Primary soot particle distributions in a combustion field of 4 kW pulverized coal jet burner measured by time resolved laser induced incandescence (TiRe-LII)

Abstract

To develop accurate models for the numerical simulation of coal combustion field, detailed experimental data using laser techniques, which can figure out the basic phenomena in a coal flame, are necessary. In particular, soot is one of the important intermediate substances in a coal flame. This paper is the first paper in the world reporting soot particle size distributions in a coal flame. The spatial distribution of the primary soot particle diameter were measured by the combination of the time-resolved laser induced incandescence (TiRe-LII) method and the thermophoretic sampling (TS) method. The primary soot particle diameter distribution was expressed by the log normal function based on the particle diameter measurement using SEM images obtained from the TS samples. The relative function between the signal decay ratio obtained by TiRe-LII and the primary soot particle diameter was defined based on the log normal function. Using the relative function, the spatial distributions of the primary soot particle diameter with the soot volume fraction were obtained. The results show that the small isolated soot regions instantaneously exist in the entire combustion field. This characteristics is different from spray combustion field. From the ensemble-averaged TiRe-LII images, it was found that the soot volume fraction and the primary soot particle diameter increases with increasing the height above the burner in any radial distance. It was also found that the volumetric ratio of small particles decreases with increasing radial distance at the region close to the burner exit. However, the variation of the soot particle diameter distribution along the radial direction becomes small in the downstream region. This tendency is caused by the turbulent mixing effect. It is expected that the accurate soot formation model will be developed in the near future by using the data reported in this paper.

Simulation of Turbulent Combustion in a Large Pulverized Coal Boiler Based on Turbulent Radiation Interaction and the Modified Soot Model

“…For the RANS solution, one can use a presumed PDF for temperature pulsation to obtain the pulsation value of . Burn 51 et al investigated the effect of component scales in PDF on temperature self-correlation, yielding values between 0 and 2.5 for C TRI 1 . Using β-PDF, C TRI values suitable for furnace pulverized coal combustion can be obtained for component distribution coefficients at different locations.…”

Two-dimensional laser-induced incandescence for soot volume fraction measurements: issues in quantification due to laser beam focusing

“…One way to mitigate this problem is to use a very long focal length lens [8] or a combination of lenses [9,10]. Another possibility is to collimate the laser sheet both in the height and thickness directions instead of using a cylindrical lens to focus the laser sheet [11], but at the expense of a lower spatial resolution orthogonal to the beam sheet. Often however, there is an expectation that the effect of a varying laser sheet width leads to less uncertainty than other uncertainties in the LII measurements.…”

Effects of ambient temperature on the combustion processes of single pulverized coal particle

“…Since volatile matter combustion is the first step in pulverized coal combustion and affects its subsequent phenomena. The investigation of the reaction kinetics of coal and optical measurement was conducted in previous studies (Ahn et al, 2016;Hashimoto et al, 2016;Lee et al, 2015). Ahn et al (Ahn et al, 2016) investigated reaction kinetics of the volatile matter from coal particle based on analyses with reduced chemical mechanism.…”

“…They showed that hydrocarbons such as aromatics, methyl and ethyl groups play important role in the ignition and flame propagation processes. Hashimoto et al (Hashimoto et al, 2016) investigated soot particle size distributions in a coal flame with the time-resolved laser induced incandescence (TiRe-LII) method and the thermophoretic sampling (TS) method. They showed that soot volume fraction and the primary soot particle diameter increases with increasing the height above the burner in any radial distance from the ensemble-averaged TiRe-LII images.…”