| OCR Text |
Show tuations do occur in this combustor. The effect of fluctuations of the air ratio of the mixture on the NOx formation was estimated numerically. First, the concentration of NOx in the flame of perfect mixing, which is formed in the post-combustion zone for various air ratios, was calculated by using the simple reaction scheme shown in Table 1. Only the Zeldovich NO formation mechanism was considered. In this calculation, the flow in the chamber is assumed to be one dimensional and adiabatic. As initial conditions, equilibrium concentrations of the components except NO and N in the adiabatic flame temperatures of each air ratio were used, and the in itial concentration of NO and N were set to zero. Although the residence time changes with the air ratio, it was set to 25 msec over the entire range of air ratios. Table 1 Considered elementary reactions and reaction rate coefficients. No. Reaction 1 N2+ 0 = NO + N 2 N + 02 = NO + 0 3 N + OH = NO + H 4 CO + OH = C02 + H 5 H + 02 = OH + 0 6 o + H2 = OH + H 7 H2 + OH = H20 + H 8 OH + OH = H20 + 0 9 H + H + M = H2 + M 10 O+O+M = 02 + M 11 OH + H + M = H20 + M 8 -.-Thermocouple (Perfect mixing) ~ Laser absorption (Partial mixing: Upstream) -+-Thermocouple (Partial mixing) -<r Laser absorption (Partial mixing : Downstream) 02~------------------------------------------~ c: 0.15 o :.;:; (13 ·s Q) "'C 12 0.1 (13 "'C c: (13 Ci5 0.05 8.90 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1 .7 Air ratio Fig.11 Comparison of standard deviations calculated from burned gas temperature fluctuations with the values obtained by laser absorption. k = A . Tn . exp(-E1RT) [mol, cal, em3, K, sec] A n E Reference 1.84 E+14 0 76250 Monat et al. 6.40 E+09 1 6280 Glarborg & Kee 3.80 E+13 0 0 ~ 5.60 E+11 0 1080 Mori et aI. 2.20 E+14 0 16600 ~ 1.74 E+13 0 9450 ~ 2.19 E+13 0 5150 ~ 5.75E+12 0 780 ~ 3.29 E+18 - 1.2 0 ~ 2.62 E+16 -0.84 0 ~ 1.50 E+ 16 0 0 ~ |
