| Along with the development of national economy progress and people’s living standards continue to improve, combustible gas energy is being used increasingly,especially clean energy began to enter people’s production and life. Followed by the combustible gas leakage may occur explosion, it will cause great harm to the safety of the lives and property of the people. And combustible gas explosion process is very complex and the influences of initial environmental conditions of combustible gas explosion is very obvious. Therefore, the study of the influence of initial conditions on the combustible gas explosion characteristics has more important practical significance. Different initial conditions of methane and oxygen mixed gas in the pipeline explosion characteristics are studied in detail through a self-made small scale pipeline system with one side completely transparent window. The study mainly including explosion flame propagation characteristics and explosion overpressure analysis, the research results are as follows:(1)According to the research results, a small scale square pipeline experimental system with one side completely transparent window was designed and built, the system including small scale pipeline, high speed photography system, ignition system, external trigger system and pressure data acquisition system, etc.(2) Complete image of oxygen and methane explosion flame propagation in small scale in the pipeline was collected by using high speed photography system. The curve of explosion flame propagation speed changes with time. The flame images can be processed by MATLAB, Explosion flame propagation velocity changes with time curve can be obtained by two methods, flame path algorithm and maximum similarity coefficient method.(3) The speed change curve under different initial conditions of methane and oxygen mixed gas explosion flame propagation with time in the small scale pipeline can be obtained by processing the experimental results. Analysis of the results, we can find that in the same equivalence ratio, with the increase of the initial pressure, the maximum speed of the explosion flame increases, and the maximum speed of the explosion flame and thereciprocal of initial pressure in numerical linear approximation. For different initial concentrations of mixed gas, there is a minimum initial pressure to form an accelerating flame. When the initial pressure is lower than the flame acceleration minimum pressure, the flame will extinguished at the head of the pipeline. When the initial pressure is higher than the flame acceleration minimum pressure, explosion flame can be accelerated in finite length, part of the situation even to the detonation state.(4) Influence of initial condition on explosion overpressure can be obtained through the analysis of explosion flame images and explosion pressure data collected by the pressure data acquisition system. Results show that when the equivalence ratio of the mixed gas is determined, and if the initial pressure is lower than the flame acceleration minimum pressure, the maximum overpressure in the pipeline is relatively low, generally about 10-14 times of the initial pressure. If the initial pressure exceeds the flame acceleration minimum pressure, explosion flame will reach the state of detonation, the overpressure in the pipeline can be about 32-44 times of the initial pressure. In addition, when the initial pressure of the mixed gas of methane and oxygen is determined, the overpressure of the explosion flame in the pipeline increases with the increase of the equivalent ratio, and the relationship between them is linear approximation. |
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