Ducted Fan Pseudo-Jets

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

sanman

Well-Known Member
Joined
Feb 24, 2021
Messages
267
=expected/estimated Specific Thrust ? [kG/kW]

BTW= CR Fan (Stator less !)...




=references...(many !)


Wow, that looked cool -- but it was electric ducted fan, right? What diameter are those fans?
Can counter-rotating ducted fan be done with mechanical transmission? Or will it be too heavy?
 
Last edited:

sanman

Well-Known Member
Joined
Feb 24, 2021
Messages
267
I came across this software for modeling things like ducted fans & turbines - anybody heard of this?

 

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
7,412
Location
krakow,poland

Malish

Well-Known Member
Joined
Oct 11, 2013
Messages
839
Location
Russia. City of Volgograd
How do you mean more shallow? You just mean shorter ducts? How does that keep intakes farther away from fan?

Duct turning radius should be larger and angle of turn should be as less as possible. On UL-39 ALBI they should placed the fan farther back from side air intakes, that will make air ducts with less degrees of turn(more shallow).
As now, there very sharp two almost 90 degrees turns in very short distance - this creates airflow separation and air turbulence in front of the fan and this causing loss of DF effectiveness!
pohon05.jpg
 

AdrianS

Well-Known Member
Joined
Jul 5, 2014
Messages
884
Location
Australia
Would the high static thrust potential of a DF help with an amphibian aircraft?

I'm thinking of something with high-ish inlets without the high CoG & thrust line.
 
Last edited:

copec

Well-Known Member
Joined
Aug 2, 2015
Messages
50
Location
Santa Clara, UT
Radiator cooling intake should be placed outside of duct(under fuselage) and exhaust could be made into the duct and fan should be located behind of radiator 🤔
Right now radiator cooling duct is taking some space of fan duct - and this is not good...
View attachment 120034

I believe their intent was to augment thrust by adding the engine heat while keeping the outside of the plane looking the same without additional intakes. It was definitely a much bigger compromise to keep the fan that far forward.
 

nestofdragons

Well-Known Member
Supporting Member
Joined
Jun 8, 2016
Messages
819
Location
Near Antwerp, Belgium
Hey, i see a lot of possible troubles when trying to design intakes for ducted fans, so ... why not use the idea of Burt Rutan? A asymmetrical installed engine. He did it on the Ares and it works fine. Intake-duct is a perfect line.
2021-01-05 ares 01.jpg 2022-01-05 Ares 02.jpg
 

nestofdragons

Well-Known Member
Supporting Member
Joined
Jun 8, 2016
Messages
819
Location
Near Antwerp, Belgium
I am just thinking out loud now. Would a ducted fan need to be small if he was installed angled?

At first, after looking at the Ares, i thought yes, but then i started drafting. In this draft you see the fuselage no longer in center and a huge duct beside it. If all is placed so CG is still central if will be less of a difficulty than a fully asymmetrical airplane like the BV141.

At first i was thinking "how do i make a nice connection between prop and engine", but ... if you simply place the engine at the same angle, that problem is gone. Placing engines at angle is not a problem at all.

Just for fun i placed a asymmetrical tail. 🤡
2022-01-05 schets vliegtuigvoorstel ducted fan.jpg
 

Malish

Well-Known Member
Joined
Oct 11, 2013
Messages
839
Location
Russia. City of Volgograd
A asymmetrical installed engine. He did it on the Ares and it works fine. Intake-duct is a perfect line.

Looking at 3 view drawing of this aircraft I don't see asymmetrically installed engine.
For me, engine is perfectly in line with centerline of fuselage - only air duct intake on left side of it. Two vertical tails can easy hold this small aerodynamic disbalance caused by single side air intake ;)
Also on the right side of fuselage look like large gun(similar as on A-10 aircraft) is located - that is why engine air intake is located only on left side - gun smog(when it's fire) wouldn't get to the engine and stall it!
 
Last edited:

cluttonfred

Well-Known Member
Supporting Member
Joined
Feb 13, 2010
Messages
9,730
Location
World traveler
IIRC, the reasons for the asymmetric intake on the Ares were 1) accommodating an engine, pilot, and a big gun in a very small airframe and 2) ensuring that the gun gasses wouldn't get sucked into the engine and cause it to stall. That's even clearer in the unbuilt two-seat variant envisioned by Scaled Composites. Note that the engine itself is installed at an angle and slightly off-center, but the actual jet-pipe directing the flow does appear to be straight and centered.

1641393524493.png
 

nestofdragons

Well-Known Member
Supporting Member
Joined
Jun 8, 2016
Messages
819
Location
Near Antwerp, Belgium
IIRC, the reasons for the asymmetric intake on the Ares were 1) accommodating an engine, pilot, and a big gun in a very small airframe and 2) ensuring that the gun gasses wouldn't get sucked into the engine and cause it to stall. That's even clearer in the unbuilt two-seat variant envisioned by Scaled Composites. Note that the engine itself is installed at an angle and slightly off-center, but the actual jet-pipe directing the flow does appear to be straight and centered.

View attachment 120084
i do think that the small angle of the exhaust is less a problem than the sharp angles which we saw in the intakes of the other designs. I would go for this kind of ducted fan proposal. Problem might be to get CG in center. Ares has the gun as counterweight for the engine. But ...it might have a very easy solution to get it done for a small jet looking homebuilt.
 

cluttonfred

Well-Known Member
Supporting Member
Joined
Feb 13, 2010
Messages
9,730
Location
World traveler
i do think that the small angle of the exhaust is less a problem than the sharp angles which we saw in the intakes of the other designs. I would go for this kind of ducted fan proposal. Problem might be to get CG in center. Ares has the gun as counterweight for the engine. But ...it might have a very easy solution to get it done for a small jet looking homebuilt.

Yes, there would be very slight losses due to the duct but nothing major. I have always liked the Ares configuration, with or without the asymmetric elements. With wider spacing of the booms it would also make a very elegant pusher prop design, probably needing to move the center section trailing edge forward for prop clearance without an extension shaft but then you could sweep the outer panels back to compensate if needed.
 

Woodenwings

Well-Known Member
Joined
Aug 2, 2006
Messages
244
Location
Toronto
RFB fan trainer. And some good reading
 

Attachments

  • 20220105_113124.jpg
    20220105_113124.jpg
    32.1 KB · Views: 11
  • 20220105_113120.jpg
    20220105_113120.jpg
    37.9 KB · Views: 15
  • 20220105_113401.jpg
    20220105_113401.jpg
    55.7 KB · Views: 15

J.L. Frusha

Well-Known Member
Supporting Member
Joined
Feb 17, 2006
Messages
1,072
Location
Luling, Texas
@Malish

I used to have several of Bob Hovey's books, especially those on structure and aerodynamics that involved the Whing Ding II. At one point I had his phone number, but his wife said he was no longer interested in aircraft and was totally focused on breeding roses. Wish I'd been able to talk to him myself.

_______________________________________________________________________________________________________________________________________

I just came across an RC Ducted Fan of the Martin X-24A Lifting Body... Aerofred has it as the "Mystery Wing" It was designed by the same people that designed the X-24A Lifting Body.

1641654281998.png
 
Last edited:
Top