A multidimensional calculation procedure is used to investigate the flow in loop-scavenged two-stroke engine with curved cylinder heads. Five different cylinder heads are considered. The curvature of cylinder head increases from case I to case IV. In case V the head curvature is further increased, but it is shaped in the radially outer region. Calculations reveal that a tumbling vortex forms after the exhaust port is closed and the vortex constantly dominates the flow structure in the cylinder throughout the compression period. With high head curvatures the vortex is well organized and occupies the entire cylinder volume in the late compression stage. Due to compression of the better organized tumbling vortex by the moving piston more energy cascades from mean flow to turbulence in the high curvature cases III and IV. As for case V, the larger clearance in the bowl center region leads to lower shear stresses and, thus, the turbulence augmentation phenomenon is less prominent than that for cases III and IV.

Issue Section:
Research Papers
Topics:
Flow (Dynamics), Two-stroke engines, Cylinders, Vortices, Compression, Turbulence, Clearances (Engineering), Exhaust systems, Pistons, Shear stress
1.
Ahmadi-Befrui, B., Brandstatter, W., and Kratochwill, H., 1989, “Multidimensional Calculation of the Flow Processes in a Loop-Scavenged Two-Stroke Cycle Engine,” SAE Paper 890841.
2.
Amsden, A. A., O’Rourke, P. J., Butler, T. D., Meintjes. K., and Fansler, T. D., 1992, “Comparisons of Computed and Measured Three-Dimensional Velocity Fields in a Motored Two-Stroke Engine,” SAE Paper 920418.
3.
Arcoumanis, C., Hu, Z., Vafidis, C., and Whitelaw, J. H., 1990, “Tumbling Motion: A Mechanism for Turbulence Enhancement in Spark-Ignition Engines,” SAE Paper 900060.
4.
Begleris, P., 1987, “Three-Dimensional Flow Predictions in Motored Diesel Engines,” Ph.D. Thesis, Imperial College, University of London.
5.
Endres, H., Neußer, H. J., and Wurms, R., 1992, “Influence of Swirl and Tumble on Economy and Emissions of Multi Valve SI Engines,” SAE Paper 920516.
6.
Fansler, T. D., and French, D. T., 1992, “The Scavenging Flow Field in a Crankcase-Compression Two-Stroke Engine-A Three-Dimensional Laser-Velocimetry Survey,” SAE Paper 920417.
7.
Gosman, A. D., and Johns, R. J. R., 1978, “Development of a Predictive Tool for In-Cylinder Gas Motion in Engines,” SAE Paper 780315.
8.
Gosman, A. D., Tsui, Y. Y., and Vafidis, C., 1985, “Flow in a Model Engine with a Shrouded Valve-A Combined Experimental and Computational Study,” SAE Paper 850498.
9.
Hadded, O., and Denbratt, I., 1991, “Turbulence Characteristics of Tumbling Air Motion in Four-Valve S. I. Engines and Their Correlation with Combustion Parameters,” SAE Paper 910478.
10.
Haworth, D. C., El Tahry, S. H., Huebler, M. S., and Chang, S., 1990, “Multidimensional Port-and-Cylinder Flow Calculations for Two- and Four-Valve-Per-Cylinder Engines: Influence of Intake Configuration on Flow Structure,” SAE Paper 900257.
11.
Heywood
J. B.
,
1987
, “
Fluid Motion Within the Cylinder of Internal Combustion Engines-The 1986 Freeman Scholar Lecture
,”
ASME JOURNAL OF FLUIDS ENGINEERING
, Vol.
109
, pp.
3
–
35
.
12.
Launder
B. E.
, and
Spalding
D. B.
,
1974
, “
The Numerical Computation of Turbulent Flow
,”
Computer Methods in Applied Mechanics and Engineering
, Vol.
3
, pp.
269
–
289
.
13.
Tsui, Y. Y., 1987, “Calculation of Three-Dimensional Flow in Motored Engines,” Ph.D. thesis, Imperial College, University of London.
14.
Tsui
Y. Y.
, and
Cheng
H. P.
,
1994
, “
Flow Calculation in a Loop-Scavenged Two-Stroke Motored Engine
,”
International Journal of Numerical Methods for Heat and Fluid Flow
, Vol.
4
, pp.
249
–
267
.
15.
Tsui
Y. Y.
,
Chen
P. J.
, and
Yu
S. J.
,
1994
, “
Flow Calculation in a Loop-Scavenged Direct-Injection Two-Stroke Engine
,”
Journal of the Chinese Society of Mechanical Engineers
, Vol.
15
, No.
1
, pp.
56
–
70
.
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