Total emission intensities of OH*, Clt*, C2", NH*. and CN* m the reaction zone, saturation currents.
unburned hydrocarbons, and NO x in the exhaust gases were measured in atmospheric pressure, hydrocarbon-ai[ flames with and without added fuel N (NO and NH3). It has been found that the overall temperature dependence of prompt NO is about I0 kcal/mol for any mixture strength and that NO concentrations are not very dependent on the kind of fuel (CH 4. C3H 8. and C4HIo) The total amount of CH radicals produced in the reaction zone is estimated by comparing NH* emission intensity wtth NO for the flame ot added fuel nitrogen, and it is shown that the amount is uniquely determined by the m~ture strength without depending on the flame temperature and is also scarcely influenced by fuel. Furthermore. the amount of prompt NO is proportional to that of total CH radicals for fuel-rich, sloichiometric, and lean flames of three different fuels. The above two experimental facts strongly suggest the CH-ongin prompt NO formation mechanism (i.e., CH + N 2 ~ HCN + N). and the rate constant is estimated to be k = 4 x 10 it exp ( -13.600/RT) cm3/mol s -I by comparing the amount of prompt NO with that of saturation current