Research On Combustible Gas In The Square Pipe Explosion Characteristics

With the transformation of national energy structure and energy strategy, liquefied petroleum gas and natural gas are becoming the main source of industrial and residential energy. All the processes including transportation, storage, usage of combustible gas are of vital importance because once the leaking gas is blended with air, there will be explosion. The exploration of the explosion feature of combustible gas and the rule of fire spreading can be better to analyze the process of fire spreading so as to reduce the damage of the accident.This paper reviewed extensive relevant literature on flame propagation home and abroad which introducing its mechanism and explosive features and pressure vessel design handbooks to research the combustion and explosion and principles,the researcher invented a square device which can reflect the flame spreading by himself. This stainless steel device was 570 mm long,120 mm in outer diameter and 80 mm in inner diameter. The front side was made of 15 mm thick quartz glass which can clearly observe the process of flame propagation and other sides were TP304 stainless steel about 20 mm thick. A complete system with flame sensor, micro-thermocouples high-frequency pressure sensor, data acquisition device and high-speed video camera were designed to collect data and meet the requirements of design and completed the main device and the additional device design, processing, installation, commissioning work.The research studies the explosion pressure, explosion limit, the speed of fire spreading and the flame front of methane of methane air blended gas explosion in the device, which has a great significance in academic field and industry.The following conclusions are verified in the experiment by the methane-air mixture explosion in the pipeline process studies to verify the reliability of the equipment:(1) under the experimental condition here the explosion limit of air blended methane gas varies between 5%-14.5%.(2) experiments show that five groups with different concentration of methane gas 6%, 8 %, 10 %, 12 %, 14 % are of explosion pressure of 0.128 MPa,0.138 MPa,0.169 MPa,0.134 MPa,0.124 MPa respectively. It is also found that when the concentration of methane gas approached 10%, the explosion pressure reached the top and then it would be increase at first and decrease gradually in the later.(3)the study explored the relationship between the spreading speed of flame and the concentration of methane gas and recorded the process of fire spreading and the transformation of flame structure under 3 conditions of concentration: rich oxygen(5.5 %), the equivalent concentration(9.5 %) and poor oxygen concentration(14.1 %).In the process of fire spreading the flame structure changed obviously, formed a special tulip structure. The time difference flame sensor calculated three concentrations of V1 = 7.5 m/s, V2 = 14.1 m/s, V3 = 10.2 m/s.(4) this study explored the influence of pressure on flame propagation. The results showed that closed conditions will produce larger(0.352 mm) thicker reaction of unburned area to the left of the thrust than the thinner one, increased the concentration of the reactants, promoted combustion, disturbed the flame waves and produced obvious flame.