Flame colour characterization in the visible and infrared spectrum using a digital camera and image processing

Abstract

An attempt has been made to characterize the colour spectrum of methane flame under various burning conditions using RGB and HSV colour models instead of resolving the real physical spectrum. The results demonstrate that each type of flame has its own characteristic distribution in both the RGB and HSV space. It has also been observed that the averaged B and G values in the RGB model represent well the CH * and C * 2 emission of methane premixed flame. Theses features may be utilized for flame measurement and monitoring. The great advantage of using a conventional camera for monitoring flame properties based on the colour spectrum is that it is readily available, easy to interface with a computer, cost effective and has certain spatial resolution. Furthermore, it has been demonstrated that a conventional digital camera is able to image flame not only in the visible spectrum but also in the infrared. This feature is useful in avoiding the problem of image saturation typically encountered in capturing the very bright sooty flames. As a result, further digital imaging processing and quantitative information extraction is possible. It has been identified that an infrared image also has its own distribution in both the RGB and HSV colour space in comparison with a flame image in the visible spectrum.

Oscillating flames in open tubes

“…In this form, digital colour cameras can be considered as a device that offers limited multi-spectral discrimination in addition to its spatial functionality. Based on this, a DFCD (Digital Flame Colour Discrimination) combustion quantification scheme has been created by Huang et al [13]. The DFCD approach has already been successfully applied in the characterisation of diffusion and premixed hydrocarbon flames; providing the trends of spectroscopic-derived CH* and C 2 * emission distributions over range of equivalence ratios [14], and the local fuel/air mixture [15].…”

Time-resolved 3D investigation of the ignition process of a methane diffusion impinging flame

“…In this form, digital colour cameras can be considered as a device that offers limited multi-spectral discrimination in addition to its spatial functionality. Based on this, a Digital Flame Colour Discrimination (DFCD) combustion quantification scheme has been established by Huang et al [11]. The DFCD approach has already been successfully applied in the characterisation of diffusion and premixed hydrocarbon flames, providing the trends of spectroscopic-derived CH* and C 2 * emission distributions over a range of equivalence ratios [12], and the local fuel/air mixture states [13].…”

Investigation of ignition process from visible to infrared by a high speed colour camera

“…Although Kapaku et al [19] visualised soot and carbon dioxide radiation intensity of an ethylene diffusion flame using a high-speed mid-infrared camera with two band-pass filters, only infrared emissions were recorded instead of both the visible and infrared. Huang and Zhang [20] imaged a methane flame under various stable burning conditions with an Olympus E-100RS digital camera. In the investigation of the infrared emission, an infrared filter was applied.…”

“…With the aid of selective digital image enhancement techniques [20], the visible CH* and C2* and the infrared emission were segmented, enhanced and visualised. Therefore a single digital high speed colour camera combined with selective digital image enhancement can be used to investigate the flame ignition process in both the visible to the infrared spectrum.…”