Design and Simulation of Two Stroke Engines

Design and Simulation ofTwo'Stroke Engines
in the designed direction of the port. A later research paper by Smyth [3.17] shows this to be
inaccurate, particularly for the main transfer ports in a loop-scavenged design, and there is
further discussion of that in Sec. 3.5.4.
Examples of the use of the calculation are given by Sweeney [3.23] and a precis of the
findings is shown here in Figs. 3.21-30. The examples selected as illustrations are modified
Yamaha cylinders, Nos. 14 and 12, the best and the worst of that group whose performance
characteristics and scavenging behavior has already been discussed in Sec. 3.2.4. The computation
simulates the flow conditions of these cylinders on the QUB single-cycle test apparatus
so that direct comparison can be made with experimental results.
(a) (b) (c) (d)
Fig. 3.22 Yamaha cylinder No. 14 charge purity plots at 29° BBDC.
(a) (b) (c) (d)
Fig. 3.23 Yamaha cylinder No. 14 charge purity plots at 9° BBDC.
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