Homebrewed Electricity > Wind
Classical US multibladed metal wind rotor....?
Adriaan Kragten:
--- Quote from: joestue on February 06, 2024, 04:12:29 PM ---
--- Quote from: Adriaan Kragten on February 06, 2024, 01:12:46 PM ---and the fact that a rather large inner part of the rotor has no blades
--- End quote ---
could a nose cone improve that problem?
--- End quote ---
Yes, a nose cone can improve that problem. However, making a large nose cone is a lot of work and I think that making the blades longer is cheaper. Blades for which the chord increases at increasing radius are designed in a time when the aerodynamic theory was not yet available. These rotors are used to drive a single acting piston pump which has a peak torque which is a factor pi higher than the avarage torque (see report KD 294). So you need a windmill rotor with a very high starting torque coefficient to get an acceptably low starting wind speed. One may have thought that this is obtained for tapered blades. In the measured curves you can see that Cq is maximal for lambda = 0 and that it has a value of about 0.48.
At Götingen one has also measured in 1932, a rotor with blades with a shape more according to the aerodynamic theory. I have added these measurements as an attachment. You can see that the maximum Cp is now about 0.36 at an optimum tip speed ratio of 1.1. The starting torque coefficient is now 0.6 at lambda = 0. Cq has a peak value of 0.62 at lambda = 0.2. So this rotor has a higher maximum Cp and a higher starting torque coefficient. I don't understand why at this moment there are still manufactures which supply water pumping windmills with blades for which the chord increases at increasing radius. Constant chord blades are much better for a low design tip speed ratio and easier to manufacture.
Rotor no 5, Göttinger Lieferungen 1932.pdf (15.46 kB - downloaded 192 times.)
MattM:
I've never seen a piston pump on one but did see a lot of lift pump versions.
Bruce S:
MattM;
I think the term piston and lift pump are one and the same.
I've had old timers call pistons for years, while others call 'em lift.
Cheers
Bruce S
Mary B:
I remember helping to pull the well rod and change the leathers on the cup on the lift pump at the farm, then reverse it and lower everything back down the well, put the well house roof back over it... major pain in the...
Bruce S:
--- Quote from: Mary B on February 07, 2024, 11:02:33 AM ---... major pain in the...
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YUP!
That and the water always ICE cold ;D.
Nice in the hot summers before A/C but , maintenance during the winter was not my cup-o-tea
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