Tunnelless wind tunnel.

[Jerry]

I've been talking about building a wind tunnel for several years now. I've actuly been gathering parts over that time.

I started an assembly a couple days ago. Do to lack of time and space I've dicided to take addvantage of my covered patio/deck area. However as per my wife this can not be a perminet installation.

So I'm making it portable. If the deck area is not being used for family gatherings or a BBQ & ect. I can role the unit into place and set up for blade or genny testing.

Once testing is done I can role to the outback storage location. I can also load it up on my small 4ftX8ft garden tractor trailer for use at my store or anywhere.

Lowes has a nice 24" X 48" garden wagon on sale at $67.98. I got one. It has sides that fold down. I left them up and used some 3" mufler clamps to hold some 5ft pices of angle iron with all them holes. This alowed framework to support parts and pices.

This way I've not harmed to wagon and its easy to unbolt and return the wagon back into a wagon for its intended use.

I replaced the original thin plastic sheet in the bed with 2 layers of 5/8" plywood.

This new bed is home to 2 each 107lb 180 volt 2 hp dc motors. After this thing is finished I estemate it will weigh in around 300lbs. The wagon says its good for 1200 lbs.

I built an 7ft high rack to hold the shaftts, bearings and pullies to support 4 each 30" air mover fan blades. I had reported ealyer they were 24" turns out they are 30"

The motors are rated 1725 rpm, allthough will go higher with higher voltage.

I'll start out with a 4" pully on the motors and 5" pullies on the blades. This will be a belt driven system.

Now the blades will ocupy a space of 63" tall X 62" wide. There is a 3" space between the blades up and down and 2" space between the blades side by side.

From the ground its 8ft to the blade tip top.

I welcome any sugjestion for spaceing addjustments. I do have room to go up with the top blade set and go wider some also.

I will try some chaneling just ahead of the blades as well as distance from the genny being tested. That distance under the covered area could as as long as 24ft.

Heres the pictures.  

I'll take picture latter when the unit is in the test area.

                          JK TAS Jerry

[willib]

Looks like its coming along nicely..

you might want to try blowing the air OUT of the tunnel , instead of blowing the air INTO the tunnel.

That's the way  ED did it..

and there would be less disturbance from the fans.

as for mounting the motors , how about mounting them below and half way between each level of fans .

kind of like a V with each motor at the bottom of the V ? and the fan pullys at the top of the V

do ya see what i mean?

[willib]

There i go again reading the post but not the topic headline..

Tunnelless windtunnel?

a few pieces of plywood could be dissassembled when you get done testing ?

[RP]

Jerry,

I've got one of those wagons too.  The pneumatic tires are nice for going over rough ground but they're a little tippy with a high centered load.  You might consider adding an outrigger for stability both in front of and especially behind the blades.

This could be a simple as a hinged 2X4 or angle iron that flips down to the ground (near vertically) on either side.

[jimjjnn]

Jerry, do you have a pilot's lisence for that?

[coldspot]

jerry-

You have to much fun !!!  

"some channeling just ahead of the blades"

Didn't ED or you or some else here on the forum

figure out that winds could be straightened out from the swirling fan blades by running it thru tubes before letting get to test area?

Like about a foot long each carpet roll cardboard tubes all stacked up to be an other rolling wall,(maybe could be on a kids wagon with extra light weight frame around it to hold together and down,?) It rolling also could be easy to play with distance.

$0.02

Anyway nice work as usual!

[Jerry]

Yes, the wind guides could be tubes. We make speaker enclosures from the cardboard tubes. A stack of these (daimeter yet to be determind?) could work.

My plan to stableize in the covered deck area is to extend a support from the roof down to the fan frame assembly.

Otherwize outriggers or ropes if its free standing in a feild.

I've thought of using that thin plastic ribin/tape stuff rather then smoke to track the wind attitude at the output of the fans.

I think this will show if the air movement is straight or swerling.

                         JK TAS Jerry

[Nando]

Jerry:

The footing of the wind mill may not able to support the system at full blowing power even though the 2 heavy motors are producing a good contra- weight, mostly is the upper two fans and their heights.

What you are building may be producing a high level of turbulent air stream because the number fans and number of blades per fan and their blade width and the blade profile.

For linear wind velocity generation is necessary to have multiple number of blades in a single shaft and a frontal linearizing channeling which is quite more demanding if there are more than one fan set up to obtain a linearized air stream.

You need another fan in the center of the fan square.

Nando

[SparWeb]

I think you should build a tunnel for the wind.  Like others suggested: Blow air OUT of the tunnel, AND pull air IN through a stack of tubes to keep the airflow straight.  Real wind tunnels also have "bell-mouths" or "settling chambers", enlarged sections that also take out turbulence.  If you don't have walls, the input airspeed will be all over the place, if you were to measure it at different places in front of the windmill under test.

How about 3 sheets of plywood hinged together?  You can fold them up when you are done, and when it's running, the 3 sheets make a square around the fans.  The box and the fan frame can hold each other up.

It limits you to 8' diameter, of course.  Accounting for wall clearance, more like 7' diameter windmill.

I'm not sure if your results will be helpful, though.  I haven't read lots of windmill test reports, but I have read aircraft propeller test reports, and they typically test props in a tunnel much bigger than the prop.  When you account for energy absorption by the windmill, there is an expansion of the airflow.

When a windmill is in free space, the streamlines can diverge without constraint.  But the air can't pass through the walls, unless the windmill is much smaller than the tunnel.  What effect that will have, I don't know, but it will be most pronounced at the tips, where most power is generated.

So... you have to have the walls, but then again, you can't.  That's no help!  Have you already thought about what you're going to do about this?