Ducted fan aircraft

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Lucrum

Well-Known Member
Log Member
Joined
Jun 10, 2008
Messages
956
Location
Canton, GA
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....
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.
 

rv6ejguy

Well-Known Member
Joined
Jun 26, 2012
Messages
3,749
Location
Calgary, Alberta, Canada
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.
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.
 

Lucrum

Well-Known Member
Log Member
Joined
Jun 10, 2008
Messages
956
Location
Canton, GA
Getting the engine out of the duct is huge I think...
I agree, my duct wraps around the shaft keeping it and the engine out of the duct.
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.
Again I agree.
 

Xanadrone

Well-Known Member
Joined
Nov 24, 2011
Messages
195
Location
Bucharest Romania
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?!)
 

cheapracer

Well-Known Member
Log Member
Joined
Sep 8, 2013
Messages
6,109
Location
Australian
Awesome looking but would anyone entertain a genuine fear of being shot at riding around in that?
 

Lucrum

Well-Known Member
Log Member
Joined
Jun 10, 2008
Messages
956
Location
Canton, GA
...I wonder only if some preliminary estimated performance data are available (maybe henryk knows more?!)
"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.
 

Xanadrone

Well-Known Member
Joined
Nov 24, 2011
Messages
195
Location
Bucharest Romania
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.
 

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
5,281
Location
krakow,poland
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.
=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...
 

Starman

Well-Known Member
Joined
May 16, 2009
Messages
2,011
Location
High in the Andes Mountains
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.)
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.
 

Mike W

Well-Known Member
Joined
Nov 3, 2012
Messages
65
Location
Doncaster Yorkshire UK
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).jpgmw2bb 001-bmp.gif
 

plncraze

Well-Known Member
HBA Supporter
Joined
May 11, 2006
Messages
1,820
Thanks for sharing that story Mike W. I remember seeing pictures of the plane in Air Progress. Sorry it didn't work out.
 

Mike W

Well-Known Member
Joined
Nov 3, 2012
Messages
65
Location
Doncaster Yorkshire UK
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
 

Doggzilla

Well-Known Member
HBA Supporter
Joined
Jun 2, 2013
Messages
2,322
Location
Everywhere USA
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.

View attachment 31138
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.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
13,225
Location
Port Townsend WA
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?
 

Doggzilla

Well-Known Member
HBA Supporter
Joined
Jun 2, 2013
Messages
2,322
Location
Everywhere USA
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?
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.
 
Top