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Bladeless turbine for lift?

  1. Feb 10, 2016 #1
    Friction Drag Lift.png I was researching Telsa turbines and was intrigued by the bladeless design where gases drag on the discs by means of viscosity and the surface layer adherence. As the discs are rotated by the gas, the gas slows down and exits through the center of the disc.

    I was wondering if we had two shafts with multiple discs on it will small air gaps and rotated them in opposite directions if we could 'drag' the air down to induce lift as the device would interact with the outside air. We could counteract the side of the disc moving air upwards with a shroud. Imagine the left shaft is rotating counter-clockwise and the right shaft is rotating clockwise. The 'top view' shows two systems working together.

    My question is, at high rotation, would this type of device create lift?
     
    Last edited: Feb 10, 2016
  2. jcsd
  3. Feb 10, 2016 #2
    If you are creating a downdraft by any means at all, the result will be a corresponding opposite force upwards (lift).
    I don't see how this setup would be particularly efficient though.
    You could turn an ordinary electric fan on it's side so it blows air downwards and generate some amount of lift.
     
  4. Feb 10, 2016 #3
    Rootone,

    Thank you for your insight. I don't believe it would be particularly efficient either, but I thought it would be interesting to explore as it would be fairly cheap to test/build and seems to be unique. If one were to test this, what would be a good material to 'grab' the air with? Styrofoam?
     
  5. Feb 10, 2016 #4
    Well as you are only experimenting with an idea there isn't a recommended material for building device like this.
    If the plan is to generate enough lift so that it can actually take off then something very light is an obvious choice.
    However you'll have to factor in the weight of whatever engine is driving the shaft and it's fuel, (or other power supply)
     
  6. Feb 11, 2016 #5
    Boundary Layer Lift (Friction Drag Lift).png
    Hopefully that is the plan, but I'm not sure it will create enough lift to take off. I agree with using something very light. I think by using discs as thin as possible and spaced closely will increase the surface area, but the weight may go up. I'm not sure. As it may work with multiple fluid types, I may do some testing it water as well. I think I'll build a test model with CDs as the discs on a shaft with ABS pipe as the outer shroud and see how well it would work and see how well it compares to other devices.

    I was also thinking of reversing the shroud, as it seems the inter-meshing of the CDs on both shafts working on the fluid in one direction (which ever direction the discs are spinning) with the dragging in the rotational direction loosely cancelled out in the overlap region.

    I'll be back with an update soon! I've uploaded what I think would be a more suitable design.
     
    Last edited: Feb 11, 2016
  7. Feb 12, 2016 #6

    JBA

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    I did a Tesla turbine principle based automotive turbine design as a senior year engineering design project many decades ago; and, based upon the gas flow study in that project, there is a flow dynamics principal that I anticipate will be a problem in applying the Tesla disc in your device.
    One of the basic fluid flow principles taken advantage of in Tesla's edge tangent inflow and center exhaust design is what is known in Computational Flow Analysis as the natural source - sink vortex flow pattern of fluid dynamic that drives a radial vortex flow from the disc edge to its center. This natural flow tendency is one factor that gives the Tesla turbine its high efficiency. (PS Tesla's genius went far beyond electricity and I am convinced he was well aware of how this flow principal would contribute to his design.)
    What you are trying to do is draw air into the edge of the disc set for a partial rotation and then eject it from that edge at a separate bottom tangent point where the two discs diverge. Due to the natural fluid vortex tendency, the air is actually going to try to continue its vortex flow around the discs (assisted by the friction of the discs as well) to the point where the top where discs converge; and, thereby create a high pressure region at that top point that will counteract the inflow of additional external incoming air from that region and potentially make your device a very inefficient lift generator.
     
  8. Feb 13, 2016 #7
    That's a very good point JBA. I also wonder if there would be a slightly lower pressure region at the bottom point where the discs diverge that creates a low pressure region that would affect the outflow as well (even with the bottom shrouds). Do you think a more efficient approach would be to simply have a Tesla turbine running in reverse so instead of the discs gaining energy from the flow and the flow exiting the center exhaust, have the discs provide energy to the flow and draw from the center (instead of the edge of the disc)?

    Thank you for providing some information about your senior engineering project, I appreciate the assistance!

    Boundary Layer Lift (Friction Drag Lift 2).png
     
  9. Feb 13, 2016 #8

    JBA

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    This configuration is basically the equivalent of a centrifugal compressor with stacked discs and no blades. It may create a pressure differential but a standard bladed centrifugal compressor with blades will be much more efficient at collecting and propelling air to its surrounding shroud.

    Because of your interest in the Tesla turbine, just one note about your above sketch, and this a detail that does not come to play until a detailed design of the Tesla concept is investigated. Your illustration shows the same inside diameter for every disc in the set; whereas, the top disc hole size must be large enough to pass the air required for all three discs and then the second disc hole can be reduced since it only has to pass the volumes below it and etc with the third disc. This can be a minor efficiency issue with only two or three discs; but, it becomes an significant issue for stacks with significantly more discs. At some point on a standard Tesla turbine design it becomes more efficient to exhaust through both sides of the case rather than just one side so as to minimize the maximum required exhaust hole size and maximize the flat clean rotating disc face area on final exhaust side disc in the set. There are a couple more details for an effective disc design that are not generally known that also required.
     
  10. Feb 13, 2016 #9
    JBA, good points again. It seems there is a lot more at play here to investigate and consider than I initially thought (as is with most things!). I will definitely consider these points when thinking of new designs. I can't thank you enough for taking the time to explain the information in such an understandable way.
     
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