I'm guessing that if you left the prop in its original (10ft) state, and increased airgap just a little (less than the present situation), you would have gotten more energy out of your genny. Lessons learned for the next genny.
Peter, The Netherlands.[ Parent ]
You seem to see clearly the relationship between turbine blades and propellers such as those on aircraft. Since the latter have been studied intensely to improve aircraft performance, there is much to read on props from sources such as the old NACA reports, which is as relevant and valuable today as it was 70 years ago. If you (or any other members here) are looking for recommendations on the topic, I could dig up quite a few.
I've seen some pretty crude wings on the site - and when the purpose it just to get some electricity to flow there's no big deal. I'm not too picky about this stuff, yet, myself. But when folks are looking for every last milliAmp, then there's one often overlooked place to look, and it's not the actual diameter of the blades (though that's important). The profile, taper and twist can boost performance, either by higher RPM in a given wind speed, or more torque holding the same speed. There are some fine examples of craftsmanship visible on this site that will only stall out after delivering high amounts of power, unhindered by surface flaws or incorrect spanwise proportions.Steven Fahey[ Parent ]
but it seems a good match: low rpm, big swept areas, low airspeeds, low (relatively) power and high efficiency.
unfortunately, most HPA teams seem to be a little reticient about thier prop parameters. I'll post if I find anything worth while. . . It's not a case of 'Save the planet,' it's a case of 'Save the humans.'[ Parent ]
http://www.ae.uiuc.edu/m-selig/ads/coord_database.html#D
They would be difficult to carve by hand for a lot of folks. Seli and company from University of Illinios group has doen a lot of windturbine work and publishes a lot.
Ron Adventure is just bad planning." -- Roald Amundsen [ Parent ]
Carving isn't as easy as the usual profiles; the hollow section makes it more difficult/more work. But can be done, if you've got the patience. I wonder if it's worth the extra effort though; how much extra power would you get in low winds?
Now, if anyone had a mold and started churning them out...
No need to re-invent the wheel. Plenty of research should be available on a/c propellors and ship props. I haven't yet looked into this though.
And even props and turbines differ, as someone else stated; didn't know about the differing efficiencies (Betz vs. 75% of props). But even on windmills lots of research have been done. It's just a matter of finding it, studying it and understanding it. Oh yeah, and applying it :-)
This is left as an exercise for the reader. Should be easy enough.... ;-)
Examining props and wing sections etc. is very very usefull but there is certainly a departure that must be remembered.
A turbine blade in my mind should be able to function over a range of angles that a prop would never be asked to work in. I don't think it would be offensive ask a turbine blade to function well at the brink of stall so I don't think it would be wise to dismiss flow augmentation.
Mike[ Parent ]
