| In recent years,combustible gas explosion accidents occur frequently,causing heavy losses.As an important part of urban public infrastructure,municipal sewage pipe network often accumulates a large amount of combustible gas and is easy to cause explosion due to its characteristics of multiple branches and strong airtightness.Therefore,it is particularly necessary to carry out research on the characteristics of flammable gas deignition and disaster propagation in municipal sewage space for the safe operation of municipal sewage pipe network.In this paper,with the help of computational fluid dynamics software Auto Rea Gas,the influence of methane concentration,the opening pressure of discharge explosion and the number of inspection Wells on the deflagging characteristics of combustible gas in the sewage space is studied.The main contents are as follows:(1)In view of the deflagration process of combustible gas in municipal sewage pipe network,a pipe network model consisting of a horizontal pipe with a length of 100 m and a height of 1.8 m and a distance of 40 m(vertical branch pipe)with a closed left end and ignition end and an open right end was established to study the deflagration characteristics of 9.5% concentration methane.The results show that the pressure time history curve and temperature time history curve of each measuring point of horizontal pipe and vertical branch pipe on both sides increase first,then decrease,and then appear helmholtz oscillation.With the increase of distance,the initial deflagration pressure peak value and flame propagation velocity of measuring points in horizontal pipeline both increased,while the initial deflagration pressure peak value of measuring points inside and outside the left vertical branch pipe first increased and then decreased,while the initial deflagration pressure peak value of measuring points inside the right vertical branch pipe remained within a larger range.The peak value of the initial dedetonation pressure of the measuring point in the air domain outside the right vertical branch pipe gradually decreases.(2)The effects of different concentrations of methane(6.5%,8%,9.5%,11% and 12.5%)on deflagration characteristics of combustible gas in sewage space were studied.The results show that with the increase of methane concentration,the peak values of initial devolution pressure,initial devolution temperature and flame propagation velocity at each measuring point in the horizontal pipeline increase first and then decrease,and all appear maximum values at 9.5% concentration.When the methane concentration is 6.5% and 12.5%,the initial deflagration pressure peaks of measuring points inside and outside the vertical branch pipelines on the left and right sides gradually decrease with the increase of distance,while the initial deflagration temperature peaks of measuring points inside and outside the vertical branch pipelines on the right and left sides basically remain at a certain level.When the methane concentration was 8%,9.5% and 11%,with the increase of distance from left and right sides of the vertical branch pipe detonation point inside and outside the initial pressure peak value present the trend of the first increases and then the left and right sides of the vertical branch pipe inside the initial peak detonation temperature measuring point less volatile,and initial deflagration outside air in pipe field measuring point temperature peak gradually decline.(3)The different opening pressure(0 kPa,5 kPa,10 kPa,20 kPa,40 kPa,80 kPa,160 kPa,320 kPa,640 kPa,1280 kPa,2560 kPa,5120 kPa and pipeline closure)was studied on deflagration characteristics of combustible gas in sewage space.Results show that with the increase of discharge opening pressure blasting,horizontal line and the left and right sides of the vertical branch pipe internal initial deflagration pressure peak value of each measuring point and the initial detonation temperature peak basically all showed a trend of increase,and the left and right sides of the vertical branch pipe outside air domain of each measuring point initial deflagration pressure peak and detonation temperature peak and decreases as a whole.However,with the increase of distance,the peak values of initial deignition pressure and initial deignition temperature of the measuring points inside and outside the vertical branch pipes on the left and right sides change sharply at the explosive discharge surface,and the flame propagation velocity of the measuring points inside the horizontal pipe shows an overall increasing trend.(4)The influence of different number of inspection Wells(0,1,2,3,4 and 5)on the deflagration characteristics of combustible gas in sewage space was studied.The results show that with the increase of the number of inspection Wells,the peak values of initial deflagrate pressure and initial deflagrate temperature of each measuring point inside and outside the horizontal pipe and vertical branch pipe gradually decrease,and the flame propagation velocity of the horizontal pipe gradually decreases.With the increase of distance,horizontal pipe inner point overall increase before initial deflagration pressure peak decreases,and present the initial detonation temperature peak first increases then decreases,and then add the change trend of decrease,and the vertical branch pipe outside air domain point initial deflagration pressure peak and detonation temperature peak decreases on the whole change trend.In the design and construction of municipal sewage space engineering,the number of vertical inspection wells can be appropriately increased to reduce the explosion disaster effect. |
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