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Research Papers: Gas Turbines: Heat Transfer

Time Averaged Net Heat Flux Reduction for Unsteady Film Cooling

[+] Author and Article Information
James L. Rutledge

Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433james.rutledge@us.af.mil

Paul I. King

Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433

Richard Rivir

Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433

J. Eng. Gas Turbines Power 132(12), 121901 (Aug 24, 2010) (6 pages) doi:10.1115/1.4001810 History: Received February 01, 2010; Revised April 24, 2010; Published August 24, 2010; Online August 24, 2010

Film cooling flow for reduction in heat flux to a gas turbine engine hot gas path component is generally assumed to be steady. However, unsteady film cooling may occur due to naturally occurring flow unsteadiness or may be induced intentionally. Analysis of pulsed or otherwise unsteady film coolant flow necessitates a reformulation of the existing steady-state technique for net heat flux reduction (NHFR). We show that addition of a cross-coupled term to the traditional steady form of the NHFR equation with time averaged quantities accounts for the unsteady effects. In the experimental technique to determine the time averaged NHFR, we present a new parameter γ to capture the combined influence of the average adiabatic effectiveness and the coupling between η and h. Measurement of γ is shown to be straightforward but requiring careful considerations beyond those required to measure η with steady film cooling.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Surface temperature response with sinusoidal fluctuations in Taw, constant h, and several C values

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Figure 2

Us′ amplitude on a semi-infinite slab undergoing sinusoidal fluctuations in Taw with constant h

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Figure 3

Nondimensional surface temperatures for sinusoidal h with 180 deg phase shift from Taw fluctuations

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Figure 4

Relative error |εhf¯|/hf¯ due to neglecting unsteady term in Eq. 36 for C=6 and 10

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