Two-dimensional two-wavelength emission technique for soot diagnostics

Abstract

A two-dimensional soot diagnostic technique has been developed as an extension of the well-known two-color pyrometry. Two flame images are simultaneously collected on a CCD at selected wavelengths through suitable optics. By use of the dependence of soot emissivity on the soot volume fraction and by comparison with images from a calibrated light source, both the temperature field and the soot distribution can be determined. Validation was carried out through data obtained with other soot diagnostic methods on ethylene diffusion and Diesel oil-rich premixed flames. The current technique readily allowed us to obtain a large amount of data for a thorough description of the soot distribution within the flame. As an example of the technique's potential, data about methane and propane diffusion flames are reported.

Field measurements of soot volume fractions in laminar partially premixed coflow ethylene/air flames

“…Laserinduced fluorescence (LIF) is based upon measurements of the fluorescence of C 2 molecules from vaporized soot [16,17]. Multiwavelength emission measurements have also been employed [18,19]. Nevertheless, the light-extinction method is advantageous, since it is both cost and time effective and often serves as a reasonable calibration tool.…”

Investigations on Soot Formation in Heptane Jet Diffusion Flames by Optical Techniques

“…A basic description on the application of the method for 2D-measurements may be found in Will et al (1995Will et al ( , 1996, and information on the uncertainties of the technique is given in Will et al (1998) and Geigle et al (2005). The principle of two-color pyrometry and information on the uncertainty of measurement are reported by di Stasio and Massoli (1994) and Cignoli et al (2001). Comparisons of temperature measurements by emission pyrometry with other techniques, in particular coherent anti-Stokes Raman spectroscopy (CARS), for the assessment of uncertainty may be found in Snelling et al (2002) and Weikl et al (2009).…”

Simultaneous soot temperature and volume fraction measurements in axis-symmetric flames by a two-dimensional modulated absorption/emission technique

“…(16) intrinsically includes soot selfabsorption. On the opposite, a methodology following the conventional twocolor pyrometry technique would require a specific processing to account for this phenomenon that can significantly affect the signals interpreted [19,30,31]. …”