火灾每年都造成巨大的经济损失和人员伤亡，常规灭火技术在灭火过程中存在需反复充装、易造成二次损失等缺点。声波灭火作为一种有效期长、无次生污染的灭火技术在近几年被广泛提及。目前，关于声波对于可燃物燃烧行为的影响研究大部分集中在声波对燃料液滴火焰或预混气体火焰的干扰特性方面，而声波对于油池火的影响，尤其是对其灭火的临界参数研究相对较少。因此，研究声波对酒精池火燃烧特性的影响、确定声波灭火的条件，有利于完善声波灭火理论和促进声波灭火技术的发展。

本文设计并搭建了一种声波灭火系统，并采用该系统研究声波作用下的酒精池火燃烧和熄灭特性。采用多通道信号分析仪测量了声波灭火系统在各种工况下产生声波的声场分布规律；通过高速摄像机记录了声波作用前后的酒精燃烧火焰的行为特征，探究了声波对酒精池火火焰形状的影响，并采用Matlab软件进行图像识别和快速傅里叶变换处理，确定了声波作用下酒精燃烧火焰的振荡频率变化规律；利用在线高精度电子天平测量了声波作用下酒精燃烧过程中的质量变化，研究了声波作用下酒精燃烧热释放速率的变化特性，进而揭示了声波对酒精池火燃烧效率的影响机制；通过对不同条件下声波扑灭酒精池火的效果进行分析，确定了声波灭火系统扑灭酒精池火的临界条件和极限距离。

研究表明，声波灭火系统产生的声压随声源功率提高而增大、随距离火源增加而减小、随声波频率增加而增大，而当声源功率增加至225W以上时，声场各处声压值的变化不大；在声波作用下，随着火源距离增加或声波频率提高，酒精池火火焰从竖直方向变化至水平方向的时间延长，同时火焰振荡频率也相应减小；研究发现声波作用于酒精池火时，从对酒精燃烧有微弱影响至能扑灭酒精池火的临界工况，酒精燃烧的质量损失速率不断增加；研究表明，声源功率和声波频率对声波扑灭酒精池火的效果具有显著影响，声源功率越大、声波频率越低，灭火效果越好，且灭火极限距离随着声源功率的提高而增大，研究对揭示声波灭火机理和优化声波灭火系统具有一定的指导意义。

Fires cause huge economic losses and casualties every year. Conventional fire extinguishing techniques have the disadvantages of repeated filling and secondary losses during the fire extinguishing process. Fire extinguishment using acoustic waves has been widely mentioned in recent years as a viable technology that has no secondary pollutions. At present, most of the researches about the influence of acoustic waves on combustions focus on the impact of acoustic waves on the flame of fuel droplets or premixed gas flames; while the impact of acoustic waves on pool fires is less. From the practical application point of view, the pool fire is closer to the actual fire scene, so in-depth study of the impact of acoustic waves on the pool fire will be conducive to the development of fire extinguishing technology using acoustic waves.

In this paper, a fire extinguishing device by acoustic waves has been designed and built. The device is used to study the burning and extinguishing characteristics of alcohol pool fires under acoustic waves. The main work includes: using a multi-channel signal analyzer to measure the acoustic field distribution of the fire extinguishing device by acoustic waves under various working conditions to obtain the working characteristics of the device; record the alcohol flame before and after the action of the acoustic waves through a high-speed camera; observe the influence of the acoustic waves on the shape of the alcohol pool fire, and use Matlab for image recognition and Fast Fourier Transformation to obtain the influence of the acoustic waves on the flame oscillation frequency; using an electronic balance to measure the change in the quality of alcohol burned under acoustic waves; calculate the change in the heat release rate of alcohol under acoustic waves, and obtain the effect of acoustic waves on the combustion efficiency of the alcohol pool fire. By analyzing the effect of acoustic waves on extinguishing alcohol pool fire under different conditions, the critical conditions and limit distance of fire extinguishment of the device are obtained.

Studies have shown that the sound pressure generated by the fire extinguishing device increases with power or frequency, and decreases with increasing distances. When the power increases above 225W, the sound pressure does not change much. When the acoustic waves act on the alcohol pool fire, as the distance and the acoustic frequency increase, the time for the flame to change from vertical to horizontal under the acoustic waves will also increase. At the same time, the flame oscillation frequency will decrease. When the acoustic waves act on the alcohol pool fire, the mass loss rates of alcohol increase from the beginning to the critical condition of the flame extinguishment. The fire extinguishing device by acoustic waves can enhance the impact of the acoustic waves on the combustion by increasing the power or by reducing the frequency.