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Rim Driven Propellers

Discussion in 'Technical Discussion' started by brian eiland, Nov 16, 2005.

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  1. brian eiland

    brian eiland Senior Member

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    Another Alternative

    Abstract

    Rim driven thrusters with structurally integrated brushless PM motors are now an established technology with an increasing range of applications. In these thrusters, the stator of the motor is housed within the thruster duct, and the rotor forms a ring around the tips of the propeller. Such high pole number motors tend to be very thin radialy, have very small length to diameter ratios, and have relatively large airgaps to accommodate corrosion protection layers on the surfaces of the rotor and stator. The relatively large diameter stator laminations of such machines tend therefore to have very thin back of core and narrow teeth, which make them expensive and difficult to manufacture. This paper proposes an alternative potentially lower cost motor topology featuring a slotless stator whose laminations are manufactured from a single strip of steel that is edge wound into a spiral (like a “slinky” and then fitted over the windings that are preformed on the outside surface of a non-conducting former. The former is also part of the sealed housing that protects the stator from corrosion in seawater. The paper discusses the design optimisation of such a motor using analytical and finite element analysis (FEA), describes a demonstrator motor and reports experimental and FEA results.

    (had trouble posting rest of article with small file size allowed...will try later to decrease size of file)

    Attached Files:

  2. Codger

    Codger YF Wisdom Dept.

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    Perhaps someone can clear up a question that keeps coming back for me.
    Perimeter driven props being more efficient makes perfect sense to me.
    However, having sharp ended blades unconnected in the centre has me scratching my head. Wouldn't there be more flex and therefore loss of efficiency as the blades deformed forwards under load? Wouldn't having them connected in the centre make for one solid structure less prone to flex and fatigue?
  3. First Pericles

    First Pericles New Member

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    Exchangeable blades. :) See Brian's post #19.

    First Pericles
  4. Codger

    Codger YF Wisdom Dept.

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    The blades shown in post #15 are connected at the centre so it's being done both ways.
    Replaceable blades is a nice feature but is there a tradeoff in overall efficiency by not having them connected at the centre?
  5. Castlerock

    Castlerock Senior Member

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    I think that having the added strength of the center hub would reduse blade flex and pitch change. Then again if you could calculate the load and flex you could design in more pitch. Now if someone would make a composite Pod Drive with this system for yachts I can see it being much lighter that the Schottel and ABB units.
  6. Highlander

    Highlander New Member

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    Several advantages

    The first thing that popped out is that the blade design can use much less material- less drag. The point of highest velocity/load is at the rim where support is best. The last picture shows a plug connecting the blades- vibration control?

    The bearings are interesting too. By using water to generate a hydrodynamic film-the wear component can be less in steady state operation than in start-stop service like a thruster.

    The only drawback is the drag caused by the tube/motor.
    For commercial displacement use this has lots of promise.
    How do you think the drag compares to the IPS design?

    Carl
  7. Dan Evans

    Dan Evans Senior Member

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    I hope I am not getting too sidetracked here, but has anyone looked at putting these in a waterjet? I know that installing a waterjet with a rim drive means that the rim drive is now inside the hull so if it leaks its going to be a bad day... The drive is already in a tunnel so I dont see why it wouldnt be easy to adapt to a jet. I think it is a great idea not having a shaft turning in the water but I dont think it is a good idea to have the rim drive mounted under the hull. It is an expensive and probably sensitive piece of equipment.

    Dan
  8. Highlander

    Highlander New Member

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    Rim drive jet

    Sure it could work and work well.
    The downside is that every major component is the most expensive way.
    1- jet housing
    2- rim drive pod, could be removable from the jet housing for service.
    3- Variable frequency drive.

    All this stuff works great and has an unknown service life in a marine environment.

    Carl
  9. Dan Evans

    Dan Evans Senior Member

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    ...seems to be a common factor in this industry
  10. brian eiland

    brian eiland Senior Member

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    Rim-Drive Impeller for Jet Pump

    You might have a look thru some of these jet pump discussions, and note in particular I suggested such a 'rim drive impeller'

    http://www.yachtforums.com/forums/technical-discussion/4470-jet-drive-vs-prop-3.html
  11. Dan Evans

    Dan Evans Senior Member

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    Sorry Brian, I wasn't trying to steal your thunder or anything. I had forgotten that you mentioned this in the prop v. jet thread.

    Dan
  12. Highlander

    Highlander New Member

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    Center Plug

    The plug connecting all the vanes may improve efficiency.
    The hole in the center (in the version with out the plug) can leak pressure in a similar way that too much tip clearance in a jet design does.

    Carl
  13. Dan Evans

    Dan Evans Senior Member

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    Research and development

    I think it is time Yachtforums opened up a R&D department;)

    Dan
  14. K1W1

    K1W1 Senior Member

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    Hi,

    I would not poo poo all of this straight away.

    From what I understand a very high profile mega yacht builder will be using this technology for it's thrusters very soon.
  15. brian eiland

    brian eiland Senior Member

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    Tidal Flow Rim Drive Generator

    Your magnetic turbine posting came to mine when I was looking for rim-drive propulsion concepts operated in reverse....as generators of electrical power in high tidal/current zones.

    I ran across this interesting site:
    Tidal Flow Generator
    http://www.openhydro.com/home.html
  16. Dan Evans

    Dan Evans Senior Member

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    K1W1,
    Any hints as to who?

    Dan
  17. brian eiland

    brian eiland Senior Member

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    Panamax super-ketch

    To be installed on the new Panamax 'super-ketch'

    "It’s not the only movable appendage below the waterline. Like an increasing number of new yachts, the Panamax ketch will take advantage of the advances in diesel electric power generation , in this case designed by MR Fertigung-Technologie GmbH, a German company based in Rostock. This allows the use of two retractable, electrically driven propellers developed by the award-winning Dutch company Van der Velden. By swinging or retracting the props into the hull the yacht's underbody will become perfectly flush when sailing, further enhancing -performance

    Instead of using a conventional engine for propulsion, the Panamax will befitted with a number of generating sets (the likelihood is four) which, as Erik Wassen put it: “Will provide a power sharing opportunity with a priority system.”

    In other words the generating sets will automatically deliver power to the numerous systems precisely when they want it and at sufficient levels, whether it be the hydraulic pumps for the big winch packages, domestic power to run the hotel systems or power for propulsion. Heavy battery banks are limited to emergency sets.

    The generating system can devote all its energy to the retractable hubless props—the blades of the propellers are set on the inner surface of the circular units, which house the electric motors themselves instead of on a central hub."


    ...more
    http://www.ybw.com/yw/blog/20070028174123blog_david_glenn.html

    http://www.balticyachts.fi/documents/Pressrelease.pdf
  18. brian eiland

    brian eiland Senior Member

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    Brunvoll News

    RIM DRIVEN THRUSTERS
    The development project of Rim Driven Thrusters continues. Design, production and testing of our prototype of 100 kW since 2003, has brought us
    invaluable experience to use as we go further with our development. We also completed additional tests on this prototype in 2006.

    The first of our larger units is scheduled to be delivered in 2007 for an offshore support vessel. This is an 810 kW tunnel thruster and is quite a departure from the first prototype.

    To supplement experimental data for this type of design, adcanced design tools are applied. One of these is Computational Fluid Dynamics (CFD). This is a tool with direct integration with our 3D CAD/CAE tools and the flow calculations can include viscosity effects, turbulent flow and cavitation.
  19. Marmot

    Marmot Senior Member

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    They put that one on a support boat for the North Sea but it seems to be the only one in existence and Brunvoll doesn't even acknowledge the product on their website anymore. I wonder what the story is?

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