"Vortex" ceiling fan !?

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Downunder35m
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"Vortex" ceiling fan !?

Post by Downunder35m »

I was asked if I could make a small, basically silent but still rather powerful ceiling fan - Whisky Tango Foxtrott !! LOL

My first thought was that such a thing is impossible for sure.
Next thought was "You don't have a ceiling fan, so you need to check one out in real conditions...."
Of course my friend had one in the living room, rather large beast with the blades spanning almost 1.2 meters....
Turned out these things are not really noisy at all - on the lowest speed....
When we cracked it up a bit the real problem was obvious.
The entire thing was not only badly balanced, the blades all had sligthy different angles.
An hour of bending, checking and sticking on some weigths provided a perfectly smooth running fan - finally something to go with for a comparison.

IMHO the only real noise created came from the actual airflow, the motor only produced a low humming noise that I can't really hear eanough from bed level.
But the real issue was that no matter what those fan blades either push a lot of air straight down up straight up - depending on how you orientate and angle them.
My friend said he wants a ceailing fan over a normal one because the airflow is less distracting during a hot summer night.
Mind you that we have winter right now and that I have no clue how anyone would test a ceiling fan for cooling during the night - I have a heated blanket on LOL
I guess my friend knows that my work won't leave much free time to devlop something that isn't invented yet - or available down here.
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Downunder35m
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Re: "Vortex" ceiling fan !?

Post by Downunder35m »

How to design a fan that moves a lot of air but won#t blow it over you when hanging from the ceiling ??

My first and dirty check came from the fan or turbine assembly of an old vacuum cleaner.
Some carboard to make a new housing tube for a smaller 555 motor.
A little adapter from a piece of aluminium tubing to be crimped onto the 555 shaft so I could thread the thing and mount the turbine.
A smoke test showed the air coes in from the center hole of the turbine and than just spreads rapidly and with a lot of twisting and turbulences when it comes of the fan assembly.
Keep in mind: The entire original housing with those divertes for the air was left out to allow a free flow out of the turbine that is as flat as possible.

For my new repulsine project I need an intake cone anyway.
So why not not create something close enough so I can test it ? ;)
Sketchup is still my prefered weapon for these things - don't judge me, I am old ;)
And my PC is rather old as well and only has 32GB of RAM installed.
Designing fluent, organic things in Sketchup is then still a pain in the behind if you don't want to simplify to level that results in clearly not fully round things...
So far I managed to created a nice vortex style intake with 4 openings going to the outside of the inlet cone.
The idea is to let the iarn into those inlets in a radil fashion - a bit like scooping it in.
It is then twisted to end up in a spiral that ends straight down.
So far so good - but I need at least three rows of these intakes at different heights....
All it it will 12, preferably 16 of these radial intakes.
But they are only secondary.
The main intake will be straigth down the center of the cone.

Current problem is to properly place and size those vortex inlets while allowing for a hyperbolic center intake.
Ideally I would like the center airflow to be just enough to "fill" the center of the straight part of the spiral together with what comes from radial intakes.
Sadly I can't find any simulator I can afford to test and optimise the design on the cumputer before trying to print it.
With enough patience my old PC will sooner or later finnish the parts I need for this stage - I hope LOL
What comes next?
Of course such a complex intake is worth nothing if from there the airflow is chopped up or "kinked" around...
Simply resvering it would certainly be an option but also make the thing rather long along the axis.
How do you make a fast spinning and slightly compressed airflow go straight again?
Of course by letting it twist its way out ;)

For the second stage of the fan I would like to use a revere approch to what Victor Schauberger did with his water utrbines that run on nothing but water - or at least that was the claim back then.
The Coanda effect works best with a really straight and flat airflow - like a wing on a plane.
But it also works rather well with all smooth furfaces, especially if you try with water.
Ever had those badly dripping coffee cans or just tried to get liquid out of a glass or mug without having it run down to the bottom and spill ? ;)
I imagine a sharp cone with a turbo fan like "blade system" as channels going into the cone, rather than having "blades".
It flattens out like a half sine wave you split and flip around - sharp point in the center ending flat at the sides ;)
These channels will create a much faster airflow than the remaing air on the surface of the cone.
As those channels also spin around the axis but in the opposite spin as they came in - the outgoing streams should cancel each other out for the spin effect.
At least if I get the volumes and flow speeds correct :(
What happens in this assembly is that the air is forced into a flat and narrow channel.
Imagine two paper plates you stack up with a little gap...
In the center our cone, acting as the corrector for the airstream.
Fast moving air create a lot of noise when coming out.
Smooth surfaces are a must...
Also letting those disks end in a venturi like outlet - the bigger the outlet the lower the airspeed.
To maximise this venturi effect and to provide an "airstream silencer of sorts", we have to include some inlets on at least one of the disks, so why not use this for a boost in the overall airflow rate coming out ? ;)
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
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Downunder35m
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Re: "Vortex" ceiling fan !?

Post by Downunder35m »

Problems realised so far while designing the air intakes....

Creating something on the screen is one thing - making it printable a totally different story.
I ran some intial tests in my slicer and there simply is no possible orientation that would allow printing it without internal support in areas you can never reach to clean out.
Best option would be to simplify the design to eliminate those overhangs as good as possible.
But that would ruin the airflow....
Splitting such a thing is certainly and option, especially with a resin printer and good accuracy - if not for the damn shrinkage...
Things just won't shrink evenly enough :(
The outlet is way less critical and I might use 3 or 4 parts to be joined.
That is per "disk" to prevent internal support - what is need to keep them apart and stable will be include in one of the disks.
Once I have the designs complete on the PC I will work on making them printable I guess.
Exploring the works of the old inventors, mixng them up with a modern touch.
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Re: "Vortex" ceiling fan !?

Post by Downunder35m »

You MIGHT now say "I could be interested" - but how is it supposed to work?

Air that is pushed outwards has to come from somewhere.
For our normal ceiling fans it means they "suck" the air in from above and "push" it downwards.
Some fancy wings provide less wind down and a bit more wind out though.
In my case though the air comes from UNDER the fan but the outgoing airflow will include the air above in terms of being sucked along.
The cone SHOULD (hopefully) create a strong enough vortex like flow going into the system.
As the air has to follow this flow it hopefully does to some distance to the fan.
If we ignore obstructions the airlow would follow the ceiling, down the walls and finally up to center of the fan again.
Should mean that right under the fan we create a dead zone with basically no airflow, just air and temeperature exchange.

Let me know what you think if you could be bothered to read all this.
I will upload some screenshots once Sketchup is finally done with the solid operation and merging....
Exploring the works of the old inventors, mixng them up with a modern touch.
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Orngrimm
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Re: "Vortex" ceiling fan !?

Post by Orngrimm »

Basically you play a game of "Move air but dont create turbulences". This is super hard and the faster the mechanical parts are moving the more difficult it gets. And its not only the RPM but also the angular speed: Even a slow moving fan may have tips which travel quite fast thru the air and thus creating more turbulences than the slower moving inner parts of the blades.

Have you checked the tips of airplanes? Normally they have Wingtips to reduce the turbulences created at the end of the wings. https://en.wikipedia.org/wiki/Wingtip_device for details.

I think the most promising path of action would be to silence a normal fan with such methods than creating a own design from scratch. the smaller the fan, the faster it has to move for the same volume of air. The faster it moves, the louder the air will get.
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Downunder35m
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Re: "Vortex" ceiling fan !?

Post by Downunder35m »

I just realised that you might wonder about two things here.... - my bad :(

Let me correct this:
I posted this in the workshop section as I think I would be rather nice if one dayy people would make a nice wooden housing or even outlet disks.
And then there is the power problem that I forgot to mention.
My plan it to have the initial fan powered by a salvaged fan motor out of a microwave.
Just so that you don't get any weird ideas about size, RPM and power requirements ;)

I gave up Sketchup for today after it crashed on me - three times in a row :(
But I did some nice experiments with some leftover printing resin.
I will write a bit about this in another post if you don't mind ;)
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To tinker and create means to be alive.
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Orngrimm
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Re: "Vortex" ceiling fan !?

Post by Orngrimm »

Again: As i understand, the main culprit after the balancing of the ceiling fan was the air itself.
As far as i understand, you want to have a
- silent
- big-airmass-moving
fan mounted on the ceiling.

Again, the smaller you make your fan (Doesnt really matter what technology), the faster something has to move to move the same amount of air. The faster something moves the harder it is to control all the flows and keeping it laminar which is required for silent air-movements.
As even the slow-turning "normal" ceiling fan made too much air-disturbances, it is easyer to figure out a way to keeping the airflow with such a fan (more) laminar than trying to design and build a small, high-RPM fan and trying to keep laminar flow intact there. The faster something moves, the harder it is to keep everything laminar.
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Downunder35m
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Re: "Vortex" ceiling fan !?

Post by Downunder35m »

Again you are right of course ;)

But I finally managed to get the parts together as one solid that does not cause error messages when getting it in the slicer.
Was a quick and overlooked the creation of some internal supports - what a pain to clean out....
What I can say....

The damn things works far better than what I expected, despite being greedy on the resin and reducing the size by 50%.
It is basically silent, no "fan" noise at all, just what the motor and some minute balance problems create.
Best of all: The air intake basically works totally as planned!
Only downside: he vortex created is rather short - but any vortext counts for a first try if you ask me.
As planned the air is mainly sucked in from the center opening.
The surrounding inlets though enforce the vortex flow and through that increase the intake capacity of the center.

For this model I still used a centrifugal fan like outlet.
It was just the easiest and quickest way to "close" the bottom and to add something for the motor mount.
Don't have a smoke generator but will search for something to make a bit more smoke that a candle you blow out - then upload a short video of th action.
Vortex fan02.jpg
Vortex fan02.jpg (154.4 KiB) Viewed 11 times
Vortex fan01.jpg
Vortex fan01.jpg (237.15 KiB) Viewed 11 times
Stay tuned for the video ;)
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
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Re: "Vortex" ceiling fan !?

Post by Downunder35m »

Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
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Orngrimm
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Re: "Vortex" ceiling fan !?

Post by Orngrimm »

OK... I misjudged your meaning of "Large airmass" to be moved. I was talking a 1-2 cubicmeters per second at least and with a speed of like 2-4 km/h to nor make a tornado in the room...
Honestly, with this volume of air pulled, you can just buy a Papst Fan like the 255M with only 5 dBA (!!!) and 2.3m^3/h
https://www.ebmpapst.com/de/en/products ... /255M.html

Or if you need more volume, take a 8412NGLE with still a basically impossible to hear 12 dBA at 33m^3/h
https://www.ebmpapst.com/de/en/products ... 2NGLE.html

But those still fall WAY short of what a slow turning LARGE ceiling fan can move. And if the fan is spinning slow enough (I talk in the region of 1 turn per 2-3 secs) it WILL be suuuper silent and still move a decent m^3 of air.
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