Research Papers

Experimental Study on Pressure Losses in Circular Orifices With Inlet Cross Flow

[+] Author and Article Information
Daniel Feseker

Werkzeugbau Siegfried Hofmann GmbH,
Lichtenfels 96215, Germany
e-mail: daniel.feseker@gmail.com

Mats Kinell

Siemens Industrial Turbomachinery AB,
Finspång 612 31, Sweden

Matthias Neef

Faculty of Mechanical and Process Engineering,
University of Applied Sciences Düsseldorf,
Düsseldorf 40476, Germany

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received February 27, 2018; final manuscript received March 25, 2018; published online June 14, 2018. Editor: Kenneth Hall.

J. Turbomach 140(7), 071006 (Jun 14, 2018) (9 pages) Paper No: TURBO-18-1046; doi: 10.1115/1.4039842 History: Received February 27, 2018; Revised March 25, 2018

The ability to understand and predict the pressure losses of orifices is important in order to improve the air flow within the secondary air system. This experimental study investigates the behavior of the discharge coefficient for circular orifices with inlet cross flow which is a common flow case in gas turbines. Examples of this are at the inlet of a film cooling hole or the feeding of air to a blade through an orifice in a rotor disk. Measurements were conducted for a total number of 38 orifices, covering a wide range of length-to-diameter ratios, including short and long orifices with varying inlet geometries. Up to five different chamfer-to-diameter and radius-to-diameter ratios were tested per orifice length. Furthermore, the static pressure ratio across the orifice was varied between 1.05 and 1.6 for all examined orifices. The results of this comprehensive investigation demonstrate the beneficial influence of rounded inlet geometries and the ability to decrease pressure losses, which is especially true for higher cross flow ratios where the reduction of the pressure loss in comparison to sharp-edged holes can be as high as 54%. With some exceptions, the chamfered orifices show a similar behavior as the rounded ones but with generally lower discharge coefficients. Nevertheless, a chamfered inlet yields lower pressure losses than a sharp-edged inlet. The obtained experimental data were used to develop two correlations for the discharge coefficient as a function of geometrical as well as flow properties.

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Fig. 1

Scheme of the cross flow main channel and the orifice, including variables found to influence the orifice discharge

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Fig. 2

The test rig with inlet flange and installed pressure taps

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Fig. 3

Effect of different l/d ratios for sharp-edged orifices

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Fig. 4

Verification of the discharge coefficient characteristics against data from Rhode and Hüning

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Fig. 5

Verification against data without cross flow (π = 1.6)

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Fig. 6

Summary of results for discharge coefficients at π=1.05: left, chamfered orifices and right, rounded orifices

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Fig. 7

Effect of constant r/d ratios on the l/d ratio at π=1.05: left, r/d=0.25 and right, r/d=1

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Fig. 8

Effect of altered pressure ratios on sharp-edged orifices with l/d=0.5, 1, 2.5, and 5

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Fig. 9

Effect of altered pressure ratios and inlet geometries on the discharge coefficient (l/d=1)

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Fig. 10

Limit of the c/w ratio at r/d=0.5 and π=1.6

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Fig. 11

Measured versus calculated discharge coefficients for chamfered inlet geometries

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Fig. 12

Measured versus calculated discharge coefficients for rounded inlet geometries




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