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Research Papers: Gas Turbines: Turbomachinery

Integrated Approach for Steam Turbine Thermostructural Analysis and Lifetime Prediction at Transient Operations

[+] Author and Article Information
Leonid Moroz

SoftInWay, Inc.,
1500 District Avenue,
Burlington, MA 01803
e-mail: L.Moroz@softinway.com

Glenn Doerksen

Sulzer Turbo Services Houston Inc.,
11518 Old La Porte Road,
La Porte, TX 77571
e-mail: glenn.doerksen@sulzer.com

Fernando Romero

Sulzer Turbo Services Houston Inc.,
11518 Old La Porte Road,
La Porte, TX 77571
e-mail: fernando.romero@sulzer.com

Roman Kochurov

SoftInWay, Inc.,
1500 District Avenue,
Burlington, MA 01803
e-mail: R.Kochurov@softinway.com

Boris Frolov

SoftInWay, Inc.,
1500 District Avenue,
Burlington, MA 01803
e-mail: boris.frolov@softinway.com

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 17, 2017; final manuscript received July 18, 2017; published online October 3, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(2), 022604 (Oct 03, 2017) (10 pages) Paper No: GTP-17-1370; doi: 10.1115/1.4037755 History: Received July 17, 2017; Revised July 18, 2017

In order to achieve the highest power plant efficiency, original equipment manufacturers continuously increase turbine working parameters (steam temperatures and pressures), improve components design, and modify start-up cycles to reduce time while providing more frequent start-up events. All these actions result in much higher levels of thermostresses, a lifetime consumption of primary components and an increased demand for accurate thermostructural and low cycle fatigue (LCF) simulations. In this study, some aspects of methodological improvement are analyzed and proposed in the frame of an integrated approach for steam turbine components thermostructural analysis, reliability, and lifetime prediction. The full scope of the engineering tasks includes aero/thermodynamic flow path and secondary flows analysis to determine thermal boundary conditions (BCs), detailed thermal/structural two-dimensional and three-dimensional (3D) finite element (FE) models preparation, components thermal and stress–strain simulation, rotor–casing differential expansion and clearances analysis, and finally, turbine unit lifetime estimation. Special attention is paid to some of the key factors influencing the accuracy of thermal stresses prediction, specifically, the effect of “steam condensation” on thermal BC, the level of detailing for thermal zones definition, thermal contacts, and mesh quality in mechanical models. These aspects have been studied and validated against test data, obtained via a 30 MW steam turbine for combined cycle application based on actual start-up data measured from the power plant. The casing temperatures and rotor–stator differential expansion, measured during the commissioning phase of the turbine, were used for methodology validation. Finally, the evaluation of the steam turbine HPIP rotor lifetime by means of a LCF approach is performed.

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References

Figures

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Fig. 1

Thirty megawatt steam turbine model

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Fig. 2

Thirty megawatt steam turbine unit—photo from power plant

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Fig. 3

Cold start-up diagram with calculation time-steps

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Fig. 4

Thermostructural analysis flow chart

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Fig. 5

Turbine flow path integrated with rotor gland seal system for 1D aerothermodynamic analysis

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Fig. 6

HPIP turbine heat convection zones discretization and flow direction

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Fig. 7

LP turbine heat convection zones discretization and flow direction

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Fig. 8

Flow path stage heat convection zones schematization

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Fig. 9

Algorithm for thermal condensation/noncondensation BC setup for transient analysis

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Fig. 10

Three-dimensional FE mechanical models: (a) and (b) HPIP; (c) LP cylinders

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Fig. 11

FE model for HPIP turbine rotor

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Fig. 12

Thermal contacts modeling: (a) blade root-to-rotor and (b) HPIP casing components thermal contacts

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Fig. 13

Turbine components temperatures at CS and steady-state operation

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Fig. 14

Turbine unit expansion scheme

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Fig. 15

HP turbine outer casing temperatures

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Fig. 16

Turbine unit casings expansion (probe C)

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Fig. 17

HPIP and LP rotors to casings differential expansion (probe B)

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Fig. 18

HPIP rotor to casing differential expansion (probe A)

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Fig. 19

Equivalent stresses during CS at critical regions

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Fig. 20

Temperatures during CS at critical regions

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Fig. 21

Equivalent stress distribution in HPIP rotor during CS

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