Direct Spectroscopic Determination of Nitric Oxide in Reciprocating Engine Cylinders

A theoretical and experimental investigation was carried out to determine the mechanism whereby nitric oxide is formed, conserved, and exhausted from the reciprocating engine combustion chamber. The equipment utilized a magnesium oxide window to transmit the infrared radiation from the combustion chamber; a monochrometer to disperse the radiation, and a cryogenically cooled semiconductor to sense and indicate the nitric oxide produced radiation.

The results confirmed the theoretical prediction based on chemical kinetics that nitric oxide, once formed in approximately equilibrium quantities in the combustion process will thereafter not disappear because the engine expansion takes place more rapidly than the kinetic processes can accommodate. The theory and measurements allow more rational explanations for the well documented influences which mixture strength, spark timing, compression ratio, and engine speed exert on oxides of nitrogen concentration in engine exhaust.