| OCR Text |
Show temperature (see Fig. 10). This effect is probably an artifact of the manner in which the furnace was heated prior to the initiation of the DOC burner testing. The furnace was typically heated using a more traditionallow-NOx burner. At times it was found that if a large amount of NOx was generated during furnace heat-up, a relatively long time was needed to purge the furnace of NOx to single-digit ppm levels. Figure 10 alludes to the fact that the DOC system will be competitive in terms of NOx emissions as compared to current-technology 10w-NOx air burners. In fact, as shown in Figs. 8-9, relatively low NOx emissions resulted even when natural gas and air were the primary reactants. CONCLUSIONS A fundamental and applied effort towards the development of an ultra-low NOx burner system for commercial furnace applications has been undertaken. The mass entrainment of a reacting natural gas jet in a high-temperature ( - 1366 K) oxidant decreased as the oxygen concf'- , tion of the oxidant increased, suggesting that chemical reaction hinders the natural aspire ;haracteristics of turbulent gas jets. The flame lift -off height of a reacting natural gas jet in a high-temperature oxidant was explored as well, with decreasing lift-off heights observed with increasing oxidant temperature and oxidant oxygen-concentration. The pollutant emission characteristics of several dilute oxygen combustion (DOC) burner arrangements were investigated in a laboratory-scale furnace (frring rate -185 kW). NOx emissions below 5.10-3 g/MJ (10 ppmd-air equivalent at 3% O2 dry) were obtained for a furnace temperatures below 1533 K (2300°F) and furnace nitrogen levels between 1 and 40% . ACKNOWLEDGMENTS This research was conducted with the support of the U. S. Department of Energy (DOE) Award No. DE-FC07-95ID13331. However, any opinions, fmdings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of DOE. Funding by Praxair, Inc. is acknowledged. In addition, the authors would like t thank Mr. Joe Keller of the Lockheed Idaho Technologies Company and Dr. Gideon Varga of the U. S. Department of Energy for their technical advice and guidance. REFERENCES [1] Kobayashi, H., "Segregated Zoning Combustion," U.S. Patent 5076779, December 31, 1991 . [2] Ricou, F. P. and Spalding, D. B., "Measurements of Entrainment by Axisymmetrical Turbulent Jets," Journal of Fluid Mechanics, Vol. 9, pp. 21-32, 1961. [3] Dahm, W. J. A. and Dimotakis, P. E., "Measurements of Entrainment and Mixing in Turbulent Jets," AIM Journal, Vol. 25, No.9, pp. 1216-1223, September 1987. [4] Liepmann, D. and Gharib, M., "The Role of Streamwise Vorticity in the Near-Field Entrainment of Round Jets," Journal of Fluid Mechanics, Vol. 245, pp. 643-668, 1992. [5] Becker, H. A. and Yamazaki, S., "Entrainment, Momentum Flux and Temperature in Vertical Free Turbulent Diffusion Flames," Combustion and Flame, Vol. 33, pp. 123-149, 1978. 14 |
