Statistical analysis of volatile combustion time-characteristics of single coal particles using high-speed OH-PLIF

To study ignition and volatile combustion processes of single particles in a group of pulverized coal particles (SPGCPs), the OH signals in the volatile flame were detected by planar laser-induced fluorescence (PLIF). The intensity variation of OH signals was used to obtain the structure information of the pulverized coal flame. In this study, a high-volatile bituminous coal (30 wt %) was burned at a gas temperature of 1700 K with 20 vol % O-2 in N-2 diluent gas. The bituminous coal particles with a size range of 60-100 mu m were seeded to a central carrier gas jet intersecting an enclosed premixed flat flame. The detailed development of volatile combustion of the same particle was obtained by using a 500 Hz OH-PLIF technique. By the statistical analysis with 173 groups of SPGCP volatile combustion, the highest probability of violent combustion occurred between T = 10-15 ms, and the probability distribution was consistent with the particle size distribution of coal powder, which conformed to the Gaussian distribution. Meanwhile, the volatile ignition process of SPGCP was visualized by the 5 kHz OH-PLIF technique. The homogeneous ignition mode is dominant in the bituminous coal flame. The combined analysis of both 500 Hz and 5 kHz OH-PLIF measurement results indicated the combustion time-characteristics of SPGCP from the ignition to volatile combustion. The high-speed PLIF technique has been proved to have great advantages in studying the pulverized coal flame.