AN EMPIRICAL DISCHARGE COEFFICIENT MODEL FOR ORIFICE FLOW

Authors

  • Duqiang Wu Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9
  • Richard Burton Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9
  • Greg Schoenau Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Keywords:

fluid power, hydraulic, flow control, orifice equation, discharge coefficient, Reynolds number

Abstract

In fluid power systems, flow control is mainly achieved by throttling the flow across valve orifices. Lumped pa-rameter models are generally used to model the flow in these systems. The basic orifice flow equation, derived from Bernoulli’s equation of flow, is proportional to the orifice sectional area and the square root of the pressure drop and is used to model the orifice coefficient of proportionality. The discharge coefficient, Cd, is often modeled as being constant in value, independent of Reynolds number.

However, for very small orifice openings, Cd varies significantly and can result in substantial error if assumed constant. In this situation, modelers usually revert to graphs or look–up tables to determine Cd. This paper provides a closed form model for Cd as a function of the Reynolds number which can be applied to different types of orifices. Based on this model, a technique to evaluate flow given an orifice area and pressure drop without having to use itera-tion is introduced.

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Author Biographies

Duqiang Wu, Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Duqiang Wu Graduate student for Ph.D. at present, Mechanical Engineering Department, University of Saskatchewan in Canada. Master (1984) at Nanjing University of science and Technology in China. Engi-neer (1986) at Shaanxi Mechanical and Electrical Institute in China. Visiting Scholar (1997) at University of Illinois at Urbana-Champaign.

Richard Burton, Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Richard Burton P.Eng, Ph.D, Assistant Dean of the col-lege of Engineering, Professor, Mechani-cal Engineering, University of Saskatch-ewan. Burton is involved in research pertaining to the application of intelligent theories to control and monitoring of hydraulics systems, component design, and system analysis. He is a member of the executive of ASME, FPST Division, a member of the hydraulics' advisory board of SAE and NCFP and a convenor for FPNI.

Greg Schoenau, Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Greg Schoenau Professor of Mechanical Engineering at the University of Saskatchewan. He was head of that Department from 1993 to 1999. He obtained B.Sc. and M. Sc. Degrees from the University of Saskatch-ewan in mechanical engineering in 1967 and 1969, respectively. In 1974 he ob-tained his Ph.D. from the University of New Hampshire in fluid power control systems. He continues to be active in research in this area and in the thermal systems area as well. He has also held positions in numerous outside engineer-ing and technical organizations.

References

Borghi, M., Cantore, G., Milani, M. and Paoluzzi, R. 1998. Analysis of Hydraulic Components using Computational Fluid Dynamics Models. Proceed-ings of the Institute of Mechanical Engineers. V212 Part C. pp. 619.

Ellman, A. and Piche, R. 1996. A Modified Orifice Flow Formula for Numerical Simulation of Fluid Power Systems. Fluid Power Systems and Technol-ogy, ASME, Vol. 3, pp. 59-63.

Gromala, P., Domagal, M. and Lisowski, E. 2002. Research on Pressure Drop in Hydraulic Compo-nents by Means of CFD Method on Example of Control Valve. Proceedings of the 2nd International FPNI PhD Symposium on Fluid Power. Modena, Italy.

Merritt, H. E. 1967. Hydraulic Control Systems. John Wiley & Sons, Inc.

Miller, R. W. 1996. Flow Measurement Engineering Handbook, 3rd. McGraw-Hill, New York.

Vescovo, G. D. and Lippolis, A. 2002. Flow Forces Analysis on a Four-way Valve. Proceedings of the 2nd International FPNI PhD Symposium on Fluid Power. Modena, Italy.

Viall, E. and Zhang, Q. 2000. Spool Valve Discharge Coefficient Determination. Proceedings of the 48th National Conference on Fluid Power. Milwaukee, Wisconsin, USA. pp. 491.

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Published

2002-12-01

How to Cite

Wu, D., Burton, R., & Schoenau, G. (2002). AN EMPIRICAL DISCHARGE COEFFICIENT MODEL FOR ORIFICE FLOW. International Journal of Fluid Power, 3(3), 13–18. Retrieved from https://journals.riverpublishers.com/index.php/IJFP/article/view/617

Issue

2002: Vol 03 Iss 3

Section

Original Article