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Prop torque question
On Sat, 31 Oct 2009 07:12:33 +0700, Bruce
wrote: Secondly because movement of the electrical generating fields is required. The specification should have been some amount of horsepower, which is really another way to specify speed and torque. Yes. I think a good starting point would be the power equations for a falling water tuurbine which is an old established technology. As a frame of reference, water falling 16 feet has a velocity of 32 feet per second. A boat under sail at 6 kts has a velocity of about 10 feet per second (2.5 meters/sec). The basic equation can be found he http://ahec.org.in/Aboutus/plant.html POWER (kW) = 5.9 x FLOW x HEAD HEAD is the comparable height to produce a velocity of 10 ft/sec in a falling body or about 1.5 feet (0.4 meters). FLOW is equal to cubic meters of water per second which should be roughly equal to the area swept by your prop times the velocity of the water. Assuming the velocity is 2.5 meters/sec and the area swept by your 20 inch prop (pi R ^2) is about .2 meters, then flow is about .5 cubic meters/sec. Plugging back into the original equation we get: KWs = 5.9 * .5 * .4 = 1.18 kw or about the same as a 100 amp alternator at 12 volts or about 1.5 horsepower. |
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