OCR Text |
Show showed close correlation of the regions in the flame producing N O and the regions producing the excited state B 0 2 . Thus, the very close tracking between the N O production rate and the boron chemiluminescence intensity that was demonstrated at atmospheric pressure for turbulent hydrogen flames is predicted to be obtained for elevated pressure combustion of both methane and hydrogen. It should be noted that the calculated NO production rate included all of the important N O production mechanisms, including the thermal (Zel'dovich), prompt (Fenimore), and N 20 mechanisms.10 " The N 2 0 mechanism, which is important at lean, lower temperature and higher pressure conditions," also has O atom reactions as key pathways to N O production. O n the other hand, the prompt N O mechanism, which is important in lower temperature, fuel rich zones, especially in flames having short post flame residence times," i: does not have a strong dependence on O atom reactions.13 In some flames, such as axisymmetric laminar diffusion flames, the prompt N O mechanism is the main N O production mechanism12 and the close correlation between N O total production and boron chemiluminescence intensity will likely not be obtained. However, for most combustion conditions, the thermal N O mechanism is an important, if not the dominant N O production pathway and w e anticipate, based on the experiments and modeling performed to date, that the boron chemiluminescence intensity will closely track the total N O production rate, as well as providing spatially resolved data on local formation rates. C H 4 Perfectly Stirred Reactor Calculations 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Equivalence Ratio Figure 7. N O and Excited State B 0 2 Rates-of-Production for Perfectly-Stirred Reactor as Function of Equivalence Ratio for CH4/Diborane/Air System; Pressure = 8 atm. Residence time = 0.5 ms. 8 |