Waterjets in an RC Model Boat

Discussion in 'Hydrodynamics and Aerodynamics' started by JGrimes, Oct 7, 2011.

  1. JGrimes
    Joined: Oct 2011
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    Location: South Florida

    JGrimes New Member

    Greetings everyone,

    I'm a master's student doing some preliminary work for my thesis which will involve installing waterjets into an RC Model boat. I'm also going to be rigging the boat with sensors to track various things relating to the boat including thrust from the jets, flow through the jets, engine RPM, etc. I was planning on measuring the pressure in the high pressure side of the waterjet and backing out the water velocity from that.

    As part of my initial work, I need to come up with estimated ranges so that I buy the correct sensors. The problem I'm running into is that I'm not sure how to estimate the pressure in the jets so I'm not sure what range my sensor needs to have.

    Any suggestions?
     
  2. DCockey
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    DCockey Senior Member

    What field will you Master's degree be in?
     
  3. JGrimes
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    JGrimes New Member

    My degree will be from Florida Atlantic University in Ocean Engineering.
     
  4. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Have you talked to the manufactuer of the jet system?

    How do you plan to calibrate the pressure you measure vs flow rate?
     
  5. JGrimes
    Joined: Oct 2011
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    JGrimes New Member

    I contacted the US distributer for the drive, but he wasn't able to provide me with much information regarding the pressure in the jet.

    As for converting the pressure to flow rate, I figured that if I knew the pressure at the high pressure side of the water jet I should be able to figure out the flow velocity If I compare it to the pressure upsteam of the waterjet. From there, I could use the crossectional area at the point of the pressure tap to determine flow velocity.
     
  6. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Jets work with acceleration and not pressure. Also, there is a pressure gradient in the nozzle and other passages. Flow rate with power applied should be one of the standard parameters available from a jet manufacturer.
     
  7. Submarine Tom

    Submarine Tom Previous Member

    JGrimes,

    You may want to start with an educated guess.

    -Tom
     
  8. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    can you give us a link to the jet pump you are using for your model ...I assume about 1 metre long ( 39 in to you yanks) and what size engine you are driving it with ....
     

  9. JGrimes
    Joined: Oct 2011
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    Location: South Florida

    JGrimes New Member

    Ok, here's the jet I'm considering using:

    http://www.graupner.de/en/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/2347/product.aspx

    That will be matched with this engine:

    http://bonzisports.com/zenoah/zenoah260.html

    The engine is a 25.4cc engine. We will be using 2 engines/jets

    This will be installed in a boat with a LOA of 84 in and a beam of about 18 in. I've been told to expect that the entire setup with this specific hull and the Graupner Jets and Zenoah engine should be able to achieve about 30 kts.

    If anyone has a suggestion about a better way to experimentally measure my voume flow rate while the model is underway, I'd welcome it. I'll happily accept any advice you have.
     
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