BALANCING CLEAN AIR AGAINST GOOD MILEAGE

Tighter control of emissions (hydrocarbons, carbon monoxide, and oxides of nitrogen) beyond the current levels that are handled by oxidation catalysts, leads to poor fuel economy because of the relationships that exist between these emissions in a typical engine. The way these 3 types of emission vary with air-fuel ratio is disussed and available techniques for improved emissions control are outlined. A 3-way catalyst appears to be the most generally applicable technology available for gasoline engines to meet emission control requirements. This system makes it necessary to maintain precise control of the air-fuel mixture. The use of spark retard and idle settings also appear to be required. Oxidation catalysts promote further burning of hydrocarbons and carbon monoxide. The active material in most oxidation catalysts is platinum; the conditions for the effective operation of this catalyst are discussed. Electronic lean-burn systems are discussed and it is noted that lean air-fuel ratios of about 18 to 1 provide substantial emission reductions. By using leaner air-fuel mixtures, the CO concentration in the exhaust at idle has been lowered from about 8 percent to less than 1 percent. Other techniques discussed here include the spark retard, the use of air pumps and air aspirators to add oxygen to the engine exhaust gas, and the exhaust-gas recirculation technique.

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  • Corporate Authors:

    Institute of Electrical and Electronics Engineers

    3 Park Avenue, 17th Floor
    New York, NY  USA  10016-5997
  • Authors:
    • Heinen, G M
    • Beckman, E W
  • Publication Date: 0

Media Info

  • Features: Figures;
  • Pagination: p. 47-50
  • Serial:
    • IEEE Spectrum
    • Volume: 14
    • Issue Number: 11
    • Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    • ISSN: 0018-9235

Subject/Index Terms

Filing Info

  • Accession Number: 00167608
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 27 1977 12:00AM