Hubless Rim Driven Propeller

Discussion in 'Boat Design' started by ascial, Feb 25, 2022.

  1. ascial
    Joined: Feb 2022
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    ascial New Member

    Hey everyone!

    I am a Master Student and I started to write the Master's Thesis about hubless Rim Driven Propeller (RDP) but I have difficulty to find hubless RDP CAD design because as you know, hubless RDP is new technology and it can be hard to draw or find its CAD design. I do not know where I start. How did you solve this problem, how can I crate hubless RDP CAD design?

    Thank you in advance.
     
  2. gonzo
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    gonzo Senior Member

    Is your thesis about the design process or an analysis of existing designs? In general the designs are proprietary and companies guard their secrets carefully; particularly with new technology. It is unlikely you will get information from them. All I have seen online are simple diagrams to explain the basic technology. However, if all you need is an approximate representation, that should not be too hard.
     
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  3. ascial
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    ascial New Member

    Hey Gonzo!

    Actually, I am interested in analysis of existing design but I could not started the CFD analysis because of lack of the CAD design of hubless RDP. I do not know where I start.
     
  4. baeckmo
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    baeckmo Hydrodynamics

    In order to make a meaningful simulation, you have to understand the basics of the device you study, otherwise you are just performing a button-pressing theatre. It includes an understanding of the design process, including the tools used, be it a drawing on a napkin or a complete 3d model. Now, as Gonzo said, you will have difficulties in finding someone acting on the commercial scene who is willing to open their archives for you and present a 3d model for free.

    I suggest that you make a rough design yourself, based on a hypothetical case with power and velocity given, maybe also operating depth (for cavitation control) and possible maximum available diameter. From there you should be able to make a simplified model for the CFD simulation (if you are up for a Master's thesis you should have basic skills in the use of CAD programme anyway). You might even start with the definition of a disc loading, as expressed by the circulation variation over the radius. That would give an idea of what is possible and what is not with a hubless rotor.
     
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  5. jehardiman
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    jehardiman Senior Member

    If this is a Master's, what is your BE in? I'd start there.
     
  6. Kayakmarathon
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    Kayakmarathon Junior Member

  7. ascial
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    ascial New Member

  8. jehardiman
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    jehardiman Senior Member

    Propeller design is a hard row to hoe, there are so many pitfalls for the under-informed. Hubless rim drives are even more strange. Good luck.
     
  9. gonzo
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    gonzo Senior Member

    I don't think there is enough independent experimental data available. All I find are advertising claims that their design is superior. I think this topic is not the best for a Master's thesis. Are you focused on propellers or do you still have a choice?
     
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  10. jehardiman
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    jehardiman Senior Member

    I know all the US Navy hub-less rim drive work from the 1980's and 90's is not out there. Not to say that it hasn't been shared in appropriate channels. Still there is other work out there, just not a lot on the details. Hub-less is the real hard part, several marketed designs proving to be operational failures.

    Exciting New EPS Thruster (& Propulsion) https://www.boatdesign.net/threads/exciting-new-eps-thruster-propulsion.9432/
     
  11. BlueBell
    Joined: May 2017
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    BlueBell . . . . .

    Ascial,

    Welcome to the Forum.

    Why?
    There are much more practical aspects of propeller design to study,
    unless you can pick up on where others left off concluding
    further research is needed to fully understand what's going on.
    RDP is not new technology.
    My understanding is minimizing hub size matters not,
    in some cases detracting from performance when minimized,
    while increasing performance when enlarged!
    Perhaps that's why there's little literature available...
    OR
    Expand your thesis looking at how hub size influences prop performance.
    OR
    How engine exhaust venting through hubs influences prop performance.
    OR
    You could likely do an entire paper just analysing hub size and shape
    at applicable RPM's and disk loads.

    Searching on this forum (top right-hand corner above) may not give you the answers
    or direction you seek but you may find links that are insightful.

    Let us know the outcome please.
    Good luck.
     
  12. gonzo
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    gonzo Senior Member

    The topic of hubless propellers covers too many topics. It is also often confused with rim-drive technology. In fact, some rim-drive propellers have a small hub. Others have blades that do not connect in the center. I agree with Blue Bell that you need to narrow the scope; particularly for a Master's thesis. You could approach it from a different way. For example, analyze the power losses introduced by the different hubs. That is a subject with extensive available data. You can then introduce the hubless rim-drive technology as a possible improvement. In a thesis, that is indicated as "next steps" or "recommendation for future study". It means that you present the background for you or others to further the investigation.
     
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  13. BlueBell
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    BlueBell . . . . .

    Ya, what he said. Brilliant.
     
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  14. CocoonCruisers
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    CocoonCruisers Junior Member

    On the CAD side Caeses or the Nemo plugin for Rhino/Grasshopper have propeller tools.
    From there you could just go about it subtractively with deletes and booleans, kicking out the hub, shortening the blade roots.
    And then stick it in a nozzle.

    But as the others pointed out the hard part will certainly be elsewhere: understanding of propeller design, scope, validation data..
     

  15. Will Gilmore
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    Will Gilmore Senior Member

    I find rim driven propellers very interesting. I knew a fellow who use to design jet engines for Pratt & Whitney. He described counter rotating propellers inside the engine and shafts within shafts within shafts, but there was a limitation to the number of shafts they could practically build for counter rotation. I always thought rim driven rotation would open up that limit.

    Perhaps a good focus of your thesis could be to take a well documented propeller design and modify it with an added rim, and remove the hub. Then do a comparison between the results.

    Take the traditional propeller and show its measurements.

    Add a rim and measure its performance.

    Remove the hub and measure the changes.

    -Will
     
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