Nitrogen Dioxide in Engine Exhaust

Presented at SAE Passenger car Meeting, Dearborn, June 11-15, 1979

John C. Hilliard

Dept. Of Mech. Eng. Wayne State University

Richard W. Wheeler

Ricardo Consulting Engrs. Sussex, England

ABSTRACT

Nitrogen dioxide emissions from diesel and gasoline internal combustion engines have been measured over a range of speed, load and AFR conditions.

Measured NO2 levels are very much higher than expected thermodynamically, with as much as 30% of the NOx emission from a diesel engine at 15% load in the form of NO2.

CONCLUSIONS:

  1. NO2 is not difficult to measure in engine exhaust both accurately and reproducebly.
  2. NO2 is generated within the cylinder for both diesel and petrol engines, the emission being load and speed dependent.
  3. Gasoline engines show a maximum NO2 at lean AFR around 17:1.
  4. Diesel engines show a maximum at very lean AFR's around 70:1 and at low speeds, where as much as 30% of the NOx emission may be in the form of NO2.
  5. 100 PPM of NO2 can be obtained from either type.
  6. ......

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