Shape Parameterization and Optimization of a Two-Stroke Engine

We demonstrate a procedure for designing and optimizing the scavenging properties of a two-stroke engine. A method of surface design, known as the partial differential equation method, is used to represent the internal geometryoftheengine.Wethenrunsteady-statecomputationale uiddynamicscalculationstoassessthescavenging e ow inside the engine. To quantify the scavenging, the trapping efe ciency is used, and calculated values of this measure are obtained for different geometrical designs. We use a locally weighted regression-smoothing model to e t the data, and then we optimize the resulting response surface. The optimization captured two local minima, one of which corresponds to accepted manufacturing practice and the other one is a new and counter-intuitive way of scavenging the engine, having optimum scavenging characteristics. Nomenclature C = contour M = mass of air n = number of particles r0 = bore of the cylinder u, v = surface parametric coordinates V = volume of air X = vector of Cartesian coordinates of surface points Xn = normal derivative along the boundary x, y, z = Cartesian coordinates xsu = derivative parameter of the transfer port, in x direction, on C0 ysl = derivative parameter of the transfer port, in y direction, on C1 ysu = derivative parameter of the transfer port, in y direction, on C0 zsu = derivative parameter of the transfer port, in z direction, on C0 a = smoothing parameter q = density Subscripts s = supplied t = trapped 0, 1 = upper and lower surface boundaries, respectively

[1]  Robert Fleck,et al.  CFD Prediction of a Two-Stroke, In-Cylinder Steady Flow Field An Experimental Validation , 1994 .

[2]  Todd D. Fansler,et al.  The Scavenging Flow Field in a Crankcase-Compression Two-Stroke Engine - A Three-Dimensional Laser-Velocimetry Survey , 1992 .

[3]  Yoshio Murakami,et al.  Improvement of pitot tube set for obtaining scavenging pictures of two-stroke cycle engines , 1988 .

[4]  Malcolm I. G. Bloor,et al.  Spectral approximations to PDE surfaces , 1996, Comput. Aided Des..

[5]  Malcolm I. G. Bloor,et al.  Using partial differential equations to generate free-form surfaces , 1990, Comput. Aided Des..

[6]  Richard Stone,et al.  Introduction to Internal Combustion Engines , 1985, Internal Combustion Engines.

[7]  C. W. Dekanski,et al.  THE COMPUTER-AIDED FUNCTIONAL DESIGN OF A MARINE PROPELLER , 1996 .

[8]  Roger Fletcher,et al.  A Rapidly Convergent Descent Method for Minimization , 1963, Comput. J..

[9]  Daniel S. Sanborn,et al.  Single Cycle Simulation Simplifies Scavenging Study , 1985 .

[10]  Alfred Jante.  Scavenging and Other Problems of Two-Stroke Cycle Spark-Ignition Engines , 1968 .

[11]  C. W. Dekanski,et al.  A parametric model of a 2-stroke engine for design and analysis , 1996 .

[12]  Gordon P. Blair,et al.  Design and Simulation of Two-Stroke Engines , 1996 .

[13]  G. P. Blair.  Studying Scavenge Flow in a Two-Stroke Cycle Engine , 1975 .

[14]  Mauro Valorani,et al.  Optimization methods for non-smooth or noisy objective functions in fluid design problems , 1995 .

[15]  Daniel C. Haworth,et al.  Multidimensional Calculations for a Two-Stroke-Cycle Engine: A Detailed Scavenging Model Validation , 1993 .

[16]  Michael J. Wilson,et al.  Generating blend surfaces using partial differential equations , 1989 .

[17]  R. G. Kenny,et al.  CFD Simulation and Validation of the Flow within a Motored Two-Stroke Engine , 1997 .

[18]  G. P. Blair,et al.  Further Developments in Scavenging Analysis for Two-Cycle Engines , 1980 .

[19]  D. Thornhill,et al.  Reducing Exhaust Hydrocarbon Emissions from a Small Low Cost Two-Stroke Engine , 1998 .

[20]  Michael J. Wilson,et al.  The automatic functional design of hull surface geometry , 1994 .

[21]  Richard Stone.  Two-stroke Engines , 1999 .

[22]  Malcolm I. G. Bloor,et al.  Efficient parametrization of generic aircraft geometry , 1995 .

[23]  Peter J. O'Rourke,et al.  Comparisons of computed and measured three-dimensional velocity fields in a motored two-stroke engine , 1992 .