抄録
Effect of fluid motion on a sonochemical reaction field is studied through measurements of multibubble sonoluminescence. A rectangular vessel with six Langevin-type transducers was used; four transducers were attached to the bottom and two to the facing side walls. The vessel was connected to an external cooling-water circulator. The intensity of sonoluminescence (SL) from air-saturated distilled water in the vessel was measured while changing the power applied to the ultrasonic transducers with and without water circulation. Behavior of the cavitation bubbles was also observed. To compare the effect of stirring operation with that of circulation of the fluid, the intensity of both SL and sonochemical luminescence (SCL) from a luminol solution in a glass beaker, which was set into the vessel filled with degassed distilled water, was measured for various rotational speed of a stirrer. The effect of circulation on SL was similar to that of stirring. The fluid motion causes cavitation-bubble size to reduce because of diffusion of bubble nucleation. Therefore the number of the bubbles attracted to the pressure antinodes by acoustic radiation pressure increased, which were repulsed without fluid motion. Both the SL and the SCL intensity increased with increasing rotational speed of the stirrer in the high ultrasonic power range, although it decreased in low ultrasonic power range. The increase of the SCL intensity was more remarkable than that of SL in high power range. The increase rate of SCL intensity by stirring at low frequency was larger than that at high frequency in the low ultrasonic power range. These confirm the existence of an optimal fluid motion for a sonochemical reaction in connection with ultrasonic power and frequency.
