622 / 2019-01-20 14:12:00

In-suit measurement of radiative properties and high temperature optical constant of hydrocarbon flames

hydrocarbon flames; radiative properties; high temperature optical constant; In-suit measurement.

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An effective method is proposed in this study to in-suit detect the radiative properties and high temperature optical constant of hydrocarbon flames. Firstly, the axisymmetric laminar ethylene diffusion flame was generated on a G黮der burner. A laser with a wavelength of 632.8 nm was applied to irradiate the ethylene flames to get the spectral radiative intensity by the spectrometer. Then, the normal transmittance at different heights of the central axis of the ethylene flames can be obtained. Thereafter, the DRESOR (Distributions of Ratios of Energy Scattered or Reflected) method was utilized to solve the direct radiative transfer problem in the ethylene flame. From the transmittances calculated by the DRESOR method and detected by laser technique, the absorption and scattering coefficient of the ethylene flames were retrieved by using the Particle Swarm Optimization (PSO) algorithm. Meanwhile, combined with the Kramers-Kronig relationship, the high temperature optical constants of the ethylene flames could be achieved from the normal transmittance obtained by the laser technique. Furthermore, in order to verify the reliability of the proposed in-suit detection method. The TSPD-TEM technique was employed to obtain the morphology parameters and concentration of soot agglomerates at different heights of the ethylene flames generated in air- and oxy-atmosphere. Then, the absorption and scattering coefficient of the soot agglomerates in flames could be calculated by the Multi-particle Mie-solution (GMM) theory. The radiative properties obtained by this method were compared with the in-suit detection results. In addition, the CoFlame FORTRAN code was also used to numerically generate the same ethylene diffusion flames, by which the morphology parameters and concentration of soot agglomerates were given. By using the GMM theory the absorption and scattering coefficient of the soot agglomerates in flames were achieved, and the calculated results were also compared with the in-suit detection results. The Analysis of the comparison results above shows that the proposed in-suit detection method is robust. It can be applied to the study of hydrocarbon flame radiative properties and high temperature optical constants, which is convenient for further analysis of hydrocarbon flame radiation heat transfer problems.