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Research Papers: Experimental Techniques

Casing Convective Heat Transfer Coefficient and Reference Freestream Temperature Determination Near an Axial Flow Turbine Rotor

[+] Author and Article Information
C. Camci, B. Gumusel

Department of Aerospace Engineering, Turbomachinery Aero-Heat Transfer Laboratory, Pennsylvania State University, 223 Hammond Building, University Park, PA 16802

J. Heat Transfer 133(8), 081603 (May 04, 2011) (9 pages) doi:10.1115/1.4003757 History: Received May 03, 2010; Revised December 13, 2010; Published May 04, 2011; Online May 04, 2011

The present study explains a steady-state method of measuring convective heat transfer coefficient on the casing of an axial flow turbine. The goal is to develop an accurate steady-state heat transfer method for the comparison of various casing surface and tip designs used for turbine performance improvements. The freestream reference temperature, especially in the tip gap region of the casing, varies monotonically from the rotor inlet to rotor exit due to work extraction in the stage. In a heat transfer problem of this nature, the definition of the freestream temperature is not as straightforward as constant freestream temperature type problems. The accurate determination of the convective heat transfer coefficient depends on the magnitude of the local freestream reference temperature varying in axial direction, from the rotor inlet to exit. The current study explains a strategy for the simultaneous determination of the steady-state heat transfer coefficient and freestream reference temperature on the smooth casing of a single stage rotating turbine facility. The heat transfer approach is also applicable to casing surfaces that have surface treatments for tip leakage control. The overall uncertainty of the method developed is between 5% and 8% of the convective heat transfer coefficient.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

AFTRF: (a) facility schematic and (b) window for the removable casing segment

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Figure 2

Removable turbine casing in (AFTRF) (smooth partial “Al casing plate” is visible)

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Figure 3

Removable turbine casing cross section (normal to the axis of rotation)

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Figure 4

Heat transfer coefficient measurement locations on the casing surface (five axial locations)

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Figure 5

Heat Transfer model for convective heat transfer coefficient measurements on the turbine casing surface (the model allows for lateral conduction losses)

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Figure 6

3D solid model and conduction analysis results on removable turbine casing surfaces

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Figure 7

Temperature distributions on the plastic spacer and aluminum casing plate (flow side)

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Figure 8

Lateral conduction from the four sides of the area facing the heater and the final energy balance (I2R=6.53 W)

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Figure 9

Energy balance in the heat transfer surface in function of power setting

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Figure 10

Simultaneous determination of convective heat transfer coefficient h and freestream reference temperature from multiple heater power settings

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Figure 11

Influence of proper freestream reference temperature on convective heat transfer coefficient

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Figure 12

Measured heat transfer coefficient h (slope) at five axial locations on the casing plate surface

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Figure 13

Distribution of the heat transfer coefficient with respect to axial position on the casing surface

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Figure 14

Influence of reference temperature measurement error δTf on δh/hδqconv/qconv=±0.01, δk=±0.221 W/m K, and δL=±25 μm (0.001 mils)

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Figure 15

Influence of heater power setting on δh/hδTH=±0.15 K, δk=±0.221 W/m K, and δL=±25 μm (0.001 mils)

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