Need verification of polynomial coefficients for Ka4-70 propeller in 37 nozzle

Discussion in 'Props' started by Tackwise, Jan 23, 2013.

  1. Tackwise
    Joined: Mar 2010
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    Tackwise Member

    I am trying to implement a propeller calculation in excel for ducted propellers (Wageningen Ka series in nozzles 19A and 37).

    I am using the coefficients from
    1) thesis of M.W.C. Oosterveld Wake adapted Ducted propellers
    2) book of J. Carlton: Marine Propellers and propulsion. (2007) table 6.17 see also page 116 on the newest edition google books

    My calculations functions well for all the propellers in the 19A nozzle, however not for the Ka4-70 in the 37 nozzle. This is due probably to incorrect input coefficients specifically for the KTQ coefficients ((Cxy)).

    Does anyone have access to another source for these coefficients?
    (such as the proceeding Ducted propeller characteristics of Oosterveld M.W.C. from RINA Symp. on Ducted Propellers in London 1973)

    Any help is much appreciated.

    Tackwise
     
  2. johneck
    Joined: Nov 2011
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    johneck Senior Member

    The book Marine Propellers and Propulsion, by Carlton has the Fourier coefficients for both 19A and Type 37 nozzles with Ka 4-70 props. I would be happy to send you an excel sheet with a dusted calculation if you would like. Send an email to me.
     
  3. johneck
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    johneck Senior Member

    I was just looking thru the data and I noticed upon closer examination, that the data in the book is not the same as the data that I have been using for the past 15-20 years! I will thru my references to see how I got revised coeffs.
     
  4. Tackwise
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    Tackwise Member

    I have encountered various small differences in some coefficients depending on the source. which made me suspicious about these, especially as my calculated KTQ graph does not correspond to the original graph. The KTT follows the right path, however I still need to verify the values.

    I am curious if the coefficients you use are significantly off, or if there are only small differences.
     
  5. johneck
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    johneck Senior Member

    The coefficients are very different, some of the changes are same figures opposite sign and some are new coefficients that are not shown in Carlton. (The 19A coeffs are identical) I am trying to find a reference for the ones I have been using, but I haven't so far. The listed reference was the Oosterveld paper, but obviously they were corrected at some later point. I first created the spreadsheet over 20 years ago in Multiplan on an original Mac! So the history is now a bit fuzzy.
     
  6. Tackwise
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    Tackwise Member

    Are the coefficients of the KTT off aswell? or are they the same? I believe the KTT are correct but some of the KTQ coefficients should be incorrect as the output values are incorrect. For the KTN coefficients I am uncertain, i believe they could also show some differences as my values do not correspont to the expected results.
     
  7. johneck
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    johneck Senior Member

    I have differences in all three sets of coeffs. Unfortunately I am still unable to find my source. I moved my office last year and may have "lost" some of my notebooks. I have attached the coefficients that i use as well as the ones from the paper.

    View attachment type37.xlsx
     
  8. Tackwise
    Joined: Mar 2010
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    Tackwise Member

    Thanks Johneck,

    I solved my coefficients error, thanks to your tables.
    The data differences are typical for typo's. I have attached the coefficient table which resulted in the correct values.

    Your table of MPP coefficients differed from my table of coefficients from MPP. However if I compare my MPP coefficients with your unknown source I only found three differences:

    • X=0;Y=0 CT =-0,162557 instead of -0,0162557 (IMO a typical typo filling an additional 0)
    • X=1; y=0 CQ =-0,0484240 instead of 0,0484240 (Again typical typo leaving out the minus sign)
    • X=4; Y=0 CT =-0,042997 instead of CTn=-0,042997

    I did not implement the last difference (X=4; Y = 0) as this did not give the expected results while the original (from MPP reference) did.
     

    Attached Files:


  9. Izugarrin
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    Izugarrin Student

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