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Research Papers

Experimental Validation of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles

[+] Author and Article Information
Timothy C. Allison

Machinery Department,
Southwest Research Institute,
San Antonio, TX 78238
e-mail: tim.allison@swri.org

Natalie R. Smith

Machinery Department,
Southwest Research Institute,
San Antonio, TX 78238
e-mail: natalie.smith@swri.org

Robert Pelton

Hanwha Power Systems,
Houston, TX 77079
e-mail: rob.pelton@hanwha.com

Jason C. Wilkes

Machinery Department,
Southwest Research Institute,
San Antonio, TX 78238
e-mail: jason.wilkes@swri.org

Sewoong Jung

Hanwha Power Systems,
Houston, TX 77079
e-mail: sewoong.jung@hanwha.com

Manuscript received September 24, 2018; final manuscript received October 29, 2018; published online February 18, 2019. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(6), 061011 (Feb 18, 2019) (9 pages) Paper No: GTP-18-1621; doi: 10.1115/1.4041920 History: Received September 24, 2018; Revised October 29, 2018

Successful implementation of sCO2 power cycles requires high compressor efficiency at both the design-point and over a wide operating range in order to maximize cycle power output and maintain stable operation over a wide range of transient and part-load operating conditions. This requirement is particularly true for air-cooled cycles where compressor inlet density is a strong function of inlet temperature that is subject to daily and seasonal variations as well as transient events. In order to meet these requirements, a novel centrifugal compressor stage design was developed that incorporates multiple novel range extension features, including a passive recirculating casing treatment and semi-open impeller design. This design, presented and analyzed for CO2 operation in a previous paper, was fabricated via direct metal laser sintering and tested in an open-loop test rig in order to validate simulation results and the effectiveness of the casing treatment configuration. Predicted performance curves in air and CO2 conditions are compared, resulting in a reduced diffuser width requirement for the air test in order to match design velocities and demonstrate the casing treatment. Test results show that the casing treatment performance generally matched computational fluid dynamics (CFD) predictions, demonstrating an operating range of 69% and efficiency above air predictions across the entire map. The casing treatment configuration demonstrated improvements over the solid wall configuration in stage performance and flow characteristics at low flows, resulting in an effective 14% increase in operating range with a 0.5-point efficiency penalty. The test results are also compared to a traditional fully shrouded impeller with the same flow coefficient and similar head coefficient, showing a 42% range improvement over traditional designs.

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References

Brun, K. , Friedman, P. , and Dennis, R. , 2017, Fundamentals and Applications of Supercritical Carbon Dioxide (sCO2) Based Power Cycles, Woodhead Publishing, Cambridge, MA.
Kimball, K. J. , and Clementoni, E. M. , 2012, “ Supercritical Carbon Dioxide Brayton Power Cycle Development Overview,” ASME Paper No. GT2012-68204.
Wright, S. A. , Radel, R. F. , Vernon, M. E. , Rochau, G. E. , and Pickard, P. S. , 2010, “ Operation and Analysis of a Supercritical CO2 Brayton Cycle,” Sandia Report, Sandia National Laboratories, Albuquerque, NM, Report No. SAND2010-0171. https://prod.sandia.gov/techlib-noauth/access-control.cgi/2010/100171.pdf
Hofer, D. , 2016, “ Phased Approach to Development of a High Temperature sCO2 Power Cycle Pilot Test Facility,” Fifth International Symposium—Supercritical CO2 Power Cycles, San Antonio, TX, Mar. 28–31. http://sco2symposium.com/www2/sco2/papers2016/Testing/069paper.pdf
Wilkes, J. , Allison, T. , Schmitt, J. , Bennett, J. , Wygant, K. , Pelton, R. , and Bosen, W. , 2016, “ Application of an Integrally Geared Compander to an sCO2 Recompression Brayton Cycle,” Fifth International Symposium—Supercritical CO2 Power Cycles, San Antonio, TX, Mar. 28–31. http://www.sco2symposium.com/www2/sco2/papers2016/Turbomachinery/055paper.pdf
Pelton, R. , Allison, T. , Jung, S. , and Smith, N. , 2017, “ Design of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles,” ASME Paper No. GT2017-65172.
David, J. , 1994, Centrifugal Compressor Design and Performance, Concepts ETI, White River Junction, VT.
ASME, 1997, “ Performance Test Code on Compressors and Exhausters,” American Society of Mechanical Engineers, New York, Standard No. ASME PTC 10. https://www.asme.org/products/codes-standards/ptc-10-1997-performance-test-code-compressors
ASME, 2004, “ Flow Measurement: Performance Test Codes,” American Society of Mechanical Engineers, New York, Standard No. ASME PTC 19.5. https://www.asme.org/products/codes-standards/ptc-195-2004-flow-measurement-(1)
Lemmon, E. W. , Huber, M. L. , and McLinden, M. O. , 2013, “ NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP,” Version 9.1, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, MD.
Allison, T. , Moore, J. , Rimpel, A. , Wilkes, J. , Pelton, R. , and Wygant, K. , 2014, “ Manufacturing and Testing Experience With Direct Metal Laser Sintering for Closed Centrifugal Compressor Impellers,” 43rd Turbomachinery Symposium, Houston, TX, Sept. 22–25.

Figures

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Fig. 1

Solid model of a 10-MWe integrally geared sCO2 compander

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Fig. 2

Compressor inlet gas density sensitivity to changes in temperature [6]

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Fig. 3

Performance comparison of range extension techniques

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Fig. 4

A novel wide-range compressor with partially shrouded impeller and casing treatment

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Fig. 5

Computational fluid dynamics prediction of sCO2 performance for the wide-range compressor

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Fig. 6

Computational fluid dynamics prediction of revised air test model

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Fig. 7

Single stage test rig layout—wide-range compressor configuration

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Fig. 8

Cross-sections of solid wall (left) and casing treatment (right) inserts

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Fig. 9

Partial assembly of test setup in rig

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Fig. 10

Casing treatment (left) and shroud side diffuser (right) inserts

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Fig. 11

Direct metal laser sintering-manufactured wide-range impeller

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Fig. 12

Torquemeter spindle-only calibration data

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Fig. 13

Bearing and windage losses versus flow coefficient

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Fig. 14

Measured head versus flow coefficients

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Fig. 15

Measured isentropic efficiency versus flow coefficient

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Fig. 16

Efficiency difference (test—CFD) versus flow coefficient

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Fig. 17

Efficiency difference (torque—thermal) versus flow coefficient

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Fig. 18

Inducer dynamic pressure spectra: (a) solid wall and (b) casing treatment

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Fig. 19

Diffuser dynamic pressure spectra at lowest flow operating point: (a) solid wall, ϕ = 0.032 and (b) casing treatment, ϕ = 0.031

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Fig. 20

Test result comparison between wide-range compressor and reference model

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