“Prompt no” measurements at high pressures

Abstract

“Prompt NO” was measured in premixed ethylene-air flames at pressures from 1 to 18 atm and equivalence ratios from 0.6 to 1.4. Flame temperatures ranged from 1600°K to 2400°K. The “prompt NO” measurements were obtained by extrapolating the linear portion of the [NO] versus time plot back to zero time corresponding to the primary reaction zone. The intercept was taken as the net integral production of “prompt NO” believed to be the result of hydrocarbon fragments attacking atmospheric nitrogen. This intercept also includes NO contributed by the accelerated Zeldovich mechanism. The results ranged from a few ppm “prompt NO” at =0.6, P=1 atm, and T=1600°K to over 300 ppm at =1.0, P=18 atm, and T=2350°K. “Prompt NO” was found to have a positive pressure dependence for equivalence ratios between 0.8 and 1.3. In the cool flames at =1.4, “prompt NO” was found to exceed the calculated equilibrium NO concentration in the burnt gas by a factor as high as 30. Burning velocity data over the same ranges of pressure, temperature and equivalence ratio were incidental to this study. The rate constant of the reaction N+NO→N2+O was found to be 24×1012 cm3/mole sec.