Research Papers: Gas Turbines: Turbomachinery

Effects of Real Gas Model Accuracy and Operating Conditions on Supercritical CO2 Compressor Performance and Flow Field

[+] Author and Article Information
Alireza Ameli

Laboratory of Fluid Dynamics,
School of Energy Systems,
Lappeenranta University of Technology,
Lappeenranta 53850, Finland
e-mail: Alireza.ameli@lut.fi

Ali Afzalifar

Laboratory of Fluid Dynamics,
School of Energy Systems,
Lappeenranta University of Technology,
Lappeenranta 53850, Finland
e-mail: Ali.afzalifar@lut.fi

Teemu Turunen-Saaresti

Laboratory of Fluid Dynamics,
School of Energy Systems,
Lappeenranta University of Technology,
Lappeenranta 53850, Finland
e-mail: Teemu.turunen-saaresti@lut.fi

Jari Backman

Laboratory of Fluid Dynamics,
School of Energy Systems,
Lappeenranta University of Technology,
Lappeenranta 53850, Finland
e-mail: Jari.backman@lut.fi

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 22, 2017; final manuscript received October 3, 2017; published online January 23, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(6), 062603 (Jan 23, 2018) (8 pages) Paper No: GTP-17-1526; doi: 10.1115/1.4038552 History: Received September 22, 2017; Revised October 03, 2017

Rankine and Brayton cycles are common energy conversion cycles and constitute the basis of a significant proportion of global electricity production. Even a seemingly marginal improvement in the efficiency of these cycles can considerably decrease the annual use of primary energy sources and bring a significant gain in power plant output. Recently, supercritical Brayton cycles using CO2 as the working fluid have attracted much attention, chiefly due to their high efficiency. As with conventional cycles, improving the compressor performance in supercritical cycles is major route to increasing the efficiency of the whole process. This paper numerically investigates the flow field and performance of a supercritical CO2 centrifugal compressor. A thermodynamic look-up table is coupled with the flow solver, and the look-up table is systematically refined to take into account the large variation of thermodynamic properties in the vicinity of the critical point. Effects of different boundary and operating conditions are also discussed. It is shown that the compressor performance is highly sensitive to the look-up table resolution as well as the operating and boundary conditions near the critical point. Additionally, a method to overcome the difficulties of simulation close to the critical point is explained.

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Fig. 3

Specific heat changes near the critical point

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Fig. 2

Geometry and mesh of the studied compressor

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Fig. 1

Mesh dependency test

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Fig. 4

Range of the RGP table and operating conditions

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Fig. 5

Accuracy of the RGP tables

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Fig. 6

Isobar look-up table accuracy check

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Fig. 7

Operation conditions. The circle indicates the inlet and squares locate the outlet boundary conditions, respectively.

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Fig. 8

Centrifugal compressor performance map at 50 krpm

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Fig. 9

Mach number at span of 0.7 (a) near the stall point and (b) near the design point

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Fig. 16

Compressibility factors at inlet and outlet

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Fig. 17

Density change with respect to the pressure ratio

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Fig. 18

Spinodal limits built into the table

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Fig. 19

Volume of the positive supercooling degree

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Fig. 10

Relative velocity vectors and Mach number at span of 0.7 around the main blade leading edge (upper is rgp-100 and lower is rgp-300)

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Fig. 11

Density field inside the impeller

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Fig. 12

Radial velocity at the impeller outlet

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Fig. 13

Operation conditions

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Fig. 14

Isentropic efficiency

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Fig. 15

Nondimensional torque



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