A New Approach to Combined Cross Correlation and Flicker Frequency Flame Monitoring for Very Low NOx Pulverised Fuel Burners

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With this technique two separate optical systems are used in each Head to achieve the necessary discrimination in range as well as angle, thus overcoming the flame discrimination problems associated with conventional single line of sight optical monitors. Each of the two optical systems comprises a lens and an associated 64 element silicon cell infra red detector array onto which flame radiation is focused. The two arrays are mounted at right angles to each other as shown as shown above. Initially, the Head is roughly positioned with respect of the flame by visual sighting. The cells in the detector arrays are then electronically scanned under the control of a microcomputer in the Head and the cell outputs cross correlated to find out which receive optimum radiation from the flame being monitored. The Head automatically locks onto these cell locations and outputs a digital correlation signal to the C D C . By using this scanning technique the need for precise alignment of the optical system during installation is eliminated. Fig 2 Sighting the Flame Boner Backr^ Detectors Flame Scan Head Boiler Front V ^ JSH/22.8.97 3