Numerical simulation study on fire development characteristics of pure electric and fuel buses
In this study,the FDS numerical simulation method was employed to investigate the similarities and differences in fire development characteristics between pure electric and fuel-powered buses.By considering the formation of jet fires resulting from the combustion of released combustible gas due to thermal runaway injection from power batteries,the study compared the heat and smoke release characteristics,as well as the fire development of buses under two typical ignition sources:the battery pack and fuel.In fire accidents involving pure electric and fuel buses with a length of 10.5 m,the fire growth rate falls between that of ultra-fast and fast fires.During the initial 500 s period,the Heat Release Rate(HRR)of the fuel bus surpasses that of the electric bus.Conversely,beyond 500 s,the electric bus exhibits a higher HRR compared to the fuel bus.The Peak Heat Release Rates(PHRR)for pure electric and fuel-powered buses are 25.4 MW and 24.2 MW,respectively,while their Total Heat Release(THR)values are 20.2 GJ and 17.5 GJ.These figures indicate that electric vehicles exhibit higher PHRR and THR compared to fuel-powered buses.Remarkably,the peak time of PHRR for electric vehicles occurs 144 s later than that of fuel-powered buses.In this paper,considering the most unfavorable scenario where the ignition source is close to the rear door and the doors and windows remain closed for 100 s in the initial stage of the fire,several notable differences are observed between electric and fuel buses.Compared to fuel buses,the ignition time of the upper interior of the electric vehicle is accelerated,while that of the lower part is delayed.Additionally,the time for breaking windows near the skylight is advanced in electric vehicles.Furthermore,during the progression of bus fires,the height of overflow fire at openings such as electric vehicle windows is greater than that of fuel vehicles.One minute represents a critical timeframe for people to escape,during which the temperature in the middle and rear sections of the compartment tends to be higher than that in the front.
safety engineeringbattery thermal runawaypure electric busfire characteristicspersonnel escape
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