Working fluid replacement in supersonic organic Rankine cycle turbines

[+] Author and Article Information
Martin White

Research Associate, Department of Mechanical, Engineering and Aeronautics, City, University of London, Northampton Square, London, EC1V 0HB

Christos N. Markides

Head of the Clean Energy, Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ

A.I. Sayma

Professor of Energy Engineering, Department of Mechanical, Engineering and Aeronautics, City, University of London, Northampton Square, London, EC1V 0HB

1Corresponding author.

ASME doi:10.1115/1.4038754 History: Received January 31, 2017; Revised October 16, 2017


In this paper the effect of working fluid replacement within an organic Rankine cycle turbine is investigated by evaluating the performance of two supersonic stators operating with different working fluids. After designing the two stators, intended for operation with R245fa and Toluene working fluids with stator exit Mach numbers of 1.4 and 1.7 respectively, the performance of each stator is evaluated using ANSYS CFX. It is then hypothesised that the stator design points can be scaled to alternative working fluids by conserving the Prandtl-Meyer function and the polytropic index within the nozzle. A scaling method is developed and further CFD simulations for the scaled operating points verify that the Mach number distributions within the stator, and the non-dimensional velocity triangles at the stator exit, remain unchanged. This confirms that the method developed can predict stator performance following a change in the working fluid. Finally, a study investigating the effect of working fluid replacement on the thermodynamic cycle is completed. The results show that the same turbine could be used in different systems with power outputs varying between 17 and 112 kW, suggesting the potential of matching the same turbine to multiple heat sources by tailoring the working fluid selected.

Copyright (c) 2017 by ASME
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