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Scavenging of a Firing Two-Stroke Spark-Ignition Engine
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Abstract
Current demands for high fuel efficiency and low emissions in automotive powerplants have drawn attention to the two-stroke engine configuration. The present study measured trapping and scavenging efficiencies of a firing two-stroke spark-ignition engine by in-cylinder gas composition analysis. Intermediate results of the procedure included the trapped air-fuel ratio and residual exhaust gas fraction. Samples, acquired with a fast-acting electromagnetic valve installed in the cylinder head, were taken of the unburned mixture without fuel injection and of the burned gases prior to exhaust port opening, at engine speeds of 1000 to 3000 rpm and at 10 to 100% of full load. A semi-empirical, zero-dimensional scavenging model was developed based on modification of the non-isothermal, perfect-mixing model. Comparison to the experimental data shows good agreement.
Until recently, two-stroke engines had been considered unsuitable for automotive use under current and pending emission regulations. With a gasoline injection system applied directly in-cylinder, however, the unacceptable short-circuiting of raw fuel during the scavenge period can be avoided. Thus, renewed interest in exploiting the potential advantages of a two- stroke engine-higher power to weight ratio, smaller package size, and fewer parts-is warranted.
The ported two-stroke requires open exhaust ports during the entire scavenge period. Some fresh air is inevitably lost to the exhaust during the scavenge process, and is not trapped in the cylinder. To attain stoichiometry in the exhaust, so that a three-way catalyst could be employed, a direct-injection (DI) two-stroke engine would require a rich trapped charge to compensate for the air which bypasses the combustion process. As this inefficiency cannot be tolerated, three-way catalysts cannot be relied upon. Instead, emissions and fuel consumption are controlled by operating lean with high levels of residual, and a knowledge of combustion gas composition is crucial to a description of the engine operating condition.
A consequence of the short-circuiting of fresh air into the exhaust is that the air-fuel ratio during combustion cannot be determined by mass measurements of the fuel and air supplied to the engine or by overall exhaust chemical analysis. Although the two-stroke charge may be stratified, an understanding of its emission characteristics is enhanced by knowledge of the over-all air-fuel ratio of the trapped charge. Further, it is desirable to determine the fraction of the in-cylinder mixture comprised of residual gases. This paper describes a measurement of the scavenging parameters of a DI two-stroke engine, from which trapped air-fuel ratio and residual fraction are calculated.
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Tobis, B., Meyer, R., Yang, J., Brehob, D. et al., "Scavenging of a Firing Two-Stroke Spark-Ignition Engine," SAE Technical Paper 940393, 1994, https://doi.org/10.4271/940393.Also In
Two-Stroke Engines: Theoretical and Experimental Investigations
Number: SP-1019; Published: 1994-03-01
Number: SP-1019; Published: 1994-03-01
References
- Boyer, R.L. Craig, D.R. Miller, C.D. “A Photographic Study of Events in a 14-in. Two-Cycle Gas Engine Cylinder,” Transactions of ASME 76 97 108 1954
- List, H. “The Charging Processes of Internal-combustion Engines With Special Reference to the Two-Stroke Cycle,” Proceedings of the Institution of Mechanical Engineers, Automobile Division 45 68 1953
- Schweitzer, P.H. DeLuca, F. “The Tracer Gas Method of Determining the Charging Efficiency of 2-Stroke-Cycle Diesel Engines,” NACA Technical Note 838 1942
- Isigami, S. Tanaka, Y. Tamari, M. “The Trapping Efficiency Measurement of Two Stroke Cycle Diesel Engine by Tracer Gas Method,” Bulletin of JSME 6 524 31 1963
- Bazika, V. Rodig, J. “A New Method of Determining the Scavenging Efficiency of Oil Cylinders,” The Engineers Digest 24 1963
- Wallace, E.J. Cave, P.R. “Experimental and Analytical Scavenging Studies Two-Stroke Opposed Piston Diesel Engine,” SAE Paper 710175 1971
- Huber, E.W. “Measuring the Trapping Efficiency of Internal Combustion Engines Through Continuous Exhaust Gas Sampling,” SAE Paper 710144 1971
- Ohigashi, S. Hamamoto, Y. “Cylinder Gas Composition of Small 2-stroke Gasoline Engine,” SAE Paper 710143 1971
- Ku, P.M. Trimble, T.F. “Scavenging Characteristics of a Two-Stroke-Cycle Engine as Determined by Skip-Cycle Operation,” Journal of Research of the National Bureau of Standards 57 325 31 1956
- Booy, R.B. “Evaluating Scavenging Efficiency of Two- Stroke Cycle Gasoline Engines,” SAE Paper 670029 1967
- Asanuma, T. Yanagihara, S. “Gas Sampling Valve for Measuring Scavenging Efficiency in High-Speed Two- Stroke Engines,” SAE Transactions 70 420 33 1962
- Hori, K. “A Method of Measuring Scavenging Efficiency and its Applications,” Bulletin of JSME 5 327 34 1962
- Hori, K. “The Influence of Volume and Period of Gas- Sampling upon the Accuracy of the Measurements of Scavenging Efficiency,” Bulletin of JSME 6 289 95 1963
- Kannappan, A. “A New Method for Evaluating the Scavenging Performance of Two-Stroke Diesel Engines,” SAE Paper 640929 1964
- Ohigashi, S. Hamamoto, Y. “Cylinder Gas Composition of Small Two- Stroke Cycle Gasoline Engine,” SAE Paper 710143 1973
- Blair, G.P. Ashe, M.C. “The Unsteady Gas Exchange Characteristics of a Two-Cycle Engine,” SAE Paper 760644 1976
- Blair, G.P. Kenny, R.G. “Further Developments in Scavenging Analysis for Two-Cycle Engines,” SAE Paper 800038 1980
- Sanborn, D.S. Blair, G.P. Kenny, R.G. Kingsbury, A.H. “Experimental Assessment of Scavenging Efficiency of Two-Stroke Cycle Engines,” SAE Paper 800975 1980
- Malkiewicz, T. “Scavenging Parameters of Two-Stroke Engines - Methods of Measurement and Calculation,” 48 439 45 1987
- Hopkinson, B. “The Charging of Two-Cycle Internal Combustion Engines.” Transactions of the NE Coast Institution of Engineers and Shipbuilders 30 433 1914
- Benson, R.S. Brandham, P.T. “A Method for Obtaining a Quantitative Assessment of the Influence of Charging Efficiency in Two-Stroke Engine Performance,” International Journal of Mechanical Engineering Science 11 303 12 1969
- Streit, E.E. Borman, G.L. “Mathematical Simulation of a Large Turbocharged Two-Stroke Diesel Engine,” SAE Paper 710176 1971
- Benson, R.S. “A New Gas Dynamic Model for the Gas Exchange Process in Two-stroke Loop and Cross Scavenged Engines,” International Journal of Mechanical Engineering Science 19 693 711 1977
- Baudequin, F. Rochelle, R “Some Scavenging Models for Two-Stroke Engines,” Proceedings of the Institution of Mechanical Engineers 194 203 10 1980
- Chen, C. Wallace, F.J. “A Generalized Isobaric and Isochoric Thermodynamic Scavenging Model,” SAE Paper 871657 1987
- Blair, G.P. “The Correlation of theory and Experiment for Scavenging Flow in Two-Stroke Cycle Engine,” SAE Paper 881265 1988
- Chen, C. Wallace, F.J. “A Phenomenological Unsteady Jet Model for Uniflow Scavenging,” SAE Paper 871658 1987
- Benson, R.S. Whitehouse, N.D. Internal Combustion Engines 2 New York Pergamon Press 1979
- Sher, E. “Scavenging the Two-Stroke Engine,” Progress in Energy and Combustion Science 16 95 124 1990
- Blair, G.P. “Correlation of an Alternative Method for the Prediction of Engine Performance Characteristics with Measured Data,” SAE Paper 930501 1993
- Sher, E. “A New Practical Model for the Scavenging Process in a Two- Stroke Cycle Engine,” SAE Paper 850085 1985
- Amsden, A.A. O'Rourke. P.J. Butler, T.D. Meintjes, K. Fansler, T.D. “Comparisons of Computed and Measured Three-Dimensional Velocity Fields in a Motored Two-Stroke Engine,” SAE Paper 920418 1992
- Gouveia, M.C. Parise, J.A.R. Nieckele, A.O. “Numerical Simulation of the Fluid Flow and Heat Transfer Processes During Scavenging in a Two-Stroke Engine under Steady-State Conditions,” Journal of Heat Transfer 114 383 93 1992
- Sweeney, M.E.G. Kenney, R.G. Swann, G.B. Blair, G.P. “Computational Fluid Dynamics Applied to Two-Stroke Engine Scavenging,” SAE Paper 851519 1985
- Diwakar, R. “Three Dimensional Modeling of the In- Cylinder Gas Exchange Processes in a Uniflow-Scavenged Two-Stroke Engine, “ SAE Paper 870596 1987
- Haworth, D.C. Huebler, M.S. ElTahry, S.H. Matthes, W.R. “Multidimensional Calculations for a Two-Stroke-Cycle Engine: A Detailed Scavenging Model Validation,” SAE Paper 932712 1993
- Sher, E. “Prediction of the Gas Exchange Performance in a Two-Stroke Cycle Engine,” SAE Paper 850086 1985
- Sher, E. “An Improved Gas Dynamic Model Simulating the Scavenging Process in a Two-Stroke Cycle Engine,” SAE Paper 800037 1980
- SAE “Recommended Practice, Engine Terminology and Nomenclature,” SAE J604 JAN86 24.01 1986