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Experimental study on the flame stability and color characterization of cylindrical premixed perforated burner of condensing boiler by image processing method

Najarnikoo, Mahdi, Targhi, Mohammad Zabetian, Pasdarshahri, Hadi
Energy 2019 v.189 pp. 116130
boilers, cameras, color, digital images, flammability, heat, image analysis, processing technology, wavelengths
In this paper, a cylindrical premixed perforated burner which is mostly used in condensing boilers is investigated by image processing methods. The burner is experimentally analyzed in its operating heating capacities (11.7–17.1 kW) and equivalence ratios (0.4–1.2). Flame properties were studied using digital images by CCD camera and color processing techniques. The method devised a procedure for finding a reliable relation between a digital image color and flame characteristics in the visible wavelength domain. It is observed that by decreasing the equivalence ratio from 1.2 to 0.4, the flame color changed from green with yellow and then blue. Besides, flame lift-off and blow off were also observed. Lower flammability limit is in the equivalence ratio of 0.44. The optimum conditions of the burner, which is defined by the stable blue flame, are found in the equivalence ratio of 0.7–0.73. Moreover, RGB analysis is used to find the stable operation of the burner. This stable optimum condition can be defined as the intersection of two intensities’ component of Red and Blue in image processing of the flame.