Inhibitory effects of varying kaolin concentrations on CH4/H2 explosion characteristics

Abstract

This study employs laser schlieren imaging and pressure measurement techniques to investigate the impact of kaolin (Ko) on the explosion behavior of CH₄/H₂ mixtures at various equivalence ratios (0.8, 1.0 and 1.2) and H₂ contents (0, 0.3 and 0.9). Results indicate that the inhibitory effect of Ko first increases and then decreases with increasing concentration, achieving optimal suppression at 175 g/m³. Under the same equivalent ratios (φ), the reduction in maximum explosion pressure (P_max) becomes more pronounced with higher H₂ addition (R). At constant R but varying φ, the suppression effect exhibits a different trend: when R = 0 and 0.3, optimal suppression occurs at φ = 0.8. Whereas at R = 0.9, the optimal suppression effect is observed at φ = 1.0, corresponding to a 30.27 % reduction in P_max. As the Ko concentration increases, dust enhances flow field instability, thereby accelerating the transformation of the flame structure. Meanwhile, higher hydrogen addition (R) intensifies chemiluminescence, and heated Ko particles to emit strong intense thermal radiation. The combined effect of these two factors causes the flame to appear bright white-yellow. A coupled analysis of flame propagation and pressure evolution reveals that, despite differences in φ, the coupled evolution of flame and pressure remains highly similar under the same R. The main distinctions arise in the timing of critical flame development stage and flame brightness. Overall, Ko suppresses explosions primarily through physical mechanisms such as endothermic cooling, dilution and isolation effects, and thermal radiation shielding, and it exhibits particularly strong suppression at high H₂ additions.