic performance was achieved with a 14-stages design where the hub radius and the flow path length are 310 mm and 1800 mm respectively.

Publication Type:	Conference or Workshop Item (Paper)
Publisher Keywords:	AXIAL TURBINE, SUPERCRITICAL CARBON DIOXIDE, MEAN-LINE DESIGN, BLADE SHAPE OPTIMISATION
Subjects:	T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Engineering

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