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Originally Posted by freebeard
My proposal most closely matches the 'gravitation water vortex' in Permalink #71. It is axial flow while the Francis turbine is centrifugal flow...............
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Yes, and as I understand it axial flow is normally more efficient.
At least was the case for the early British jet engines of Frank Whittle (
that did not use axial flow).
Go to about the middle of the page, I know this is apples to oranges comparison, but it's the best I can do for now.
https://en.wikipedia.org/wiki/History_of_the_jet_engine
Quote:
British aircraft engine designer, Frank Halford, working from Whittle's ideas, developed a "straight through" version of the centrifugal jet; his design became the de Havilland Goblin.
One problem with both of these early designs, which are called centrifugal-flow engines, was that the compressor worked by accelerating air outward from the central intake to the outer periphery of the engine, where the air was then compressed by a divergent duct set-up, converting its velocity into pressure.
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It's the inherent redirecting energy at right angles that lowers the efficiency of centrifugal designs I do believe.
Some can argue that it's a trade off between velocity and pressure, but with water I don't think that's the case, as water is not compressible.