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Experimental Ducted Fan Aircraft Designs

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Doggzilla

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One of these days someone will try it on a ducted fan.

I wonder why they perform better. I’m betting it’s because it allows faster air velocity without faster tip speeds.

For any tip speed the contra rotating props will almost certainly have better exhaust velocity
 

Hephaestus

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One of these days someone will try it on a ducted fan.

I wonder why they perform better. I’m betting it’s because it allows faster air velocity without faster tip speeds.

For any tip speed the contra rotating props will almost certainly have better exhaust velocity
There's a big NACA paper on contra rotating.

I keep trying to envision a nice chain drive gearbox so you could run pairs side by side. Probably a nightmare exceeding psru development though...
 

Blackhawk

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This is from the internet and applies to almost all modern 4 Stroke Liquid Cooled engines; including
4 Stroke Jet Ski engines:

"There are many myths and misconceptions about engine cooling, but the truth is your engine’s
cooling system must perform a balancing act. It needs to extract enough heat to keep your engine happy,
yet maintain enough heat to keep it operating efficiently.
That means keeping the engine in the 180- to 210-degree F range"

This link below is for Rotax 4 Tech engine cooling; you'll see at 0.41/0.42 where the cooling system thermostat
opens once the engine has reached the correct operating tempture; so it operates exactly like your cars engine.


With a correctly matched radiator these engines will be very suitable for aircraft use, especially with their light
power to weigh and supercharger
 

Malish

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-I think,the way of gaining engine power is "one way"...

=better is to finde moore efficiant thrustars,today=Conter Rotating Fans /propellers .
It's may worth it, or may not - weight and complexity may be very high price to pay. Russian strategic bomber maybe fastest turboprop(800km/h), but noise, vibration and complexity - is way "over head":wonder:
Медведьсвоей-тайги-не-отдаст.jpg
Even Airbus using single fan on E-fan aircraft, but they have money and capability to build anything if it would be worth it.
20140715-airbus-e-fan-farnborough-001.jpg
 

vhhjr

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I put together a two fan contra-rotating unit a couple years ago and have a little data from it. I used two brushless motors each driving a three blade prop. The unit was run in three configurations:
1. Front motor driving, rear prop free wheeling
2, front motor driving, rear prop fixed
3. Both motors driving

The data is attached along with some papers on the subject. Basically, I got about 4 lbs of thrust with one motor driving and 7 lbs with both driving. Not quite double the thrust for double the power input. I'm sure with properly designed rotors instead of three blade props I could do better.

It is my understanding there are only two reasons complex CR props are considered: To reduce torque effects during high power take-offs and maneuvering, and to increase the power per ft2 of prop disc area thus reducing propeller diameter.
 

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Urquiola

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As discussed, SAE paper 741091, by Dow people, shows a propylengycol based cooling fluid is better than usual ethylenglycol fluids, that are poisonous. One of such fluids is produced by Pequinsa, in Navarra, formerly an Spanish company, but now in the mr Sores/ Soros orbit.
Deutz, in Cologne, Germany, has some oil cooled industrial engines; oil does not increase in volume with temperatures below the water freezing point, which could destroy engine block. About the heat transport and other features of oil and water and other fluids, please refer to the 'BOSCH manual of automobile technic'. NACA/ NASA air intakes do worse than the common type of square or round intakes, looking at front of wind. Salut +
 

BJC

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NACA/ NASA air intakes do worse than the common type of square or round intakes, looking at front of wind. Salut +
Right.

NACA submerged inlets were devised to provide high performance flush air intakes through surfaces reasonably parallel to the local airflow. They never were intended to accept ram air, even though a walk through the HBA section at Oshkosh reveals many placed for ram, with rounded sides to the ramp, and devoid of the proper inlet lip.


BJC
 

henryk

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I used two brushless motors each driving a three blade prop.
"( d) The axial gap between the rotors significantly affects the aeroacoustic performance of a contra-stage. The real-time analysis of sound signals has revealed that the excessive noise levels for closely spaced contra-rotors are associated with the direct compounding of blade passing frequencies, the frequency compounding being absent if the"r otors are placed far apart resulting into significant reduction in noise levels."

=not clear to me (with my poor English !)

I see , the Differential gear for CR propellers is very efficiant (and simple!)

https://www.dropbox.com/s/ky1z5jc9g3srohq/Dym - zwolnione tempo.mp4?dl=0

=circa 30 % moore thrust with the same propellers !
180/230, 50/80 , 50/70 kG thrust forces...
 
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Hephaestus

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I'd expect like single rotors and fixed vanes there's some rules on how to make it efficient.

But the acoustics definitely need to be considered... RC DFs are not the most pleasant sounding in general.
 

Malish

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NACA/ NASA air intakes do worse than the common type of square or round intakes, looking at front of wind.
NACA submerged inlets were devised to provide high performance flush air intakes through surfaces reasonably parallel to the local airflow.
Protruding air inlets creates disturbing airflow behind of them and we definitely didn't wonted that this(disturbed) airflow going into the air duct - that reason we're installing flush air intakes. Plus, protruding air intakes create "parasite" air resistance(drug) - that is why flush air intakes widely used in hi performance aircraft.
mJHRy.jpg
 

Doggzilla

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Technically those are protruding. They are on the gear housing bulge.

But placing them on an existing protrusion does eliminate any additional drag that would have occurred behind it.

So definitely an improvement.
 

BJC

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The Glasair III uses a NACA flush inlet for aspirating the IO-540 engine. One owner, who made several speed modifications, reported that greatly reducing the size of the inlet provided the largest speed gain of all of his mods. Note that, when sized properly, the drag was reduced and the engine produced more power.

Original size shown here:

66C64591-7DEF-452F-8D78-E9D1CA5E4415.jpeg


BJC
 
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