| Summary: | 碩士 === 國立海洋大學 === 機械與輪機工程學系 === 84 === Comparing with other fuels, liquefied petroleum gas (LPG)
bears the characteristics of low combustion emmissions. From
domestic and abroadexperiences, the engine performance generally
tends to decrease when agasoline engine changes to be fueled
with LPG. Howener, the engine per-formance should not differ so
much when inferring from the aspects of LPG fuel properties of
heating value and theoretical air/fuel ratio. The effects of
the engine operating parameters, such as ignition timing, air/
fuel ratio, and copmression ratio on LPG engine performanceare
experimentally studied in this thesis. The results show that,
withoutadditional engine tuning, the torque output of an LPG-
fueled engine atlow and mid- speeds is lower than that of a
gasoline-fueled one. The maximum torque output occurs at a lower
engine speed. At high engine speeds, the torque output decreases
abruptly and the HC emmissions increases suddenly. The
occasional misfiring and rough engine operationat high engine
speeds suggest insufficient supply of LPG fuel, which is further
confirmed by the measurements of exhaust emissions. That is the
reason which cause the lower performance of an LPG-fueled engine
than thatof a gasoline-fueled one. It have been shown by
experiments that the braketorque and horse power are improved by
advancing ignition timing and increasing compression ratio. At
mid- and high engine speeds, the braketorque and horse power of
the LPG-fueled engine improve significantly when the air/fuel
mixture ratio are controlled to the stoichiometric value.
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