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Old 08-24-2018, 06:46 PM   #71 (permalink)
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Originally Posted by freebeard View Post
I'm gathering parts for a 1Kw gravity vortex watermill. I've got a washing machine motor, a housing made from parts (a dog kennel and a ventilator!) and two outboard motor propellers to choose from (3-blade metal and 6-blade plastic). All I need now is a shaft to connect the propeller to the motor/generator and an optional extension tube that necks down from 14" to ~7".

Do you think it would be better to square the tips of the blades and put it in a duct, or leave the tips and put it below the end of the duct?
I don't know what I found humorous about your post as I haven't been drinking or anything, just didn't expect it.

I'm picturing something like the below.

Gravitation water vortex power plant

The gravitation water vortex power plant is a type of micro hydro vortex turbine system which is capable of converting energy in a moving fluid to rotational energy using a low hydraulic head of 0.7–3 metres (2 ft 4 in–9 ft 10 in). The technology is based on a round basin with a central drain. Above the drain the water forms a stable line vortex which drives a water turbine.

It was first patented by Greek-Australian Lawyer & Inventor Paul Kouris in 1996[1], who was searching for a way to harness the power inherent in a vortex.[dubious – discuss]

Later, Austrian Inventor Franz Zotlöterer created a similar turbine while attempting to find a way to aerate water without an external power source.[2]
My guess is that ducted systems are more efficient.

Ducted fan
A ducted fan is a propulsion arrangement whereby a mechanical fan, which is a type of propeller, is mounted within a cylindrical shroud or duct. The duct reduces losses in thrust from the tips of the props, and varying the cross-section of the duct allows the designer to advantageously affect the velocity and pressure of the airflow according to Bernoulli's principle. Ducted fan propulsion is used in aircraft, airships, airboats,[dubious – discuss] hovercraft and fan packs.[1]

Ducted fans normally have more and shorter blades than conventional propellers and thus can operate at higher rotational speeds.[dubious – discuss]


A pump-jet, hydrojet, or water jet is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller (axial-flow pump), a centrifugal pump, or a mixed flow pump which is a combination of both centrifugal and axial designs. The design also incorporates an intake to provide water to the pump and a nozzle to direct the flow of water out of the pump.[1]
Energy is going to squirt out the ends of the blade tips (right angles?) and will not be contained in the system if there is no containment duct. A bad thing in my opinion.

I'm just making this up as I go along, if anyone has direct experience please chime in. I've only messed with my hovercraft duct before.

EDIT: This looks to be pre-duct, not post duct or in-duct.
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