Pipeline Premixed Combustible Gas Explosion And Explosion Suppression

Flammable gases explosions can cause great casualty and economic loss. Since flammable gases usually flow in pipelines, the investigations into propagation of explosion waves and its suppression technology become one of key points of explosion researches.Experimental investigations are carried out to analyze variation regulations of parameters in flow field and their couple relations as explosion waves and flame propagating along tube or through multi-layer mesh construction. The main work and conclusions of this paper are as follows:(1)Experimental apparatus used for explosion and explosion suppression of flammable gases in tube are designed and set up. With premixed ethyne-air gases, experimental investigations about explosion waves and flame propagating in tube are dealt with. Experimental conditions are set as follows: Stoichiometric rate and atmospheric pressure are used for initial concentration of Ethyne and initial pressure; the inside diameter and length of tube, which is closed at ignition end and open at the other, are 81mm and 1.4-2.9m respectively; multi-layer mesh construction made of stainless steel, is vertical to tube axle.(2) According to experimental results, the variations of overpressure and flame can be described as four and three phases respectively. Some empirical formulae about, such as peak value of precursory shock waves, relative time and relative position of the of precursory shock waves and flame front, the variations of overpressure with time, the relationships between combustion time and flame propagation velocity and measuring points, are obtained. At precursory shock wave segment, overpressure-increasing curves are regular. With acceleration of pressure increasing rate, the farther measuring point is apart from ignition point, the faster pressure-increasing rate is. The width of combustion region is far bigger than theoretical value in turbulent combustion theory. Difference value of peak overpressure and reactive pressure for the second time can provide references for explosion prevention in tubes.(3) Preliminary study on deflagration to detonation (DDT) process is made. It is found that precursory shock waves still travel before the flame front, and the distance between them decreases gradually. Flame front closely follows Shockwaves at the same speed, and location of peak overpressure is coincident with flame front.(4) Based on theoretical model, flame propagation speed is computed and compared with experimental value. Empirical formula about flame propagation speed in tube is obtained.(5) The effects of multi-layer mesh construction on flame propagation in tubeare analyzed. Empirical formulas about relationship between critical values, include of quenching speed, quenching pressure difference and quenching amount (the product of quenching speed and quenching pressure difference), and geometrical parameters, such as layer, screen mesh and wire diameter, are obtained. Suppression effects of multi-layer mesh construction on explosion waves are introduced, and mathematical relations between decreasing rate of the maximum overpressure and three geometrical parameters are obtained.