| The deflagration is one of the potential security threats in the production,transportation and application of oil and gas energy.The aviation kerosene with high flash point is a kind of hydrocarbon fuel for aircraft,which has the advantages of high calorific value and stable combustion.In some military fields,there is a potential risk of local deflagration in the long and narrow cabin storing aviation kerosene under severe collision and external force strike.Active deflagration suppression is one of the important means to effectively prevent deflagration hazards.The traditional deflagration suppression agents such as water,dry powder,inert gas and so on are weak in fire extinguishing ability and there are some problems in the practical application process.The application research of new deflagration suppression agents with high efficiency and environmental protection also has an urgent industrial demand.In this paper,high flash point aviation kerosene JP-5 and a new gas deflagration suppression agent FK-5-1-12 were taken as the research objects.The purpose is to study the deflagration of JP-5 steam-air premixed gas and the release and combustion inhibition characteristics of FK-5-1-12 through experiments,numerical simulation and theoretical analysis.The influence mechanism of fuel concentration,deflagration container volume and ignition energy on deflagration pressure,temperature and flame velocity was analyzed.The numerical prediction model of deflagration process and theoretical calculation model of pressure rise process were established.A new gas deflagration suppression agent FK-5-1-12 was introduced.Based on numerical simulation,two-phase flow pressure calculation was carried out in the process of pipeline release,the design process of deflagration suppression system was optimized,and the verification test of combustion suppression efficiency was carried out,so as to systematically study the deflagration problem of high flash point aviation kerosene in terms of harm and prevention.The research work of this paper is as follows:Firstly,the deflagration experiments of JP-5 steam-air premixed gas were carried out in 1m~3 and 8 m~3 closed pipes.The variation of deflagration pressure,flame propagation velocity and temperature under different fuel concentrations,pipe volumes and ignition energy was studied.The results show that the trend of the maximum increase rate of deflagration pressure corresponds to the change of flame surface,and the increase process of deflagration pressure experiences two acceleration-deceleration changes.Under the laboratory conditions,the deflagration concentration limit range of jp-5 is 0.7% to 7.1%.When the stoichiometric concentration is close to 1,the deflagration pressure can reach 5 to 6 times of atmospheric pressure.Compared with the deflagration pressure and the maximum pressure rise rate,the negative oxygen condition with the fuel concentration close to the stoichiometric ratio has the strongest deflagration hazard.When the fuel concentration,initial state,ignition conditions and length diameter ratio remain unchanged,the increase of pipeline volume only leads to the extension of pressure rise time.With the increase of ignition energy,the deflagration pressure,flame propagation velocity and temperature increase obviously.Secondly,based on the premixed combustion model and large eddy simulation,the numerical simulation method of deflagration process of fuel with stoichiometric concentration of 1 in a closed pipe was established.The deflagration dynamics in complex environment was analyzed by changing the ignition position and obstruction ratio.The numerical simulation results of deflagration process show that compared with the case of igniting in two end of the pipe,the case of igniting in the center has higher pressure rise rate,shorter duration of deflagration flame propagation process and stronger harmfulness.On the one hand,the existence of obstacles leads to the increase of flame turbulence and the acceleration of flame propagation;On the other hand,the over stretching of flame limits the diffusion of deflagration flame to unburned zone.Compared with the case without obstacles,obstacles aggravate the intensity of deflagration,and there is a critical blockage ratio to maximize the enhancement effect.Thirdly,under the assumption of isothermal and adiabatic conditions,the theoretical calculation models of premixed gas deflagration pressure rise stage in the close pipe were established.The effectiveness and applicability of the model were verified by the experimental data of JP-5 and LPG deflagration.In the two models,the pressure rise rate is directly proportional to the burning velocity and deflagration pressure,inversely proportional to the length of the pipe,and positively related to the ratio of the maximum deflagration pressure to the initial pressure.The calculation results of the two models can reflect the trend of pressure rise and predict the peak pressure.The adiabatic model takes into account the variation of reactant and product temperature with pressure,which has higher calculation accuracy and can meet the requirements of engineering calculation.Finally,the pipeline release process experiment of FK-5-1-12 was carried out,the numerical simulation hydraulic calculation method was established by using mixture model and evaporation phase change model,the design process of deflagration suppression system was optimized combined with medium-term pressure idea,and the combustion system inhibition experiment with an average heat release rate similar to JP-5 deflagration(11.7 KW)was designed and implemented to verify the application effect of FK-5-1-12.The release experiments of FK-5-1-12 show that FK-5-1-12 is a single-phase flow in the cylinder outlet and a two-phase flow in pipe flow respectively,and the two-phase flow is close to that of haloalkane 1301.Based on the idea of medium-term pressure,a two-phase flow calculation method of FK-5-1-12 was established.The error between the pressure drop calculation results and the experimental data is less than 10%.On this basis,the design method of FK-5-1-12 deflagration suppression system was summarized,and the combustion system suppression experiment was designed and implemented.The results show that FK-5-1-12 can effectively block the temperature and oxygen concentration in the three elements of combustion,quickly extinguish the combustion process similar to the average heat release of JP-5 deflagration,and the suppression effect is obvious. |
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