First, the mechanism of isolated capture
The fibrous layer filter material is composed of many single fibers. First, the trapping mechanism of single fibers is studied. When the dust-containing airflow flows around the fiber body, the interception effect, inertia effect, diffusion effect, electrostatic effect, and gravity effect occur, thereby trapping the dust particles.
- Inertial effect
When the dust particles move along the streamline close to the fiber body, the gas flows around, and the larger mass dust particles deviate from the streamline by the inertial force, move tangentially, and collide with the fiber to be trapped.
- Interception effect
When the dust particles move along the streamline close to the fiber body, most of the fine dust particles flow around with the airflow, and only the dust particles with a radius greater than or equal to the distance between the center of the dust particle and the fiber edge are caught by the fiber interception.
- Diffusion effect
The particles with a particle size of ≤0.1μm produce irregular Brownian diffusion under the action of the thermal movement of fluid molecules, leaving the streamline and being trapped by the fibers. For 0.1 μm particles, the diffusion distance can reach 17 μm per second at room temperature. The smaller the particle size and the higher the temperature of the dust-containing gas, the more obvious the diffusion benefit.
- Electrostatic effect
The dust particles or fibers are charged by friction induction or an external electric field. When the polarities of the two charges are opposite, under the action of the Coulomb force, the dust particles are attracted by the fibers and trapped.
- Gravity effect
When the particle size of the dust particles is larger, the mass is heavier, and the velocity of the airflow is lower, the dust particles are separated from the movement trajectory under the action of gravity, and the fiber surface is settled and collected.
In addition, there is the van der Waals effect of intermolecular attraction, the thermally induced migration effect caused by the temperature difference, and the concentration diffusion effect caused by a concentration difference.
The above various trapping effects are described by using single fibers as isolated trapping groups. In fact, the filtering function is a large number of fiber aggregates arranged in a certain organizational structure, and the fibers affect each other. At the same time, filtering. The process is usually not a single effect for publication, but multiple effects at the same time. The trapping effect of various trapping effects varies with the size of the dust particles and the level of the flow velocity.
It can be seen that for dust particles with a particle size greater than 1.0 μm, the inertial collision, gravity and interception effects are dominant, and for particle particles with a particle size less than 0.2 μm, the molecular diffusion and electrostatic effects are dominant; when the flow velocity is greater than 15 cm/s The inertial collision effect is strengthened. When the flow velocity is less than 5 cm/s, the effects of gravity, interception, and diffusion are obvious.