火场通信不畅的问题，严重干扰着消防救援工作的开展。建筑火灾环境对火场通信的影响规律，是公共安全领域亟需研究的问题。本文研究了建筑火灾烟气对火场通信电磁波衰减的影响规律，探索影响机理，寻找烟气参数与影响效果的关系，建立火灾烟气影响下的火场通信室内传播衰减模型，揭示火灾烟气在火场通信不畅中发挥的作用。本文的主要工作和成果如下：1、对建筑火灾烟气影响电磁波衰减的机理进行了研究，分析了烟气中微小固体颗粒、可燃物热解或燃烧产生的气相产物、温度不均匀的空气和水汽四种可能影响电磁波衰减的成分，揭示了烟气颗粒对电磁波的吸收是影响电磁波衰减的主要作用，指出了烟气颗粒粒径、粒子数浓度和介电常数是影响电磁波衰减的主要因素，得出了电磁波衰减系数与烟气减光系数的线性关系。2、开展了火灾环境下电磁波与烟气作用的实验研究。实验表明，酒精油盆火焰对350MHz电磁波衰减无明显影响。研究发现，火灾烟气能够导致火场通信电磁波产生明显衰减，接收信号强度随烟气减光系数的增大而减小。接收信号强度的衰减值有明显的频率选择性，350~400MHz频率的电磁波存在明显衰减，而500、600和1000MHz频率的电磁波则无明显变化。设计了烟气电磁波衰减实验装置，在可控条件下测量了烟气对电磁波的影响。实验发现，电磁波的最大衰减系数呈明显的频率选择性，在电磁波频率为355MHz和360MHz时值较大。实验得出了不同频率电磁波衰减系数与烟气减光系数线性关系的比例系数。3、建立了建筑火灾烟气影响下的火场通信传播衰减模型。通过分析火场通信电磁波在室内的发射和接收、视距传播、反射和衍射四类过程，建立了基于烟气分布的传播衰减模型，并利用火灾环境实验结果对模型进行了修正。得出了自由空间传播时的信号最大传输距离与烟气减光系数的关系，得出了室内信号最大传输距离与墙壁地板衰减的关系。研究表明，在满足烟气浓度、通信距离和墙壁地板衰减条件的基础上，火灾烟气能够明显缩减室内信号最大传输距离，从而影响火场通信。揭示了火灾烟气对火场通信影响的规律，为火场通信方案的优化提供了科学依据。
The instability of fire scene communication will jeopardize the effectiveness of fire rescue operations. As a result, it’s in urgent need to study the influence of building fire environment on fire scene communication. The influence of building fire smoke on the attenuation of electromagnetic waves was studied in this article. The relationship between smoke parameters and attenuation effect was discovered. An assessment model was proposed to quantitively estimate the attenuation effects of fire smoke on electromagnetic waves. The study has revealed that the fire smoke played an important role on the deterioration of fire scene communication.A theoretical analysis of the influence mechanism of building fire smoke on electromagnetic waves was conducted. Four different compositions in fire smoke, which may influence the quality of communication, were investigated: small solid particles, gaseous product from the burning or pyrolysis of fuel, air with heterogeneous temperature and water vapour. The results indicated that the absorption of smoke particles was the most influential factor. A model, which depends on three parameters of the smoke particles (smoke particle size, number concentration and dielectric constant) was developed to calculate the attenuation coefficient of electromagnetic waves. The linear relationship between the smoke obscuration coefficient and electromagnetic wave attenuation coefficient was developed.Experiments were also conducted to investigate the attenuation effect of fire smoke on electromagnetic waves under fire environment. It showed that alcohol oil basin flame had no obvious effect on the attenuation of 350 MHz electromagnetic waves. It was found that fire smoke could cause obvious attenuation of electromagnetic waves in fire scene communication, and the receiving signal strength decreased with increasing smoke obscuration coefficient. The electromagnetic wave attenuation was frequency-dependent. Electromagnetic waves of 350-400 MHz had obvious attenuation in experiments, while electromagnetic waves of 500, 600 and 1000 MHz did not have. A smoke experiment apparatus was developed to evaluate the electromagnetic wave attenuation effect of smoke under controlled experimental conditions. The maximum electromagnetic wave attenuation coefficient was found to be frequency-dependent. Electromagnetic waves with the frequency of 355 MHz and 366 MHz had the largest attenuation coefficient. The proportionality coefficient between smoke obscuration coefficient and attenuation coefficient of electromagnetic waves were measured.An indoor propagation and attenuation model of fire scene communication under the influence of building fire smoke was developed. The emission, receiving, line-of-sight propagation, reflection and diffraction of electromagnetic waves were studied. The model was developed based on smoke distribution function and was corrected by results of the fire environment experiment. The correlation between the signal maximum transmission distance in free space and the smoke obscuration coefficient was studied. The correlation between the indoor signal maximum transmission distance and wall-floor-attenuation was developed. When the smoke concentration, communication distance and wall-floor-attenuation satisfied certain conditions, building fire smoke would shorten the signal maximum transmission distance obviously, and then the fire scene communication was affected. The result reveals the influence law of fire smoke on fire scene communication and provides scientific basis for the scheme optimization of fire scene communication.
