Cavitating vortex flow generated by a stationary volute casing and a rotating centrifugal impeller

Three devices for treating contaminated water using a cavitating vortex have been developed and tested. The first device uses stationary twin volute casings to generate cavitating vortices. Observation of the collisions among the opposing counter-rotating vortices revealed that their end portions whirl, that the vortices never collide head-on, and that they eventually separate into several small vortex strings. The second device is simply half of the first device. A single volute casing is used, and the vortex flow collides with a solid wall. The third device uses a centrifugal impeller and a circular swirling chamber to generate a cavitating vortex. A high absolute circumferential velocity at the impeller exit induces a strong vortex in the chamber. The vortex cavitation is smoother than in the first two devices, and the end portion of the vortex whirls in the same manner as that generated in the first device. Installation of an orifice at the exit of the swirling chamber reduced the diameter of the flow passage and thereby accelerated the rotating and axial flow velocities. Testing showed that this third device produces fine, even-sized cavitation bubbles that are uniformly distributed in the collision chamber, which is the ideal condition for water treatment.