高次モード曲げ振動板,縦共振ホーンおよび磁気ひずみ振動子からなる空中用強力超音波音源とその応用

抄録

This paper deals with the generation of aerial intense ultrasound field and its applications (such as the agglomeration of an aerosol and sonic drying). We could generate an intense ultrasound field (160 dB at about 20 to 28kc/s ia n chanber. By coupling a magnetostrictive vibrator with a metallic exponential horn in longitudinal half wave resonance provided with a higher mode flexural vibration plate. (See Fig. 1) Let a sound level be expressed by the airthmetic mean value of the maximum sound pressure of standing waves in the axial direction of the chamber, and it increases with increases of the area and the amplitude at the center of the plate. On the other hand, it decreases with an increase of the capacity of the chamber. (See Fig. (4, 5) It also decreases with a rise of temperature in the chamber. (See Fig. 7, 8) Then, we applied the intense ultrasound field to the agglomeration of an aerosol and sonic drying from which satisfactory effects were obtained noiselessly. In the experiment of smoke agglomeration, a tube made of acryl with a thickness of 4 mm, an insede diameter of 60 mm and a length of 1000 mm was used as a chamber. We measured the relation between the degree of agglomeration and the flow speed of an aerosol in the chamber. The aerosol was incense stick smoke. The degree of agglomaration was calculated from the output of a photo-cell densimeter. (See Fig. 16, Eq. 2) It was found from this experiment that the longer the retention time of the aerosol in the retention time of the aerosol in the chamber and higher a sound intensity level were, the higher the degree of agglomeration was. (See Fig. 17) As for the experiment of sonic drying, a sponge of vinyl chloride and silica-gel grains were used as test pieces. An apparatus for the former test piece is shown in Fig. 18 and one for the latter is shown in Fig. 19, 20. As the result of this experiment, drying time and the final water content were found to be less than those by air flow drying. (See Table 2, 3) These experimental results show the same effect as in audio frequency ranging from 0. 6 to 5 kc/s. (See Table 1)