| Summary: | 碩士 === 南台科技大學 === 機械工程系 === 100 === The objective of this study was to observe the effects of intake oxygen concentration on the emissions during the cold start period of an SI engine. The intake air with a given oxygen concentration was premixed in a bag which was then attached to the intake manifold to the engine. Three oxygen concentrations were tested, namely 21%, 25%, and 30%. For 21% oxygen intake air, CO and HC emissions were higher during the 180s of the cold start period. For the case of 25%, the air-fuel ratio approached stoichiometric ratio quickly 90s after starting the engine, indicating that 25% oxygen in the intake air could shorten the high CO and HC emission period. NOx emission was not raised noticeably. For the case of 30%, the oxygen sensor started to operate in closed-loop control 30s after starting the engine and the engine ran unstably afterwards.
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