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Research Papers: Gas Turbines: Controls, Diagnostics, and Instrumentation

Experimental Investigation Into Thermal Behavior of Steam Turbine Components—Temperature Measurements With Optical Probes and Natural Cooling Analysis

[+] Author and Article Information
Gabriel Marinescu

e-mail: gabriel.marinescu@power.alstom.com

Wolfgang F. Mohr

e-mail: wolfgang.mohr@power.alstom.com

Andreas Ehrsam

e-mail: andreas.ehrsam@power.alstom.com

Paolo Ruffino

e-mail: paolo.ruffiono@power.alstom.com

Michael Sell

e-mail: michael.sell@power.alstom.com
Alstom, Power
Baden 5401, Switzerland

Contributed by the Controls, Diagnostics and Instrumentation Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 31, 2013; final manuscript received September 10, 2013; published online November 1, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(2), 021602 (Nov 01, 2013) (10 pages) Paper No: GTP-13-1334; doi: 10.1115/1.4025556 History: Received August 31, 2013; Revised September 10, 2013

The steam turbine cooldown has a significant impact on the cyclic fatigue life. A lower initial metal temperature after standstill results in a higher temperature difference to be overcome during the next start-up. Generally, lower initial metal temperatures result in higher start-up stress. In order to optimize steam turbines for cyclic operation, it is essential to fully understand natural cooling, which is especially challenging for rotors. This paper presents a first-in-time application of a 2D numerical procedure for the assessment of the thermal regime during natural cooling, including the rotors, casings, valves, and main pipes. The concept of the cooling calculation is to replace the fluid gross buoyancy during natural cooling by an equivalent fluid conductivity that gives the same thermal effect on the metal parts. The fluid equivalent conductivity is calculated based on experimental data. The turbine temperature was measured with pyrometric probes on the rotor and with standard thermocouples on inner and outer casings. The pyrometric probes were calibrated with standard temperature measurements on a thermo well, where the steam transmittance and the rotor metal transmissivity were measured.

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References

Figures

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Fig. 1

IP steam turbine instrumentation

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Fig. 2

The IP steam turbine arrangement

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Fig. 3

(a) Flexible pyrometric probe as used in gas turbine applications. (b) The measurement chain as used for the in-house developed pyrometer.

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Fig. 4

The USC autoclave. On the left the full view, on the right the detail of the box.

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Fig. 5

The steam transmittance at 20 bar and 600 °C. The calculated curve using the HITRAN database [13], the low resolution data of Goldstein [10], and our experimental results from the FTIR spectrometer.

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Fig. 6

Effect of purging on the lenses contamination in a real steam turbine (left not purged, right purged)

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Fig. 7

Rotor temperature measured at optical probes OT1, OT2, and OT3

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Fig. 8

Inner and outer casing temperatures measured at T11.1, T24.1, Tm33, and Tm42

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Fig. 9

Thermal boundary conditions to simulate the steam ingestion

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Fig. 10

Meshed model for natural cooling analysis

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Fig. 11

Base load. Initial condition for natural cooling.

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Fig. 12

The iterative process

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Fig. 13

The overconductivity function K(T)

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Fig. 14

The “thickness” property

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Fig. 15

Calculated and measured temperature at T11.1

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Fig. 16

Calculated and measured temperature at Tm33

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Fig. 17

Calculated and measured temperature at OT1

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Fig. 18

Temperature distribution at 2 h after natural cooling start

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Fig. 19

Temperature distribution at 10 h after natural cooling start

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Fig. 20

Impact of the ambient temperature

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Fig. 21

Impact of the different parameters on the rotor temperature at OT1

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