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Research Papers: Gas Turbines: Turbomachinery

Numerical Study of Multistage Transcritical Organic Rankine Cycle Axial Turbines

[+] Author and Article Information
L. Sciacovelli

DynFluid Laboratory,
Arts et Métiers ParisTech,
151, Boulevard de l'Hôpital,
75013 Paris, France
e-mail: luca.sciacovelli@ensam.eu

P. Cinnella

DynFluid Laboratory,
Arts et Métiers ParisTech,
151, Boulevard de l'Hôpital,
75013 Paris, France
e-mail: paola.cinnella@ensam.eu

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received January 16, 2014; final manuscript received January 25, 2014; published online February 28, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(8), 082604 (Feb 28, 2014) (14 pages) Paper No: GTP-14-1031; doi: 10.1115/1.4026804 History: Received January 16, 2014; Revised January 25, 2014

Transonic flows through axial, multistage, transcritical organic rankine cycle (ORC) turbines are investigated by using a numerical solver including advanced multiparameter equations of state and a high-order discretization scheme. The working fluids in use are the refrigerants R134a and R245fa, classified as dense gases due to their complex molecules and relatively high molecular weight. Both inviscid and viscous numerical simulations are carried out to quantify the impact of dense gas effects and viscous effects on turbine performance. Both supercritical and subcritical inlet conditions are studied for the considered working fluids. In the former case, flow across the turbine is transcritical, since turbine output pressure is subcritical. Numerical results show that, due to dense gas effects characterizing the flow at supercritical inlet conditions, supercritical ORC turbines enable, for a given pressure ratio, a higher isentropic efficiency than subcritical turbines using the same working fluid. Moreover, for the selected operating conditions, R134a provides a better performance than R245fa.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Ideal expansion curve for CO2

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Fig. 2

Ideal expansion curves for R134a

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Fig. 3

Ideal expansion curves for R245fa

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Fig. 4

View of the computational grid (384 × 48 cells)

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Fig. 5

Wall-pressure distributions on different grids for case SUPR134a (inviscid simulations)

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Fig. 6

Wall-pressure distributions on different grids for case SUPR134a (viscous simulations, Baldwin–Lomax turbulence model)

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Fig. 7

Skin-friction coefficient distributions on different grids for case SUPR134a (Baldwin–Lomax turbulence model)

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Fig. 13

Mach number for SUPR134a case

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Fig. 14

Fundamental derivative of gas dynamics for SUPR245fa case

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Fig. 15

Speed of sound for SUPR245fa case

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Fig. 16

Mach number for SUPR245fa case

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Fig. 17

Fundamental derivative of gas dynamics for SUBR134a case

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Fig. 18

Speed of sound for SUBR134a case

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Fig. 19

Mach number for SUBR134a case

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Fig. 20

Fundamental derivative of gas dynamics for SUPCO2 case

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Fig. 8

Wall-pressure distributions for case SUPR134a (viscous simulations). Effect of the turbulence model.

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Fig. 9

Skin-friction distributions for case SUPR134a (viscous simulations). Effect of the turbulence model.

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Fig. 10

Pressure evolution for SUPR134a case

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Fig. 11

Fundamental derivative of gas dynamics for SUPR134a case

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Fig. 12

Speed of sound for SUPR134a case

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Fig. 21

Speed of sound for SUPCO2 case

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Fig. 22

Mach number for SUPCO2 case

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