Laser-fluorescence measurements of nitric oxide in low-pressure H2/O2/NO flames

The concentration profiles of NO in low-pressure (76 Torr) H2/O2/Ar flames to which nitric oxide is added are measured by pulsed laser-induced fluorescence. Temporally resolved fluorescence measurements are used to determine the collisional deexcitation rates needed to convert time-integrated fluorescence signal into oxide concentration. Five flames are studied with H2/O2 equivalence ratios of 0.88, 0.98, 1.22, 1.37, and 1.50. In these flames the collisional deexcitation rate decreases rapidly above the burner surface as the density decreases with increasing temperature. A 20 percent decrease is observed for the lean flames, and a 30 percent decrease for the rich flames. Within the precision of the measurement technique (+ or - 10 percent), no significant removal of nitric oxide is observed in these flames.