Soot temperature and concentration measurements from colour charge coupled device camera images using a three-colour method

Abstract

The three-colour method has been developed in order to turn chromatic information in charge coupled device (CCD) camera images of combustion into flame temperature and soot concentration measurements. The method showed the following advantages over the two-colour method from which it is derived: only one camera is needed; no further calibration is required once the response curve of the camera is known; it does not rely on light intensity but on ratios between colour components, making it easy to adapt to different operating points with different name brightness. The results on temperature evaluation were compared with a thermodynamic model, and better agreement was found in the late stages of the cycle, when the radiation from chemical reactions becomes negligible. The error analysis showed that the calculations for soot concentration are ill-conditioned, but when the results are integrated to give a soot loading the accuracy is improved and there is clear evidence of soot evolution and destruction during combustion.