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RESEARCH PAPERS: Bubbles, Particles and Droplets

Simulation of Film Cooling Enhancement With Mist Injection

[+] Author and Article Information
Xianchang Li

Energy Conversion & Conservation Center, University of New Orleans, 2000 Lakeshore Dr., New Orleans, LA 70148-2220xli8@uno.edu

Ting Wang

Energy Conversion & Conservation Center, University of New Orleans, 2000 Lakeshore Dr., New Orleans, LA 70148-2220

J. Heat Transfer 128(6), 509-519 (Dec 09, 2005) (11 pages) doi:10.1115/1.2171695 History: Received April 05, 2005; Revised December 09, 2005

Cooling of gas turbine hot-section components, such as combustor liners, combustor transition pieces, and turbine vanes (nozzles) and blades (buckets), is a critical task for improving the life and reliability of them. Conventional cooling techniques using air-film cooling, impingement jet cooling, and turbulators have significantly contributed to cooling enhancements in the past. However, the increased net benefits that can be continuously harnessed by using these conventional cooling techniques seem to be incremental and are about to approach their limit. Therefore, new cooling techniques are essential for surpassing these current limits. This paper investigates the potential of film-cooling enhancement by injecting mist into the coolant. The computational results show that a small amount of injection (2% of the coolant flow rate) can enhance the adiabatic cooling effectiveness about 30–50%. The cooling enhancement takes place more strongly in the downstream region, where the single-phase film cooling becomes less powerful. Three different holes are used in this study including a two-dimensional (2D) slot, a round hole, and a fan-shaped diffusion hole. A comprehensive study is performed on the effect of flue gas temperature, blowing angle, blowing ratio, mist injection rate, and droplet size on the cooling effectiveness with 2D cases. Analysis on droplet history (trajectory and size) is undertaken to interpret the mechanism of droplet dynamics.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Computational domain and film hole configurations

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Figure 3

Grid independence study (slot jet)

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Figure 4

Temperature distribution of air-film cooling with and without mist injection (slot jet)

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Figure 5

Effect of 2% mist injection on temperature distribution at different locations (slot jet)

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Figure 6

Adiabatic film-cooling effectiveness and mist enhancement (2D slot)

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Figure 7

Wall temperature distributions of air-film cooling on the cooling surface for both round and fan-shaped holes

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Figure 8

Centerline and spanwise average adiabatic cooling effectiveness and mist-cooling enhancement (roundhole)

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Figure 9

Centerline and spanwise average adiabatic cooling effectiveness and mist-cooling enhancement (fan-shaped hole)

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Figure 10

Cross-sectional temperature distributions and velocity fields in the streamwise direction (film cooling without mist)

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Figure 11

Spanwise distributions of cooling effectiveness for round and fan-shaped holes (film cooling without mist)

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Figure 12

Comparison to other studies (centerline cooling effectiveness of the round hole)

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Figure 13

Effect of mist concentration on adiabatic cooling effectiveness for a 2D slot film cooling

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Figure 14

Effect of droplet size on adiabatic cooling effectiveness for a 2D slot film cooling

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Figure 15

Droplet trajectories predicted with stochastic tracking (2D slot case)

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Figure 16

Effect of mist injection on the slot jet air film cooling with different blowing ratios

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Figure 17

Effect of mist injection on the slot-jet air film cooling with different blowing angles

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Figure 18

Effect of mist film cooling with different mainstream temperatures

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