การออกแบบและศึกษาคุณลักษณะของหัวฉีดคลื่นเหนือเสียง / สาวิตรี แสงแก้ว = Design and study of the characteristics of ultrasonic nozzles / Sawitree Saengkaew
The objective of this research is to design and to study the characteristics of the ultrasonic nozzles, in which are used to generate the uniform droplets. The ultrasonic nozzles of which were made of two types of different transducers i.e. the piezoelectric and resonator transducers were investigated the parameters affecting on the characteristics of the nozzles. Those parameters are the frequency and intensity of ultrasonic wave, the liquid flow rate and properties and the operating air pressure. Furthermore, the dust suppression efficiency in the rock crushing plant obtaining from the nozzles was compared with those obtained from the conventional nozzles. In the first part of the study, it is found that water droplet sizes produced from the piezoelectric transducer ultrasonic nozzles operating with the frequency ranges of 34-56 kHz are in the range of 42-59 microns. The higher operating frequency, the smaller droplet sizes. Meanwhile the droplet sized is increased in the range of +-15 microns by loweringthe intensity of ultrasonic wave from 2-8 watts or increasing the liquid flow rate from 22-250 mm3/s. Further study in effects of the liquid properties, it is revealed that the liquid with low surface tension gives rise to smaller droplets. The high viscosity liquid is found unable to be atomized. Spray pattern from this nozzle was cylindrical with its diameter of 1 cm. For another type of the nozzle, i.e. the resonator, it is seen that the water droplet sizes are between 25 and 39 microns. Likewise, the droplet size is increased either in the range of +-10 microns by reducing the operating air pressure from 2-3 kg/cm[superscript 2] or in the range of +-12 microns by increasing the liquid flow rate from 833-7,600 mm3/s. It is also clear that the liquid properties have no significant effect on the droplet sizes. Importantly, this nozzle can be used to atomize the high viscosity liquid. The conical-cone spray pattern is obtained from this nozzle with a cone angle of 35 degree and a diameter of 20 cm. The smaller droplet sizes and the narrower size distributions are obviously obtained from both types of the nozzles compared to those obtained from the other conventional nozzles. Taken the dust suppression efficiency of these two nozzles into considerations, it is found that the efficiency beyound 90% is obtained from the resonator nozzle with the liquid flow rate as low as 8,500 mm3/s. In addition, it is interesting to note that the use of the ultrasonic nozzle would reduce the problem of the nozzle clogging and the humid of the water-sprayed processing rock. In an economic aspect, it is shown that for the single ultrasonic nozzle, the capital and instalation cost is 1.5 times and the operating cost 0.4 times of the nozzles used in the present rock crushing plant.
