# Influence of Acoustic Streams on the Efficiency of Ultrasonic Particle Agglomeration
## 2 Materials and Methods  
### Test Bench  
To study the agglomeration process of 2.5 \(\upmu\)m particles and to conduct comparative studies in the presence of vortex flows and without them, a bench implementing ultrasonic agglomeration and subsequent capture of aggregated particles was used. The test bench consists of agglomeration chamber (Figure 1) and sequentially installed cyclone based on the design of VNIIOGAZ CN-15 with a capacity of 10 m\({}^{3}\)/h. The cyclone outlet tube is connected to the air handling unit. The developed and manufactured agglomeration chamber of the bench (RF Patent No. 2759506) is suitable for implementation of various conditions and modes of exposure to high-intensity ultrasonic vibrations due to the application of different types of ultrasonic  
Figure 1: Schematic diagram of the ultrasonic agglomeration chamber: 1—ultrasonic vibrating system; 2—piezoelectric transducer; 3—concentrator; 4—disk radiator; 5—reflector; 6—inlet tube; 7—polluted gas; 8—outgoing gas-dispersion flow (to cyclone); 9—aggregated particles; 10—outlet tubes; 11—amplitude distribution; 12—vortex flows; 13—housing; 14—radiator flange; \(\lambda_{G}\)—distance between radiator and reflector. transducers, and owing to the possible resonance amplification of vibrations by changing the distance between radiator and reflector [29]. Two ultrasonic oscillating systems (No. 1, Figure 1) with disk radiators (No. 4, Figure 1) of two different types creating uneven or uniform distribution of vibrations for ultrasonic impact with and without flow generation were used as a source of ultrasonic impact in the agglomeration chamber. A reflector (No. 5, Figure 1) with a centrally placed inlet tube (No. 6, Figure 1) is installed across the disk radiator. The process of particle aggregation in the agglomeration chamber takes the following course. The gas flow enters the tube (No. 6, Figure 1) installed in the center of the reflector (No. 5, Figure 1). After that, the gas-dispersion flow spreads uniformly from the central area to the periphery. In the process of propagation, the flow is affected by ultrasonic vibrations generated between the surfaces of radiator (No. 4, Figure 1) and the reflector (No. 5, Figure 1). The gas flow (No. 8, Figure 1) and aggregated particles (No. 9, Figure 1) are discharged through outlet tubes (No. 10, Figure 1). The design of the agglomeration chamber allows us to adjust the height of the reflector position to achieve fine-tuning of the resonance mode (standing wave mode in a gas medium). When the distance between the radiator and the reflector ensures the generation of a standing wave, the effectiveness of the treatment is increased by means of increasing the sound pressure level. The test bench was equipped with measuring and auxiliary equipment. A noise meter Ecofizika-110A (<<OKTAVA-ElektronDizayn>>, Moscow, Russia), with microphone--VMK-401 (<<Vibropribor>>, Yaroslavl, Russia) and microphone preamplifier R200-27 (<<OKTAVA-ElektronDizayn>>, Moscow, Russia) was used to measure the main parameter (i.e., sound pressure level). The TIPAS-1 (IPCET SB RAS, Biysk, Russia) aerosol dispersion characteristics measuring instrument, which enables monitoring the aerosol parameters, was used to measure the dispersion properties of the aerosol. TIPAS-1 consists of two units:  
1. The first unit implements the optical method of small-angle scattering (radiator, reflector) and is designed to measure micron aerosol particle sizes and concentrations in the range of 1-100 \(\upmu\)m and 0.009-8.0 g/m\({}^{3}\);
2. The second unit implements the optical spectral transparency method (radiator and reflector) and is designed to measure submicron aerosol particle sizes and concentrations in the range of 0.1-2 \(\upmu\)m and 0.009-8.0 g/m\({}^{3}\). Sampling to determine the mass concentration of particles was carried out at the inlet of the agglomeration chamber and at the outlet of the cyclone.