Design and Simulation of Two Stroke Engines

Chapter 6 - Empirical Assistance for the Designer
is changed to 1.25 and 2, i.e., the limit values in Eq. 6.2.12, then the values of d2 and d3
become 61 and 92 mm, and 50 and 82 mm, respectively. The higher the value of the horn
coefficient, then the more "extreme" becomes the area profile of the diffuser with respect to
length along it.
Another useful feature of Prog.6.2v2 is that there is available a second page of line-print
output. This gives the manufacturing data for the various cones of the expansion chamber so
that they may be marked out, cut out, and rolled from flat sheet metal, then subsequently seam
welded into the several cones. The cones and parallel sections are butt welded to form a pipe
for either competition or dynamometer testing. An example of the actual line-printer output
of the manufacturing data for the racing engine design of Fig. 6.22 is shown in Fig. 6.23. In
that figure, RX and RY are the radii from the center of a circle marked on the metal sheet, and
(|) is the angle of the flat sheet segment. This information alone is quite sufficient to permit the
complete marking of the sheet metal. The extra information for the chords, CHX and CHY,
allows an alternative method of marking out the flat sheet metal segment, or provides a crosscheck
on the accuracy of setting out the angle
DIFRJSmCCNES
CONES L2, L3 & L4
38 56 89
56 89 116
229 152 0
473 265 249
702 417 326
119 174 264
177 274 346
14.5 38.3 64.1
TAIL
PIPE
GONE
22
116
200
47
247
64
332
85
CONE
DIMENSIONS
FLAT PLATE
DIMENSIONS
Fig. 6.23 Manufacturing data for the expansion chamber given by Prog.6.2v2.
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