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Non-Isentropic Analysis of Varying Area Flow in Engine Ducting
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Abstract
In two previous papers to this Society (1, 2)* an ‘alternative’ method was presented for the prediction of the unsteady gas flow behaviour through a reciprocating internal combustion engine. The computational procedures led further to the prediction of the overall performance characteristics of the power unit, be it operating on a two- or a four-stroke cycle. Correlation with measurements was given to illustrate its effectiveness and accuracy.
In the ducts of such engines there are inevitably sectional changes of area which are either gradual or sudden. A tapered pipe is typical of a gradual area change whereas a throttle or a turbocharger nozzle represents a sudden area change. In those previous papers it was indicated that a fuller explanation, of the theoretical procedures required to predict accurately the unsteady gas flow in such duct sections would be given in a later paper to this Society; this is that necessary publication.
The theory of gradual and sudden area changes is presented, together with computational illustrations of its application to real geometrical cases. The theory includes non-isentropic effects at such area changes and inherently solves the mass continuity, energy and momentum equations at each section.
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Citation
Blair, G. and Magee, S., "Non-Isentropic Analysis of Varying Area Flow in Engine Ducting," SAE Technical Paper 932399, 1993, https://doi.org/10.4271/932399.Also In
References
- 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 in SP883 24
- 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 and in SP945 20
- Blair G.P. Goulburn J.R. “The Pressure-Time History in the Exhaust System of a High-Speed Reciprocating Internal Combustion Engine” Society of Automotive Engineers, Mid-Year Meeting Chicago, Illinois May 15-19,1967 SAE Paper No. 670477
- Benson R.S. Garg R.D. Woollatt D. “A Numerical Solution of Unsteady Flow Problems” Int.J.Mech.Sci. 1 253 1960
- Poloni M. Winterbone D.E. Nichols J.R. “Comparison of Unsteady Flow Calculations in a Pipe by the Method of Characteristics and the Two-Step Lax-Wendroff Methods” Int.J.Mech.Sci. 29 1987
- Ledger J.D. “A Finite Difference Approach for solving the Gas Dynamics in an Engine Exhaust” Int.J.Mech.Sci. 17 5 271 1975
- Chapman M. Novak J.M. Stein R.A. “A Non-Linear Acoustic Model of Inlet and Exhaust Flow in Multi-Cylinder Internal Combustion Engines” Winter Annual Meeting ASME, Boston, Mass. 83-WA/DSC-14 November 1983
- Blair G.P. “Correlation of Measured and Calculated Performance Characteristics of Motorcycle Engines” Funfe Zweiradtagung Technische Universität Graz, Austria 22 23 April 1993
- Blair G. P. “The Basic Design of Two-Stroke Engines” Society of Automotive Engineers Warrendale, Pennsylvania February 1990 672 SAE ref. no. R-104 1-56091-008-9
- Benson R.S. “The Thermodynamics and Gas Dynamics of Internal Combustion Engines” 1 2 Clarendon Press Oxford 1982
- Blair G.P. Johnston M.B. “Unsteady Flow Effects in the Exhaust Systems of Naturally Aspirated, Crankcase Compression, Two-Stroke Cycle Engines” SAE Farm, Construction and Industrial Machinery Meeting Milwaukee, Wisconsin September 11-14, 1968 SAE Paper No. 680594 .
- Blair G.P. “Unsteady Flow Characteristics of Inward Radial Flow Turbines” Doctoral thesis The Queen's University of Belfast May 1962
- Bingham J.F. Blair G.P. “An Improved Branched Pipe Model for Multi-Cylinder Automotive Engine Calculations” Proc.I.Mech.E. 199 D1 1985 65 77
- Blair A.J. Blair G.P. “Gas Flow Modelling of Valves and Manifolds in Car Engines” Proc.I.Mech.E. International Conference on Computers in Engine Technology University of Cambridge April 1987 131 144