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Research Papers

# Effect of Radial Location of Nozzles on Heat Transfer in Preswirl Cooling Systems

[+] Author and Article Information
V. U. Kakade, G. D. Lock, M. Wilson, J. M. Owen

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, U.K

J. E. Mayhew1

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, U.K

1

Present address: Rose–Hulman Institute of Technology, IN.

J. Turbomach 133(2), 021023 (Oct 26, 2010) (8 pages) doi:10.1115/1.4001189 History: Received July 27, 2009; Revised August 05, 2009; Published October 26, 2010; Online October 26, 2010

## Abstract

This paper investigates heat transfer in a rotating disk system using preswirled cooling air from nozzles at high and low radius. The experiments were conducted over a range of rotational speeds, flow rates, and preswirl ratios. Narrow-band thermochromic liquid crystal (TLC) was specifically calibrated for application to experiments on a disk, rotating at $∼5000 rpm$ and subsequently used to measure surface temperature in a transient experiment. The TLC was viewed through the transparent polycarbonate disk using a digital video camera and strobe light synchronized to the disk frequency. The convective heat transfer coefficient $h$ was subsequently calculated from the one-dimensional solution of Fourier's conduction equation for a semi-infinite wall. The analysis was accounted for the exponential rise in the air temperature driving the heat transfer, and for the experimental uncertainties in the measured values of $h$. The experimental data was supported by “flow visualization,” determined from CFD. Two heat transfer regimes were revealed for the low-radius preswirl system: a viscous regime at relatively low coolant flow rates, and an inertial regime at higher flow rates. Both regimes featured regions of high heat transfer where thin, boundary layers replaced air exiting through receiver holes at high radius on the rotating disk. The heat transfer in the high-radius preswirl system was shown to be dominated by impingement under the flow conditions tested.

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## Figures

Figure 1

(a) Typical gas turbine rotor-stator system with preswirled cooling air; (b) simplified model

Figure 2

Photograph of TLC on disk rotating at 5000 rpm (Reϕ=1×106, λT=0.12)

Figure 3

Typical variation in air temperature with time

Figure 4

Variation in hue during transient experiment

Figure 5

(a) Heat transfer coefficient in circumferential section; (b) computed streamlines in radial section—Case 1

Figure 6

(a) Heat transfer coefficient in circumferential section; (b) computed streamlines in radial section—Case 2

Figure 7

Radial variation in heat transfer coefficient determined by 30°C and 40°C crystals: (a) Case 2 and (b) Case 1

Figure 8

Viscous regime (a) radial variation in Nu; (b) radial variation in Nu Reϕ−0.8; inertial regime (c) radial variation in Nu; (d) radial variation in Nu Reϕ−0.5

Figure 9

Computed streamlines in the tangential plane at the receiver hole radius rb: (a) Case 3, (b) Case 4, and (c) Case 5

Figure 10

Heat transfer coefficient in isometric view for high-radius preswirl system: (a) Case 3, (b) Case 4, and (c) Case 5

Figure 11

Circumferential variation in Nu Reϕ−0.5 for high-radius preswirl system

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