Ducted fan aircraft

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

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  1. Mar 24, 2014 #181

    Doggzilla

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  2. Mar 24, 2014 #182

    Brian Clayton

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    I second that.....wow.

    If this works and performs well, it has a shot at becoming a very popular air plane (if kits/plans are going to be done). I would not be embarrassed to see it in my hangar...Very cool....
     
  3. Mar 24, 2014 #183

    Lucrum

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    I certainly hope it works, if for no other reason than I'm attempting something similar myself. I've hesitated to say anything for fear of being seen as a detractor. But I see some potential issues though. What I assume is a custom gear box and those drive shafts protruding into the ducts for starters.
     
  4. Mar 24, 2014 #184

    rv6ejguy

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    Getting the engine out of the duct is huge I think, possibly justifying the gearbox and driveshafts. Only flight time will tell for sure. There is just too much speculation out there and a dearth of solid, real world performance information on flying ducted fan designs. I think the work they are doing is great on this project.
     
  5. Mar 24, 2014 #185

    Lucrum

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    I agree, my duct wraps around the shaft keeping it and the engine out of the duct.
    Again I agree.
     
  6. Mar 25, 2014 #186

    Xanadrone

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    Great looking plane indeed!
    It should also fly well, according to some classic "beauty = functionality" quotes.

    I wonder only if some preliminary estimated performance data are available (maybe henryk knows more?!)
     
  7. Mar 25, 2014 #187

    cheapracer

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    Awesome looking but would anyone entertain a genuine fear of being shot at riding around in that?
     
  8. Mar 25, 2014 #188

    Lucrum

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    "This is a sport two place aircraft PJ-II(pistonJet) utilizing "Ducted fan" system. Powered by "GM LS6" aeroconversion engine(by Team-38,Inc) via gearbox/multiplicator(ratio 1:1.4) witch turns two(69cm diameter)fan's. This engine provided 388hp at 5000rpm. We did run ground testing of the system. We're had static trust of 350+kg at 4000rpm. We're believe at airspeed 150-160km/hr(climb out speed), engine will turn 5000rpm.
    Cruise speed estimated 350km/hr(4000rpm) at 2000m.

    Aircraft spects:

    Length = 9.05m
    Wing span = 8.5m
    Height = 3.0m
    Mtow =1000kg
    Wing area =10m/sq
    Max fuel = 280liters"





    I haven't followed the thread intently but I was thinking henryk was the designer for some reason.
     
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  9. Mar 25, 2014 #189

    Xanadrone

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    Thank you for the specs, Lucrum ! (even if I guess that the "1:1.4 gearbox/multiplicator" is in fact a 1.4:1 reduction unit.)

    P.S. Our Polish colleague henryk is not the designer of the PJ-II, but his knowledge of Russian helps him - and us through his postings - to be informed about the latest eastern HB-aviation evolutions.
     
  10. Mar 25, 2014 #190

    Lucrum

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    Thanks, I didn't know that. Has the original designer built a PJ-II I wonder?
     
  11. Mar 25, 2014 #191

    henryk

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    =it is multiplicator gear...


    =my construction is with no geared impeller + ejector system=

    http://www.reaa.ru/yabbfiles/Attachments/Reshotka.jpg

    =with radial concentric inlets...
     
  12. Mar 26, 2014 #192

    Starman

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    That transmission is not a reducer but an increaser due to the small diameters of the fans/

    The fan from the fanjet engine on a Learjet takes 2000 hp to operate and produces 70% of the thrust of the engine. That fan turns at 15,000 rpm at top speed.
     
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  13. Mar 28, 2014 #193

    Mike W

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    Although not as awesome as the PJ-11. I designed and built a single seat aircraft fitted with a ducted fan back in the 1970's, when this form of propulsor was being explored by many aircraft manufacturers with aircraft such as the Fanliner and Trainer, Cessna XMC, Optica and many others.

    My aircraft was the MW2 Excalibur which was entered in a design competition instigated by a Cornish businessman in 1973. Originally the aircraft had a two blade pusher propeller. I then discovered that propeller manufacturer Dowty Rotol had produced a 36" diameter ducted fan for the defunct Short Sky Spy drone. This aircraft took off vertically from the back of a vehicle then transited to level flight using the duct as an annular wing. Working at BAe on Concorde at the time I knew some of the Dowty Engineers on the project and so managed to obtain a couple of fans and also the technical backup to design the duct.

    On completion of the MW2 design I moved to Bodmin and built the aircraft. IN 1976 it had it's one and only flight which was followed by a disagreement with the sponsor resulting in me leaving the project and it never flew again. It can now be seen hanging from the ceiling in a shopping centre in Devon. I learned much from the experience in more ways than one.

    The fan was manufactured from fiberglass and had five blades with four fixed and curved stator vanes at the rear of the duct which supported the fan and bearing assembly. The fan was designed to rotate at 4500 RPM. Originally the 1600 VW engine could not achieve this and so larger 1830cc barrels and a Weber carburettor were fitted. Fitting larger valves lost 100 RPM due to blanking of the valve by the cylinder head. The highest RPM achieved was 4300

    In answer to a few of the questions from previous threads in this forum.

    There are a couple of documents by the Society of Automotive Engineers in Wichita based on papers by DGM Davies of Dowty Rotol, covering the design of ducted fans their reference numbers are 75053 and 770457. They are still available at a small cost.

    One of the graphs shows thrust against airspeed comparison for a 7ft propeller and a 4.4 ft propulser 320 BHP engine at 2000 RPM. The static thrust of the fan is 20% greater than a propeller. It then blends with the propeller curve at 60 KTS and above 150 KTS the propulsor produces slightly more thrust. The MW2 certainly had good acceleration on take off.

    The tip clearance had to be very small. A graph in one of the reports shows the effect of tip clearance on thrust. I made the duct with a recess at the fan blade location and filled it with rigid PVC foam, this allowed the fan cut its own minimum tip clearance.

    The fan was extremely noisey, very reminiscent of a Stuka on a bomb run. Dowty's engineers thought they could reduce this by modifying the angle of the aircraft nacelle boat tail to improve the airflow into the duct.

    I believe the MW2 was the first ducted fan aircraft to fly in the UK. It flew before the Dowty BN Islander fitted with two propulsors and the Edgley Optica.

    Two pictures attached showing the MW2 including the first and only flight.

    MW2 B 001-bmp (1).jpg mw2bb 001-bmp.gif
     
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  14. Mar 28, 2014 #194

    henryk

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    =no moore pictures?\very interesting...=thrust/hp \
     
  15. Mar 30, 2014 #195

    henryk

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    Last edited: Mar 30, 2014
  16. Mar 30, 2014 #196

    plncraze

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    Thanks for sharing that story Mike W. I remember seeing pictures of the plane in Air Progress. Sorry it didn't work out.
     
  17. Mar 30, 2014 #197

    Mike W

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    With hindsight, I think that unless you want a jet fighter look a like, the extra weight of duct and shaft and construction complexity, coupled with a possible noise problem, that a propeller is the better option for small light aircraft. Probably why there are not many ducted fan aircraft about.

    Attached is a picture of the aircraft as it is today after my successor re sprayed it and finished off the engine cover blisters.

    MW2 TM-jpg.jpg
     
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  18. Mar 31, 2014 #198

    Doggzilla

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    Personally, I believe that ducts need a step forward before they can really reach their potential. Between the development costs, the lack of faith in general, and a general disdain for them... ducted fans have a hard battle to fight.
     
  19. Mar 31, 2014 #199

    BBerson

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    The modern turbofan ducts on corporate jets and airliners are incredibly quiet.
    I think it is because they use an extended duct which is far out in front. And the fan is supersonic. Could a supersonic inlet be sucking the noise in...like a black hole?
     
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  20. Mar 31, 2014 #200

    Doggzilla

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    The ducts are indeed more silent, as any vibration is also given off by the housing as well... which is in contact with subsonic air. Not to mention the exhaust, which is pretty obvious.

    That said, I believe much of the noise from ducted fans is due to vibration and the duct equivalent to P factor, which is reduced as the blade speeds increase. A turbine blade is cutting through the air at a much higher speed, and so any difference in air across the blades is far less in relation to the rotational speed, making each pulse that much less intense.

    I also believe that changing the stiffness of the duct changes the frequency given off by air rushing over it... and that a turbofan produces less noise because there is less excess air in the high pressure section... as turbojets compress and expel vastly more air than they combust, while turbofans direct excess air through the fan section.
     

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