Experimental study on eliminating various typical fire smokes by ultrasonic field

To explore the effectiveness of acoustic agglomeration technology in eliminating urban fire smoke, an experimental setup for eliminating continuous smoke is built. This study uses airborne ultrasonic transducers as the sound source, with resonant frequencies are 13, 16, 18, and 20 kHz, respectively. Typical urban fire smoke is produced by the combustion of materials such as polystyrene (PS), polyvinyl chloride (PVC), carton, cotton, pine sawdust, and birch sawdust. The effects of ultrasonic frequency, sound pressure level, residence time and initial concentration on the elimination of both single material smoke and mixed material smoke types are investigated. Results indicate that the 16 kHz sound waves are most effective for PS, PVC, and carton smoke, whereas the optimum frequency for birch smoke is between 16 and 18 kHz. The optimal frequency of mixed smoke is significantly influenced by particle size and the ratio of large to small particles. When the sound pressure level is 142–154 dB, and the residence time is 4 s, the visibility of all types of smoke increased from 1 m to above the safe escape threshold (2.5 m). Furthermore, higher initial concentrations of smoke result in more effective elimination.