| Combustible gases explosion acts as a serious obstacle to China’s industrial production,and greatly threatens life health of workers and property safety. The serious consequences ofthe accidents have caused a great deal of psychological trauma for victims in the accidents onboth the physical and psychological aspects, also have been reduce the enthusiasm of ordinarylabourers. Propane gas is an inindustrial production commonly used as rawmaterialsofpetrochemical, and its security issues can not be underestimated. Therefore, studying onmechanism and rules of the flame of propane gas explosion provide a good preventiom ofaccidents, draw more and more attention by researchers in many aspects.Pipelines with different rough degrees were designed and placed in the horizontalpipeline device for gas explosion test designed and manufactured by Security TechnologyResearch Center for Fire and Explosion Prevention in North University of China. Theapplication of high-speed camera technology helps observe explosion flame of propane inpipeline with various rough degrees at room temperature and normal atmospheric, thanks tothese device and technology, propane-air mixed gas explosion mechanism was studied anddiscussed in certain degree, and the main research contents were as follows:(1)The explosion limit concentration of propane ranges from3%to11%under theconditions of room temperature and normal pressure, and the equivalent concentration was5%.(2)The location with biggest gas explosion flame speed in the pipeline was determined.By changing the high-speed camera shooting location, on the front, in the middle and in the end of the pipeline on the equivalent concentration of propane, flame propagation speed wasmeasured respectively. Results show that the flame speed is the largest on the front, followedby that in the middle, smallest in the end of the tube which presents a process trend from ahigher speed to lower, due to the energy loss in the process of transmission, friction resistance,caused by external cooling, etc.(3)On equivalent concentration of propane, propane-air mixture explosion flame showssteady laminar flame burningstate first and then shifts to a turbulent state, so the stability ofthe flame front structure tends to be unstable, that is to say, the spherical front at the start ofthe flame experiences a continuous tensile deformation, and the flame brightness weakensunceasingly, until the pressure wave breaks the explosion venting membranes. As for thespeed, it rapidly reached a peak of about137m/s in the initial period, then decreased after acertain extent, as a result of shock resistance. After that, flame propagation velocity increasesgradually in the laminar burning state. Later slight drop appears due to the turbulence effect,wall friction and other effects until the last high-speed out of the vent film.(4)Pipe wall roughness has a significant impact on the propane explosion. Tests werecarried out at different size of the tube roughness at1mm,2mm,3mm. Results show that withthe pipeline roughness increasing, the propane explosion appears more severe and flamebrighter, at the same time explosion flame propagation speed increases, that is to say,roughness existing pressents a role more promotion than inhibition to explosion flames. Whenthe length of the rough mesh changed among20cm,40cm and70cm in test, it was found thatflame characteristics presented a similar performance at the length of70cm and20cm whilethe more explosion intensity, the lighter flame and the more faster flame propagation speedappeared at40cm. which indicase that the length of the rough mesh plays a limited incentiverole to the explosion within a certain range, but after reaching a peak, inhibition is more thanincentives which hinders the spread of explosion flame. In a word, increased roughnessaccelerates the explosion flame propagation speed, leads to a more violent explosive reaction,therefore, controling the size of the roughness of the pipeline will effectively prevent andcontrol combustible gas explosion in practice. |
PDF Full Text Request