飞机货舱低气压环境对火灾探测参量影响研究

Experimental investigation on the influence of low pressure on fire detection signals in aircraft cargo compartment fires

旨在为飞机货舱火灾探测系统设计和研制提供理论支撑,在飞机货舱环境模拟实验舱内开展了70kPa、80kPa、90kPa和100kPa下正庚烷火灾实验,分析了低气压环境对顶棚温度、烟气密度和气体浓度火灾探测参量的影响规律。低压下空气密度较小,卷吸系数减小,导致顶棚最高温升增加,顶棚温度衰减变快。同时,低压下烟气密度降低,并与压力呈指数关系,指数系数约为0.946,扩展了前人研究结果的应用范围。CO浓度最大值随压力降低而增加,且CO增长速率与压力呈负指数关系。CO2增长速率随着压力降低而略有减小。

In this work,experiments of n-heptane fires were conducted in a simulated aircraft cargo compartment at 70 kPa,80kPa,90 kPa and 100 kPa to study the influence of low pressure on fire detection signals including the ceiling temperature,smoke density and gas concentration.The purpose is to provide theoretical basic on the design of fire detection systems for aircraft cargo compartments.Because of the low air density in low pressure,the entrainment coefficient decreases.Therefore,the maximum ceiling temperature increases,and the ceiling temperature decays faster in low pressure.Besides,the smoke density decreases in low pressure and is proportional to ambient pressure with exponential factor 0.946.The maximum value of CO concentration increases and its increase rate increases by a minus exponential factor in low pressure.The maximum value of CO2 concentration and its increase rate decrease slightly with decreasing pressure.