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

The three-colour method has been developed in order to turn chromatic infor mation in charge coupled device (CCD) camera images of combustion into flam e temperature and soot concentration measurements. The method showed the fo llowing advantages over the two-colour method from which it is derived: onl y one camera is needed; no further calibration is required once the respons e 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 ope rating points with different flame brightness. The results on temperature e valuation were compared with a thermodynamic model, and better agreement wa s found in the late stages of the cycle, when the radiation from chemical r eactions becomes negligible. The error analysis showed that the calculation s for soot concentration are ill-conditioned, but when the results are inte grated to give a soot loading the accuracy is improved and there is clear e vidence of soot evolution and destruction during combustion.