Experimental Study Of Flame Spread Over PE And ETFE Wire Under Sub-atmospheric Conditions

The wire insulation consists of polymeric material,generally speaking,it can be ignited easily and spread continuously.There is a dripping phenomenon of insulation during flame spread process.This phenomenon is,nevertheless,quite complicated since it consists of multi-phase,multi-dimensional time-dependent heat and mass transfer with chemical reactions in each phase,which cause big difficulties for fire safety.Besides,the air pressure in the aircraft cabin is about 80kPa and even lower in space vehicle.The oxygen concentration in space vehicle is about 30%,which is different with experiments on the ground.So it is necessary to build experimental setup to simulate sub-atmospheric pressure and high oxygen concentration environment.In this article,we use NiCr-PE wire,Cu-PE wire and NiCr-ETFE wire based on the investigation of former research.We build sub-atmospheric cabin and flame spread platform to study the effect of air pressure and oxygen concentration on flame spread rate and flame shape.The dripping process of NiCr-PE wire and Cu-PE wire is analyzed emphatically.In terms of theoretical research,this article study the dripping physical process and heat and mass transfer based on the droplet evaporation model.A simplified model based on mass conservation equation was established to reveal the dripping cycle(t0)and critical diameter(Dcr).In terms of experimental research,firstly,the theoretical t0 and Dcr is validated with the experimental results conducted in a low air pressure cabin.Secondly,this article compare the effect of air pressure and oxygen concentration on flame spread rate.We give the definition of the upper dripping limit and lower dripping limit and obtain the regularity of upper and lower dripping limit at different oxygen concentration.Finally,the research compare the NiCr-PE and NiCr-ETFE wire flame shape and spread rate based on the experimental results.