Radiation Tomography of Sooting Diffusion Flames
When soot is present in combustion, it usually dominates the radiative transfer process, and it is well known that very large conversions of chemical enthalphy to radiative loss can occur in sooting laboratory flames. Diagnosis of sooting flames, therefore, is important if the effects of soot radiation are to be accurately predicted. A sooting flame temperature measurement technique has been demonstrated that is based on emission/absorption tomography. The approach applies the algorithms of Fourier transform tomography to deconvolve local soot absorption coefficient and Planck function (temperature) from sets of parallel, line-of-sight measurements. The technique has the advantage that it is experimentally simple, and does not require involved data reduction. For soot-size particles, there is also no sensitivity of the inferred temperature to possibly uncertain medium parameters. Its main limitation seems to be that it will not work well for vanishingly small absorption, but this could be overcome in practice by seeding to some reasonable level of absorption, and then performing all work at the wavelength of a seed resonance. While in principle limited to optically thin flames, accurate corrections for moderate optical thickness can often be made. A self-consistent comparison of measured, global radiation from a sooting ethylene flame with a radiative transfer calculation based on measured temperature and soot absorption parameters has been performed.
KeywordsDiffusion Flame Burner Surface Soot Volume Fraction Planck Function Vertical Slit
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