NO Production and Destruction in a Methane/Air Diffusion Flame.
NO Production and Destruction in a Methane/Air Diffusion
Smyth, K. C.
Combustion Science and Technology, Vol. 115, 151-176,
nitric oxide; diffusion flames; kinetics; lasers;
Concentration profiles have been measured for naturally
occurring NO in a lamainar CH4/air diffusion flame
burning on a rectilinear Wolfhard-Parker slot burner at
atmospheric pressure. Linear laser-induced fluorescence
of the [see journal article] (0,0) transition was
excited using a frequency doubled tunable dye laser and
detected with a dielectric filter/photomultiplier tube
combination. The observed fluorescence signals have
been corrected for (1) the Boltzmann population in the
R1(17) rotational level of the ground vibronic state and
(2) collisional quenching rates as a function of the
local temperature and collider concentrations. The
resulting relative concentration profiles have been
calibrated using tunable diode laser absorption
measurements of Hill and Miller. Both the overall NO
production/destruction rates and the contributions from
individual elementary steps have been derived; the later
analysis utilizes previously measured profiles of H, O,
OH, CH, and CH3 as well as an estimated 3CH2 profile.
The NO profile measuremnets alone do not distinguish its
dominant production pathway in this co-flowing CH4/air
flame, since the contribution of prompt NO production is
obscured by competing CHi + NO destruction reactions.
As a consequence of these reburn reactions, the observed
peak NO concentrtions are observed to closely track the
maximum temperatures. A reaction path analysis and
determination of NO fluxes strongly indicate that prompt
NO production outweighs the thermal route, but
uncertainities in determining the relative contributions
to instantaneous NO production are large.