Measurement Of Flame Temperature And Radiative Properties Based On Spectral Analysis And Image Processing

With the growing global energy crisis and increasing emphasis on environment issues, the combustion efficiency improvement for reducing combustion emission and the new combustion technology development become an important research content. The flame temperature is considered as one of the important parameters which reflect the state of combustion, the accurate temperature measurement is important for understanding the combustion process and improve the combustion theory research. The flame temperature is coupled with radiation parameters, so the reconstruction of temperature and radiation parameters become an effective method. Flame images and radiation spectrum contain amount of information related to flame temperature and radiation parameters, many parameters could be obtained using those information, such as average temperature, emissivity, flame temperature and radiation medium volume fraction, This paper will study how to use the radiation spectrum and the image for measurement these parameters, the detailed description is as below.An experimental investigation was presented on the measurement of flame temperature and emissivity in a Municipal Solid Waste incinerator using a spectrometer system and a flame image detection system. The spectroscopy analysis showed that strong Na (590nm) and K (767nm) emission occurs in the visible spectrum of the flame. Firstly, the two-color method (with3nm wavelength interval) is used for calculating the temperature and emissivity of the flame, and then the gray wavelength range was determined by the emissivity distribution. The results indicated that except for the Na and K emission lines, the continuous spectrum from500nm to900nm met the gray property. Since the Na and K emission lines deviate away from the central wavelengths of R and G in the spectral response curves of the CCD camera, so the two-color method can be used to calculate the temperature and emissivity images by the flame image detection system. The experiment was carried out in eight measurement points of the three different across-section.A simulation investigation for simultaneous reconstruction of distributions of temperature and soot volume fraction from nomonochrome visible image in an axisymmetric sooting flame is presented. In the study, many different reconstruction algorithm were firstly discussed, the results shown that using the Tikhonov regularization algorithm can get better performance when selected the appropriate regularization parameter. Self-absorption term was alse considered, it found that underrating the temperature and over estimating soot volume fraction will be occurred at axis of flame when neglected self-absorption term. It proved that the accurate distributions of temperature and soot volume fraction could be obtained with large optical thickness such as6times, this method could be wide used for measurement the flame of different fuels.Experimental study of simultaneous reconstruction of distribution of temperature and soot volume fraction of the C2H4flame from visible image using Tikhonov regularization algorithmcan algorithm is presented. Firstly, the flame radiation spectrum collected by spectrometer and then judgement of gray property was carried out, so the distribution of emissivity and absorption was obtained. Secondly, high-resolution images of flame (1mm/65pixels) were obtained using image processing techniques, then those images were used for measurement of temperature and soot volume fraction by solving radiative transfer equation with considering character of absorption. The two-dimensional axial symmetry distribution of temperature and soot volume fraction was obtained under three different quantity of C2H4flow.Experimental study of axisymmetric, laminar coflow ethylene flame in O2/N2and O2/CO2atmospheres diffusion is presented. Firstly, the two-dimensional distributions of temperature and soot volume fraction of30%、40%、50%of oxygen concentration in O2/N2and O2/CO2atmospheres were obtained, respectively. The measurement results indicated the peak soot volume fraction distribution along the radial direction beside the peak temperature and the peak gradually close to the flame center with the height increases, these similar to combusion in air; in O2/N2atmospheres, the flame temperature rised with the increase of oxygen concentration but the soot volume fraction declined slightly when oxygen concentration reached50%; in O2/CO2atmospheres, the flame temperature and the soot volume fraction all rised with the increase of oxygen concentration; combustion in O2/N2atmospheres, the flame temperature, the soot volme fraction, the length of flame and the flame radiation intensity is higher than those in O2/CO2atmospheres with the same oxygen concentration; the length of flame could be good calculated using Roper model in O2/N2atmospheres but not in O2/CO2atmospheres; the flame height prediction results in O2/CO2atmosphere have been improved when the Roper empirical formula modified.