Smurf1976 wrote:Large hydro plants generally use Pelton (high head) or Francis (medium head) turbines however Kaplan (low head) turbines are also used.
This is indeed true, its a pressure versus flow problem.
Francis turbines look pretty good for efficiency but the very complex compound curved blade shape, and the design of the outer scroll feeing it are extremely complex.
Something I have never seen tried is the adaption of a turbocharger exhaust turbine to mini hydro application.
Guess what, it has the exact identical blade and scroll design to a Francis turbine in minature.
Not only that the turbo exhaust turbine is made from austenetic (high temperature stainless steel) and will never rust or erode. These are really beautiful precision made turbines in a very small size.
Older turbine housings are raw cast iron and rust badly. But since about 1970 exhaust turbine housings are cast iron that contains a lot of nickel, so they no longer rust.
I sent a turbocharger turbine over to a guy in the US to try out on his own mini hydo. Never heard from him again. I think he may have had a heart attack or something. Never posted anymore on any of the forums, he simply dropped out of sight.
A real pity, I was becoming pretty excited about the idea.
If you look at pictures of the huge francis machines, and pictures of turbocharger turbines, they are identical in every respect. The physics is identical, and turbos have been developed to very high efficiencies.