| OCR Text |
Show excitation scans like those shown in Fig. 3. The temperature profile, shown in Fig. 4, rises quickly, attaining a value of 1620 ± 40K in the flame front where the CH is at maximum concentration, and reaches a burnt gas temperature of about 1800K. The temperature at the CH peak: was checked using LIF excitation scans in two different electronic band systems belonging to this radicaL The results are in excellent agree-ment: measurements in the A-X system near 431 nm yield 1600 ± 60K, the B-X measurement at 395 run resulted in 1620 ± 60K. Relative concentration profiles were performed in order to locate the peak CH concentration for two flames with different stoichiometry: <l> = 1.15 and 1.00. The results are shown in Fig. 5 (where they have been placed on an absolute basis through the measurement described in the next section). The relative measurement itself yields useful information, since the ratio of CH concentration between the rich and stoichiomenic flame is 1.35 ± 0.06. This compares to a calculated ratio of 1.6. The profiles themselves are in reasonable but not perfect agreement with mCKiel results, showing that we understand well but not fully all the chemical reactions responsible for producing and removing CH. 2000 I 1800 1600 ~ 1400 11200 ~ 1 ~ 1000 ,t 800 600 400 a 2 3 Height Above Burner (an) Figure 4. Temperature profile of the lean propane/ air flame at 40 Torr obtained through OH A-X LlF excitation scans. The continuous line is a fit to the set of experimental points. M- 2.0e+12 E ~ GJ '0 g 1.Se+12 ~ Ui c: o c 1.0e+12 G ~ E :l Z S.0e+11 :t: <.J - Experiment I I --_Model _A - 1\ !I \7 .=10 15 _~/ ..... \ \ \ \ \ \ \ \ \ \ , , ~ O.Oe+O , !------ 1 0.0 0.2 0.4 0.6 0.8 1.0 1.2 10 Height above the burner (an) Ftgure 5. CH number densities measured by LlF for stoichiometric and rich flames, and results obtained from a kinetic model applied to the same flames. |
