Study On The Explosion Characteristics Of Typical Combustible Gases Under Weak Constraint Conditions

As the main components of clean energy,methane and hydrogen have increasingly become indispensable energy sources in production and life.However,Methane and hydrogen have unique properties such as wider flammable range,higher diffusion rate,lower ignition energy and greater combustion speed,but at the same time,the mixed gas is easy to leak and mix with air to form explosive gas clouds during transportation,storage,supply and use,which are easy to be ignited by external ignition sources.The explosion risk of methane and hydrogen air mixture is greatly increased,and the explosion will cause great damage to surrounding buildings and residents’lives and property,and destroying social harmony and stability.In order to study the explosion characteristics of methane and hydrogen in air under weak constraint conditions,a series of explosion experiments were carried out using latex balloon as reaction vessel.Combined with Chemkin and improved colorimetric temperature measurement technology,the characteristics of flame propagation velocity,explosion overpressure and temperature field distribution of methane/air,hydrogen/air and hydrogen/methane/air at different concentrations as well as the influence factor was studied.The experimental results showed that.When methane/air,hydrogen/air and hydrogen/methane/air premixed gases propagate in latex balloon,the flame propagation velocity was oscillating.For methane/air and hydrogen/air premixed gases,the average flame velocity reaches the maximum when the combustible gas concentration was 10%and 30%respectively,which were 2.12 m·s^-1 and 3.57 m·s^-1,respectively.For hydrogen/methane/air premixed gases,the average flame velocity increases with the increase of concentration.Chemkin numerical simulations showed that,the peak overpressure of methane/air and hydrogen/air explosion were positively correlated with the concentration of combustible gas.When the concentration of methane was 10%,R155could accelerate the chain reaction of CO₂ generation.The chemical reaction was the most thorough and the peak overpressure reaches the maximum.When hydrogen concentration was 30%,R38 increased the density of active groups and enhanced the deflagration intensity by generating OH and O radicals.The results of colorimetric temperature experiments showed the temperature in the center and edge of the methane/air flame was higher than that in other areas.With the increasing of the methane concentration,the temperature distribution of the explosion flame increased first and then decreased,and reached the highest value when the concentration was10%.For hydrogen/air deflagration flame,it was found that there was a positive feedback relationship between flame temperature and brightness,and higher flame brightness means higher flame temperature.Furthermore,the static time had significant influence on flame propagation velocity and explosion peak pressure,and the optimal static time was 6 min.Different hydrogen contents leaded to different temperature distribution status of hydrogen/methane/air premixed gas flame.When hydrogen content was less than 70%,methane dominated the combustion of mixed gas,and the temperature of the flame front was lower than that of the interior.Under the influence of water vapor,the position of the interior high temperature area rised.When hydrogen concentration was greater than or equal to 90%,hydrogen dominated the combustion of the gas mixture.The internal temperature of the flame was low and the edge temperature was high.The edge temperature of the flame increased with the increasing of hydrogen concentration.The mole fraction of H,O and OH radical increased with the increasing of hydrogen,which accelerated the gas flame propagation.The formation rate of H,O and OH radical were faster at low hydrogen concentration（X≤70%）and high hydrogen concentration（X≥90%）.When 70%<X<90%,the formation rate of H,O and OH radical were slow.In the sensitivity analysis,the sensitivity coefficients of R11,R52,R53 and R98 increased with the increasing of hydrogen concentration,and the inhibition effect on pressure rise increased,while R3,R38 and R84 promoted the explosive reaction,and the methane and hydrogen in the mixture reacted with active free radicals,but the actual effect was completely opposite.This indicated that the presence of methane inhibits the combustion of hydrogen to some extent.Compared with methane,hydrogen/methane/air mixture had a higher explosion pressure,and the peak overpressure and maximum pressure rise rate gradually increased with the increasing of hydrogen concentration,but the sensitivity of maximum pressure rise rate decreased with the increasing of hydrogen concentration.Figure[37]Table[11]Reference[127]...