A decomposition method for the simultaneous reconstruction of temperature and soot volume fraction distributions in axisymmetric flames

Abstract

This paper presents a method for the simultaneous reconstruction of temperature and soot volume fraction distributions in axisymmetric flames. In the proposed method, the radiation temperature and emissivity are determined using a multi-wavelength method. Then, based on the decomposition of the emissivity, the soot volume fraction distribution is reconstructed. Accordingly, the temperature distribution is calculated using the reconstructed local radiation source terms under a single wavelength. Based on a correction formula proposed in this paper, a further correction process is conducted, and the soot volume fraction and temperature distributions are successively obtained. Simulations are conducted with the temperature and soot volume fraction distributions at two different heights from the flame burner of an axisymmetric ethylene laminar diffusion flame. In the simulations, normal random errors are superimposed, and the radiation temperature and emissivity are calculated based on the intensities at three wavelengths corresponding to the R, G, and B channels of color cameras. Good agreement with the assumed data is obtained, which verifies the performance of the proposed method. Additionally, comparison with the results obtained using the widely-used two-color reconstruction method indicates that the proposed method exhibits a more stable performance with smaller errors. Moreover, the proposed method can take advantage of measurement at multiple wavelengths. Based on the multi-wavelength data captured using a hyperspectral imaging device, the measurement results of an axisymmetric ethylene laminar diffusion flame using the proposed method are also presented.