Ducted fan aircraft

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kenkad

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Nov 25, 2011
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53
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union grove, al 35175
Malish,
when I look at your posts 107, 109, and 112, it appears that you have two sets of duct support blades, one row with 7 and one row with 11. I assume you did this because there is a body joining point right aft of the 5 blade fan and you have to maintain the roundness of the duct at that point/region. In post 107, you say that these counteract the swirl! How is that possible when they are symmetrical/inline with the duct? Your 5 blade fan creates a swirl and there is no counter rotating fan to remove the swirl. Maybe I am misinterpreting your pictures.
 

Doggzilla

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Everywhere USA
Malish,
when I look at your posts 107, 109, and 112, it appears that you have two sets of duct support blades, one row with 7 and one row with 11. I assume you did this because there is a body joining point right aft of the 5 blade fan and you have to maintain the roundness of the duct at that point/region. In post 107, you say that these counteract the swirl! How is that possible when they are symmetrical/inline with the duct? Your 5 blade fan creates a swirl and there is no counter rotating fan to remove the swirl. Maybe I am misinterpreting your pictures.
I have a stupid idea...what about using a single nozzle and using the counter rotating flows to counter each other as they recombine, with fewer guide vanes?

Scrubbing losses on the intake trunk are not insignificant for sure --and separation is also a problem on a non contracting duct more than one with a non constant-decreasing, cross section and is one of the main differences between a ducted propeller (with a bell mouth creating a contracting duct in effect and accelerating the boundary layer by the airfoil effect when the stagnation point is on the outerside of the intake ) and a buried fan - without boundary layer bleeds on the intake and fairly clean flow into the intakes it could be hard to get the optimum blade loadings downstream at all times --the transition from a square section intake to a round disc face also introduces problems (even to standing vortices in the corners --it was Frank Whittle who foresaw this as a problem in centrifugal compressors and was found also in superchargers by Hooker --the Moller Slycar uses the reverse of a round intake to an expanded square exit and this is also a problematic geometry --few other homebuilts have used an internal shrouded propulsor so much will be learnt from this work .

PS there was a Mazda rotary powered 'ducted propulsor' homebuilt flown at Mojave in the early 70s but I haven't heard of it since -any one know details ?
Speaking of that, the f-22 does just fine with fixed inlets, it relies on the extra air just pouring off the sides. The external drag is a fraction of the drag of an internal ramp like the f-14. Duct drag and improper dynamic thrust/impulse thrust are absolutely the biggest factors. Note that the most efficient jets have no ducts...all prodded engines...and twin spools that allow for a wide range of dynamic thrust and impulse without a nozzle... But that relies on designs with a hot section.
 

Topaz

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...PS there was a Mazda rotary powered 'ducted propulsor' homebuilt flown at Mojave in the early 70s but I haven't heard of it since -any one know details ?
Is that the one David Thurston talks about in his various books, especially Design for Safety?
 

Malish

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Oct 11, 2013
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Russia. City of Volgograd
To Danger Zone,

We couldn't use wooden blades. They weight to much. Our blades made from Carbon fiber and hollow. Their weight, about 110 gram's each. When we had fan failure, only damage we had, was cosmetic(scratches and nicks) to contaminating ring and stator. And I was glad, that we had that failure on the ground. It's proved, that our aircraft , wouldn't have catastrophic airframe damage from fan failure. This mean's aircraft would be controllable for emergency landing.P6190596 (Large).jpgP8300661 (Large).jpg
 

Malish

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Oct 11, 2013
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Russia. City of Volgograd
To kankad:

Support with 7 blades has symmetrical profile and holds fan bearing housing. Behind the fan is swirl counteract devise. It has 11 C-shaped blades. On photo it's difficult to see. When we did experiments with Ducted fan propulsion system, we did find out that airflow swirl behind the fan, was about 20 degrees. So we made swirl counteract stator with C-shaped blades, to change airflow radial angle to 0 degrees. Both stators don't support the duct. One support the fan housing, an other acts as swirl remover. Fuselage/air duct split was made only to have easy reach to the fan itPicture 013 (Medium).JPGDCP_4600 (Large).jpgP4170531 (Large).jpgself. For service and inspections.
 

kenkad

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Nov 25, 2011
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union grove, al 35175
Malish,
Thank you for your response. That is interesting that you used a thin wire with tufts to determine swirl angle. Very interesting photographs. I was wondering if you had done some type of laser doppler velocity measurements. Do you have a photograph with the static swirl blades and tuft result? It would be very interesting to know the velocity profile across the duct after your swirl blades. I suspect you would like to know that as well. Again, thank you for responding.

Do you know if EADs did the same thing like you did since I could not determine if they used or are planning to use contra rotating fans. Had you considered using belt drive to get rid of the drive shaft in the duct? Just curious!
 
Last edited:

WALEED

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Oct 27, 2013
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Sudan
Greetings,,,

Actually I joined the group recently , and my great pleasure to know the people's idea in this forum . I am Extremely excited by this kind of idea , but a few of Performance flaw will take place . I can't determine whether the the ducted fan Piston engine can suit with the Aircraft you meant or not , because at the preliminary stages we need to know the Performance Categories Such like :- the Power required , Maximum Take off weight , dry Operating weight ,.. and then we can decide which engine could Produce a suitable Power available with lowest possible fuel consumption , based on world Aviation regulatory bodies Demands. Conclusively I think it needs a study of how much R.P.M and torque can it produce as you said and especially the thrust in the piston Engine driven Aircraft Produced by the Propeller Pitch Setting ...


Thanks ,,,
 

danmoser

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Feb 1, 2010
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641
Location
Sandy, Utah, USA
Interesting topic.. ducted fans have been a long time interest of mine..
I've done some RC models which incorporated ducted fans, but not conventional installations.. long story.

For those interested in utilizing ducted fans, I highly recommend the publication "Ducted Fan Design" by F. Marc de Piolenc and George E. Wright Jr.
..from here: Mass Flow

Mistakes often made include using jet engine inlets as a model for ducted fan propulsion systems, and confusing shrouded propellers with ducted fans.. these have entirely different characteristics, and you should not ignore the subtleties.
Certainly, for most applications, it's hard to beat a good ol' open propeller, but there are some niche applications where ducted fans might have an advantage... one I'm interested in is boundary layer ingestion for combined fuselage drag reduction and propulsion efficiency gain..
 

Malish

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Oct 11, 2013
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Russia. City of Volgograd
To kenkad,

We did check airflow after the anti swirl stator. It's pretty much strait. But I couldn't find any photos. We're thinking about the belt drive, but after some research, we had toDCP_4709 (Large).jpgDCP_4714 (Large).jpgDCP_4716 (Large).jpg drop this idea. 400 hp is to much for the belts.
 

Malish

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Oct 11, 2013
Messages
534
Location
Russia. City of Volgograd
To danmoser.

I did read everything I could find about Ducted fan. Including "Ducted Fan Design" by F. Marc de Piolenc and George E. Wright Jr. I know about shortcommings of ducted fan aircraft, compare to conventional prop driven aircraft. I don't expect speeds of jet and even prop aircraft. It would have top speed about 200 knots. But hole idea is to have an aircraft, that looks and handles like jet aircraft. But be in price range with Glassair II and Lanceair Legasy aircraft.
 

Malish

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Messages
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Russia. City of Volgograd
I know that a lot of "dark areas" in Ducted fan aircraft design. After we came out with final aircraft configuration, first thing we did, is to built 25% scale RC model. This size we picked because it will be as close as possible aerodynamically to a real aircraft. Our main goal was to determent flying characteristic of airframe itself, so we can start to built master model of aircraft and making molds. Same time we're experimenting with ducted fan propulsion system. Model flew very well. We tested it for slow flight, stalls, spin recovery and maneuverability. We're pleased with results. Here is video(sorry for amateur quality):
PJ-II 1/4th Scale Model - YouTube
 

delta

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May 26, 2011
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Brookside Utah
I know that a lot of "dark areas" in Ducted fan aircraft design. After we came out with final aircraft configuration, first thing we did, is to built 25% scale RC model. This size we picked because it will be as close as possible aerodynamically to a real aircraft. Our main goal was to determent flying characteristic of airframe itself, so we can start to built master model of aircraft and making molds. Same time we're experimenting with ducted fan propulsion system. Model flew very well. We tested it for slow flight, stalls, spin recovery and maneuverability. We're pleased with results. Here is video(sorry for amateur quality):
PJ-II 1/4th Scale Model - YouTube
You could have said "The Beginning" at the end of your video. That is my wish for your and your project... Good luck...
 

henryk

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Mar 8, 2010
Messages
5,281
Location
krakow,poland
To henryk,

Are you asking about model?

Electric impellers 120mm in diameter. Model weight =16kg. Static trust 2x4kg = 8kg.View attachment 27865
-yes,thankyou!

-impellers are greate and with a big adventages=

Paraglider Thrusters - YouTube

Prototype of Tricke powered by Ducted Fan. Dusek,

Kermitt paratrike with ducted fan - YouTube

=low and slow...
"
dreamsci 1 rok temu
Hi This prototype for testing has 25Kg thrust so just straight and level with an 80Kg pilot. The next one with 40Kg thrust or 60Kg burst thrust, i project a climb rate of 1 to 2 m/s. I'll let people know once it gets in the air.
"
 

Malish

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Oct 11, 2013
Messages
534
Location
Russia. City of Volgograd
To kenkad.

I strongly believe, that Ducted fan aircraft need's to have, a simple drive system(at leas for home/experimental build aircraft). All this staff, about counter rotating fan's, will only complicate things. More weight and technical problems will not pay off. And I'm a little sorry(who new about financial crisis of 2008, PJ-I will be flying by now), we went from SINGLE FAN aircraft, to two ducted fan airplane. Yes, it's look more like jet fighter, but it's become more complicated. My original plans was a simple DIRECT drive Ducted fan system airplane. No gearbox(it's weight to), only one drive shaft(ls less weight again) and only one fan(960mm in diameter). We did build R/C model of this aircraft. IPicture 040 (Medium).JPGPicture 046 (Medium).JPGPicture 048 (Medium).JPGt's preformed very well. And we're test run the fan system for it to. Everything looked good. This was PJ-I. We're still planing to build this aircraft(if finances will be available). It's a strait/tapered low wing airplane. We could use molds from fuselage of PJ-II, up to aft of engine compartment. Change only tail section. Also we can use molds off rear tail surfaces(just change them a little). This aircraft will be lighter(then PJ-II), and could preform aerobatics.
 
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