Study On The Deflagration Characteristics And Suppression Of Hydrogen/Methane/Air Premixed Gas

Natural gas has been widely used,however,due to its own combustion characteristics of the restrictions,such as high ignition temperature,burning limit narrow and low burning rate,its combustion efficiency can't meet the demand of energy efficient utilization in practical applications.Adding hydrogen to natural gas can decrease the ignition energy and combustion rate of mixed fuels which greatly raises the fear of fire and explosion accident.In order to make the hydrogen/methane/air premixed fuel safely used in the production practice,the experimental research on the deflagration characteristics and inhibition of hydrogen/methane/air premixed gas has been carried out in this paper.The experimental contents include the study of deflagration law of premixed gases under different conditions,the characterization of powders,the determination of optimum concentration of explosion suppressing powder under methane condition,and the characteristics and mechanism analysis of premixed gas explosion suppression.The main achievements of this study are as follows:Experimental study on the effects of turbulence,pipe length and different ignition position on flame propagation characteristics and found that when the hydrogen addition ratio less than 70%,the turbulence of gas deflagration promoted;when hydrogen addition ratio is greater than 70%,the gas explosion under the condition of static pressure is higher than the turbulence condition of explosion pressure.In the process of propagation and propagation of the long tube flame,there are tulip flame structures under the addition of hydrogen,while the short tube can't be found.The evolution of the flame front could be divided into three categories according to IP and?.When?was less than 0.75,the overpressure presented periodic oscillation only under the conditions that the ignition position was in the middle or the rear of the pipe.Moreover,the closer the ignition position was to the vent,the longer the oscillation time would be.The detonation of premixed gas is suppressed by the powder explosion suppression system,and the effects of powder on flame structure,explosion pressure and flame propagation speed are analyzed.The optimum concentrations of four explosion suppressor powders for methane explosion inhibition were 0.24g/L for Mg?OH?₂,0.2g/L for NaHCO₃,0.24g/L for Ferrocene and 0.2g/L for NH₄H₂PO₄,respectively.In inhibiting methane explosion,sodium bicarbonate powder is superior to the other three kinds of powder.When hydrogen is added in a lower proportion,sodium bicarbonate and ammonium dihydrogen phosphate powders break the flame front,while the other two powders do not appear.The four powders of NaHCO₃,NH₄H₂PO₄,Ferrocene,and Mg?OH?₂,had no inhibitory effect when the proportion of hydrogen was more than 80%,70%,100%and 80%respectively.In terms of flame propagation speed,NaHCO₃ and NH4H2PO4,had a good inhibitory effect on premixed gases with low hydrogen addition ratio.When the hydrogen ratio was 20%,the flame velocity of them both propagated uniformly.When the hydrogen addition ratio is high.Ferrocene on premixed gas has a good inhibitory effect,when the hydrogen addition ratio was 80%Ferrocene powder under the action of the premixed gas maximum flame propagation speed is only 41m/s,and NaHCO₃,NH₄H₂PO₄ and Mg?OH?₂,were 102m/s,155.1m/s and 131.8m/s.The above research results have great theoretical significance and practical values for hydrogen/methane explosion prevention and control.