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Research Papers: Flows in Complex Systems

Impact of Orifice Length/Diameter Ratio on 90 deg Sharp-Edge Orifice Flow With Manifold Passage Cross Flow

[+] Author and Article Information
W. H. Nurick

 Science and Technology Applications LLC (STA), Moorpark, CA 93021wnurick@verizon.net

T. Ohanian

 Science and Technology Applications LLC (STA), Moorpark, CA 93021

D. G. Talley

Air Force Research Laboratory, Edwards Air Force Base, AFRL/PRSA, 10 East Saturn Boulevard, Edwards AFB, CA 93524-7660

P. A. Strakey

Energy Systems Dynamics Division, National Energy Technology Laboratory, Morgantown, WV 26505

J. Fluids Eng 131(8), 081103 (Jul 15, 2009) (10 pages) doi:10.1115/1.3155959 History: Received June 04, 2008; Revised April 17, 2009; Published July 15, 2009

The available information describing the various stages of flow conditions that occur as the flow transitions from noncavitation to cavitation (turbulent flow), supercavitation, and finally separation in sharp-edge 90 deg orifices is extensive. However, although sharp-edge orifices in cross flow represent a significant number of injection schemes inherent in many applications, data for this configuration are sparse or nonexistent. This study is intended to increase the database and understanding of the driving variables affecting the flow in all of these conditions. Tests were carried out in a unique test facility capable of achieving large variations in back pressure, flowrate, and operating upstream pressure. The configuration and test ranges of this study includes orifice length/diameter ratios from 2 to 10, upstream pressures from 7.03kg/cm2 to 105.1kg/cm2, orifice/manifold area ratio of 0.028 to 0.082, and manifold cross flow velocity of from 410 cm/s to 1830 cm/s. The results for these small area ratio configurations support two different first order models, one for cavitation and the other noncavitation both in turbulent flow. Under cavitation conditions the discharge coefficient is related to the contraction coefficient and the cavitation parameter to the 1/2 power. In the noncavitation flow regime the head loss is related to the loss coefficient and the dynamic pressure at the orifice exit. Both the head loss and contraction coefficient were found to be a strong function of the ratio of manifold/orifice exit velocity. Equations are provided defining the relationships that allow determination of the contraction coefficient, discharge coefficient, and head loss between the contraction coefficient, as well as the loss coefficient and operating conditions. Cavitation parameter values for cavitation inception, cavitation, and supercavitation are also provided. The potential flow theory was shown to predict the contraction coefficient when upstream (manifold to vena-contracta) losses are minimal.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Photograph documenting eddy formation and separation (3)

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Figure 2

Photographic documentation of bubble formation and jet behavior (20)

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Figure 3

Manifold/orifice design and flow configurations evaluated

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Figure 4

Illustration of constant flowrate in the cavitation zone

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Figure 5

Illustration of linear relationship between Cc and Kcav0.5

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Figure 6

Impact of velocity ratio on contraction coefficient; L/D=5

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Figure 7

Impact of velocity ratio on contraction coefficient; L/D=10

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Figure 8

Impact of velocity ratio on the fraction of total energy loss−L/D=10

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Figure 9

Impact of velocity ratio on the fraction of total energy loss−L/D=5

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Figure 10

Impact of velocity ratio on the fraction of total energy loss−L/D=5

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Figure 11

Potential flow model Cc prediction versus experimental Cc−L/D=10

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Figure 12

Potential flow model Cc prediction versus experimental Cc−L/D=5

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Figure 13

Illustration of linear relationship between HL and KE2 at various manifold cross velocities

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Figure 14

Pressure drop versus orifice kinetic energy (all three configurations)

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Figure 15

Correlation of HL coefficient for 90 deg sharp-edge orifice

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Figure 16

Comparison of predicted versus data defined loss coefficient

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Figure 17

Comparison of the results of this study with Idelchik correlation (3)

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