Ka 4-55 with nozzle no. 19A – discrepancy

Discussion in 'Props' started by PetterM, Jan 20, 2015.

  1. PetterM
    Joined: Sep 2004
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    PetterM Senior Member

    Using the factors presented in: Wake Adapted Ducted Propellers, M.W.C. Oosterveld, PhD-thesis Delft University of Technology, Year 1970.
    I am getting a good match on the thrust coefficient but a discrepancy on the torque coefficient when comparing calculated values using the polynomials to the chart. Have I mistyped or are some of factors wrong?

    Also not sure what the factor 0 7 is meant to be used for?
     

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  2. PetterM
    Joined: Sep 2004
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    PetterM Senior Member

    Does anyone know if the polynomial factors are published anywhere else?
     
  3. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    Hi Petter, seems a bit odd. It's ok up to ~etamax, but kq~zero with kt=zero... no way.

    Have you checked other P/D values as well?
     
  4. NavalSArtichoke
    Joined: Oct 2013
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    NavalSArtichoke Senior Member

    It's not clear which factor you are referring to.
     
  5. PetterM
    Joined: Sep 2004
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    Location: Norway

    PetterM Senior Member

    Its more or less the same pattern for all the valid P/D for the Ka 4-55 screws.

    When I read in the factors for Ka 4-70 both the torque and the thrust matches perfectly.

    I have used the factors from:
    Oosterveld, M.W.C. Wake Adapted Ducted Propellers.
    NSMB Wageningen Publication No. 345.
    June 1970.

    and Marine Propellers and Propulsion by John Carlton

    Trying to find a second reference to check.
     

  6. PetterM
    Joined: Sep 2004
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    PetterM Senior Member

    The equations are polynomials using factors up to A6,6 B6,6 and C6,6 (see attached image)
    The polynomial coefficients table also gives a value for A0,7 etc for some of the screws (see attached image) its not clear to me what this should be used for.
     

    Attached Files:

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