A Research On The Pressure Fields Of Unconfined Flammable Gas Cloud Explosions

During the transportation, storage, processing and using of nammable gases, thecloud explosion may hapPen if the mixture of flammable gases and air caused bytheir leakage towards air is accidentally ignited. The cloud explosion has made greatdamage to people and proPerty loss. Statistic data show that the portion of numbersof accidents caused by cloud explosion to those of total ones reached as far as 46%,42% and 60% in petfoleum, plastics, rubber synthetization and natural gas industryrespectively. Moreovef, the damage and property loss from such an accident is muchhigher than other industrial accidentS.The experimental research on weak ignition cloud explosion fOcused on someexperimental results under particular circumstances, which is not enough to draw aconclusion. On one hand of engineering, mT Equivalency Method, a kind ofempirical mode1, is limited to make a rough estimation for far field of explosions. Onthe other hand, theoretical research is far from completed. For instances,Self Resemblance Method oversimplified the static combustion model. ThOMulti-energy Model needs too much subjective judgment during application despiteits some reasonability Numerical simulation works for solving the equations of fluidmechanics, and there are still other problems unanswered such as chemical reactiondynaxnics, turbulencc equation near barriers.This paPer in theory considered the cloud explosion as two coupling processes.One is the flammable gas combustion that causes gas temperature rise and gasvolume increase, which pushes the air around it fOrward and can be solved by meansof finite geometrical cell method and even-energy adding method. The other is tl1epropagation of pressure wave, which is only a gas dynamics problem and can besolved through gas dynamics equations. In exPeriment, a systematical exPerimentalresearch on the pressure field of cloud explosion in open space and the pressuredistribution on plate bAners outSide cloud was conducted. The paper also tried tofind out the strengthening of barriers to cloud could explosion pressure. The purposeof experiment is to gain somo fundamental rules by test data-analysis and rectify thetheoretical results. The major work and conclusions of present paper are asl. The semi-sphere cloud was aimed to build physical model of unrestricted gascloud explosion. The mathematical model was established through the analysis ofgas dynamics, thermodynamics and combustion physics. After integrating themomentum conservative equation and mass conservative equation the explosion fieldcan be calculated asn = Icy(E -- I)[2E rs,.= + nn-- 1(E -- I) n.: ] + l: =/).,,I - r r (h 2 r2. TWo difficulties were overcome during building the gas explosion experimentalsystem. Firstly, safety was the prior consideration because of the great danger ofexplosion experiment. Therefore, a new open gas cloud explosion experimental basewith safety protection equipment was deve1oped. Secondly, concerning that thewhole explosion process was so rapid that it would complete within dozens ofmilliseconds the explosion pressure synchronically high speed data-collection systemwas specially designed which is consisted of pressure sensors, A/D transformef,data-collection tinit, computer and automaticaIly electric-ignition equipment. Thedynamic responding time of this system was less than 0.00l second andmeasurement precision was in level 0.5.3. A systematical experimental research on unrestricted flammab1e gas cloudexplosion was conducted. The relationship between explosion pressure and the cloudradius, the distance from ignition point is gained by regressing the experimentaI dataand deviation analysis. that isAP = A Air4. A new computer progop describing the unrestricted cloud explosion processthrough combining the finite geometry cell method and even-energy adding methodand integration of mass and momentum conservative equations. The deviationbetween com...