Design and Simulation of Two Stroke Engines

Design and Simulation of Two-Stroke Engines
Fig. 7.29 The fundamental principle for the reduction of hydrocarbon
on emissions and fuel consumption.
in the relatively short time period from exhaust port closure until the ignition point before the
tdc position. Put in the simplest terms, if the end of the fuel injection of the gasoline is at 90°
before the ignition point, and the engine is running at 6000 rpm, this implies a successful
evaporation and mixing process taking place in 0.0025 second, or 2.5 ms. That is indeed a
short time span for such an operation when one considers that the carburetted four-stroke
cycle engine barely accomplishes that effect in a cycle composed of 180° of induction period,
followed by 180° of compression process, i.e., four times as long. In the simple two-stroke
cycle engine, the induction process into a "warm" crankcase for 180° of engine rotation helps
considerably to evaporate the fuel before the commencement of the scavenge process, but
even then does not complete the vaporization process, as is pointed out in the excellent presentation
by Onishi et al. [7.8]. Further discussion on this is in Sec. 7.4.2 dealing with direct
in-cylinder fuel injection.
Stratified charging
The potential difficulty regarding the adequate preparation of the frel and air mixture
prior to the combustion process opens up many solutions to this design problem. The patent
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