Ducted Fan Pseudo-Jets

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
6,601
You've pointed out that over 100mph, the increases in drag lower the efficiency of the ducted fan propulsion.

Would you be willing to consider the idea of trying to ionize airflow inside the duct, in order to reduce drag?
Ionized airflow is more laminar than regular air (diatomic gas) and therefore less turbulent with lower drag characteristics.
Please consider that because duct is surrounding the airflow, it provides better opportunities to ionize that airflow.
There are multiple possible methods of ionization: contact ionization, corona discharge, helicon antenna
Ionizing air requires energy, and the energy consumed might be way more than any gains. Engineers have been doing this stuff for decades and they know a lot more than we do.
 

sanman

Well-Known Member
Joined
Feb 24, 2021
Messages
238
Ionizing air requires energy, and the energy consumed might be way more than any gains. Engineers have been doing this stuff for decades and they know a lot more than we do.
It doesn't require that much energy - at least not compared to running the ducted fans themselves - and the airflow doesn't have to be fully ionized. Just enough has to be ionized, or enough plasma injected into the airflow that it will sufficiently cut down on the drag. The thing is that these engineers are trying to do this for wings -- ie. the outer surface of the aircraft.
Nobody's flying ducted fan pseudo-jets -- they aren't a very common type of aircraft -- so nobody's thought to try the ionization trick for them.

But given the airspeed limitations of ducted fans are particularly due to drag effects, it could be especially worthwhile to try it on them.
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
6,601
It doesn't require that much energy - at least not compared to running the ducted fans themselves - and the airflow doesn't have to be fully ionized. Just enough has to be ionized, or enough plasma injected into the airflow that it will sufficiently cut down on the drag. The thing is that these engineers are trying to do this for wings -- ie. the outer surface of the aircraft.
Nobody's flying ducted fan pseudo-jets -- they aren't a very common type of aircraft -- so nobody's thought to try the ionization trick for them.

But given the airspeed limitations of ducted fans are particularly due to drag effects, it could be especially worthwhile to try it on them.
Ionized air (and plasma) are extremely reactive and might destroy the fan or duct, too.
 

Tiger Tim

Well-Known Member
Joined
Apr 26, 2013
Messages
4,119
Location
Thunder Bay
With regards to ion/plasma augmentation of a power system, it’s probably miles to light years ahead of what this forum is for. Your best bet if you truly believe in it would be to prove it, patent it, and make your millions from there.
 

sanman

Well-Known Member
Joined
Feb 24, 2021
Messages
238
Ionized air (and plasma) are extremely reactive and might destroy the fan or duct, too.
Turbines and their ducts also have hot gases flowing through them, but they use suitably resistant materials.
Likewise, it may be that an ionization-augmented fan duct may use some kind of protective coating layer to avoid long term erosion.
Maybe ionization doesn't have to be switched on until sufficiently high airspeeds, where the drag effects become more relevant.

However cold plasmas are not known to be very destructive, and dentists even use them to sterilize parts of a patient's mouth without destroying tissue.
(Just as a ducted fan exhaust can be referred to as a "cold jet", likewise a gas (eg. air) that has ben ionized without being heated can be referred to as a "cold plasma")


With regards to ion/plasma augmentation of a power system, it’s probably miles to light years ahead of what this forum is for. Your best bet if you truly believe in it would be to prove it, patent it, and make your millions from there.
Well, ionized airflow solutions are already being developed to provide drag reduction for the road transportation industry:


I figure that the aircraft industry has to at least keep up with road vehicles.
Aircraft typically travel faster, and drag is more of an issue of concern for them than for road vehicles, which travel slower.

Ducted fans should also be better at noise reduction compared to open propellers/propfans, in addition to being safer. To then make them more fuel efficient through drag reduction could then make them a much more appealing choice for light aircraft.
 
Last edited:

speedracer

Well-Known Member
Joined
Feb 4, 2020
Messages
252
Turbines and their ducts also have hot gases flowing through them, but they use suitably resistant materials.
Likewise, it may be that an ionization-augmented fan duct may use some kind of protective coating layer to avoid long term erosion.
Maybe ionization doesn't have to be switched on until sufficiently high airspeeds, where the drag effects become more relevant.

However cold plasmas are not known to be very destructive, and dentists even use them to sterilize parts of a patient's mouth without destroying tissue.
(Just as a ducted fan exhaust can be referred to as a "cold jet", likewise a gas (eg. air) that has ben ionized without being heated can be referred to as a "cold plasma")
I've never seen a "successful"ducted fan on a homebuilt, but then, I don't get out much. By successful I mean giving the same or better performance as an UNducted fan (propellor). Can anyone point one out? Thanks.



Well, ionized airflow solutions are already being developed to provide drag reduction for the road transportation industry:


I figure that the aircraft industry has to at least keep up with road vehicles.
Aircraft typically travel faster, and drag is more of an issue of concern for them than for road vehicles, which travel slower.

Ducted fans should also be better at noise reduction compared to open propellers/propfans, in addition to being safer. To then make them more fuel efficient through drag reduction could then make them a much more appealing choice for light aircraft.
 

sanman

Well-Known Member
Joined
Feb 24, 2021
Messages
238
I've never seen a "successful"ducted fan on a homebuilt, but then, I don't get out much. By successful I mean giving the same or better performance as an UNducted fan (propellor). Can anyone point one out? Thanks.
Check out these two:



 

Malish

Well-Known Member
Joined
Oct 11, 2013
Messages
721
Location
Russia. City of Volgograd
Ducted fans should also be better at noise reduction compared to open propellers/propfans, in addition to being safer. To then make them more fuel efficient through drag reduction could then make them a much more appealing choice for light aircraft.
DF are less noisy then prop and safer on the ground - this is the fact!
And they are good for light aircraft - if someone not planing flying to fast(more than 150mph!), and most GA aircraft and pilots don't fly much faster!
 

Cardmarc

Well-Known Member
Joined
Jun 16, 2021
Messages
72
Can you reference where to find this book you quoted from? Take a look at this ducted fan intake and fan design and tell me your insights?
 

Malish

Well-Known Member
Joined
Oct 11, 2013
Messages
721
Location
Russia. City of Volgograd
Can you reference where to find this book you quoted from? Take a look at this ducted fan intake and fan design and tell me your insights?
I(personally) think this car/plane will NEVER fly - remember my words ;)
Or it's may fly - but not very good!
I don't believe in flying cars - to much difference in use(compromises need to be made) and regulations in their use(particularly on the roads).
 
Last edited:

Toobuilder

Well-Known Member
Log Member
Joined
Jan 19, 2010
Messages
5,362
Location
Mojave, Ca
Anything can be made to fly faster - but, at what cost? Why to worry about that for light GA aircraft?
The easy answer is that for some people it is speed that brings utility. More speed means more utility.

But if I was to flip your question around, I might ask: If we only need to go 150 MPH or less, then why even bother designing anything new? I mean, there are HUNDREDS of well proven, existing GA airplanes that fit in this category. Electrics, parafoils, motorgliders, biplanes, RV's, ultralights, spamcans, and classics. Virtually any mission and price range under the sun - why spend the time on "just one more"?

If I only want to go 150 MPH, I pick an airplane and write a check; but if I want to take the speed from 200 knots in cruise to 250, my options are very limited and THAT is going to take some inventing.
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
6,601
OK, send me a video when the "flying car" is registered as a car for highway speeds and is certified as an airplane that actually flies.
And when it's able to accelerate to 90 MPH with the drag of wings on it.

I'm quite sure that a Cessna 150 with the wings off would accelerate a whole lot better than that Switchblade, and a 150's acceleration has never been anywhere near spectacular.
 

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
6,744
Location
krakow,poland
  • Like
Reactions: BJC
Top