PSI - Issue 77

Nikola Čajová Kantová et al. / Procedia Structural Integrity 77 (2026) 170 – 176 Čajová Kantová et al./ St ructur al Integrity Procedia 00 (2026) 000 – 000

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Fig. 2. The created mesh of 4-tubular separator with the inserted screw construction for flow direction.

Two boundary conditions were established: the mass flow rate at the inlet and the pressure at the outlet. The mass flow rate, derived from the velocity measurements obtained via anemometer during the combustion of solid fuel, was determined to be 0.0356 kg/s. The outlet pressure, set in accordance with the STN EN 13240 standard, was -12 Pa (Backa et al., 2025; STN EN 13240, 2002). A two-phase model was utilized to simulate the motion of particulate matter within the flue gas. The airflow dynamics were governed by the Navier-Stokes equations. Lagrangian particle tracking techniques were employed to model particle motion. The SST turbulence model k-omega was applied for simulation. 3. Results and Discussion Compared to the ordinary tubular electrostatic precipitator, the 4-tubular precipitator has increased the collection area by up to 1.6 times. With the increased collection area, the efficiency of particle capture also increases. However, to ensure high efficiency, it is also necessary to ensure a uniform flow of flue gas with contained particles through all tubes. Therefore, the screw construction was placed into the 4-tubular separator with the aim to direct the flow of flue gases. Fig. 3 shows the velocity distribution in the cross-section of both models: with the screw construction and without it. The velocity range is from 0 to 2.6 m∙s−1 based on the highest reached velocity in this cross -section of the models. Based on the results, it can be concluded that flue gases flow non-uniformly when the screw construction was not included. After including this construction, it caused flue gases to flow more uniformly which has a good impact on the efficiency of the electrostatic precipitator. The numerical results indicated that the average velocities in the four tubes of the electrostatic precipitator without an inserted screw construction varied significantly. Tube 2 exhibited the highest average velocity of 1.157 m/s, while tube 1 had the lowest at 0.249 m/s, then tube 3 reached an average velocity of 1.025 m/s and tube 4 had an average velocity of 0.253 m/s. These findings suggest that construction for obtaining uniform flow is necessary. After including an inserted screw construction, the velocities in the tubes were numerically closer each other as follows: tube 1 with an average velocity of 0.605 m/s, tube 2 with an average velocity of 0.935 m/s, tube 3 with an average velocity of 1.032 m/s and tube 4 with an average velocity of 0.772 m/s. Fig. 4 shows the particle velocity in the model with the inserted screw construction. These particles form the second phase in a two-phase flue gas flow, mirroring the velocity of the flue gas. Fig. 4 confirms that the flue gas has been more uniform. The highest velocities were achieved when the flue gas passed through the screw construction.