# Influence of Acoustic Streams on the Efficiency of Ultrasonic Particle Agglomeration
## 3 Results
### Determining the Optimum Gas Flow Rate  
At the next stage, the gas-dispersion flow rate, at which the maximum efficiency of particle capture is ensured, both with and without acoustic impact was determined. The studies were conducted under the following conditions: the sound pressure level was 165 dB; and initial mass concentration \(N_{inlet}\) = 2 \(\times\) 10\({}^{-2}\) g/m\({}^{3}\). The gas flow rate varied from 2.5 to 10 m\({}^{3}\)/h. Microtalc Jetfine T1 CA with particle diameter d\({}_{50}\) = 1 \(\mu\)m, d\({}_{95}\) = 3 \(\mu\)m was used as a dispersed material in the research. The bulk density of microtalc is 0.9 g/cm\({}^{3}\); the true density is 2.8 g/cm\({}^{3}\). The studies were carried out at an air temperature of 22 degrees (the temperature was measured at the chamber exit and did not change during the experiments; the radiators were thermostatted) and a relative humidity of 35%. During the research, it was established that the protrusions and depressions of the stepped disk radiator create disturbances in the gas-dispersed flow, therefore the influence of the created disturbances on the efficiency of particle collection was determined. Therefore, a control experiment (without ultrasonic influence) was carried out using both types of radiators (the radiators were not excited). Figure 8 shows the dependence of particle capture efficiency on gas flow rate and the dependence of the particle size at the outlet of the agglomeration chamber on the flow rate. The dependence of the efficiency of particle collection on the velocity of the gas-dispersed flow is extreme. The presence of the extremum is due to the mutually opposite dependence of the size of the formed particle agglomerates and the efficiency of particle collection in the cyclone on the air flow speed. As the flow speed increases, the efficiency of the cyclone increases due to an increase in the centrifugal force acting on the particles in the cyclone (Figure 8A). However, at the same time, the size of the aggregates formed in the agglomeration chamber decreases due to a decrease in the residence time of the particles in the ultrasonic field (Figure 8B). This leads to a limitation in the growth of the efficiency of the agglomeration chamber--cyclone system. Figure 8: _Cont._  
It follow form the obtained curves that the best gas flow rate, at which the maximum capture efficiency is provided, is 6.2 m\({}^{3}\)/h both when using flat and step disk radiator. However, without ultrasonic impact, the optimum flow rate was 8-10 m\({}^{3}\)/h, which corresponds to the optimum flow rate for a cyclone. It has been established that the vortices formed when installing a stepped disk do not affect the agglomeration of particles. The obtained values of capture efficiency are presented in Table 2.  
As can be seen from the table, the difference in the collection efficiency values does not exceed the measurement error. Thus, it was found that without ultrasonic exposure, the type of radiator does not affect the collection efficiency. The results obtained made it possible to ignore the influence of the disk stages on the gas flow velocity field. Therefore, for the case without ultrasonic exposure, only one graph is shown, based on average efficiency values for both types of disks. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Disk Transducer Type** & **Flat Radiator** &
\begin{tabular}{c} **Step-Function** \\ **Radiator** \\ \end{tabular} & **Average** & \(\Delta\) \\ \hline
**Flow Rate, m\({}^{3}\)/h,** & & **Capture Efficiency, \%** & \\ \hline
2.5 & 15.2 & 14.8 & 15 & 0.4 \\
5 & 40.5 & 41.5 & 41 & \(-1\) \\
6.2 & 47.5 & 48.5 & 48 & \(-1\) \\
7.5 & 51 & 51 & 51 & 0 \\
10 & 52.5 & 51.5 & 52 & \(1\) \\
12.5 & 43.5 & 44.5 & 44 & \(-1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Capture efficiency without ultrasound.