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Abstract
The effect of secondary air injection (SAI) on exhaust hydrocarbon (HC) and carbon monoxide (CO) emission has been investigated in a spark- ignition (SI) single cylinder engine operating at steady–state condition. An experimental study was performed to develop a more fundamental understanding of the effects of SAI on exhaust gas emissions and catalyst light-off characteristics in a modern SI engine. The effects of several design and operating parameters of secondary air injection (SAI) such as secondary air flow rate and air injection location were investigated to understand the mixing and heat loss. Time- resolved HC and CO concentrations were tracked from the cylinder head exhaust to the catalytic converter outlet. Oxidation characteristics of HC and CO are monitored with a Fast response CO and HC emission analyzer and exhaust gas temperatures with thermocouples. Effects of exhaust air-fuel ratio (A/F), location of SAI, and engine-A/F have been investigated. Results prove that HC and CO reduction worth increases as the location of SAI is closer to the exhaust.