基于数值模拟的公交车火灾发展过程及特性研究

Numerically simulated study on the characteristic features and spreading process of the bus fire

采用数值模拟方法研究典型型号公交车的火灾发展过程,探讨车门打开对火情发展和人员逃生的影响。通过描述火源、公交车的结构及其内饰物的属性,研究车厢内关键位置的温度分布、能见度及CO和O2体积分数的变化规律,以揭示公交车的火灾发展、烟气运动过程及对人员安全逃生的影响。结果表明:车门打开后由于供氧充足,明显加速了火势的蔓延和烟气扩散,并使得燃烧温度显著提高;打开车门后20 s内,车门附近能见度和O2体积分数显著增高,CO体积分数有所降低,是乘客逃生的关键时间。

The paper aims to disclose the spreading process and the characteristic features of the communal bus fires in addition to the investigation of the effects of the ventilation conditions on the combustion behavior and personnel excavation. As is known,bus fires occur from time to time and cost hundreds of lives in recent years all over the country,getting to be a blasphemous source leading to social instability. However,there hasn＇t been found any available efficient methods for preventing and eliminating such bus fire disasters so far due to the lack of thorough understanding of the inherent mechanism and characteristics of bus fires. Starting from this need,we have conducted a series of numerical simulation researches over the typical characteristic features of bus fires in a simplified model of Yutong ZK6128 HGK bus,in order to trace their occurring and spreading process and the combustion behaviors in this paper. At the same time,we have also made a discussion of the effects of the door-opening on the fire propagation and the passengers＇ evacuation. Of all the influential factors on the bus fire,we have made careful and thorough examination of such factors,as the temperature distribution,the visibility,CO and O2 concentration variation in the critical positions inside the bus by depicting the fire source,configuration of the bus and the fuel properties in hoping to disclose the fire starting,propagation,smoke movement and the effects of evacuation. For example,the fire source is located in the middle of the bus tailing section with an area of 1. 35 m × 0. 3 m and heat releasing rate is 500 k W / m2. It is assumed that,things would be better if the driver were to detect the fire source and then opened the doors to evacuate passengers in no more 30 s after the fire started.The results demonstrate that the spreading of the fire and smoke propagation tends to be accelerated dramatically and the combustion temperature is likely to increase promptly due to the adequate oxygen supply with the doors open. Therefore,during the 20 s after opening the doors,the visibility and O2 concentrations near the doors are likely to be enhanced noticeably,and,then,CO concentration were to drop down. Thus,the critical time for the passengers to escape would be just 20 s after the doors opened.From what is said above,it can be concluded that the results of our study can serve as a reference to the bus fire prevention and passenger evacuation.