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PVC and Steel Blades

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  • zedhead@juno.com
    Hey, As soon of you may know from a previous posting, I and three classmates are currently working on developing a low-cost, durable, locally constructable
    Message 1 of 2 , Apr 1 2:13 AM
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      Hey,

      As soon of you may know from a previous posting, I and three classmates are
      currently working on developing a low-cost, durable, locally constructable
      Darrieus type water turbine for use in rural sub-Saharan Africa. We have chosen
      the Darrieus turbine (Or possibly the slightly more complex Gorlov helical
      turbine) because it can be used in streams with heavy sediment load and variable
      heights. No civil works are necessary as we are planning on attaching this
      turbine to a raft system that will also contain a generator. We are planning on
      using DC current and running a pump / mill / battery bank on shore in a small
      power house.

      Currently, we are looking at designing the blades for the turbine. Most turbines
      now are constructed using expensive, unavailable techniques, such as extrusion
      or composites. We have a limited set of materials and machining techniques that
      can be used to make these blades.

      What I am currently experimenting with is a turbine blade constructed as
      follows:

      PROFILE: NACA 0020
      TIP TO TAIL LENGTH (not chord): 6"
      HEIGHT: 30"

      The blade will be constructed by placing three different PVC (or possibly steel)
      pipes along the center axis of the blade. The first pipe will be 1" in
      diameter, the second 1.25", and the pipe in the tail will be 0.5". A
      sheet of 20 gauge stainless steel will be wrapped around these pipes (once they
      are properly placed to give the correct hydrofoil shape) and pop riveted at the
      end. The sheet will also be pop riveted (using countersink rivets) to the pipes
      themselves. When attached to the holder plates at the top and the bottom, the
      blade will be welded to the plates to make the interior waterproof. The PVC
      pipes themselves will extend through holes made in the plate so that they can
      add structural support to the system. Three blades will be arranged on a 40 in
      diameter holder plate at 7-9 degree angles of attack. A stainless steel rod will
      be used as the turbine shaft to join the turbine with the raft and generator.

      QUESTIONS I HAVE:
      1) Has anyone tried / seen anything similar to this before? I know ribs have
      been used in the tip to tail direction, but this ribbing system seemed to not
      have been used.

      2) How would I calculate the bending / buckling of the blade's center? Would I
      just need to consider the PVC pipe and find how it would bend? How would I model
      the system?

      3) Is there some sort of waterproof coating that could be used over the steel
      plate to further prevent leakages?

      4) How will the higher weight of the steel (When compared to composites) play
      into the system dynamics?

      5) Any questions or comments? I really am looking to get feedback on this design
      and also suggestions about alternate designs.

      Thanks for all your help!


      Matt Zedler
      MIT Class of 2007
      Mechanical Engineering
      (804) 814-7197
      mzedler@...

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    • dimitar partenov
      Hi, My name is Dimitar, In my opinion this is not so good design. For small power you can use wood blades cover with epoxy resine with glass ...
      Message 2 of 2 , Apr 1 4:41 AM
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        Hi,
        My name is Dimitar,
        In my opinion this is not so good design. For small
        power you can use wood blades cover with epoxy resine
        with glass
        --- "zedhead@..." <zedhead@...> wrote:
        >
        >
        > Hey,
        >
        > As soon of you may know from a previous posting, I
        > and three classmates are
        > currently working on developing a low-cost, durable,
        > locally constructable
        > Darrieus type water turbine for use in rural
        > sub-Saharan Africa. We have chosen
        > the Darrieus turbine (Or possibly the slightly more
        > complex Gorlov helical
        > turbine) because it can be used in streams with
        > heavy sediment load and variable
        > heights. No civil works are necessary as we are
        > planning on attaching this
        > turbine to a raft system that will also contain a
        > generator. We are planning on
        > using DC current and running a pump / mill / battery
        > bank on shore in a small
        > power house.
        >
        > Currently, we are looking at designing the blades
        > for the turbine. Most turbines
        > now are constructed using expensive, unavailable
        > techniques, such as extrusion
        > or composites. We have a limited set of materials
        > and machining techniques that
        > can be used to make these blades.
        >
        > What I am currently experimenting with is a turbine
        > blade constructed as
        > follows:
        >
        > PROFILE: NACA 0020
        > TIP TO TAIL LENGTH (not chord): 6"
        > HEIGHT: 30"
        >
        > The blade will be constructed by placing three
        > different PVC (or possibly steel)
        > pipes along the center axis of the blade. The first
        > pipe will be 1" in
        > diameter, the second 1.25", and the pipe in the tail
        > will be 0.5". A
        > sheet of 20 gauge stainless steel will be wrapped
        > around these pipes (once they
        > are properly placed to give the correct hydrofoil
        > shape) and pop riveted at the
        > end. The sheet will also be pop riveted (using
        > countersink rivets) to the pipes
        > themselves. When attached to the holder plates at
        > the top and the bottom, the
        > blade will be welded to the plates to make the
        > interior waterproof. The PVC
        > pipes themselves will extend through holes made in
        > the plate so that they can
        > add structural support to the system. Three blades
        > will be arranged on a 40 in
        > diameter holder plate at 7-9 degree angles of
        > attack. A stainless steel rod will
        > be used as the turbine shaft to join the turbine
        > with the raft and generator.
        >
        > QUESTIONS I HAVE:
        > 1) Has anyone tried / seen anything similar to this
        > before? I know ribs have
        > been used in the tip to tail direction, but this
        > ribbing system seemed to not
        > have been used.
        >
        > 2) How would I calculate the bending / buckling of
        > the blade's center? Would I
        > just need to consider the PVC pipe and find how it
        > would bend? How would I model
        > the system?
        >
        > 3) Is there some sort of waterproof coating that
        > could be used over the steel
        > plate to further prevent leakages?
        >
        > 4) How will the higher weight of the steel (When
        > compared to composites) play
        > into the system dynamics?
        >
        > 5) Any questions or comments? I really am looking to
        > get feedback on this design
        > and also suggestions about alternate designs.
        >
        > Thanks for all your help!
        >
        >
        > Matt Zedler
        > MIT Class of 2007
        > Mechanical Engineering
        > (804) 814-7197
        > mzedler@...
        >
        >
        ___________________________________________________________________
        > Speed up your surfing with Juno SpeedBand.
        > Now includes pop-up blocker!
        > Only $14.95/month -visit http://www.juno.com/surf to
        > sign up today!
        >
        >
        >
        >
        >



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