This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Coefficients of Discharge at the Aperatures of Engines
Annotation ability available
Sector:
Language:
English
Abstract
This paper reports on the experimental evaluation of certain aspects concerning the mathematical modelling of pressure wave propagation in engine ducting. A particular aspect is the coefficient of discharge of the various ports, valves or apertures of the ducting connected to the cylinder of an engine or to the atmosphere. The traditional method for the deduction of the coefficients of discharge employs steady flow experimentation. While the traditional experimental method may well be totally adequate, it is postulated in this paper that the traditional theoretical approach to the deduction of the discharge coefficient from the measured data leads to serious inaccuracies if incorporated within an engine simulation by computer. An accurate theoretical method for the calculation of the discharge coefficient from measured data is proposed.
The paper presents experimental results for the coefficients of discharge for several duct end geometries such as orifices, plain ends, bellmouths and the exhaust port of a two-stroke engine cylinder, and demonstrates that the conventional method for the deduction of the coefficient of discharge may be used only as a comparator for these geometries but leads to serious computational errors if used within a computer simulation. The paper contrasts and compares the values of coefficients of discharge determined by the postulated and the traditional methods, based on the same experimental measurements for the several duct end geometries.
The paper presents further theoretical confirmation that the postulated theoretical approach is justified and accurate, by comparison of the predictions of measured flow rates by the postulated and the traditional theories with the theoretical results from a CFD analysis of an identical duct end geometry. The CFD analysis and the postulated theoretical approach match almost perfectly whereas the traditional method does not.
Recommended Content
Authors
Topic
Citation
Blair, G., Lau, H., Cartwright, A., Raghunathan, B. et al., "Coefficients of Discharge at the Aperatures of Engines," SAE Technical Paper 952138, 1995, https://doi.org/10.4271/952138.Also In
References
- Kirkpatrick S.J. Blair G.P. Fleck R. McMullan R.K. “Experimental Evaluation of 1D Computer Codes for the Simulation of Unsteady Gas Flow Through Engines - a First Phase” SAE International Off-Highway Meeting Milwaukee September 1994 SAE Paper no. 941685 18
- Blair G.P. “An Alternative Method for the Prediction of Unsteady Gas Flow through the Reciprocating Internal Combustion Engine” Society of Automotive Engineers International Off-Highway & Powerplant Congress Milwaukee, Wisconsin September 9-12 1991 SAE Paper No. 911850 and also in SP883 137 162
- Blair G.P. “Correlation of an Alternative Method for the Prediction of Engine Performance Characteristics with Measured Data” Society of Automotive Engineers, International Congress Detroit, Michigan March 1993 SAE paper No. 930501 20
- Blair G.P. “Correlation o Measured and Calculated Performance Characteristics of Motorcycle Engines” Graz, Austria 22-23 April 1993 5 16
- Blair G.P. Magee S.J. “Non-Isentropic Analysis of Varying Area Flow in Engine Ducting” Society of Automotive Engineers International Off-Highway & Powerplant Congress Milwaukee, Wisconsin September 13-16 1993 SAE Paper No. 932399 77 94
- Blair G.P. “Non-Isentropic Analysis of Branched Flow in Engine Ducting” Society of Automotive Engineers, International Congress Detroit, Michigan March 1994 SAE paper No. 940395 55 72
- Blair G.P. Kirkpatrick S.J. Fleck R. “Experimental Validation of 1-D Modelling Codes for a Pipe Containing Gas of Varying Properties” Society of Automotive Engineers, International Congress Detroit, Michigan March 1995 SAE paper No. 950275 93 106
- Blair G.P. Kirkpatrick S.J. Mackey D.O. Fleck R. “Experimental Validation of 1-D Modelling Codes for a Pipe System Containing Area Discontinuities” Society of Automotive Engineers, International Congress Detroit, Michigan March 1995 SAE paper No. 950276 107 120
- Blair G.P. “ Design and Simulation of Two-Stroke Cycle, Engines ” SAE Warrendale, Pennsylvania 1996
- Bingham J.F. “Unsteady Gas Flow in the Manifolds of Multicylinder Automotive Engines” The Queen's University of Belfast October 1983
- Blair G.P. McConnell J.H. “Unsteady Gas Flow Through High-Specific-Output 4-Stroke Cycle Engines” SAE Farm, Construction & Industrial Machinery and Powerplant Meetings Milwaukee September 1974 SAE Paper no. 740736
- Agnew D.D. “What is limiting engine air flow. Using Normalised Steady Air Flow Bench Data” SAE Motorsports Engineering Conference Dearborn December 1994 SAE Paper no. 942477
- Cartwright A. Fleck R. “A Detailed Investigation of Exhaust System Design in High Performance Two-Stroke Engines” SAE Motorsports Engineering Conference Dearborn December 1994 SAE Paper no. 942515
- Schlichting H. “ Boundary Layer Theory ” McGraw-Hill 6th New York 1968