Jp. Gore et Nj. Zhan, NOX EMISSION AND MAJOR SPECIES CONCENTRATIONS IN PARTIALLY PREMIXED LAMINAR METHANE AIR CO-FLOW JET FLAMES/, Combustion and flame, 105(3), 1996, pp. 414-427
Measurements of visible flame heights, global radiative heat loss frac
tions, distributions of mole fractions of stable gas species, and poll
utant emission indices in laminar partially premixed flames burning va
rious fuel-rich mixtures of CH4 and air in an overventilating co-flow
of air are reported. Mole fractions of CO2, CO, H-2, O-2, N-2, CH4, C2
H4 and C2H2 were measured, using sampling and gas chromatography, at s
everal radial locations at three different heights above the fuel tube
for a fixed fuel flow rate and six different fuel tube equivalence ra
tios. Mole fractions of H2O were inferred from the dry based measureme
nts. With increasing levels of partial premixing following effects are
observed: (1) the visible flame height decreases and the overall flam
e color changes from yellow to blue; (2) the radiative heat loss fract
ion first decreases and then reaches a constant value; (3) the mole fr
actions of CO decrease and those of CO2 and H2O increase in the lean p
arts of the flame; (4) mole fractions of C2H2 decrease and those of C2
H4 first increase and then decrease in the rich parts of the flame; (5
) mole fractions of CO and H-2 first decrease slightly and then increa
se in the rich parts of the flame; and (6) the O-2 mole fractions at t
he point of negligible CH4 mole fraction decrease. Measurements of emi
ssion indices for NO, NOx, CO and HC show that, for a fixed fuel flow
rate and overall equivalence ratio, an optimum level of partial premix
ing exists.