Ducted fan aircraft

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

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  1. Oct 29, 2013 #141

    Doggzilla

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    Great work, it's finally nice to see a ducted fan that looks viable. People question ducted fans, but they have been proven as lift fans for almost half a century.
     
  2. Oct 29, 2013 #142

    Vigilant1

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    They are efficient for low speed/static thrust, but not for high speeds. As Malish implies, this will be for looks and a jet "feel". For performance/efficiency at typical homebuilt cruise speeds, the open prop wins.

    Malish, good luck with the project, it looks very interesting. The guys running Wankel engines are always looking for a way to take advantage of the simplicity, power-to-weight ratio, and inherent high RPM capability of those engines without need for a gearbox. One builder in the US (Perry Mick) used a ducted fan on his pusher aircraft, but later abandoned the unit and went with a propeller for better performance. I'm sure there can be improvements in these designs. Best wishes for success.
     
  3. Oct 29, 2013 #143

    DangerZone

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    Wasn't Perry Mick's EZ considered a shrouded prop aircraft, as was Pussy Galore before they removed the shroud?
     
  4. Oct 30, 2013 #144

    Malish

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    As I said, I'm not looking for jet speed aircraft. Most GA/sport pilots would like to have an aircraft flying at speed's of 200mph.
    Russian Yak-18T can fly at this airspeed to. I'm joking. May bee 150. Airplane 004.jpg Airplane 005.jpg Picture 001.jpg
     
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  5. Oct 30, 2013 #145

    Doggzilla

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    The first problem I see is that his nozzle is designed in the absence of the aircraft, the internal cross section of the flow gets larger towards the nozzle, because the fuselage is protruding into the intake. The cross section of the duct might as well be a reverse bell, decelerating the flow. Of course its not going to cruise or climb well. In effect, he used a standard blimp duct profile, but blimps dont have fuselage in front of the fan. The fuselage needs spacing to open up the intake. The effective cross sections has to be taken into account, not just the external radius of the shroud.

    Note that the fantrainer has a large intake which has the nozzle constricted by the rear fuselage, and the intake is significantly behind the fuselage to avoid constriction. The fantrainer has 40% higher wing loading than its competition of similar power to weight ratios, and yet has higher cruise, and almost twice the climb. Like I say, internal duct design/profile is number one priority. A quick search of 500-650hp twins shows that the fantrainer kicks the crap out of anything I can find. The idea is anything but a failure.

    The fantrainer did not fail because it was a bad idea, it failed because military training often comes with the purchase... so the seller uses their own trainers and the buyer has no need for their own.
     
  6. Oct 30, 2013 #146

    Vigilant1

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    There's no reason you can't go 200MPH, it'll just take more HP and fuel than if an open prop were used. And I know it will look cool.
     
  7. Oct 30, 2013 #147

    Doggzilla

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    Like I said, the fantrainer significantly outperforms prop aircraft of the same power to weight ratio, especially for its wing area, and almost twice the rate of climb of 600hp twins at similar weights. The problem is not ducted fans, but designs with clear flaws.

    There is nothing wrong with ducted fans, the issue is the design of the ducts being novice in nature and not following even the most basic theories, such as the venturi effect.

    The fantrainer has 650hp, has wings only 6% larger than a Mooney M20... is 5100lbs at gross weight, and yet it can fly 225kts and climb at 3000ft/min. Its right in the middle of twin territory, except that no twin is climbing 3000ft/min. Its a bit impressive that something with 40-50% less wing area can compete in any way. Fans arent necessarily inefficient. I mean, it sure kicks the crap out of the EA-500, which uses the same engine.
     
  8. Oct 30, 2013 #148

    Vigilant1

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    That's why, in the 35 years since it flew, it's been so extensively copied. Not. Manufacturers who would sell their mothers for a small increase in fuel efficiency aren't adopting ducted fans for the simple reason that they are not more efficient than open props at these airspeeds. They've got the money to do the research, and the research tells them that open props are better for this mission. Really.

    The Fantrainer was designed to look and "feel" like a jet and to save money (in fuel use) compared to a small jet. The idea was to cheaply give students a jet-like experience. Two-seat turboprop trainers continue to sell well, the Fantrainer never did.
     
  9. Oct 31, 2013 #149

    Doggzilla

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    Im going to disagree. First off, the EA-500 has the same engine as the Fantrainer and is more fuel efficient than the PT-6 counterparts that sell like crazy. The EA-500 saves substantially, and yet its a total failure. The fantrainer is even more efficient than the EA-500... it blows away anything with a similar turbine.

    That said, the aircraft industry obviously does not work on numbers alone. Most companies are struggling, let alone a new an unaccepted technology. I mean, the diesels blew away everything else offered in GA, and yet they failed terribly. Efficiency and performance have less to do with it, the problem is squarely tied to the corporate nature of GA customers these days, with arrogant and mechanically inept managers calling the shots from every angle.

    I once had a room of people yelling at me, actually really yelling at me, because I insisted a plane could do something that not only was in the POH, but that I had actually done with the chief pilot. The arrogance and ignorance is becoming absurd in the GA community.
     
  10. Oct 31, 2013 #150

    rv6ejguy

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    The Fantrainer has similar performance to the PC-7 overall considering the PC-7 has 100 less hp. I don't see any major advantages in speed, celing or ROC.

    The aero diesels such as the Thielert and SMA were failures because they were more expensive, less reliable and required more maintenance than existing legacy SI GA piston engines. In short, they were more expensive to operate per hour (all costs in) despite lower fuel burn.
     
  11. Oct 31, 2013 #151

    Vigilant1

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    The FanTrainer's little brother was the FanLiner. It was produced by the same team that produced the FanTrainer, it was the subject of lots of R&D, and I'm sure the duct design was not hindered by any gross oversights. Conveniently, the size and HP fall right into the light aircraft realm that is most familiar to many of us. Results:

    ..................................FanLiner.....................Cessna 152
    Max Gross Weight: .......1653 Lbs.......................1670 lbs
    Engine HP:....................114 HP..........................110 HP
    Rate of Climb:................650 ft/min................... 750 ft/min
    Cruise Speed:............... 112 MPH .................. ..123 MPH (107 Knots)

    This version of the Fanliner proved too noisy, so gearing and a larger engine were fitted later. Eventually, the project was abandoned.

    We can argue about the accuracy of the C-152 POH info and the info provided by the manufacturers of the FanLiner, but it doesn't look, on the face of it, like they found a more efficient way to push an airplane through the sky. The C-152 has approx 150 sq ft of wing area compared to the Fanliner's 100 sq ft, which surely helps the Cessna's ROC. But the strut-braced, draggy Cessna should have been left in the dust at cruise by the much cleaner (looking) Fanliner. The source of the Fanliner's underperformance is an exercise left to the reader.

    Sources:
    Fanliner wikipedia page
    Cessna 152 POH
     
    Last edited: Oct 31, 2013
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  12. Oct 31, 2013 #152

    Malish

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    As I said before. This project is in experimental stage. May bee something will need to be change. Only experiment will show. Like everything in aviation, need to have trade off. Like an amphibian aircraft, it's doesn't have good boat and airplane characteristic's. Same things with Ducted Fan airplane. I'm not looking for speed, economy or anything else. Just to have an aircraft, that look's and fly like a jet aircraft, but at fraction of the cost of real jet aircraft.
     
  13. Oct 31, 2013 #153

    Malish

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    Don't make mistake with turbine engine intakes. In Ducted fan it's different. It's not jet engine, where you need a lot of speed air to go thru the duct. It's sort of propeller working in it own environment. Angle of incidence of the blades are much lager, then in open prop. As soon fan begin to turn, it's will create airflow through the duct. This is main difference of the open propeller and the fan. All it's about air mass flow to generate the trust.
     
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  14. Oct 31, 2013 #154

    Doggzilla

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    I think we can agree on this one, especially since the fanliner uses the same wing as the AA-5, so we can actually have a control. But it wasnt a total failure, it was simply average.

    That said, in designs with limited prop size, it can nearly allow for full size prop performance. A ducted fan could be useful to avoid prop strikes... or to make aircraft more compact. For instance, a fan on a lake amphib could bring the engine substantially closer to the fuselage, lowering the CG. Or it could be used on aircraft that either cannot have long landing gear, or have landing gear integrated into the fuselage, like sailplanes.

    Every design has its merits, just have to find them.
     
  15. Nov 4, 2013 #155

    henryk

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  16. Nov 4, 2013 #156

    Vigilant1

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    As they mention, an ejector is good for static thrust (if you've got a jet/turbojet that is already aboard for other reasons). Not much applicability to cruise flight, but might be something to look at for VTOL (as that study does).
     
  17. Nov 5, 2013 #157

    henryk

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    -we can fold the ejector ring for cruise=

    http://www.reaa.ru/yabbfiles/Attachments/hustawka_multiplikatorwidelec_016_001.jpg

    ТримфибиÑ.JPG Решотка.jpg =with closed ejector duct...
     
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  18. Nov 8, 2013 #158

    henryk

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  19. Nov 10, 2013 #159

    danmoser

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    Reducing fuselage drag via boundary layer suction, combined with propulsive efficiency boost via boundary layer ingestion (AKA wake immersed propulsor) .. an excellent synergy of technologies.
    But the devil is in the details.. I'd be interested to study analysis and test results on this concept.. efficiency and cool looks.. what more do you want? ;)
     
    Last edited: Nov 10, 2013
  20. Nov 10, 2013 #160

    Doggzilla

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    Practicality first, then performance...
     

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