Simultaneous Measurement of Three-Dimensional Soot Temperature and Volume Fraction Fields in Axisymmetric or Asymmetric Small Unconfined Flames With CCD Cameras

A nonintrusive measurement technique is presented numerically for simultaneous measurement of three-dimensional (3D) soot temperature and volume fraction fields in the axisymmetric or asymmetric flames with charge-coupled device (CCD) cameras. CCD cameras were introduced to capture the flame images for obtaining the line-of-sight radiation intensities. The distributions of local emission source under two wavelengths can be deduced through solving the reconstruction matrix equation by the least-square QR decomposition method from the knowledge of the line-of-sight radiation intensities of the flames. The two-color distributions of the local emission source were used to retrieve the soot temperature and volume fraction distributions. The effects of the discrete ray number of CCD cameras, the number of CCD cameras, and the system signal-to-noise ratio $(SNR)$ on the measurement were investigated. The results show that for accurate measurement of soot volume fraction field, the CCD cameras number should not be less than four and the system $SNR$ can be as low as 54 dB. The proposed technique can be capable for reconstructing the 3D soot temperature and volume fraction fields in both axisymmetric and asymmetric flames well.