Numerical analysis of the influence of vortex acoustic flows on the efficiency of agglomeration

It is known and experimentally proven many times that ultrasonic vibrations in the gas phase contribute to the appearance of stationary acoustic flows. Since the flows are caused by energy losses during absorption of oscillations, and they do work against the frictional forces that cause this absorption, then these flows have a vortex character. According to numerous studies and developments in the field of inertial dust separation, at a centripetal acceleration of 10 m/s2 or more, local compaction of particles is observed near the periphery of the vortex flow. Due to this, particles are captured in existing devices based on the inertial dust separation principle. In this regard, the article presents the results of theoretical studies of the potential for the use of acoustic flows for a local increase in the concentration of particles and, consequently, an increase in the efficiency of agglomeration. A model of the influence of vortex acoustic flows on the efficiency of agglomeration is proposed. As a result of the numerical analysis of the model, the fundamental possibility of a significant (more than 4 times) increase in the efficiency of ultrasonic agglomeration of submicron particles due to the formation of vortex acoustic flows in the resonant intervals was revealed.

NUMERICAL ANALYSIS OF THE INFLUENCE OF VORTEX ACOUSTIC FLOWS ON THE EFFICIENCY OF AGGLOMERATION

В статье представлены результаты численного эксперимента, показывающие, что акустические потоки, формирующиеся в резонансном газовом промежутке, обеспечивают повышение эффективности агломерации субмикронных частиц не менее 4 раз. Разработана численная модель процесса ультразвуковой агломерации, впервые учитывающая вихревое движение взвешенных частиц в акустических потоках. A model of the influence of vortex acoustic flows on the efficiency of agglomeration is proposed. As a result of the numerical analysis of the model, the fundamental possibility of a significant (more than 4 times) increase in the efficiency of ultrasonic agglomeration of submicron particles due to the formation of vortex acoustic flows in resonant gaps has been revealed.

The Limits of Fine Particle Ultrasonic Coagulation

This paper describes the studies conducted in order to identify the limits of ultrasonic exposure’s effect on the fine particle coagulation process. It has been established as a result of the studies that ultrasonic exposure with a sound pressure level of 160 dB is capable of ensuring coagulation of particles sized 2.5 µm with efficiency δ = 83%. An increase of the coagulation up to 13% is induced with generation of swirling flows. The suggested approach to increasing the coagulation efficiency owing to vortex-type flows between the radiating and reflecting surfaces ensures efficiency of coagulation δ = 96 %. The implementation of this approach has shown that with generation of vortex-type acoustic flows, it makes the most sense for a concentration of particles of 18×10−3 g/m3. Incremental efficiency at such concentrations amounts to 50%.

Effect of Ultrasonic Treatment on Solidification Quality of ESR Ingots

A novel electroslag furnace with the ultrasonic treatment was fabricated in this study. The effect of ultrasonic treatment on the compact density and segregation degree of alloys were studied. Results show that the distribution of carbon, silicon, manganese, chromium and phosphorus become uniform with increase of the ultrasonic power when the ultrasonic power is between 0 and 700 W. But when the ultrasonic power increases to 1,000 W, segregation of alloy elements increases instead. The reasonable ultrasonic power is favorable for improvement of compact density of electroslag remelting (ESR) ingots. When the ultrasonic power increases to 700 W from 0, compact density of ESR ingots increases to 0.9618 from 0.9479 and decreases to 0.9517 when the ultrasonic power increases to 1,000 W. This occurrence is attributed to the cavitation and acoustic flows effect of the ultrasonic which break off the dendritic crystal in the mushy zone and increase crystal nucleus. At the same time, the heat transfer and mass transfer are accelerated which make the distribution of temperature and alloying element more homogeneous. But the excessive ultrasonic power is not conducive to the improvement of solidification structure.