Study on the influence of coal dust particle size on the structure and propagation characteristics of explosion flame in Hartmann tube

Coal dust explosions in coal mines can result in numerous casualties and substantial property damage. This study investigates the flame propagation characteristics of coal dust explosions in a Hartmann tube through theoretical analysis and experimentation. The flame propagation characteristics during coal dust explosions with varying particle sizes were investigated using high-speed cameras and schlieren cameras to simultaneously capture the temporal and spatial development of flames from two perspectives: tube position and outlet. The results indicate that particle size significantly affects flame propagation. Flames produced from burning small particles of coal dust are densely packed and compact, while flames from larger particles exhibit more irregular shapes, suggesting that a more intense reaction leads to brighter light radiation on the flame surface. These morphological variations correspond to distinct combustion regions and mechanisms. In addition, during the formation of coal dust clouds, turbulence-induced phenomena create vacancies within the flames as they propagate. This results in coal dust adhering to and agglomerating on the tube wall, leading to an absence of flames near both sides of the wall. Furthermore, increasing coal dust particle size contributes to a thicker preheating zone for flames. Specifically, for particles smaller than 53 μm, this thickness measures approximately 5 mm. Clustered flames with irregular fronts characterize the combustion behavior within micron-sized coal dust particles. A comprehensive understanding of these variations in particle size, along with the spatial evolution characteristics of flames, is essential for developing effective prevention and control measures against coal dust explosions from a theoretical perspective.