Research Papers: Gas Turbines: Turbomachinery

Operational Improvements for Startup Time Reduction in Solar Steam Turbines

[+] Author and Article Information
Monika Topel

Department of Energy Technology,
Royal Institute of Technology,
Stockholm SE-100 44, Sweden
e-mail: monika.topel@energy.kth.se

Magnus Genrup

Department of Energy Sciences,
Lund University,
Lund SE-221 00, Sweden
e-mail: magnus.genrup@energy.lth.se

Markus Jöcker

Siemens Industrial Turbomachinery AB,
Finspång SE-612 83, Sweden
e-mail: markus.jocker@siemens.com

James Spelling

Department of Energy Technology,
Royal Institute of Technology,
Stockholm SE-100 44, Sweden
e-mail: james.spelling@energy.kth.se

Björn Laumert

Department of Energy Technology,
Royal Institute of Technology,
Stockholm SE-100 44, Sweden
e-mail: bjorn.laumert@energy.kth.se

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 9, 2014; final manuscript received August 12, 2014; published online November 11, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(4), 042604 (Apr 01, 2015) (8 pages) Paper No: GTP-14-1336; doi: 10.1115/1.4028661 History: Received July 09, 2014; Revised August 12, 2014; Online November 11, 2014

Solar steam turbines are subject to high thermal stresses as a result of temperature gradients during transient operation, which occurs more frequently due to the variability of the solar resource. In order to increase the flexibility of the turbines while preserving lifting requirements, several operational modifications for maintaining turbine temperatures during offline periods are proposed and investigated. The modifications were implemented in a dynamic thermal turbine model and the potential improvements were quantified. The modifications studied included: increasing the gland steam pressure injected to the end-seals, increasing the back pressure and increasing the barring speed. These last two take advantage of the ventilation and friction work. The effects of the modifications were studied both individually as well as in different combinations. The temperatures obtained when applying the combined modifications were compared to regular turbine cool-down (CD) temperatures and showed significant improvements on the startup times of the turbine.

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Fig. 1

Steam flow paths through the labyrinth seals during (a) turbine operation and (b) stand-still

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Fig. 2

Steam flow paths in the disks and blades of the turbine for (a) friction and (b) ventilation [17]

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Fig. 3

Turbine thermal dynamic modeling scheme

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Fig. 4

Temperature improvements in the rotor and casing after individually applying each of the three improvements to the HPT and LPT

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Fig. 5

Temperature profiles along the axial direction if the casing and rotor of the HPT and LPT for nominal temperature state and CD states

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Fig. 6

Temperature improvements in the rotor and the casing of the HPT after applying the combined modifications

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Fig. 7

Temperature improvements in the rotor and the casing of the LPT after applying the combined modifications




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