Numerical Simulation of Acoustic Agglomeration and Experimental Verification

Tiwary, R.; Reethof, G.

doi:10.1115/1.3269412

Cited by 38 publications

(12 citation statements)

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“…Tiwary and Reethof 19) found that particles of initial diameter of 5 mm grew faster when exposed to acoustic fields of higher sound pressure levels. The sound frequency and pressure levels tested were 2000 Hz and 140-160 dB, respectively.…”

Section: Explanation On the Effects Of Sound Waves On Thementioning

confidence: 99%

Acoustically Controlled Behavior of Dust Particles in High Temperature Gas Atmosphere

et al. 2004

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The present study focuses on the behavior of dust particles in a high temperature gas atmosphere exposed to powerful standing sound waves. Six resonance frequencies within the range of 0-1 000 Hz were chosen for the experiments because they provide high values of sound pressure in the working space. The particles (0.1ϳ80 mm) were produced by evaporating a sample of Zn at temperature about 1 173 K under Ar atmosphere, cooling the Zn vapor and transferring the formed particles to a sonoprocessing chamber for sound exposure. The particle samples were taken at the upper place of the chamber, and the samples were analyzed for size distribution and number density in the gas phase.Application of sound waves is found to result in enlargement of particles (acoustic agglomeration), and reduction of their number density and concentration in the gas. The experiments showed that the particle agglomeration is enhanced as the sound pressure amplitude increases, while the effect of sound frequency played a smaller role in the particle behavior. In the frequency range tested, the most evident agglomeration effect was obtained at frequencies of 210 and 991 Hz at which a 50 % increase in particle size and 60 % decrease of particle number density in exhaust gas can be achieved in comparison to the corresponding values without sound application. The experimental results are discussed on the basis of the orthokinetic mechanism in relation to the acoustically forced oscillation and collision between the differently sized particles.KEY WORDS: powerful sound wave; sound frequency; sound pressure; high temperature exhaust gas; dust particles; acoustic agglomeration; particle number density; particle weight concentration.

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Section: Explanation On the Effects Of Sound Waves On Thementioning

confidence: 99%

Acoustically Controlled Behavior of Dust Particles in High Temperature Gas Atmosphere

et al. 2004

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“…Hoffmann [5] and Dong et al [6] used Dianov's analytical solution as the major refill mechanism. As mentioned before, this solution is limited for particles aligned along the direction of the sound wave, so in their studies small particles enter the Figure 13 Schematics of the refill mechanisms proposed by Tiwary and Reethof [13,20] (a), Hoffmann [5] and Dong et al [6] (b), and in this paper (c).…”

Section: Discussion Of the Computational Resultsmentioning

confidence: 99%

“…Many kinds of mechanisms, such as Brownian motion of aerosols, turbulent gas motion, and gravitational effect of aerosols, have been proposed as the refill mechanisms. However, the refill factor based on these mechanisms gives agglomeration rates several orders of magnitude lower than the experimentally observed rates [3,13,20]. Since the acoustic wake effect was revealed to play a significant role with micron-sized particles, some researchers [5,6,8,13,20] tried to use it as the major mechanism to explain the rapid refilling in acoustic agglomeration.…”

Section: Discussion Of the Computational Resultsmentioning

confidence: 99%

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Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

et al. 2012

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We numerically simulate the hydrodynamic interaction of aerosol particles due to the acoustic wake effect under the Oseen flow condition. Attraction is found for two nearby particles with an orientation angle of 0 to 50° with respect to the acoustic field, and weak repulsion is found outside this range. Good agreement is obtained between the numerical results and experiments in the literature. We study the influence of particle size, sound wave frequency and the particle separation. The result shows that the acoustic wake effect plays a significant role in acoustic agglomeration. It could be either the major agglomeration mechanism of monodisperse aerosols or the major refill mechanism for polydisperse aerosols to supplement orthokinetic interaction. Acoustic agglomeration is a process in which intense sound waves produce relative motions and collisions among aerosol particles. It can significantly shift the particle size distribution of an aerosol from smaller to larger sizes in a short time of the order of 1 s. Acoustic agglomeration has potential use in air pollution control as an aerosol preconditioning process to enhance the performance of conventional particle filtering devices, which are inefficient for retaining particles smaller than 2.5 m [1]. Acoustic agglomeration is governed by complex interaction mechanisms. The most significant ones are orthokinetic and hydrodynamic interactions [2]. Orthokinetic interaction is the most obvious mechanism. Particles with different sizes are entrained differently into the oscillating motion of the medium because of the differences in particle inertia. The relative motion leads to the approach and collision between particles. In one acoustic cycle, each larger particle sweeps a certain volume by its motion relative to smaller particles, and collects all the smaller particles in it. This volume is defined as the agglomeration volume. The mechanism of orthokinetic interaction was well summarized by Mednikov [3] and improved by other researchers [4][5][6]. Nevertheless, this mechanism cannot explain agglomeration of monodisperse aerosols or the way in which the agglomeration volume is refilled once it is emptied after one cycle.Hydrodynamic mechanisms are those which produce particle interactions through the surrounding medium because of hydrodynamic forces and the asymmetry of the flow field around the particle [1]. These mechanisms are generally considered to be the main acoustic agglomeration mechanisms for monodisperse aerosols because they are also active for same-sized particles [7]. Hydrodynamic mechanisms mainly include mutual radiation pressure and the acoustic wake effect [5,6,8,9]. The mutual radiation pressure is the effect due to the nonlinear interactions produced between the particle scattering wave and the incident field. However, so far, there is still no experiment to confirm this effect as a cause of agglomeration, and theoretical studies show that the mutual radiation pressure is much less important than the acoustic wake effect in acoustic agglome...

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“…Tiwary [9] studied ash-laden gas with the sound intensity of 170dB and frequency of 1000-3500 Hz by acoustic agglomeration. And the best sound intensity is 150-160dB and the frequency is 1-2kHz.…”

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confidence: 99%

The Study on the Removal of Ultrafine Particles

Cheng¹,

Cai²,

Zhao³

et al. 2015

Proceedings of the 3rd International Conference on Advances in Energy and Environmental Science 2015

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Ultrafine particles PM2.5 produced during combustion is the main source of environment pollution and has raised the widespread concern around the world. There are several studies about acoustic agglomeration currently, but its removal efficiency is not high, so the scholars have proposed to join the seed particles on the basis of acoustic agglomeration, to increase the removal efficiency. In this paper, we propose to join seed particles with ultrasonic atomization and analyze the advantages of using ultrasonic atomization. This is another effective method to improve the removal efficiency.

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Numerical Simulation of Acoustic Agglomeration and Experimental Verification

Cited by 38 publications

References 0 publications

Acoustically Controlled Behavior of Dust Particles in High Temperature Gas Atmosphere

Acoustically Controlled Behavior of Dust Particles in High Temperature Gas Atmosphere

Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

The Study on the Removal of Ultrafine Particles

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