Suppression And Enhancement Of Combustible Gas Explosion In Closed Chamber By Powder Suppressant

Focus on the grim situation of the combustible gas explosion protection,the experiments on explosion and suppression of methane/air mixture in a closed chamber with a volume of 100 L were carried out.Based on the active explosion suppression method,the powder suppressant was used and was driven by nitrogen,which was produced by the gas generator.The practical effect of nitrogen as a powder propellant on explosion was clarified.The suppression and enhancement influence of the key parameters on explosion,which include trigger time,powder concentration,particle size and type were revealed qualitatively.The main conclusions are as follows:?1?Methane/air mixture explosion characteristic parametersThe propagation velocity of explosion flame is the highest when it reaches the near wall surface.The explosion pressure corresponding to the maximum pressure rise rate is about half of the peak pressure.In the whole explosion process,the flame propagation is ahead of the pressure growth.?2?Effect of nitrogenWith the delay of the contact moment between the nitrogen jet and the flame,the explosion suppression effect of nitrogen will be weakened,and the disturbance effect on the explosion will activate the explosion process,which indicate that nitrogen has a negative impact on the explosion under certain conditions.After filling a small amount of ultrafine NH₄H₂PO₄ powder into the suppressor,the impact of the nitrogen-powder jet on the explosion gradually changed to a positive effect.10 g powder is enough to offset the negative impact of nitrogen as a propellant on the explosion.?3?Effect of trigger timeThe initial rising time of explosion pressure is critical for the suppressor to trigger to realize the effective explosion suppression.When the trigger time is before or near the initial rising time of explosion pressure,the explosion suppression effect depends on the reasonable matching between the trigger time and the powder concentration.The explosion will be intensified when the trigger time is lags behind the initial rising time of explosion pressure.?4?Effect of powder concentrationThe effect of powder suppressant on explosion is not completely positive,which means the explosion will be intensified if the concentration of powder is insufficient to block the propagation of flame at the initial stage.The reaction between the powder and the flame has a dual effect of disturbance and suppression.The suppression effect will gradually exceed the disturbance effect with the increase of powder concentration,which can be reflected on the difficulty of spread flame propagation restrictions.?5?Effect of particle size and typeThe sequence of superiority performance about the selected powder suppressants is as below: ultrafine NH₄H₂PO₄>ordinary NH₄H₂PO₄>NaHCO₃>SiO₂.