Kinetic Property Research On Superfine Ammonium Phosphate Fire Extinguishing Agents In Inhibiting Single Compartment Fire

Super fine fire extinguishing powder(SFFEP)was a new kind of halon optional fire extinguishing agent.It was environmental friendly,less caustic,lower poisonous and highly effective.It could be widely used in portable,fixed or total flooding fire extinguishing system.In this dissertation,the dynamic performances of SFFEP and interaction law of SFFEP with flame were discussed in single compartment fire suppression process,which provided fundamental research for its further development.Firstly,raw powder was grinded by planetary ball mill.Then,the products were surface treated with methyl silicone oil in high-speed mixed heating device.Laser particle size analyzer,scanning electron microscopy and other apparatuses were used to test its performances.Results showed that D₅₀,the medium particle size of SFFEP,was 6.00μm and D₉₀was 13.53μm.Its moisture absorption rate was 2.56%and its bulk density was 0.53 g·cm^-3.Its water repellence and fluidity property was suitable.Particle size distribution of products was uniformly and no conglomeration was observed.All performances of products were beyond the requirement of standard GA578-2005.Particle concentration measurement based on laser attenuation principle was designed to establish a set of laser measurement device which determined the laser absorption coefficients of different kinds of SFFEP with different particle sizes.Filtrating and weighing measurement was used to calibrate the particle concentration data.The quantitative relationships between particle concentrations and laser attenuation rates with fixed laser measurement path length were established.Results showed that laser absorption coefficient value of SFFEP depended on its particle sizes rather than its types.Fire extinguishing concentrations of 4 SFFEPs with different types or particle sizes were mensurated by the modified cup burner and the laser measurement device. Measurement data accorded with the literature report data.Results also showed that the particle sizes of the same type SFFEPs were smaller,the fire extinguishing efficiency were higher.As to B class fire model,SFFEPs based on NH₄H₂PO₄ powder or on NaHCO₃ powder with similar particle sizes had similar fire extinguishing efficiency.In 10 m³ single compartment,particle concentration changes at measurement point were mensurated in real time by laser measurement device and dynamic performances of SFFEP were studied.By the experimental results,particle concentration could be 80～100g·m^-3on the SFFEP flowing path.When fire extinguishing agent stream impinged on room walls,the high particle concentration region could be formed at roof,bottom or walls.This characteristic of concentration distribution could be called "wall effect". SFFEP motion process in single compartment consisted of extinguishing agent flowage, particle diffusion and sedimentation process.Particle concentration at roof was lower only because of fine particle diffusion.At half height or bottom of compartment,higher particle concentration kept up longer time because of particle sedimentation.Simulation of SFFEP flowing process in single compartment model was studied by computational fluid dynamics software "Fluent".According to the simulation results, SFFEPs were firstly discharged from nozzle to the bottom of the compartment.After impingement on the bottom,SFFEPs moved to the walls and then moved to the roof along the walls.The simulation process was in agreement with the law of the particle concentration measurement process.But flowing time error between simulation and experiment was discussed.It was concluded that flowing time error was caused by instrument measurement error and simplification in simulation process.The interaction laws between SFFEP and 4 fire model such as center fire,corner fire, shelter fire and ceiling fire in single compartment were studied.K-thermocouples were used to test temperature change of them under conditions of 500g or 1000g discharged SFFEPs.Results showed that SFFEP could be used in total flooding fire extinguishing and could suppress above-mentioned 4 fire model at different locations.Center fire and corner fire which were on the agents' flowing path could be quickly extinguished with adequate particle concentration.Shelter fire and ceiling fire were gradually suppressed by gently increased powder concentration with particle diffusion.