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An Experimental Comparison of Loop and Cross Scavenging of the Two-Stroke Cycle Engine
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English
Abstract
In a previous paper (6)* SAE 850178, the authors pointed out that the single-cycle gas simulation rig which they had developed would prove to be an invaluable experimental tool for the development of two-stroke cycle engine cylinders to attain better scavenging and trapping efficiency of the fresh charge. This paper reports on the use of that now proven experimental technique to examine one of the longest running, and hitherto unresolved, discussions in the field of small two-stroke cycle engines: is loop-scavenging really superior to cross-scavenging? All of the cross-scavenging tests in the paper are compared to tests conducted on loop-scavenged cylinders of the same basic geometry and which were reported previously to SAE. The main conclusion from the experimental investigation is that cross-scavenging is superior to loop-scavenging at low or modest scavenge ratios but is inferior at high scavenge ratios. However, another approach to cross-scavenging yields a design which retains and enhances the superiority at low or modest scavenge ratios and is at least equal to the very best loop-scavenging designs at the highest scavenge ratios. Equally important, this new cross-scavenging design lends itself to incorporation into a closely spaced multi-cylinder design without deterioration of those high scavenging and trapping efficiencies. The conclusions to be drawn from the tests on the new cross-scavenging design are that a potential exists for improving power and specific fuel consumption by 25% over the best loop-scavenging design.
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Authors
- G. P. Blair - Dept. of Mechanical and Industrial Engineering The Queen's University of Belfast
- R. G. Kenny - Dept. of Mechanical and Industrial Engineering The Queen's University of Belfast
- J. G. Smyth - Dept. of Mechanical and Industrial Engineering The Queen's University of Belfast
- M. E. G. Sweeney - Dept. of Mechanical and Industrial Engineering The Queen's University of Belfast
- G. B. Swann - Dept. of Mechanical and Industrial Engineering The Queen's University of Belfast
Citation
Blair, G., Kenny, R., Smyth, J., Sweeney, M. et al., "An Experimental Comparison of Loop and Cross Scavenging of the Two-Stroke Cycle Engine," SAE Technical Paper 861240, 1986, https://doi.org/10.4271/861240.Also In
References
- Blair G.P. Houston R.A.R. McMullan R.K. Steele N. Williamson S.J. “A New Piston Design for a Cross-Scavenged Two-Stroke Cycle Engine with Improved Scavenging and Combustion Characteristics” Transactions SAE 841096
- Blair G.P. Ashe M.C. “The Unsteady Gas Exchange Characteristics of a Two-Cycle Engine” Transactions SAE 760644 1976
- Blair G.P. “Studying Scavenge Flow in a Two-Stroke Cycle Engine” Transactions SAE 750752 1975
- Blair G.P. Kenny R.G. “Further Developments in Scavenging Analysis for Two-Stroke Engines” Transactions SAE 800038 1980
- Sanborn D.S. Blair G.P. Kenny R.G. Kingsbury A.H. “Experimental Assessment of Scavenging Efficiency of Two-Stroke Cycle Engines” Transactions SAE 800975 1980
- Sweeney M.E.G. Kenny R.G. Swarm G.B. Blair G.P. “Single Cycle Gas Testing Method for Two-Stroke Engine Scavenging” Transactions SAE 850178 1985
- Sweeney M.E.G. Swann G.B. Kenny R.G. Blair G.P. “Computational Fluid Dynamics Applied to Two-Stroke Engine Scavenging” Transactions SAE 851519 1985