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Analytically Predicted improvements in the Scavenging and Trapping Efficiency of Two-Cycle Engines
ISSN: 0148-7191, e-ISSN: 2688-3627
Published February 01, 1988 by SAE International in United States
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The effects of using trapezoidal shaped protuberances over the squish region of the piston bowl on the characracteristics of the air exchange process of a uniflow, two-cycle diesel engine is investigated analytically. The CONCHAS multidimensional code is used in this analysis. The engine geometry and boundary conditions simulates the operation of an experimental engine at maximum load and speed.
The predicted air breathing characteristics of the engine with a base case protuberance are compared against those without a protuberance. The effect of protuberance height is studied by repeating the calculations with protuberance heights above and below the base case. The effects of the radial position of the protuberance are also studied by comparing similar calculations with protubeances at larger and smaller radius than those of the base case. The results are presented in terms of cylinder total, fresh air and residual gas mass prediction plots, as well as flow rate predictions at the valves and ports for each case. The detailed features of the flowfield are represented in terms of velocity vector plots, fresh air concentration contour plots and zero vertical velocity vector plots at selected crank angles. Predictions are evaluated by comparing the results against the base reference case.
In review, the predictions show that the engine scavenging and trapping efficiencies are influenced considerably by the use of a protuberance. With proper choice of the location and height of the protuberance, it is possible to improve the volumetric, trapping and scavenging efficiency of the engine at the same time. Basic physical reasons for these improvements are described through evaluation of the predictions.
CitationUzkan, T., "Analytically Predicted improvements in the Scavenging and Trapping Efficiency of Two-Cycle Engines," SAE Technical Paper 880108, 1988, https://doi.org/10.4271/880108.
- Taylor, C.F. The Internal Combustion Engine in Theory and Practice MIT Press Second 1965
- Benson R.S. Whitehouse N.D. Internal Combustion Engines Pergamon Press 1979
- Schweitzer, P.H. Deluca, F. “The Tracer Gas Method of Determining The Charging Efficiency of Two-Stroke Cycle Diesel Engines” NACA-TN 838
- Taylor, C.F. Rogowski, A.R. “Scavenging the 2-Stroke Engines” SAE Trans. 62 487 1954
- Kyrtatos, N. P. koumbarelis, I. “A Three Zone Scavenging Model For Two-Stroke Engines” Paper presented in congress on Modelling of IC Engines Valencia Spain June 1987
- Diwakar, R. “Multidimensional Modelling ofr the Gas Exchange Process in Uniflow-Scavenged Two-Stroke Diesel Engine” Int. Symp on Flows in IC Engines-3 ASME Publ. 28 107 115
- Uzkan, T. Hazelton, J.R. “The Influence of Swirl on the Fresh Charge Stratification in an IC Engine Combustion Chamber” SAE Paper No. 860466
- Uzkan, T. Savage, T. Hazelton, J.R. “The Effects of Piston Bowl Shape Modifications on the In-Cylinder Flow Characteristics of the EMD-710 Engine” ASME Paper No. 85-DGP-23 1985
- Kotlin, J.J. Dunteman, N.R. Chen, J. Heilenbach, J.W. “The General Motors EMD Model 710 Series Turbocharged Two-Stroke Cycle Diesel Engine” ASME Paper No 1985
- Cloutman, L.D. Dukowicz, J. K. Ramshaw J D Amsden, A.A “CONCHAS-SPRAY: A Computer Code for Reactive Flows with Fuel Sprays” Los Alamos National Lab. Report LA-9294- MS May 1982
- El-Tahry, S.H. “A Numerical Study on the Effects of Fluid Motion at Inlet Valve Closure on Subsequent Fluid Motion in a Motored Engine” SAE Paper No. 82003