Flammable Liquid Cloud Explosion Relief Experimental Study

With the aid of self-designed-cylindrical installation and on the basis of largequantities of normal venting experiments, for explosion relief ventexperiments, namely, without abnormal phenomena of pressure after venting, this paperendeavors to explore the influences upon venting, including pressure variations ofcontainers inside and outside, their interaction and the phenomena of the secondaryexplosions. All the studies are carried out on the condition of changing the location ofignition source, vent area and vent pressure. in addition, data-collection system andflow-field-display system are used to observe the changing process.The experiments combine pressure measure with optical measure. Few predecessorsincluding foreign researcher in this field did so. According to the experiments, when thevent mouth is opened, high pressure, produced inside the container, will flow outside andform the jet due to insufficient dilation. Its typical structure is the existence of shock wavein the flow field. To measure changes of pressure outside the existence a series ofpressure sensor are placed along the axis. Through the pressure-time profiles whether thesecondary explosions happen can be judged outside the vent mouth. At the same time, theexperiment try to avoid the effect from Mach-pin in the shock wave structure and betterthe phenomena of the secondary explosions through pressure measure. After repeatedmeasure, it's discovered that the Mach-pin can be evaded in the directions of rays whichdeviate from axis 30.Therefore, this can make pressure characteristics (in the flow fieldoutside the vent mouth)clear.Through plenty of experiments, this paper gives a tentative explanation for abnormalphenomena of pressure in the secondary explosions and the mouth-explosions duringventing. After the analysis of experiment result, the author has revealed the secondaryexplosions are relatively complicated. Because they are at random and are influenced byflammable media, burning state, vent mouth area and vent pressure, which are likely toresult in turbulence and vortex at the vent-mouth. Moreover, with the existence of the jetflame and lots of mixed fuels that fail to bum, whether there will be the secondaryexplosions at last also depends on these decisive factor. this paper analyzes thephenomena of the secondary explosions and discusses the factor that cause abnormalphenomena during venting, especially the secondary explosions. Finally, someconclusions are drawn as follows:1. Whether venting happen hinges upon the ratio of fuels. various venting results lie in different equivalent ratio of mixed gas. In other word when the equivalent ratio is. it tendsto bring about the secondary explosions.2. The location of ignition source has an effect on venting. if we ignite at the tail-end Itis easy to cause the secondary explosions. While a the center, we will avoid it.3. Vent pressure can effect on the process of vent, the strong pressure is easy to producethe secondary explosions.The researches of abnormal phenomena of the secondary explosions during venting ina relatively comprehensive way lay a foundation of further study in this field infuture. But, the mechanism of the secondary explosions is extremelycomplex; moreover, the researcher in the field is still at an early stage, so further studyand exploration are needed.