Fig. 8 Experimental apparatus
The air with the entrained droplets flowed through the separator which was placed 2.5 m downstream from the atomizing nozzle as shown in Fig. 9. The upper wall of the duct before and after the separator had holes in which a droplet trap was inserted for the measurement of the droplet size distribution and mass flow rate.
The microphotographs of water droplets and efficiency curves are shown in Fig. 10 and Fig. 11 respectively.
Fig. 9 Test section viewed from the upper side of duct
Fig. 10 microphotographs of water droplets
Fig. 11 separation efficiency
3. THE SEPARATOR BY COULOMB FORCE
3.1 Principle of separation
In Fig. 12, when the direct current voltage is applied to the positive pole (collecting pole) to be connected with an earthed line and the negative pole (discharge pole), getting to be the critical value, insulation is locally destroyed in air near the discharge pole and so-called corona discharge generates. The livelier this discharge becomes, the livelier the ionization of aerial molecule, too, becomes, and a lot of positive and negative ions occur. Positive ions are immediately neutralized by the discharge pole and negative ions run toward the collecting pole as shown in Fig. 12.
It is assumed that the collision among particles in fluid of the turbulent flow condition can be ignored and that the particles, which made negative ion in the electric charge move to the collecting pole according to the shortest course, like the radius of the cylinder.
Now, when the air entrained water droplets flow into such a powerful direct current electric field these droplets are instantaneously made negative at the electric charge. These charged droplets move toward the collecting pole by the Coulomb force and were collected on the surface of that pole while they receives the viscous drag of air. This Coulomb force is shown in the product of the amount of electric charge of droplet and the electric field intensity.
3.2 Equations of motion of a droplet
The equations of motion of a droplet in the test section as shown in Fig. 13 are given as foll
m・d2/dt2=f-m・g=0 (34)
