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TECHNICAL PAPERS

Fan-Shaped Hole Effects on the Aero-Thermal Performance of a Film-Cooled Endwall

[+] Author and Article Information
Giovanna Barigozzi

Dipartimento di Ingegneria Industriale,  Università degli Studi di Bergamo, Viale Marconi 24044, Dalmine (BG), Italygiovanna.barigozzi@unibg.it

Giuseppe Benzoni, Giuseppe Franchini

Dipartimento di Ingegneria Industriale,  Università degli Studi di Bergamo, Viale Marconi 24044, Dalmine (BG), Italy

Antonio Perdichizzi

Dipartimento di Ingegneria Industriale,  Università degli Studi di Bergamo, Viale Marconi 24044, Dalmine (BG), Italyantonio.perdichizzi@unibg.it

J. Turbomach 128(1), 43-52 (Feb 01, 2005) (10 pages) doi:10.1115/1.2098788 History: Received October 01, 2004; Revised February 01, 2005

The present paper investigates the effects of a fan-shaped hole endwall cooling geometry on the aero-thermal performance of a nozzle vane cascade. Two endwall cooling geometries with four rows of holes were tested, for different mass flow rate ratios: the first configuration is made of cylindrical holes, whereas the second one features conical expanded exits and a reduced number of holes. The experimental analysis is mainly focused on the variations of secondary flow phenomena related to different injection rates, as they have a strong relationship with the film cooling effectiveness. Secondary flow assessment was performed through downstream 3D aerodynamic measurements, by means of a miniaturized 5-hole probe. The results show that at high injection rates, the passage vortex and the 3D effects tend to become weaker, leading to a strong reduction of the endwall cross flow and to a more uniform flow in spanwise direction. This is of course obtained at the expense of a significant increase of losses. The thermal behavior was then investigated through the analysis of adiabatic effectiveness distributions on the two endwall configurations. The wide-banded thermochromic liquid crystals (TLC) technique was used to determine the adiabatic wall temperature. Using the measured distributions of film-cooling adiabatic effectiveness, the interaction between the secondary flow vortices and the cooling jets can be followed in good detail all over the endwall surface. Fan-shaped holes have been shown to perform better than cylindrical ones: at low injection rates, the cooling performance is increased only in the front part of the vane passage. A larger improvement of cooling coverage all over the endwall is attained with a larger mass flow rate, about 1.5% of core flow, without a substantial increase of the aerodynamic losses.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cascade and endwall cooling geometry—(a) CONF1 and (b) CONF2

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Figure 2

Detail of hole geometry—(a) CONF1 and (b) CONF2

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Figure 4

Inlet boundary layer profile (X∕cax=−80%)

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Figure 5

Secondary kinetic energy loss coefficient, vorticity, and velocity vectors (X∕cax=150%)—solid endwall

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Figure 6

CONF2 Secondary kinetic energy loss coefficient (primary), vorticity, and velocity vectors—(a) MFR=0.5%; (b) MFR=0.75%; (c) MFR=1%; (d) MFR=1.5%; and (e) MFR=2.5%

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Figure 7

Spanwise (a) loss distribution (primary) and (b) flow angle deviation at different MFR—CONF2

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Figure 8

Mass-averaged primary and thermodynamic secondary energy loss coefficients versus MFR percent

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Figure 9

Mass-averaged primary and thermodynamic secondary energy loss coefficients versus M1

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Figure 10

CONF1 local BR values for variable MFR

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Figure 11

CONF2 local BR values for variable MFR

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Figure 12

Adiabatic effectiveness distributions for the different injection conditions and the two geometries

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Figure 13

Pitch-averaged adiabatic effectiveness distributions at different MFR—(a) CONF1 and (b) CONF2

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Figure 14

Axial and pitch-averaged adiabatic effectiveness distributions versus MFR

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