Ducted fan aircraft

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by jthunt, Mar 17, 2012.

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  1. Dec 4, 2019 #1621

    Lendo

    Lendo

    Lendo

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    I love the idea of a Ducted Fan, I've seen some attempts but all seemed to end up less efficient than an open prop, I've never really understood why. I've spoken to one Aeronautical Engineer who is redesigning an aircraft his Dad designed here in Australia some years back, he says it can be done well for specific applications - he should know, but I think there are too many variables.
    George
     
  2. Dec 4, 2019 #1622

    henryk

    henryk

    henryk

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    =ducted fans are lower surface as open propellers are...
    (greater surface load,lower specific thrust !)

    -EJECTOR duse can help,aspatially at low speed (taxi,climbe...)

    http://www.reaa.ru/yabbfiles/Attachments/hustawka_multiplikatorwidelec_016_001.jpg
     
  3. Dec 5, 2019 #1623

    Doggzilla

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    It’s likely because we have been using the wrong sizing on older ducted fans.

    Compare the PJ-2 to other ducted fans and the other fans are far too large for their power.

    The PJ has almost 200hp per small fan. Many other ducted fans have 200hp with a very large fan. Yet the PJ is much faster despite having a very similar power to weight ratio, and probably similar drag.

    It’s very obvious that older ducted fans were using far too large fans.
     
  4. Dec 5, 2019 #1624

    jbiplane

    jbiplane

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    My customer on paramotor testing my 2-stroke 294cc boxer engine in ducted fan. Cannot spread photos without his permission. What trust do you need?
     
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  5. Dec 5, 2019 #1625

    cluttonfred

    cluttonfred

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    Just a concept at this point, but looking for something comparable to what the same 25 hp engine can do through a full-size prop and redrive but in a smaller package.
     
  6. Dec 5, 2019 #1626

    henryk

    henryk

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    =30 HP (7000 RPM), 70 kG thrust
     
  7. Dec 7, 2019 #1627

    henryk

    henryk

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    =old experiment with tube drag decreasing (tandem mode)

    -single tube=circa 30 deg.
    -tandem=circa 5 deg,
     

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  8. Dec 7, 2019 #1628

    Doggzilla

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    Awesome Malish!

    That just made my day!
     
  9. Dec 7, 2019 #1629

    henryk

    henryk

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    Last edited: Dec 7, 2019
  10. Dec 8, 2019 #1630

    henryk

    henryk

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    Last edited: Dec 8, 2019
  11. Dec 8, 2019 #1631

    Malish

    Malish

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    Here how new fan blade look like, compere to old one. PC082080 (Large).JPG
    New blade - is "master model" made on 3D printer.
     
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  12. Dec 8, 2019 #1632

    Doggzilla

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    Good work Malish!

    If you have any problems with the plastic attachment flange, I have seen people 3d print with metal inserts. You should be able to add an insert to mimic the steel base of your carbon blades.

    Also, I wonder what will happen if you change thickness to allow higher angle of blades before compressor/fan stall. May allow different RPM range if that’s something you are interested in.
     
  13. Dec 8, 2019 #1633

    henryk

    henryk

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  14. Dec 9, 2019 #1634

    henryk

    henryk

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    https://www.dropbox.com/s/ky1z5jc9g3srohq/Dym - zwolnione tempo.mp4?dl=0
    https://www.dropbox.com/s/htftd6ttj1b2emj/Dym.mp4?dl=0

    =auer experiments with CR differentially drived propellers=>25 % thrust gain...

    <10 % weight increase.

    I think,ducted CR should be better, NO stator need ! (see smoke trajectory...)
     
  15. Dec 9, 2019 #1635

    Doggzilla

    Doggzilla

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    Very interesting. It appears to be squeezing the exhaust like turbine exhaust squeezes during shock diamonds.

    It’s like a Venturi caused by the different inertia of the air flow and still air. The flow is very fast but surrounded by still air. This pulls the still air inward and squeezes the flowing air into a tight well controlled flow.

    But why this only happens with twin props I do not know. It must be how it affects the center of the flow.
     
  16. Dec 9, 2019 #1636

    Lendo

    Lendo

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    henryk, Good find, the Ligeti -Stratos (ducted-fan) was the one I mentioned previously, his Son is reverse engineering the concept as all documents were lost when he was killed. A modification to the design tested at low altitude, as directed by CASA.
    George
     
  17. Dec 9, 2019 #1637

    henryk

    henryk

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    =this aiflow is focused/concentrated and so powerfull=no possibility to stay in it
    for thrust force read !!!
    (I should read =235 kG=in lying position !)

    https://www.dlr.de/bt/desktopdefault.aspx/tabid-8196/14020_read-35636/

    =CR FAN

    https://slideplayer.com/slide/3853756/13/images/3/Thrust+Augmenting+Ejector.jpg

    =EJECTOR for thrust augmentation...
     
    Last edited: Dec 9, 2019
  18. Dec 11, 2019 #1638

    henryk

    henryk

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    =steel core forks can be made from carbon/kevlar composites...
     
  19. Dec 11, 2019 #1639

    henryk

    henryk

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    https://innowacjablog.files.wordpress.com/2019/11/flaris229237.pdf

    =polish 5-place jet with BRS (rocket) + 6 ? auter airbags for soft landing !!!

    -another polish patent=dynamic breake for pataschute=allmost ZERO speed landing...

    https://airsafe.pl/

    BTW= iff Vlanding=5 m/s and distance 0.05 we get deceleration

    a=V^2/2s=25/0.1=250 m/s^2 ( circa 25 "G" !!!)

    =for 7 m/s = 50 "G"
     

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