货舱动态变压环境与细水雾协同灭火抑爆机制

With the rapid development of big aircrafts, a wider range of commercial cargo goods are with high danger of fire and explosion, especially for those involving lithium battery or aerosol explosive products, and the application of new aviation aluminum/magnesium alloy materials, introduce new challenges on the fire protection of big aircraft. With the full-scale simulated dynamic pressure cargo compartment chamber, heat release rate calorimeter, burning resistant test rig and lithium batteries thermal runaway and explosive platform, this project plans to construct the “fire emergency dynamic pressure process” and multiple hypobaric hypoxia environment, which can be used to perform experiments of the equivalent fire load combustion, cargo compartment fire resistance, lithium battery explosion, water mist fire and explosion suppression, as well as the relevant numerical modeling. Meanwhile, by the exploring the mechanism of depressurization fire suppression and landing pressurization re-burning, studying the influence on the micro structural failure and burning resistant by the pressure-induced fire variation, the fire hazard degree could be classified during the whole “fire emergency dynamic pressure” process. This project also plans to study the thermal runaway propagation and explosion characteristics of lithium batteries with different numbers and different states of charge under different low and dynamic pressures. Besides, the water mist flow field and spatial temporal distribution in the cargo compartment will be explored. The mechanisms of water mist collision and coagulating carbon particles, weakening the smoke extinction coefficient and attenuating the heat radiation will be revealed too. In addition, this project wants to investigate the controlling effect of two-phase water mist on the explosion overpressure phenomenon, exploding flame and shockwave propagation. Then the synergistic suppression mechanism of fire and explosion in cargo compartment with dynamic pressure and water mist would be revealed.

大飞机发展迅猛，民机货舱货物种类繁杂且不乏含锂电池或气溶胶易爆品，航空铝/镁合金新材料应用，对大飞机火灾防护提出新的挑战。采用全尺寸动态变压标准舱和热释放速率测定仪、航空材料耐火性测试和锂电池燃爆实验台，构建近真实货舱“火灾应急变压”和多种低压低氧环境，开展等效火灾载荷燃烧、舱体耐火性能、锂电池燃爆和细水雾灭火抑爆实验及数值模拟。.研究货舱降压抑灭火和降落升压火灾复燃机制，探究动态变压引起火行为变化对舱体微细观结构损伤和耐火性能影响，获得“火灾应急变压”过程灾害危险性阶段划分；研究不同低压和动态变压环境下不同数量和荷电状态锂电池热失控传播和燃爆特性；探究货舱细水雾雾场绕流和时空分布特性，揭示动态变压环境下细水雾碰撞凝并碳颗粒、减弱烟气消光系数及隔离衰减热辐射机制，考察双流体细水雾对锂电池和气溶胶爆炸超压效应、爆炸火焰和冲击波传播的控制作用。综合分析，获得动态变压和细水雾协同灭火抑爆机制。

大飞机发展迅猛，民机货舱货物种类繁杂且不乏含锂电池或气溶胶易爆品，航空铝/镁合金新材料应用，对大飞机火灾防护提出新的挑战。降压抑灭火是飞机巡航中货舱火灾的首要应急处置措施，防火内衬层是货舱最直接有效的耐烧穿屏障。为了探究由降压抑灭火带来的动态变压环境对火行为的控制作用和火灾烧穿能力的影响机制，开展了一系列动态变压环境下的油池火灾和防火内衬层耐烧穿实验。实验结果表明：降压可以通过降低质量燃烧率和辐射热通量来抑制火灾，但难以完全消灭火灾，降压会增加油池类火灾的火焰高度并抬升火焰的高温区，导致火焰与货舱天花板上的衬板直接接触。防火内衬层限制了火焰高度、空气卷吸和热气流逸出，升高后的火焰在内衬层下方形成射流燃烧，增大了火焰与内衬层的接触面积，而且增强了对火灾的热反馈作用。低压下的质量燃烧速率曲线是平滑的，火焰波动频率较低，由降压引起的质量燃烧速率的降低导致燃烧时间更长，火焰高温区与内衬层的接触时间增长。在低压火灾情况下的防火内衬层的烧损膨胀区域和碳化区域均较大，背面温度也更高，火灾损伤更为严重。.采用全尺寸动态变压标准舱构建近真实货舱“火灾应急变压”和多种低压低氧环境，开展开放空间和货舱受限空间内气溶胶燃爆和细水雾灭火抑爆实验。实验表明：民机货舱受限空间内与开放空间内燃爆及火焰传播机制不同，货舱内气溶胶燃爆火焰向前后方均发生爆炸传播，在开放空间气溶胶气云运动和燃爆传播均在喷射口前方区域且向前传播；点火能量越大气溶胶燃爆强度越大，民机货舱受限空间内气压越高气溶胶燃爆强度越高，低气压条件下空气密度和氧分压浓度较低，形成气溶胶体积且扩散不充分，燃爆获得氧气难度增大，燃爆强度降低。气溶胶燃爆受细水雾控制作用明显，细水雾不同触发阶段对爆炸影响作用机制不同，低浓度细水雾环境对燃爆有一定增强作用，浓度增大到一定程度后可以抑制燃爆。