There is a growing interest in organic Rankine cycle (ORC) turbogenerators because they are suitable as sustainable energy converters. ORC turbogenerators can efficiently utilize external heat sources at low to medium temperature in the small to medium power range. ORC turbines typically operate at very high pressure ratio and expand the organic working fluid in the dense-gas thermodynamic region, thus requiring computational fluid dynamics (CFD) solvers coupled with accurate thermodynamic models for their performance assessment and design. This article presents a comparative numerical study on the simulated flow field generated by a stator nozzle of an existing high-expansion ratio radial ORC turbine with toluene as working fluid. The analysis covers the influence on the simulated flow fields of the real-gas flow solvers: FLUENT, FINFLO, and ZFLOW, of two turbulence models and of two accurate thermodynamic models of the fluid. The results show that FLUENT is by far the most dissipative flow solver, resulting in large differences in all flow quantities and appreciably lower predictions of the isentropic nozzle efficiency. If the combination of the turbulence model and FINFLO solver is adopted, a shock-induced separation bubble appears in the calculated results. The bubble affects, in particular, the variation in the flow velocity and angle along the stator outlet. The accurate thermodynamic models by Lemmon and Span (2006, “Short Fundamental Equations of State for 20 Industrial Fluids,” J. Chem. Eng. Data, 51(3), pp. 785–850) and Goodwin (1989, “Toluene Thermophysical Properties From 178 to 800 K at Pressures to 1000 Bar,” J. Phys. Chem. Ref. Data, 18(4), pp. 1565–1636) lead to small differences in the flow field, especially if compared with the large deviations that would be present if the flow were simulated based on the ideal gas law. However, the older and less accurate thermodynamic model by Goodwin does differ significantly from the more accurate Lemmon–Span thermodynamic model in its prediction of the specific enthalpy difference, which leads to a considerably different value for the specific work and stator isentropic efficiency. The above differences point to a need for experimental validation of flow solvers in real-gas conditions, if CFD tools are to be applied for performance improvements of high-expansion ratio turbines operating partly in the real-gas regime.
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e-mail: j.harinck@tudelft.nl
e-mail: teemu.turunen-saaresti@lut.fi
e-mail: p.colonna@tudelft.nl
e-mail: rebay@ing.unibs.it
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Computational Study of a High-Expansion Ratio Radial Organic Rankine Cycle Turbine Stator
John Harinck,
John Harinck
Process and Energy Department, Faculty of Mechanical, Maritime and Materials Engineering,
e-mail: j.harinck@tudelft.nl
Delft University of Technology
, 2628 CA Delft, The Netherlands
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Teemu Turunen-Saaresti,
Teemu Turunen-Saaresti
Fluid Dynamics Laboratory, LUT Energy, Faculty of Technology,
e-mail: teemu.turunen-saaresti@lut.fi
Lappeenranta University of Technology
, 53850 Lappeenranta, Finland
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Piero Colonna,
Piero Colonna
Process and Energy Department Faculty of Mechanical, Maritime and Materials Engineering,
e-mail: p.colonna@tudelft.nl
Delft University of Technology
, 2628 CA Delft, The Netherlands
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Stefano Rebay,
Stefano Rebay
Department of Mechanical Engineering,
e-mail: rebay@ing.unibs.it
University of Brescia
, 25123 Brescia, Italy
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Jos van Buijtenen
Jos van Buijtenen
Tri-O-Gen B.V.
, Nieuwenkampsmaten 8, 7472 DE Goor, The Netherlands
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John Harinck
Process and Energy Department, Faculty of Mechanical, Maritime and Materials Engineering,
Delft University of Technology
, 2628 CA Delft, The Netherlandse-mail: j.harinck@tudelft.nl
Teemu Turunen-Saaresti
Fluid Dynamics Laboratory, LUT Energy, Faculty of Technology,
Lappeenranta University of Technology
, 53850 Lappeenranta, Finlande-mail: teemu.turunen-saaresti@lut.fi
Piero Colonna
Process and Energy Department Faculty of Mechanical, Maritime and Materials Engineering,
Delft University of Technology
, 2628 CA Delft, The Netherlandse-mail: p.colonna@tudelft.nl
Stefano Rebay
Department of Mechanical Engineering,
University of Brescia
, 25123 Brescia, Italye-mail: rebay@ing.unibs.it
Jos van Buijtenen
Tri-O-Gen B.V.
, Nieuwenkampsmaten 8, 7472 DE Goor, The NetherlandsJ. Eng. Gas Turbines Power. May 2010, 132(5): 054501 (6 pages)
Published Online: March 3, 2010
Article history
Received:
December 30, 2008
Revised:
May 8, 2009
Online:
March 3, 2010
Published:
March 3, 2010
Citation
Harinck, J., Turunen-Saaresti, T., Colonna, P., Rebay, S., and van Buijtenen, J. (March 3, 2010). "Computational Study of a High-Expansion Ratio Radial Organic Rankine Cycle Turbine Stator." ASME. J. Eng. Gas Turbines Power. May 2010; 132(5): 054501. https://doi.org/10.1115/1.3204505
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