A Picture is Worth a Thousand Words

This is fascinating. A rim driven prop. Because it's not driven by a shaft to the center, the designers could do anything they wanted with the hub and blade roots. You might expect a minimal hub to tie the blades together, but no. Apparently the blades contribute so little thrust at their inner area, better to simply leave them off.

 

I knew a jet engine engineer who worked for Prat Whitney. He told me about turbines that ran with multiple shafts inside each other to spin successive turbines. Apparently, there's a limit to the number of shafts that could be fit inside each other to turn successive blades. I imagine this hubless concept could really open up the the limitations in design.

 

So how do you get the external ring and its workings out of the way of business ? How would it be actually fitted to a boat ? Inside a circular duct ? I am confused by it

 

I'd like to see bench test performance data on this and how it compares to a conventional prop in a duct.

 

This was my thought as well. I looked at the photo and pictured the "ring" mounted upside down, the blue base being attached to the bottom of the hull. The "ring" could be fared for efficiency I suppose. I wonder though. We hit a lot of debris out on the water, sticks and branches up to logs, garbage and sometimes ground the boat. Those blades look kinda delicate compared to that chunk of bronze that's currently pushing me around. Still, there might be a way to protect the vanes.....

 

Like this?

 

That is a shaft drive ducted prop, how is the annular disc rotated, in the new idea ?

 

Exactly as it is in the first image. I know what that is. The kort nozzle is not particularly different in proportion. It has a massive connection to the hull. In this case for steering. But as far as the rim driven prop goes, compared to this extremely common arrangement, it has far less drag, and far less vulnerability than the shaft driven prop in the kort nozzle.

 

-Will

 

Seems like a lot of seal area involved

 

Is it designed for boats?
At a guess it would look to be more suitable to move fluids through pipework.

 

If Voith is engaged in this, it will be a possible way for Yachts.
Voith Inline Thruster & Voith Inline Propulsor | Voith https://voith.com/corp-en/drives-transmissions/voith-inline-thruster-propulsor.html

Edit: pic added

 

Imagine if you were to arrange a series of these thrusters in a tube where each was turning in the reverse direction to its neighbors and they turned progressively faster along the tube.

-Will

 

The most interesting aspect to me, is how the blades don't meet in the middle.

 

I have personal knowledge that this concept was explored about 35 years ago when it was first (as far as I know) proposed. Yes, the blades shouldn't meet in the middle. Yes, it has extensive maintenance and material issues. No, it is not a Kort Nozzle.