Harris turbine

[joes8120]

Tree fell on olive barrel housing and turbine was exposed to weather for several months (second home). Rotor magnets as well as stator magnets have surface rust on them. Regressed bearings and reassembled. Will rust prevent power production? Not enough water to test but when spun by hand I get voltage.

Also had a second nozzle installed and run a smaller nozzle when creek is full. Main nozzle is 1/2 in. Wondering why power production goes down when second nozzle turned on. Penstock is full. 225 ft of 2 inch pipe; 45 ft of head. Produce about 120 watts with 1/2 in nozzle alone.

[thirteen]

Just a few ideas. wrong angle on added nozzle. loss of water volume with two nozzles, unbalanced water flow or added restriction in lines. turbine not able to clear the water properly. 13

[joestue]

Maximum hydropower is available at the 2/3rds point for dynamic/static pressure.

furthermore the efficiency of your turbine may be highly velocity dependent, particularly if your generator is rpm locked to the battery voltage.

I would measure the mechanical power with a pony brake while adjusting the nozzle diameter, then design the generator after that. hope its close to what you have now but you may find twice the power available if you match the rpm correctly to the turbine and nozzle. if its a pelton or turgo, you can change the number of spoons of course.

[hydrosun]

Rust will probably not be a problem. Don Harris left his without a cover for years as a test of durability.
When you add a second nozzle the running pressure will be reduced. Especially if you have tees after reducing the pipe size before the turbine. A pressure guage as close as possible to the nozzles will show if that is the problem. Another possiblity is the adjustment of the magnets needs to be done.
Chris

[joestue]

if they have adjustable magnets then you're set. 
 here is a typical efficiency curve, there is a lot to gain if you take the time to get the operating point set correctly.
http://www.codecogs.com/users/23287/SpecSpeed-and-Unit-Conditions-0012-1.png

do you get something like 100 gallons per minute free flow right out of the 2 inch pipe? if so, the highest power should be around 50-56 gallons a minute at 30 feet of dynamic pressure, or theoretically 300 watts of power, at 50% efficiency you're looking at 150 watts. i would try and do better than what you've got now, but it sounds like you you are at the point where you need to make small adjustments, +/- 10-30% range. i can't find my nozzle diameter calculator so i couldn't tell you to increase or decrease the diameter, or add a second nozzle. given that you lost power adding the second one, you might need to reduce the number of spoons/blades to get the rpms back up due to the decrease in dynamic pressure causing a slower stream of water. or increase the flux in the generator so it can push more amps at the lower rpm.