Free vortex cyclones are used in various industrial fields because of their high performance, simple structure and low equipment investment.
It is very important to estimate a pressure loss of the cyclone to design a process.
Cyclone pressure loss has been studied from various viewpoints in the past. However, most studies left the effect of the centrifugal force out of consideration.
In this paper, an inner flow of a cyclone was visualized from the deposition pattern of tracer particles on the cyclone wall. Then, a coiled tube model was proposed to estimate the pressure loss of a cyclone, and its plausibility was tested through its comparison with experimental pressure loss.
It was found that a rotation number of the inner flow in a cyclone cylindrical part doesn't depend on cyclone inlet velocities. A coiled tube model was useful to estimate the pressure loss of the cyclone. To estimate a flow affected by a centrifugal force, it is more effective to think of it as a flow in a coiled tube rather than in a straight tube.

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The deposition of aerosol particles and pressure loss in a coiled tube has been studied assuming it to be a bent tube which is used in various industrial fields.
Theoretical expressions for particle deposition velocity have been obtained by taking account of turbulent diffusion, gravitational and centrifugal settling, simultaneously. The deposition velocity decreases with air velocity in the laminar flow region. It has a minimum in the transient region between the laminar and turbulent flow regions. In the turbulent region, it increases sharply because of the strong centrifugal force effect, but the effect of turbulent diffusion depends upon the combination of tube diameter and coil diameter of tube, i. e., turbulent diffusion acts positively for larger D_c/D but negatively for smaller D_c/D. It agreed fairly well with experimental deposition velocity.
Pressure loss of a coiled tube with D_c/D ranging from 6.9 to 80 is measured. As a result, it is found that the smaller is D_c/D, the larger the friction factor is, and the larger the transient Reynolds number from laminar to turbulent flow region is, the smaller is D_c/D because of the strong centrifugal effect. Then, based on the experimental results, approximate expressions for that have been obtained and shown to be valid for the laminar and turbulent flow regions, respectively.

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Sub-micron particles may not easily deposit themselves on the ground but penetrate into our respiratory tract together with contaminated gases. The performance of the electrostatic granular bed filter is investigated in order to reduce the sub-micron particle emission from a coal fired power station.
The collection efficiency of the electrostatic granular bed filter increases with increase in the applied voltage and decrease of the filtration velocity. The sphere particles are more suitable than the non-sphere particles as the bed particles. Because the packing structure of the spherical particles very easily becomes uniform. The minimum fractional collection efficiency appears in the range of 0.1-1μm, but it is still higher than the efficiency attained by conventional electrostatic precipitators.

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Air filters (ULPA, HEPA) are used to remove fine particles from the air in clean rooms, but recently air contamination with minute quantities of gases or mist, etc. are a threat to the safety of workers and have become a problem. The conventional air filteration method is not effective to solve this problem.
In order to overcome this difficulty, we have developed a new air cleaning system which removes fine particles and gases simultaneously by heterogeneous nucleation and also has an air conditioning function. In this study, we have analyzed the nuclear condensation phenomena theoretically, verified the performance of test equipment fabricated by us, and confirmed that the system removes both fine particles and gases at a high efficiency of more than 99.8%.

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A highly charged particle of a few micrometers in radius is strongly vibrated to induce a secondary flow around the particle. The flow brings submicron particles to the space around the charged particle where the electrostatic gradient force becomes strong enough to adsorb the submicron particles on the charged particle. The experimental result shows that the electostatic scavenging rate is greatly enhanced by the hydrodynamic effect.

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The dust cleaning mechanism of a pulse jet-type bag filter was experimentally investigated using various types of plane fabric filters. The time change of pressures up and downstream of the filter, and the displacements of the filter and dust surface were measured in order to relate their characteristics to the dust cleaning. Using a high speed video camera, the dust cleaning process was observed.
As a result, the rapid inversion of pressures up and downstream of the filter and its inflation are found to be essential to enhance the dust removal as well as the dust detachability of the filter surface. The instance at which the dust layer separates from the filter surface was related to the difference between the displacements of the filter and the dust surface. It is revealed that the cracking of the dust cake takes place after the separation. The size of separated dust fragments seems to be larger for higher dust detachability, and a schematic model for the dust cleaning process is proposed based on these results.

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