This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Multidimensional Calculation of the Flow Processes in a Loop-Scavenged Two-Stroke Cycle Engine
Annotation ability available
Sector:
Language:
English
Abstract
A multidimensional computational method is employed to investigate the details of the in-cylinder flow and gas exchange process in a loop-scavenged two-stroke cycle spark-ignition engine. The engine geometric compression ratio is 15:1 and the study pertains to the operating condition of 5000 rpm.
The inlet and outlet boundary conditions (c.f. the instantaneous thermodynamic properties and the intake and exhaust mass flow rates) were obtained from a gas dynamic calculation procedure. This enabled incorporation of the effect of the pressure waves causing strong flow oscillations in the scavenge and exhaust ports.
The results reveal that the in-cylinder flow structure established early during the scavenge phase comprises of a three-dimensional loop and a pair of toroidal vortices. This vortex structure is responsible for impairment of the scavenging efficiency. The flow structure was found to be sensitive to the details of the scavenge system layout. The occurence of ‘reverse’ flows through the scavenge and exhaust ports, caused by pressure wave oscillations in the port system, markedly affects the in-cylinder flow structure and mixing process. Furthermore it was found that the isothermal model of scavenging characterization is inadequate for engine operating conditions.
Recommended Content
Authors
Citation
Ahmadi-Befrui, B., Brandstatter, W., and Kratochwill, H., "Multidimensional Calculation of the Flow Processes in a Loop-Scavenged Two-Stroke Cycle Engine," SAE Technical Paper 890841, 1989, https://doi.org/10.4271/890841.Also In
References
- Sweeney, M.E.G. Swann, G.B.G. Kenny, R.G. Blair, G.P. “Computational fluid dynamics applied to two-stroke engine scavenging” SAE paper 851519
- Plohberger, D. Mikulic, L.A. Landfahrer, K. “Development of a fuel injected two-stroke gasoline engine” SAE paper 880170
- Blair, G.P. Ashe, M.C. “The in-steady gas exchange characteristics of a two-stroke cycle engine” SAE paper 760644 1976
- Sato, K. Kido, K. “Simulation of the gas exchange process in a small two-stroke cycle engine (1st report, theoretical treatment); (2nd report, comparison between experimental and theoretical treatments)” JSME Bulletin 26 217 1983
- Sher, E. “An improved gas dynamic model simulating the scavenging process in a two-stroke cycle engine” SAE paper 800037 1980
- Sher, E. “Prediction of the gas exchange performance in a two-stroke cycle engine” SAE paper 850086 1985
- Johns, R.J.R. “A unified method for calculating engine flows” ASME 84-DGP-1P 1984
- Brandstätter, W. Johns, R.J.R. “Computer simulation of external and internal turbulent flows in the automotive industry” Supercomputer Applications in Automotive Research and Development Proceedings of the Int. Conf. Zürich Oct. 1986 Cray Research Inc. Marino C.
- Ahmadi-Befrui, B. “Assessment of variants of the k-ε turbulence model for engine flow applications” ASME paper 87-FE-11 1987
- Smyth, J.G. Kenny, R.G. Blair, G.P. “Steady flow analysis of the scavenging process in a loop-scavenged two-stroke cycle engine - a theoretical and experimental study” SAE Paper 881267 1988
- Hille, P. Vehrenkamp, R. Schulz-Dubois, E.O. “The development and structure of primary and secondary flow in curved square ducts” J. Fluid Mech. 151 219 241 1985
- Schmidt, M.C. Whitelaw, J.H. Yianneskis, M. “Flow in out-of-plane double S-bends” Proceedings of the 6th Symp. on Turbulent Shear Flows Toulouse Sept. 1987
- Kurokawa, J. Morikawa, M. “Accelerated and decelerated flows in a circular pipe (1st report, velocity profile and friction coefficient)” Bulletin of JSME 29 249 March 1986
- Sumida, M. Sudou, K. “Pulsating flow in curved pipes (3rd report, axial velocity profile)” Bulletin of JSME 29 256 October 1986
- Tiederman, W.G. Privette, R.M. Phillips, W.M. “Cycle-to-cycle variation effects on turbulent shear stress measurements in pulsatile flows” Experiments in Fluids 6 265 272 1988
- Ahmadi-Befrui, B. “Analysis of flow evolution in the cylinders of motored reciprocating engines” University of London 1985