Experimental And Modelling Research Of Combustion Of Flexible Polyurethane Foam Under Radiative Heating

Flexible polyurethane foam(FPUF)is widely used in commercial and residential buildings.However,as a typical flammable material,FPUF is highly prone to pyrolysis and combustion when heated by external radiation.FPUF fires release a lot of heat and toxic gases,causing serious injuries,deaths,and property damage.In this thesis,experimental and modelling research on FPUF combustion is conducted.Firstly,the FPUF combustion is studied by fire propagation apparatus(FPA)with different radiant heat fluxes(20 kW m-2～50 kW m-2)and sample thicknesses(20 mm～40 mm).Based on the mass loss rate,heat release rate,and gas phase product generation rate,FPUF combustion includes three stages:the first stage is mainly FPUF pyrolysis and toluene diisocyanate(TDI)combustion,the second stage is primarily polyol combustion,and the third stage is mainly char oxidation.The peaks of the mass loss rate curve and the heat release rate curve in the second stage are higher than the corresponding peaks in the first stage.The generation rates of CO and CO2 are larger under stronger radiant heat flux and larger sample thickness.Under the experimental conditions of this study,the ignition temperature of FPUF is about 353℃.Subsequently,regarding the three parameters of sample bottom temperature,sample thickness,and radiant heat flux,this paper quantitatively analyzes their influence on FPUF combustion by the independent effect of a single parameter and the combined effect of multiple parameters.Therefore,the mass and heat release rate models are established based on the Box-Behnken design method.The results of variance analysis and global sensitivity Sobol method show that the mass and heat release rate models are the most sensitive to the sample bottom temperature under the independent effect of a single parameter.The order of sensitivity of the mass model to multiple parameters is:sample bottom temperature × sample thickness>sample bottom temperature squared>sample thickness squared.The order of sensitivity of the heat release rate model to multiple parameters is:sample bottom temperature squared>sample thickness squared.Finally,two-dimensional axisymmetric FPUF ignition models of heat transfer and heat transfer-reaction are developed.The heat transfer ignition model includes heat conduction,heat convection,and heat radiation,while the heat transfer-reaction ignition model couples the two-step pyrolysis reaction of FPUF.The results show that the heat transfer-reaction ignition model is in better agreement with the experimental results,and the chemical reaction sub-model plays an important role in the FPUF ignition model.