建筑火灾高温烟气环境中超声波传播特性的研究

When an ultrasonic wave propagates in the fire scenario, coupling the influence of high temperature and smoke particles, the propagation characteristics present a unique form. Thus, the study of ultrasonic propagation characteristics in fire scenario can obtain the inversion of fire environment which can support to solve the problem of poor visibility. The project research the absorption and scattering effect of the smoke particle while an ultrasonic wave passes through, with the consideration of the smoke particle’s fractal condensation structure. The scattering model will be built to reveal the influence of smoke structure and environmental parameters (viscosity coefficient, density, etc.) to the smoke scattering. The smoke particle size distribution in the building fire scenario and the environmental parameters variation with the temperature were studied. Combined with the smoke scattering model, to reveal the relationship between the ultrasonic intensity and propagation speed with the smoke density and the temperature under the action of coupling by high temperature and smoke particles. The smoke spread rule in a typical room-corridor space was studied to analyze the non-uniform structure of the smoke. With the relationship between the ultrasonic intensity and propagation speed with the smoke density and the temperature, the ultrasonic propagation model in the building fire scenario was built, and the fire environment inversion algorithm is put forward. The research result can support to solve the low visibility problem which causes the firefighters cannot see clearly in the smoke scenario giving rise to the casualties, the tardiness of evacuation and rescue.

超声波在火场烟气环境中传播时，受高温和烟颗粒的耦合作用，其传播特性呈现特有的表现形式。对超声波传播特性的研究为火场环境反演，解决当前火场低能见度问题提供重要的支持。本项目结合烟颗粒独特的分形凝聚体结构，研究烟颗粒对超声波的吸收、散射作用，建立烟颗粒对超声波的散射模型，揭示颗粒形态、环境参量（粘性系数、密度等）对烟颗粒散射的影响规律；研究建筑火灾烟颗粒粒径分布规律和环境参量温度变化规律，基于烟颗粒对超声波的散射模型，揭示高温和烟颗粒耦合作用下超声波强度、传播速度随烟气浓度、温度的变化关系；研究建筑内典型房间-走廊空间的烟气迁移规律，揭示烟气的非均匀流场结构，结合超声波强度和传播速度随烟气浓度、温度的变化关系，建立建筑火灾烟气环境超声波传播模型，并以此提出火场环境反演算法。为解决当前火场低能见度导致消防人员无法辨识火场环境引发的伤亡、火场疏散搜救缓慢等问题提供必要的理论支持。

火场的低能见度环境导致消防救援工作的缓慢和消防人员的大量伤亡，本项目拟将超声波探测技术引入到火场环境侦测之中，对超声波在火场烟气环境中的传播特性进行了深入研究，主要研究内容包括：将火场烟气环境视为烟颗粒与空气混合的颗粒介质环境，重点研究温度、烟颗粒浓度两大火场特征参数对超声波传播速度、衰减系数的影响关系。.（1）分析了空气环境中，超声波传播速度、衰减系数与温度的变化关系；理论和实验结果表明：空气环境中超声波传播速度与温度成直线上升关系，而衰减系数则随着温度的增加先升高再降低，在350 K出现拐点；.（2）分析了烟气环境中单个烟颗粒的形态特征和粒径分布特征，从黏性吸收、热传导吸收、介质本身吸收、结构损失、电声损失、散射损失等六大方面探讨了烟颗粒对超声波的衰减机制，建立了烟气环境中超声波传播模型，研究了烟气环境中声速、声衰减与超声波频率、环境温度、颗粒粒径、颗粒浓度的变化规律，理论结果表明：烟气环境中超声波传播速度与空气环境中区别不大，温度仍占主导作用，而超声波衰减系数相对空气环境明显增大，烟颗粒对超声波的衰减占主导作用；.（3）搭建了均匀烟气环境模拟实验装置，以正庚烷、木垛、棉绳、聚氨酯等为燃料，研究了不同烟气环境中超声波传播速度、衰减系数与温度、烟气浓度的变化关系，实验结果与理论结果基本吻合；.（4）搭建了房间-走廊烟气环境实验装置，分析了走廊顶部和底部烟气的温度分布规律，研究了非均匀烟气环境对超声波测距误差的影响，探讨了非均匀烟气环境超声波误差修正方法；.（5）基于以上研究成果，提出了基于挡板法的超声波传播速度纠正模型，研制了超声波避障火场辅助行走小车，为辅助消防人员火场行走提供了重要的理论和技术支持。