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Show The isoconcentration lines of CH .. and O2 indicate that the fuel was effectively separated from the combustion air and the mixing rate between the two was low. This is reflected by the gradual increase of temperature over a large distance (- 1 meter) from the burner inlet. The slow rate of mixing is a result of damping of turbulence through the stratification of the flow by the high swirl imparted to both the primary and secondary air jets. As a result of this process the energy released from the oxidation of fuel is gradual and therefore a relatively low peak flame temperature (1800 K) was obtained. CONCLUSIONS An experimental investigation has been carried out with a fleXIble experimental lowNOx burner of novel design. The burner is designed to achieve staged combustion by a combination of radial flow stratification and axial air staging in the flame. The burner produces a near field mixing pattern in which fueVair mixing is suppressed by radial flow stratification close to the burner but is then promoted by a toroidal recirculating flow further downstream of the burner. Parametric experimental studies carried out in the flame tunnel of the MIT CRF permitted optimization of the burner for low-NOx and CO emissions by determining favorable conditions for the radial distributions of the air flow and the swirl velocity at the exit from the burner and for the central fuel injection velocity and angle. The results showed that for several operational modes of the burner input variables, highly stable flames with low NOx and CO emission levels were attainable. The data reported here are initial results only; there are indications that further reduction of NOx emission can be obtained with the new radially stratified flame core (RSFC) burner. ACKNOWLEDGEMENTS Financial support from a consortium of utility companies: Empire State Electric Energy Research Corporation (ESEERCO), Eniricerche, Electric Power Research Institute (EPRI), Ente Nazionale Per L'Energia Elettrica (ENEL), Florida Power and Light Company, and Southern California Edison Company are gratefully acknowledged. We thank ABB-CE for their expression of readiness in producing a commercial burner should our experiments be successful. The authors are indebted to Ms. Bonnie Caputo for the production of the many drafts and the final form of the paper. REFERENCES 1. Morita, S., Kiyama, K, Jimbo, T., Hodozuka, K, and Mine, K, "Design Methods for Low-NOli Retrofits of Pulverized Coal Fired Utility Boilers", EPRI/EP A Joint Symposium on Stationary Combustion NOx Control, Mar, 1989. 2. Lisauskas, R.A, Reicker, E.L, and Davis, T., "Status of NOx Control Technology at Riley Stoker", EPRI/EPA Joint Symposium on Stationary Combustion NOx Control, Mar, 1989. 6 |
