Experimental Research On Images Of Flame Temperature And Emissivity In Coal-Fired Furnace

The process of pulverized-coal combustion in large-scale boiler of power station is a complex physical and chemical reaction occurred under the condition of large space, frequent fluctuation and having conspicuous character of three dimensional, so the monitoring of combustion status is very important to safety, economy and cleaning of boilers in operation. The measurement of flame temperature and emissivity is a complex and important issue, and they are essential for the development of combustion theory and technology. Recently, many researchers have studied the technology of visualization of temperature of flame. The technologies of optics, acoustics, image process are applied in visualization of temperature of flame.Based on Wien Radiation Law, this paper presents a calibration method of color radiant images of flame. Through this method, three monochromatic radiant intensity distribution images for the red (R), green (G) and blue (B) colors under their representative wavelengths can be gained; with the assumption of flame gray radiant property, flame temperature and emissivity distribution images can also be calculated. Experiments show that, using the smaller R/B gains can increase the flame temperature range which can be measured by the image detectors. With the temperatures higher, example of more than 1200℃, only red and green colors can be used actually. Calibration results also shows that the setting of white balance of CCD affects the measurement of temperature used by double-color method, so the proper white balance of CCD should be selected.The experiments were done in a W 300 MW boiler. Images of flame were captured by a flame detector in the different altitude of the same wall, and the images of temperature and emissivity are given. The results of the experiment can reflect the level of the temperature and emissivity, and accord with the practical combustion state of flame in the boiler.The study of the images of flame temperature and emissivity in boiler acts as primary research of the realization of visualization of temperature, and it is important for increasing accuracy of temperature measurement. At the same time, the images of flame temperature and emissivity can also act as a monitoring method. It is easy to assist unit operators developing combustion diagnosis and accident analysis, and improves the security and economy of boiler.