OCR Text |
Show The C O correlation could serve well as a high swirl, extinction/quenching indicator. However, for the low swirl blow-off mechanism, the plotted chemiluminescence data do not immediately offer any correlations. T o investigate this further, a value was desired to represent the difference between the axial blow-off force and the recirculatine, anchoring force. This momentum difference was calculated as axial momentum - tangential momentum 2 c 2 2 , U $ • U PoUo"PexW m~ ZT-where p„ = reactant density pex = product density w = tangential velocity u„ = bulk axial velocity S = input swirl number T0 = reactant temperature Tex = recirculated gas temperature The bulk axial velocity was calculated from the input flow rates, and the recirculated gas temperature was assumed constant at 1500°F. The low swirl blow-off O H chemiluminescence levels were plotted in terms of this parameter in Figure 9. Each point represents the normalized O H chemiluminescence level at blow-off. The plot shows similar trends for both injectors and could be in closer agreement if more accurate values were used for the velocities and temperatures (especially at higher momentum differences). 1.0 i 0.8 O _ 0.4 Blowoff Decreasing Swirl Stable 0 2 . •Counter-swirl • Co-swirl 0.0 ; ' r- 8 10 11 12 Momentum Difference Figure 9: Low Swirl Blow-off OH Levels These trends offer hope that a single chemiluminescence measurement could provide feedback for C O , NOK , and stability levels. CONCLUSIONS Chemiluminescence from flame radicals was investigated as an indicator for important reaction features with the hope of using this simple technique as a feedback sensor for combustion active control. The advantages of this technique are its robust nature, ease of use, relative economy, and fast response. Signals were captured of O H , C H , and C 0 2 chemiluminescence in the reaction at the burner throat. These measurements were taken for two very different fuel injection strategies (co-swirl and counter-swirl) over their entire operating ranges. |