changes in vane axial turbine design for free flow wind turbine vs wind turbine

[NukeManSoon]

I understand the basics of vane axial wind turbines with the airfoil shapes and the pitches to the wind, but I was wondering how the angles of the blades should change due to the higher densities and overall lower speeds of water. What percentage of the swept area should be occupied by turbine blading, I am just having trouble envisioning the different turbine designs for different speeds and densities of moving fluids, I have only received minimal training on turbines with my naval nuclear power training, we mostly focus on steam turbines and the process of fission. I appreciate any input.

[spinningmagnets]

By "vane axial wind turbine" I think you may be referring to a VAWT. The acronynm is for Vertical Axis Wind Turbine.

Do a search for "Benesh" and "Lenz2", they are apparently the most productive wind VAWT's, but due to low RPM's thay are mostly used for 12-volt production, or mechanical work.

I have not heard of any VAWT's being used underwater for hydro-electric production.

The two main considerations for hydro are volume of flow, and elevation of head (height of feed-water above the gen). The higher the column of water (in an enclosed pipe) the greater the pressure at the bottom coming out of the outlet. High pressure is desireable because it allows you to generate useful power from a small-diameter device that can provide high RPM's with a small volume of water.

For low head (a few feet), a Poncelet style of wheel might extract the most available energy from the available flow (curved buckets, flat blades cause wasteful turbulence).

Low RPM's might make low voltage (12 VDC) the most useful option for low head sites. Gearing to increase generator speed might be possible, but will cause some efficiency losses, and add complexity with costs.

At around 5ish feet, a "breast shot" wheel (water added just above the axle) becomes useful, around 7-10 feet, an "over shot" wheel (water fed to the top) can use the weight of the water to make gearing more useful.

20ish to 80ish feet, you should research small "Turgo" and "Pelton" high-speed wheels.

Nearing 100 feet of head or more, you can use a small hydro-turbine that resembles a turbocharger impellor. If this is an option for you, high-RPM's make higher voltage an option, and high-voltage alternating current (120 VAC, 240 VAC) travels distance much better.

I haven't built a hydro system yet, but this is what I've read here from the archives.

[wdyasq]

"I have not heard of any VAWT's being used underwater for hydro-electric production."

Gorlov - http://tinyurl.com/3xyfft

Ron

[NukeManSoon]

I meant a turbine that rotates horizontally. I was just wondering maybe some angles of the blades for low speed water turbine maybe a 3-4 mph stream of water.

[wdyasq]

If you are speaking of a high efficiency 'propeller', it would need to be calculated. It has the same 'problems' a wind turbine has (HVAT) of twist and such.

If you are truly interested look up those from "HPV" - human powered vehicles, Pay special attention to those used in watercraft.

Ron

[zeusmorg]

 A VAWT is specifically designed for wind since wind direction changes, then it's possible to harvest some energy this way.

 With water you have a directed flow, so it's possible to capture more energy with a water wheel, pelton or other form of water turbine.

 Using a Vawt in water just creates a lower % of captured energy, it could (and has) been done, but you'd get more energy out of traditional water wheels.

  If you'd give more information of your stream, like head, gpm of flow, and stream width we may be able to point you in a better direction on how to capture the most energy from it. There are a lot of dedicated sites on the internet that will help guide you in ideas for a good stable hydro system.

[DanG]

Propulsor would be a good keyword to explore.

[Phssthpok]

I also saw a story on TV (Modern marvels - history channel??) documenting the installation of some VAWT's in the tidal flow basin of some river on the east coast (Hudson river - NYC??). Looked and functioned exactly like a downwind VAWT so it could swivel and capture energy from the tides in both directions. Memory is a bit fuzzy, but I seem to recall it was a three blade affair of around 15 feet dia. Maybe a tad larger.

For what it's worth.