Ducted fan aircraft

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

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  1. Oct 7, 2018 #1261

    Malish

    Malish

    Malish

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    All we're standing again, ducted fan is different than prop in shroud.
    Don't mistake it for jet engine also.
     
  2. Oct 7, 2018 #1262

    Riggerrob

    Riggerrob

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    ————————————————————
    Ducted fans produce maximum thrust at low speed (tugboat speed) like VTOL hovering.
    However, eventually parasite drag - on the duct - dominates.
     
  3. Oct 7, 2018 #1263

    Malish

    Malish

    Malish

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    Yes it is.
    I new this from beginning, but this was a compromise to have JET looking aircraft

    pIMG_0050.jpg
     

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    Last edited: Oct 7, 2018
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  4. Oct 7, 2018 #1264

    Malish

    Malish

    Malish

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    PJ-II aircraft couldn't be compered to an other aircraft - it's powered by DUCTED FAN pIMG_0056.jpg pIMG_0151.jpg
     
    Last edited: Oct 7, 2018
  5. Oct 7, 2018 #1265

    pictsidhe

    pictsidhe

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    Anyone care to suggest which pseudo-jet is better than the PJ-II?
    I think it's very clever myself. Other than the ducted fan, it's actually a fairly conventional plane with reasonable performance very cunningly disguised as a jet fighter.
    Could be improved with some red star markings, but that's just me.

    Yes, ducted fans have a trade off vs props when prop size is not restricted. Long ducts are particularly bad. Notice that the PJ has shortish ducts...
     
  6. Oct 7, 2018 #1266

    henryk

    henryk

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    -is it possible to improove duct inlets shape?
    (inner part,for static thrust gaining...)

    http://www.esotec.org/hbird/DrawGIFs/Bellmouth.gif
     
    Last edited: Oct 7, 2018
  7. Oct 7, 2018 #1267

    Malish

    Malish

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  8. Oct 7, 2018 #1268

    henryk

    henryk

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  9. Oct 7, 2018 #1269

    Malish

    Malish

    Malish

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    Это ПУТИН, всё ПУТАЕТ.
    STUPID MAN in power
     
  10. Oct 7, 2018 #1270

    henryk

    henryk

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    >70 bill.$ =big power!
     
  11. Oct 7, 2018 #1271

    rv6ejguy

    rv6ejguy

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    Malish, I like the photo of the PJ-II climbing out from behind. I don't think I've seen that one before.

    This discussion about prop vs. fan was only directed at one member here who keeps trying to tell us that fans will give far superior performance to propellers in the 100-300 knot range. I've provided a couple of examples to show that's not true and you've stated that also and was not your goal.

    I believe everyone here on HBA thinks your project is awesome and wishes to see it succeed.

    I realize lack of money is probably the biggest thing slowing your project down at the moment. While I can't help financially, if we can help with any CNC'd parts production, let us know. My contractors will have some excess capacity available starting in November and can do small parts runs at pretty reasonable prices. You can see some of the parts we make here: http://sdsefi.com/sdsaero.htm

    Also, I'd be happy to help market your airplane via our website and other contacts we have in the Experimental world. We get about 50,000 visits to our website every month and that might give you some more exposure or help find an investment partner.

    Keep up your good work!
     
    Last edited: Oct 7, 2018
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  12. Oct 7, 2018 #1272

    henryk

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  13. Oct 10, 2018 #1273

    rv6ejguy

    rv6ejguy

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    I've been reading a few papers on the UL39 project, especially regarding the fan development. One paper stated:

    ..."tone noise generated by the fan is present in the perceived acoustic spectrum. Therefore, during its
    future operation, the UL-39 aircraft may not fulfil the requirements concerning noise given
    by legislature. With these issues in mind, a new fan will be designed which will take into
    account the necessity of reducing noise while being capable to improve the aircraft flight
    performance at the same time."

    From the flight videos, the fan noise is quite pronounced and at a frequency human ears find objectionable.

    Another paper studies the causes of the noise and ways to mitigate them. Seems like a lot is due to the interaction of the fan flow impinging on the stator in this design.

    I can't find any recent documents on how or if a re-design of the fan and the aircraft is going forward after the loss of the prototype. Does anyone in Europe know what's happening with this project?
     
  14. Oct 10, 2018 #1274

    henryk

    henryk

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    -UL-39 ALBI wing was repaird,
    was demonstrate at AERO 2017

    http://www.nieuwenhuize.com/blog/aero-friedrichshafen-2017-a-report-3/

    (probably new rotor set...)

    and flown from graas airfield this year...


    -from auer experiments with conterrotating propellers we can see much moore
    silent work ,streamlined ,concentrated stream withaut stator!
     
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  15. Oct 10, 2018 #1275

    Vigilant1

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    I can imagine how that could happen . . . web_1696-500x500.jpg
     
  16. Oct 10, 2018 #1276

    pictsidhe

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    Increasing the spacing between rotor and stator would help a lot. It may be that the angles are a little out, too.
     
  17. Oct 10, 2018 #1277

    Malish

    Malish

    Malish

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    Hi Ross,
    Ducted fan has better performance over open prop to flying speed of about 120-150 MPH and to keep up with open prop, we need to have more powerful engine, even with that, our PJ-II "dreamer" wasn't design to fly faster than 250 MPH. Main reason for that, our aircraft design for safely operation by average GA pilot and not by professionally trained pilot to fly fast jet aircraft.
    But main advantage of our aircraft(after it's look and flying like jet fighter), that it's climb about 3000 FPM at flying speed 100-120 MPH at sea level.
    About ducted fan nose level - it's lower than prop aircraft with engine at same HP! It's just sound different - more like leaves blower or vacuum cleaner. Just after PJ-II "Dreamer" fly's by, "rumbling" nose from exhaust of LS engine can be hearing, only because exhaust stuck's coming out into the fan duct's and don't have mufflers.

    Thanks about your offer to help, we're definitely will look at this.

    DSC_0295_zpsriitzpuq.jpg tmp_19215-aIMG_87941413477843.JPG
     
  18. Oct 10, 2018 #1278

    rv6ejguy

    rv6ejguy

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    I watched your videos again and on the UL39. The PJ-II is noticeably quieter and with a lower frequency than the UL39 (perceived easier on the ears) and yes you can hear the V8 sound a bit in there too. Seems you have good climb performance without stators. I think the UL39 with the split duct has a lot of inlet flow separation impinging on the fan compared to your straight, open duct. The UL39 papers discussed this as well. I think your concept of docile handling is a good idea for safety and a big selling point for lower time pilots used to flying more normal GA aircraft.
     
  19. Oct 10, 2018 #1279

    Malish

    Malish

    Malish

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    When we're first designed PJ with single fan, we're didn't like split duct airflow separation before fan, that was another reason to go for two duct system.
    And for safely handling of our aircraft we're used thick wing profile and off cause this is bad for high speed aircraft.
    UL-39 reminds me more BD-5 aircraft. Look like they have different mentality building UL-39 - lower scale replica of real L-39, like usually build RC ducted fan replica aircraft.
    And we're also have the stator's on our PJ-II "Dreamer", maybe because of that it's climb better than UL-39. I can't belive that their team, with all support and resources from the college af aviation, could do that.
    We didn't have that kind of support.

    ___________________2_002 (Large).jpg DCP_4716 (Large).jpg P4170529 (Large).jpg PC170972 (Large).jpg
     
  20. Oct 10, 2018 #1280

    rv6ejguy

    rv6ejguy

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    Thanks for these photos to see your developments. Yes, I saw the massive financial and technical support on the UL39 in their videos- even with a full scale fuselage in a wind tunnel and CFD simulation. You guys are doing amazing work with your more limited resources and money. :)
     

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