Variation of explosion strength parameters in hydrogen/titanium dust two-phase systems

The advancement of titanium-based solid-state hydrogen storage technologies and titanium manufacturing processes inherently involves the formation of hydrogen/titanium dust hybrid mixtures, which present substantial explosion hazards. To investigate the explosion behavior of such two-phase systems, this study systematically examined the variation patterns of explosion intensity parameters in hydrogen/titanium dust hybrid systems using a standardized 20 L spherical explosion vessel. The experimental matrix covers hydrogen volume fraction ranging from 0% to 30% and titanium dust mass concentrations from 100 to 700 g/m³. Specifically, titanium dust concentrations were tested at seven discrete levels (100, 200, 300, 400, 500, 600, and 700 g/m³), while hydrogen volume fractions were selected at eight critical values (4%, 5%, 10%, 15%, 20%, 25%, 29%, and 30%). Dynamic parameters, including explosion pressure and rate of explosion pressure rise, were synchronously recorded. Furthermore, the phase composition and surface chemical states of explosion residues were characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). This integrated approach provides in-depth insights into the macroscopic evolution of explosion intensity with varying gas-solid ratios and elucidates the underlying microscopic reaction mechanisms. Experimental results demonstrate that hydrogen volume fraction critically modulates explosion severity. The explosion pressure exhibits a characteristic three-stage dependence on hydrogen volume fraction: it initially decreases, reaching a minimum at 4% H₂, subsequently increases to a maximum at 29% H₂, and finally declines at higher volume fractions. Correspondingly, the maximum rate of pressure rise rate decreases to its lowest value at 4% H₂ before increasing continuously up to 30% H₂. The maximum explosion pressure shows an analogous trend, peaking at 29% H₂ after an initial reduction, while the maximum rate of pressure rise reaches its minimum at 4% H₂ and peaks at 30% H₂. Residue analysis indicates that at low hydrogen volume fraction (<4%), incomplete oxidation of titanium predominates, thereby reducing explosion intensity. Beyond the critical threshold of 4% H₂, hydrogen self-combustion promotes titanium-nitrogen reactions and facilitates the transition from heterogeneous to homogeneous combustion, significantly enhancing explosion severity. This investigation provides fundamental insights into the explosion dynamics of hydrogen/titanium dust mixtures and delivers essential parameters for risk assessment and safety mitigation in related industrial applications.