低压环境下玻璃纤维/酚醛树脂燃烧特性

Combustion properties of glass fiber/phenolic resin at low ambient pressures

火灾事故严重威胁飞机的安全运行。航空运输环境为低压环境,低气压会对火灾的发生发展产生重大影响。民用运输飞机的壁板材料均为复合材料,美国联邦航空管理局和中国民航局均要求实验验证其防火特性。该文选取空客某型飞机夹芯结构壁板材料(A壁板)和层压型壁板材料(B壁板)作为研究对象。A壁板由上下层树脂基面板、中间层芳纶蜂窝芯和胶黏剂组成,B壁板为树脂基玻璃纤维增强层压板。分别在四川康定(61 kPa)和广汉(96 kPa)研究其隔热性能、点燃时间、质量损失和烟气特性。结果表明:A壁板隔热性能在低压下下降约26.0%,B壁板隔热性能几乎不受压强影响,A壁板隔热性能明显优于B壁板;压强通过影响对流热损失和临界质量通量影响点燃时间,A壁板点燃时间在低压下缩短16%,B壁板点燃时间受压强影响较小;压强影响燃烧速率,A、B壁板质量损失率和质量损失速率在低压下均有降低;在不同气压环境下2种壁板O_(2)最大消耗量、CO和CO_(2)产生量峰值对应时间基本一致,低压环境下O_(2)消耗量、CO和CO_(2)产生量峰值均高于常压环境。该文初步研究了气压对壁板材料燃烧特性的影响,可为机舱防火救援等提供理论参考。

[Objective]Accidental fires seriously threaten the safe operation of aircraft.Air transportation environments typically have low ambient pressures that can significantly influence the occurrence and spread of fire.The wallboards in civil aircraft are generally made of composite materials.The Federal Aviation Administration of the United States and the Civil Aviation Administration of China require that the fire resistance characteristics of these materials be experimentally verified.This study investigated a sandwich structure panel(panel A)and a laminated panel(panel B)of an Airbus aircraft to understand the influence of ambient pressure on aircraft fires and to enable the earliest possible detection,management,and prevention of aircraft fires at the low ambient pressures typically encountered in such situations.Panel A was composed of upper and lower resin base panels,with an aramid honeycomb core and adhesive middle layer,whereas panel B was a resin-based glass fiber-reinforced laminate.[Methods]The effects of ambient pressure on the thermal insulation,ignition time,mass loss,and smoke characteristics of the panels A and B were studied using self-built,low-pressure,oxygen-enriched combustors in Kangding,Sichuan Province(61 kPa)and Guanghan,Sichuan Province(96 kPa),respectively.The thermal insulation characteristics of the panels were studied by measuring the temperature on the back surface of the panel after heating the front surface for 60 s with a heating rod.The effect of pressure on the convective heat loss was studied using the ideal gas relation.The mass loss during the fire was recorded by an electronic balance,and the smoke generation was recorded in real time by a smoke analyzer.[Results]The temperature of the back surface of panel A was 692.3℃at atmospheric pressure and 512.4℃at low pressure with a decrease of about 26.0%.The temperature of the back surface of panel B at normal and low pressures was 810.5℃and 820.9℃,respectively.Furthermore,the temperature variation as a function of time was almost the same under either pressure condition for panel B,indicating that changes in the ambient pressure in the range studied had almost no impact on the insulation of panel B.The heating rate of panel B was higher than that of panel A,demonstrating the superior thermal insulation performance of panel A.Regarding the effect of pressure on the convective heat loss,the measured ignition times were in good agreement with the analytical model.The ignition time for panel A was reduced from 24.16 s to 20.34 s,i.e.,reduced by 16%.Pressure variations had less influence on the ignition time for panel B.Variations in the pressure affected the rate of combustion;the mass loss for panel A decreased from 8.7%to 4.9%,and the peak mass loss rate decreased from 68.7×10^(-3)g·s^(-1)to 22.8×10^(-3)g·s^(-1),whereas the mass loss for panel B decreased from 5.8%to 4.8%and the peak mass loss rate decreased from 35.0×10^(-3)g·s^(-1)to 12.5×10^(-3)g·s^(-1).The time of the maximum O_(2)consumption and the time of the CO and CO_(2)production peaks of either kind of panels were almost the same under different pressure environments,whereas the maximum O_(2)consumption and CO and CO_(2)production peaks in the low-pressure environment were higher than those at atmospheric pressure.[Conclusions]This preliminary study on the effect of pressure on the combustion characteristics of aircraft panels finds that pressure has a significant impact on the occurrence and spread of aircraft fires.This study can provide theoretical support for cabin fire prevention and fire rescue under different pressure environments.