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A Precessing Jet (PJ) burner has been developed which enhances large scale turbulence by means of a naturally occurring fluid-mechanical phenomenon. A highly stable gas flame is produced without air swirl, quarl or a bluff body stabiliser. The resulting natural gas flame is lower in temperature and is more luminous than flames from many conventional burners so that it reduces NO x emissions while achieving almost total burnout of combustibles. The high luminosity indicates potential for increased fuel utilisation efficiency in process industries where radiation heat transfer is important. For one configuration of the PJ burner firing natural gas in an 18MW industrial cement kiln, NO x emissions are shown to be reduced by 75% with a simultaneous reduction in CO when compared with the original turbulent jet burner. Photographs of these flames show that the PJ burner produces a more rapidly spreading and more luminous flame. For another configuration, firing natural gas in a 25kW laboratory furnace, the radiation spectra of the flame produced by the PJ burner are compared with a high quality commercial swirl burner. The mean radiation intensity produced by the PJ burner is some twenty times that of the commercial burner in the visible spectrum and the normalised fluctuating intensity is about 50%, some five times that of the commercial burner in the visible range. Good potential for flame detectability is therefore apparent. Mean intensity is shown to increase by a factor of three with the addition of swirl to the air. |
