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Show 3. A torus metal disk electrode improved fl ame stabi lization in the IGT burner, as ev idenced by reduced CO and THC, while NOx emissions were maintained at low levels (0.6 to 0.7 vppm, at 15 % O2) : 4. The electrical system consumed negligible power (less than 5 W or 0.002 % of the design firing rate). 5. To enhance flame stability at higher firing rates, it may be necessary to increase the voltage or power supplied to the electrodes. Thus further study is recommended. The hoped for further decrease in NOx probably did not occur because electric field stabilization produced more complete combustion, and thus greater total energy release, in the combustor. The use of improved electrodes should enable operation at higher values of excess air with reduced NOx' VII. ACKNOWLEDGEMENTS We gratefully acknowledge the support of the Gas Research Institute under GRI Contract No. 5089-260-1884, the encouragement of the program . managers, Dr. T. Roose and 1. Kezerle, and discussions with Dr. R. Gemmer. We would also like to thank Dr. D. Keil and W. Feierabend for their probe design work and S. Hauptmann, V. Hoffmann, and R. Orlando who built and tested them at AeroChem and R. Orlando who participated in testing at IGT. Our thanks also go to W. Kunc of IGT's staff for helping us carry out a successful series of experiments and to M. Khinkis for his advice. The electrode tests could not have been performed without Maxon's engineering and fabrication support and donation of materials. Special thanks go to W. Coppin and W. Cummings of Maxon; it was a pleasure to work with them. VIII. REFERENCES 1. Calcote, H.F. and Berman, C.H., "Increased Methane-Air Stability Limits by a dc Electric Field," in Fossil Fuel Combustion, S.N. Singh, Ed., PD Vol. 25 (ASME, New York, 1989) p. 25. 11 |