火灾烟气危害定量评价模型THVCH及其应用

为更加准确地评价实际火灾烟气的危害性,针对以往烟气毒性定量评价方法N-GAS和FED模型的不足,提出了一种新的火灾烟气危害性定量评价模型THVCH(Toxicity,Heat and Visibility Comprehensive Harmfulness)。实际火灾烟气的危害包括烟气毒性和烟气高温辐射。两者都具有时间累积效应,人员在火灾环境中的暴露时间越长,所受到的伤害越大。烟气的遮光性是影响火场中人员暴露时间的重要因素,低能见度下人员疏散所需要的时间是高能见度的3.8倍。THVCH模型在考虑烟气毒性的同时兼顾了能见度对人员暴露时间的影响以及高温辐射对人体的伤害。以重庆开县5.5火灾为工程背景,运用大涡模拟技术对其火灾过程进行数值重构。在此技术上采用N-GAS、FED和THVCH模型对不同阶段的火灾危害性进行了评价,证明了火灾烟气危害评价中考虑能见度和高温辐射的必要性。

Fire smoke toxicity quantitative evaluation model THVCH and application

The paper is aimed to present a new fire-smoking hazard evaluation model known as the fire smoke harmfulness THVCH(toxicity,heat and visibility comprehensive harmfulness) to replace the previous N-GAS and FED smoke toxicity quantitative evaluation method in hoping to increase the evaluation accuracy.As we know,most smoke hazard comes from the smoke toxicity and high-temperature thermal radiation in the real fire accidents.Under the same fire-causing environment,the longer people stay in the fire,the greater damage they would have to suffer,for the exposure time and the fire-smoking spreading both have accumulative effect.In addition,such hazards are strongly affected by the smoke visibility,and the evacuation time in the condition of low visibility can be made 3.8 times as long as in a smoke-free environment.Besides,the visibility also affects personnel exposure time and the damage of human bodies caused by extremely high temperature.For example,the May-5 Kaixian building fire(in Chongqing),was managed to be reconstructed by using the large eddy simulation method,with the fire smoke hazard evaluated by N-GAS,FED and THVCH model in different stages.At the 1 000-th second after the fire broke,the smoke visibility was restricted to 2.3 meters,and the human evacuation time increased to 133 second,which was much longer than that of smoke free environment.In the third period(1 000-1 133),we managed to work out the smoke toxicity value with the N-GAS and FED model,the smoke toxicity value computed by N-GAS and FED model was about 0.6,though safe for human evacuation,yet dangerous,for the smoke heat radiation value indicated in THVCH model was 1.03,which implied the fire environment was dangerous.Thus,it can be seen that the main difference between THVCH and the past evaluation model lies in that THVCH model took into account the smoke heat radiation effect whereas the previous model only considered the smoke toxicity.Thus,the fire simulation result helps us to see that the smoke heat radiation may lead to the increase of the fire.In addition,heat radiation may cause bigger damage than the smoke toxicity in case there exists flashover.Through the real fire simulation and analysis,smoke visibility and high-temperature radiation prove to be the main influential factors on fire fighting and prevention.