Experimental study on the overpressure and flame propagation of hybrid hydrogen/aluminum dust explosions in a square closed vessel

•Hybrid explosion experiments of hydrogen/aluminum dust in a 5-L square closed vessel are studied.•The addition of hydrogen obviously affects the explosion overpressure and flame propagation.•The maximum flame propagation velocity of hydrogen/aluminum dust hybrid mixtures has three stages.•Particle combustion mode and hydrogen–aluminum flame interactions are established. The overpressure and flame propagation of hydrogen/aluminum dust hybrid explosions are studied in a 5-L square closed vessel. Aluminum dust was mixed with hydrogen with concentrations of 0%–30%. The results show that there are certain hydrogen concentrations that affected the changing trend of the maximum pressure rise Pex and the maximum rate of pressure rise (dP/dt)ex. When the hydrogen concentration is lower than the certain concentration, the Pex and the (dP/dt)ex are approximately equal to those of pure aluminum dust. When the hydrogen concentration is higher than the certain concentration, the Pex and the (dP/dt)ex increase notably. As the hydrogen concentration increase to more than 20%, the flame front separation can be observed. The addition of hydrogen can significantly affect the ignition delay time and the flame propagation velocity of the hybrid mixtures. There are three stages in the relation of the maximum flame propagation velocity vmax with the hydrogen concentration: in the first stage, the vmax is almost equivalent to that of pure aluminum dust. In the second stage, the vmax increases slightly. In the third stage, the vmax increases significantly, which can exceed more than 50 times the vmax of pure aluminum dust.