Dual-frequency ultrasonic emitter system for dust and smoke coagulation

Relevance. The lack of effective, safe and environmentally friendly methods for settling suspended solid particles and smoke in processes related to the extraction, transportation and processing of minerals, and fire extinguishing. Aim. Development and research of a dual-frequency ultrasonic emitter system to improve the efficiency of settling hazardous dust and smoke suspensions. Methods. Experimental studies aimed at obtaining data for constructing radiation patterns, calculating the linear attenuation and acoustic power of ultrasonic emitters. Results and conclusions. The authors have developed the ultrasonic disk emitters, consisting of a piezoelectric modernized transducer, made according to the Langevin design scheme and a bending-oscillating emitter, equipped with reflectors, phase-aligning cones and horns. They developed the experimental stand, consisting of two simultaneously operating ultrasonic disk emitters with close natural resonant frequencies and a sound pressure meter. It was shown that the use of reflectors increased the total sound pressure of two ultrasonic emitters by 3–3.5 dB. The angle of the main lobe of the directivity pattern was ±7.5 degrees. The use of phase-aligning cones ensured the formation of acoustic oscillations in one phase from oscillating surfaces in different phases and increased the sound pressure of the system by 8–9 dB. When two ultrasonic emitters simultaneously act on the air environment, a zone of occurrence of beats at a low frequency of acoustic oscillations (300 Hz) is formed, while the sound pressure reaches 97.6 dB at a distance of 1 m and 77.1 dB at a distance of 20 m. It was established that the sedimentation of cement dust occurs at least 300 times faster than with natural sedimentation, and less than 50 times faster than with the implementation of the effect of one disk emitter of the same area. The time of action required for the sedimentation of smoke arising from the combustion of pine sawdust did not exceed 10 seconds to establish a visibility range of at least 10 m.