Research Papers

Overspray and Interstage Fog Cooling in Gas Turbine Compressor Using Stage-Stacking Scheme—Part I: Development of Theory and Algorithm

[+] Author and Article Information
Ting Wang, Jobaidur R. Khan

Energy Conversion & Conservation Center, University of New Orleans, New Orleans, LA 70148-2220

J. Thermal Sci. Eng. Appl 2(3), 031001 (Nov 17, 2010) (10 pages) doi:10.1115/1.4002754 History: Received May 11, 2010; Revised September 21, 2010; Published November 17, 2010; Online November 17, 2010

Compressor intercooling has traditionally been employed to reduce compressor work and augment gas turbine output power. Conventional intercooling schemes are usually applied through nonmixed heat exchangers between two compressor stages or by cooling the outside of the compressor casing. Any cooling schemes that may affect the flow field inside the compressors have not been favorably considered due to concerns of any disturbance that might adversely affect the compressor’s performance stability. As the inlet fog cooling scheme has become popular as an economic and effective means to augment gas turbine output power on hot or dry days, consideration has been given to applying fog cooling inside the compressors by injecting fine water droplets between stages (i.e., interstage fogging). This paper focuses on developing a stage-by-stage wet compression theory for overspray and interstage fogging that includes the analysis and effect of preheating and precooling at each small stage of the overall compressor performance. An algorithm has been developed to calculate the local velocity diagram and allow a stage-by-stage analysis of the fogging effect on airfoil aerodynamics and loading with known 2D meanline rotor and stator geometries. Thermal equilibrium model for water droplet evaporation is adopted. The developed theory and algorithm are integrated into the systemwise FogGT program to calculate the overall gas turbine system performance.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Preheat and precool effect on air due to evaporative cooling. This figure only qualitatively represents the gas (air+water vapor) behavior. The entropy change due to water evaporation is not included.

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Figure 2

Qualitatively T-s diagram illustration of different phases during a wet compression (not to scale).

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Figure 3

(a) T-s diagram with actual data for all the species. Note: The air-only line almost coincides with the mixture line and cannot be clearly seen in this figure. (b) Amplified air and mixture T-s path with actual to-scale data.

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Figure 4

Rotor-stator staging

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Figure 5

Velocity diagram for rotor inlet at stage 1

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Figure 6

Velocity diagram at rotor exit

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Figure 7

Velocity diagram at rotor inlet

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Figure 8

Flow chart of simulation for rotors and stators from second stage





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