Observation of detailed structure of turbulent pulverized-coal flame by optical measurement. (Part 2, Instantaneous two-dimensional measurement of combustion reaction zone and pulverized-coal particles)

The purpose of this study is to elucidate of the primary air combustion zone in pulverized-coal combustion by means of advanced laser-based diagnostics with high temporal and spatial resolutions. An open-type burner is fabricated to apply various optical measurement techniques. In this paper, simultaneous measurement of OH-planar laser-induced fluorescence (PLIF) and Mie scattering images of pulverized-coal particles is performed, and the spatial relationship between the combustion reaction zone and the pulverized-coal particle zone is examined. It is found that, in the upstream region, combustion reaction occurs only in the periphery of the clusters of pulverized-coal particles where the high-temperature burnt gas of a methane pilot flame is entrained and oxygen supply is sufficient, and that, in the downstream region, however, combustion reaction can be seen also within the clusters of pulverized-coal particles. This is because, in the downstream region, the devolatilization process of the coal particles proceeds with the temperature rise of the particles, and the mixing process between the volatile matters and ambient air is prompted. From these results, it can be said that the present diagnostic techniques are effective for evaluating the pulverized-coal flames.