GOE 222 profile

[poikkis]

Hi,

I liked to use goe 222 blade profile on one of my windgenny projects,

(without twist & tapper) just straight profile all the way from the base to the top.

I got the actuall profile, but how do you define

the profile size (width & height) ?

At this point i only know the blade length.

Thanks m8's

[bob g]

i don't have an answer, but i do have a question

why would you want to use such a profile with no twist or taper?

just curious i guess.

is it because of relative ease of manufacture? or some other concern?

thanks

bob g

[gizmo]

Its actually a good all rounder profile.

OK, I'm biased, there is a guy on my site who sells that profile in extruded PVC.

http://www.thebackshed.com/Windmill/PVCBladeOrders.asp

A few people have used this profile on their windmills now, including me. Its not a high speed profile, but its got very good low RPM power, lots of torque, and runs quiet. I have one forum member who has put a set on his axial flux windmill and he's seen 2.5kw at 480 RPM, so the blades do work.

The GEO222 is also used on the Windcharger windmills, and you can buy replacement blades from Royal Fabrication. http://www.royalfabrication.com/

Glenn

[bob g]

now that was a direct answer,,, thanks

as for the profile, i really like the camber

a bit more an i would be thrilled, but why gripe about a bit?

very cool that somebody made up the pvc extruded blades, very interesting

bob g

[Dave B]

Just an addition to Glenns comment. Royal Fabrication is happy to carve the 222 profile for custom orders as indicated on their website  http://www.royalfabrication.com/ as

 well as direct replacement blades for the Wincharger series. Dave B.

[wdyasq]

Airfoil profiles are written to 'coordinates' and are scalable. The notation is usually a percentage of the "X" dimension and the corresponding top and bottom in the "Y" dimension.

As an example, a NACA2312 is a 12% airfoil. If the 'cord' is 10", the 'depth' or 'thickness' will be 1.2" - 12% of the cord length. The coordinates define the width and height.

Ron

[poikkis]

Thanks for the info Ron.

But how to define the cord lenght then, when you know the blade lenght ?

So if blade lenght is 3 meter how much will be the profile x,y

And yes Bob you got it right...

Mainly because it´s so easy to manufacture them from the foam/fibreglass

vs. blades wich have twist & taper.

Alltought it would be very intresting to hear (even rough) estimate

how much better the standard twist & taper blade will perform vs. GOE222

Are the diffrence minor or major ...

regards

Poikkis

[SDSUMetalHead]

The chord length is the length from tip to tip of the airfoil profile.  But think of it this way...if you have a bow from a bow and arrow. The bow itself bows out and so the chord length would be the string length at its initial position. So if you had a airfoil that curves outward and then back in, the chord length would be the distance between the outer blade tip to where the airfoil begins. But I believe since your airfoil profile would be looking at the blade from the side view (imagine looking at a plane wing from the side of the plane), the chord length is from the leading edge to the trailing edge. I am guessing there is a relationship somewhere on this profile that would say if you have an x feet long blade you need the blade to be y amount thick and so you need a chord length of z. Then they probably have a scaling relationship you can use. I might look into it later, but I am sure someone else already knows where it is.

[dlenox]

gizmo,

excuse me but 2.5kw @ 480rpm?

I don't think so...

Dan Lenox

[dlenox]

gizmo,

May have answered too quickly - should have added - what is the diameter you are talking about?

Dan

[dlenox]

gizmo,

sorry, need to check my meds. brain is all hay-wired here today.

dan

[poikkis]

Any idea, what is the cord lenght on those 18'

http://www.royalfabrication.com/performance.htm

[dsmith1427]

For a different profile, NACA63-418, I used the average chord length from the following blade calculator:

http://warlock.com.au/tools/bladecalc.php

I built a prototype turbine that worked but the PMA is still in the planning phase.

Don

[SparWeb]

I think the question is about choosing the correct airfoil chord.

If that's the case, then a simple rule of thumb is 10% "solidity".  In aerodynamics, the solidity of a rotor is the percent of the swept area that is actually taken up by material.

For example, if each blade is 1m long, and has a chord of 10 cm, then three of these blades will have 0.30 square meters of surface area.  The whole swept area will be a circle of 2m diameter: 3.1 square meters.  In that case, the solidity ratio is 0.3/3.1, or 9.5%, which is pretty close.

The chord can vary from root to tip.  If you want a narrow tip, then the root must be bigger to give the same area and solidity.  

Solidity of 10% is sufficient for many types of wind generator, but it is a secondary factor beside the diameter.  Most people assume that a certain size of rotor means a certain power output, but matching the prop to a generator can be a challenge if you are attempting to get it right "on paper".  However, a diameter a few percent larger is MUCH better than having the chord wrong by a few percent.

I spent a year fiddling with a motor conversion generator getting it to match with the 8-foot prop.  Fortunately in my case I had "too much" prop to begin with, so improvements to the generator brought them in line.  

[poikkis]

Thank you Steven.

Based on that 10% formula, it seems that my straight GOE-222 3meter blade

should have chord lenght around of 30cm

and from there i can calculate the rest what i need.

Thank you so much.

Regards

Poikkis

[gizmo]

3.25 meter diameter ( 10.6 feet ) in a 55kmh wind ( 34mph ).

http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=1860&PN=1

and here's the build

http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=1612&PN=2

Glenn

[SparWeb]

You're welcome, Poikkis.

Don't forget, you are free to adjust the chord for various reasons (convenience of mounting it to the hub, for example).  I threw out 10% as a guide because that's what most small wind turbines end up with.  If you were to look at the very large wind turbines, in the 100's of kW range, you would find solidities closer to 5%.  The larger scale gives them advantages that we do not have with our small scale aerodynamics.

If you are still unsure, use a chord that gives more than 10% solidity.  You might find it interesting to measure blade designs such as the Dans' and Hugh Piggott's for their proportions.  I haven't done so, myself, so I don't know what you would find.

But now I'm curious, too!  :-)

[SamoaPower]

10% solidity might be a bit much unless you're going to run fairly slow blades.

[SparWeb]

SamoaPower,

Hey we haven't heard from you in a while.  Good to know you're still out there.  How have your projects been going?

Of course I thought of that graph, but I actually decided to not use it.  It's not a "prescriptive" graph, even though it makes a point about the interrelationship of these two factors.  I would rather point out to the OP that the load imposed by the generator is MUCH more important at determining the operating TSR of the prop, and some given wind speed, than the angle of the blades.  This is counter-intuitive, but there is a way to explain it - it would just get me side-tracked from the point at hand.

[SamoaPower]

Steven,

Good to see you're still bright and bushy-tailed about RE. Most of my projects have been put on indefinite hold due to some health issues but I still lurk about. Only thing really going at the moment is evaluation of Lithium ion batteries for RE. I'll post something once I have some conclusions.

I believe that graph was derived empirically from existing designs at the time rather than from a hard analytical process. Could be wrong.

I guess I look at that graph from the opposite direction from what you elude to. Rather than determining a TSR from solidity, I think the usual rotor design process picks a design TSR and uses that to select solidity.

I certainly agree that other factors can have a large impact on actual running TSR. I don't quite understand your comment about blade angle however, as solidity is about rotor area.

One thing that needs to be considered in selecting solidity is the rotor torque, primarily start-up torque.

Good to hear from you.

Bill

[richhagen]

When I set them up on the computer, the order goes something like this for each incremental distance out from the hub:  I scale them by multiplying by the desired chord length, which is obtained from a mathmatical theoretical model. Next I rotate them to the desired pitch angle, also obtained from a theoretical mathmatical model, by converting the resulting coordinates into polar coordinates, which simplifies this because you can simply add the angles.  Then I convert the coordinates back to rectangular coordinates and adjust them such that they remain within the blank that I will be carving them from.  Then I run the results, which I generate as a table of coordinates, through a script for my tool offsets which generates the g-codes which the tool needs to run.  This is probably not the standard design approach, but it works for me.  Rich  

[SparWeb]

"...I don't quite understand your comment about blade angle however, as solidity is about rotor area..."

Oops, I was typing too quickly I suppose.  TSR is the reciprocal of the angle of the blades.  I did mean that loading is more important than the CHORD of the blades.

After datalogging from my wind turbine, I can attest that my rotor-generator combination runs the whole range of TSR from 2 to 12, depending on the stator wire connections I select, and the windspeed.  Wind power goes up with the cube of wind speed, but generator power only by the square, so TSR is usually high in strong wind.