| Summary: | 碩士 === 國立成功大學 === 機械工程學系 === 86 === Abstract The effect of injection
pressure, injection duration and injection timing othe exhaust
concentration in the valve overlap condition of thespark-
ignition engine has been studied by experiment. The experiment
wascarried out with 150㏄, 4-stroke cycle, air cooled engine.
The exhaust gases CO and HC concentration were measured at the
several fuel injectiontimings on the valve lap condition. The
result obtained was summarized as follows： 1.Effect of fuel
injection pressure：in order to increase its pressure level, the
injection pressure gradually increased, that means its
penetrationcapabilities and distance will be also increased.
Thus, kinematics of thefuel vapor will be increased, too. That''s
why there are more fuel vapor canaccommodate and attach on the
cylinder wall. Most easily and likely to result a dampened
cylinder wall. In the circumstances of the heavily wall-wetting
on cylinder , discharged of HC emissions also will be gradually
increased, but in respect to CO, the influence could not be too
much obvious. 2.Effect of fuel injection duration：by
comparing with the discharge of injection pressure, the
situation is very similar. However, it''s all about air-fuel
ratio. Since the injection duration flow has not been increased
or exceeded its time and measurement, then the cylinder wall
will not likely to have the same situation or condition of the
serious wall-wetting as increasingthe injection pressure, but
the end results are very similar. 3.Effect of fuel injection
timing：over the engine cycle, the injection timing at the
overlap time, because of the valve overlapping , it causes that
the fuelcan''t vaporize completely, then, this will conclude a
heavily wall-wetting on cylinder.In this situation, those un-
burned fuel will be leaked out to produce more emissions.
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