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摘要

The exhaust gases of an i.c. engine are catalytically purified by passing secondary air into the catalytic bed at a higher rate than is required for a complete oxidation of the unburnt matter. The air is introduced at points distributed throughout the bed. The mixture of exhaust gases and air has a ratio of oxidising to reducing components which rises from below stoichiometric at the inlet to above stoichiometric at the outlet of the catalytic bed. The delivery of secondary air is proportional to the engine speed and need not be altered when the load changes. At high loads, the NO percentage in the exhaust gases is high and the catalyst volume below the stoichiometric ratio automatically becomes smaller. During deceleration, greater quantities of unburnt matter will be issued and the volume above the stoichiometric ratio will be increased.