(Degree) (Major) jr /..5) Title PARTIAL RECIRCULATION OF DIESEL EXHAUST FOR THE REDUCTION OF OXIDES OF NITROGEN

Abstract approved or professor) Oxides of nitrogen are a concern as effluents to atmospheres because they participate in photochemical reactions which produce smog, because they attenuate sunlight which gives the atmosphere a reddish brown cast, and because of their toxic properties and the health hazards associated with the photochemical products they pro-duce. Oxides of nitrogen are formed during the heterogeneous com-bustion of the diesel engine. When the locally overlean regions are subjected to high temperatures, nitric oxide (NO) is formed from the nitrogen and oxygen in the air. Nitrogen dioxide (NO2) is formed slowly from the nitric oxide. The concentration of oxides of nitrogen formed is a function of the fuel-air ratio; the concentration magnitud