Air Rotor Testing

[scorman]

Actually, it will be trivial for me to get you the data you desire, once I figure out the other flaws in my measurement technique releated to the artificial wind source.

I have a DC supply and a precision 1 ohm resistor to measure current flow already installed on the hardware ...all I have to do for each geometry of turbine rotor, is turn off the wind source and run the blades by electric power as a fan in the same direction without any load resistor present ...the rpm is linear with voltage and easy to calibrate ...I will wait until I have some "optimum" configurations, then see if there is any useful data to report back.

If there is substance to your premise, then the best performing turbine should be the one that requires the least amount of power at any particular rpm which relates to TSR and WS peformance curve.

Stew Corman from sunny Endicott

[SamoaPower]

Great Jerry! I admire your get-up and go style.

I don't have much direct knowledge of wind tunnel design but have a few comments.

You might consider installing some fixed vanes in front of the fans to help in straightening out the swirling air flow. I think I'd space them a couple of feet from the fans.

I suspect there will be quite a bit of spreading of the air flow over a 24' distance with an open "tunnel". You may have to move things a bit closer together to get enough speed at the rotors to spin them up to a suitable test RPM.

Pick calm days for your testing - one disadvantage of an open "tunnel".

It appears that you want to do simple comparative testing, as I do, so the instrumentation will also be easy. Just keep everything the same for each test.

Go for it Jerry!

[finnsawyer]

The air "thrown off the tip" may not be wasted.  There is no reason that it could not do some work before it is thrown off.  In any case, this link tends to confirm such a process experimentally, although the effect doesn't seem to be very large:

http://allentech.net/about/images/windtunnel-flow-280w.gif

I hope the link takes and is of some use.

[Jerry]

Hi SamoaPower.

The area I'll be using is actuly enclosed on sides, top, bottom and kinda at the fan end.

And Yes camparitive testing of 4ft blades is the goal. However I think I'll have room for up to 7ft or maybe even 8 ft?

I'm on my way now to my diary to post what I've got so far.

                       JK TAS Jerry

[southpaw]

As far as I can tell driving a wind turbine blade with a power source and measuring the input power will give no usefull data to compare  to thrust, velocity or the volume of air moved. An anomometer will measure wind speed but driving the cups with a motor will not give you any information about its efficiency. Driving wind turbine blades will just create turbulence, unless the blades have no airfoil or twist and are just flat boards set at an angle.  

The blades would have to be designed as propellers and as such would have no value as wind driven blades on a turbine.

Southpaw

[rpcancun]

Im not sure if southpaw is on the same theory but heres sumthing i thought

may help....

[southpaw]

Yes same idea I'm just not very good with the graphics thing. Thanks for the illustrations.

Southpaw

[SamoaPower]

Southpaw,

"The blades would have to be designed as propellers and as such would have no value as wind driven blades on a turbine."

You're absolutely right, of course. I didn't mean to imply that one could simply take a wind turbine rotor, as it is, and run it like a propellor. The blade angle needs to be reversed and the twist (if any) also needs to be reversed. I did mention the reciprocity thing.

The idea is to be able to use a practical testing protocol to evaluate the various rotor/blade parameters, such as solidity, number of blades, airfoil, aspect ratio, twist and taper. In other words, a research tool.

As a point aside, blade twist and taper is highly over-rated as a necessity to an efficient rotor. It only buys a few percent. I have a constant chord, zero twist rotor with a Cp of 0.42, although it is meant for variable pitch. The airfoil has a much larger effect.

Thanks for bringing this to everyone's attention.

[southpaw]

SamoaPower

Perhaps the moderators could set up a poll to gather some of the basic information with regard to the various blade configurations and alternator types and thier output at various wind speeds. This would put a lot of information in one spot for comparison purposes. Not very accurate but would be very interesting.

Southpaw

 

[TomW]

Southpaw;

Submit a new poll and I will stick it out front.

Hint: You can attach a poll to a new thread as an option below the main text entry area.

Cheers.

TomW

[rpcancun]

No problem,..always willing to share what little I know whithout negative or insultive comments like "uhh, can you read and understand English?

It's sad when the moderator(s) have resort to such nasty negative comments as opposed to helpfull motivating comments,...as the saying goes

"theres one in every crowd"

 keep pushing no matter how bad you get bashed.

Some of us will still try to help