| Natural gas and other combustible gases are widely used in industrial production,gas supply and other fields.Because of the flammable and explosive characteristics of flammable gas,once the flammable gas leaks,it is very easy to cause accidents,resulting in casualties and property losses.It is of great significance to study the propagation mechanism of detonation wave formed by combustible gas in pipeline and its suppression measures for the safe use of combustible gas.Taking methane as the main experimental gas,this paper studies the applicable conditions of the criterion for determining the propagation limit of detonation wave,which isλ=πD(λ is the cell size of detonation and D is the pipe size),defines the influencing factors of the propagation limit of detonation wave,and puts forward two measures for suppressing detonation according to these influencing factors,and analyses the effect of the measures for suppressing detonation wave.Through the above research,the propagation law of detonation wave in the near limit state and the conditions under which the two measures can play a significant role are clarified,which provides theoretical and experimental basis for preventing detonation accidents and providing effective measures to suppress detonation.The main work and conclusions of this paper are as follows:(1)The applicable condition of the criterion of determining the propagation limit of detonation wave is defined,and the influencing factors of the propagation limit of detonation wave are studied.In macro-size pipelines(round tubes with diameter D=36 mm),the stability of mixed gases(judged by the rules of cell structure during detonation)determines the applicability of the criterion for determining the propagation limit of detonation wave:for the unstable mixed gases in macro-size pipelines(with irregular cell structure during detonation),the criterion is established as λ=πD;when the mixed gases are unstable,the criterion is established as λ=πD.The criterion for determining the propagation limit of detonation wave is invalid when the quality of detonation wave decreases.In micro-sized pipes(annular pipes with sizes of 2 mm,4.5 mm and 7 mm),the criterion of the detonation propagation limit is not λ=πD.The above results show that the stability of gas and boundary conditions have a great influence on the propagation of detonation wave.Accordingly,the following two measures are put forward to suppress detonation.(2)The suppression effect of porous absorbing materials on detonation wave propagation is studied.Three kinds of porous absorbing materials with different sizes(L/D=3.85,7.69 and 15.38,respectively)were used in the experiment.For the short porous absorbing material,its inhibition effect on detonation wave propagation is remarkable only at the critical(minimum pressure condition for self-sustained propagation of detonation wave)and sub-critical(below critical pressure),but not at the supercritical(pressure greater than critical)conditions.The detonation suppression effect of absorbing material is positively correlated with its length.(3)The suppression effect of obstacles(orifices)on detonation wave propagation is studied.The diameter of the round hole of the orifice plate is d=7 mm,10 mm,15 mm,and 20 mm.Obstacles have a significant inhibitory effect on the detonation of stable gas mixtures.The critical pressure of stable gas mixtures(the lowest pressure that detonation can maintain)increases significantly with the decrease of pore diameter D.The inhibitory effect on the detonation of unstable gas is not obvious,and the inhibitory effect becomes worse when the initial pressure of detonation increases. |
