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A New Piston Design for a Cross-Scavenged Two-Stroke Cycle Engine with Improved Scavenging and Combustion Characteristics
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English
Abstract
This paper describes a unique design of deflector piston for a cross-scavenged two-stroke cycle engine which incorporates the advantages of good scavenging, rapid combustion and reduced thermal loading on the piston. Test results are presented to confirm this statement from two small capacity outboard marine engines and comparisons are made between the experimental test results from the modified and standard power units; of significance is the reduced fuel consumption rate of the modified engines in both cases. A high bmep 400 cm3 single cylinder engine is designed, constructed and tested so as to determine the extent of deflector burning under conditions of high thermal loading.
On all three engines the ignition timing for best power is shown to be in the 21-24° btdc region, by comparison with 32-38° btdc conventionally. The spark plug seat temperatures are reduced to 150 C maximum at peak power by comparison with 250-280 °C normally. Startability is unaffected by the new piston design whilst the idle and low speed engine behaviour could be superior to a conventional deflector piston type engine which means it is considerably better than a loop-scavenged engine.
Photographs of the scavenge flow are presented from experimental tests which would indicate that the scavenge characteristics of this new piston design could be very good.
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Authors
- G. P. Blair - Dept. of Mechanical & Industrial Engineering, The Queen's University of Belfast, N. Ireland
- R. A. R. Houston - Dept. of Mechanical & Industrial Engineering, The Queen's University of Belfast, N. Ireland
- R. K. McMullan - Dept. of Mechanical & Industrial Engineering, The Queen's University of Belfast, N. Ireland
- N. Steele - Dept. of Mechanical & Industrial Engineering, The Queen's University of Belfast, N. Ireland
- S. J. Williamson - Dept. of Mechanical & Industrial Engineering, The Queen's University of Belfast, N. Ireland
Topic
Citation
Blair, G., Houston, R., McMullan, R., Steele, N. et al., "A New Piston Design for a Cross-Scavenged Two-Stroke Cycle Engine with Improved Scavenging and Combustion Characteristics," SAE Technical Paper 841096, 1984, https://doi.org/10.4271/841096.Also In
References
- Lanchester F. W. Pearsall R. H. “An Investigation of Certain Aspects of the Two-Stroke Engine for Automobile Vehicles” Proceedings of the Institution of Automobile Engineers February 1922
- SAE Cumulative Index of Technical Papers 6th 1965 1981 April 1982
- Blair G. P. The Queen's University of Belfast “Deflector Piston Two-Stroke Engine, British Patent Application” 23 November 1983 number 8331289
- Blair G. P. Cahoon W. L. “A More Complete Analysis of Unsteady Gas Flow through a High-Specific Output Two-Cycle Engine” SAE Congress Detroit Jan. 1972 SAE 720156
- Blair G. P. Ashe M. C. “The Unsteady Gas Exchange Characteristics of a Two-Cycle Engine” SAE Meeting Milwaukee Sept. 1976 SAE 760644
- Sweeney M. “An Investigation of Scavenging Flow in Small Two-Stroke Engines” First Year Research Report The Queen's University of Belfast, Dept. of Mech./lnd. Engineering Report No. 1558 1983
- Blair G. P. Cahoon W. L. “Design and Initial Development of a High-Specific Output 500 cc Single-Cylinder, Two-Stroke, Racing Motorcycle Engine” SAE Congress Detroit Jan. 1971 SAE 710082