Wikipedia:Reference desk/Archives/Science/2018 September 21

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September 21

Baker Dam turbines, continued dialog

In response to the dialogue about dams on Baker Lake.

But these are NOT low-head dams. The new low-head turbine technology is simply not required, and there are tradeoffs if it's used unnecessarily. And if you look at satellite photos of Baker lake on Googlemaps, you can clearly see the special nets employed to capture fish and move them around the dam. And you can read about them as well, in Wiki articles.

If the Baker-dam turbines are EITHER Pelton OR Francis, what would they likely be? What’s your best guess, and can you justify making it?

Thanks again!Rossroderick (talk) 00:41, 21 September 2018 (UTC)

Several sources list head ranges from 200 or 500 metres up to 1500 metres for Pelton turbines, and from 20 or 80 metres up to 500 or 750 metres for Francis turbines ( https://www.slideshare.net/BKLR/hydraulic-turbines, http://164.100.133.129:81/econtent/Uploads/16-Hydraulic%20Turbines%20%5BCompatibility%20Mode%5D.pdf and https://www.youtube.com/watch?v=k0BLOKEZ3KU&vl=en ). It would also depend on flow rate, see the "Hydraulic turbine selection" graph at page 40 of the second source. So I would say a Francis turbine. Prevalence 02:28, 21 September 2018 (UTC)

When this query was first posted, I did quite a bit of digging around, but decided not to post with a non-definitive reply. But since you ask for "best guess" (with choice limited to Pelton vs. Francis), here's my evaluation: in 1925, Francis turbines were installed; by 1988 they were Peltons. The latter is supported by your description of the hydraulic piston mechanism. The Pelton impulse-jet uses a synchronization device (perhaps using pistons) which I equate as sort of the inverse of the mechanism developed in WW1 for machine guns on airplanes. On airplanes, the machine guns were synchronized such that the bullets would miss the propeller blades, whereas the Pelton device would synchronize the water-jet impulses such that they would hit the turbine blades -- in just the right spot for maximum efficiency. If need be, I could peruse my internet history and (hopefully) find photos/documents that lead me to this (e.g: archived 1925 photo of newly-installed turbines on one of the Baker dams that were not Pelton, probably Francis and archived government document that evaluated Peltons, noting their installation within the system that includes the Baker dams -- but not specifically those dams). So, my "best guess" is that the current primary turbines are Pelton, augmented by some "fish-friendly" system. —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 03:38, 21 September 2018 (UTC)

Its very odd that no one, not the owner nor management nor locals made any effort to offer some more detailed documentation.

Additionally, after trying to research about it for some time, it also struck me that homeland security may just now look over my shoulder "virtually live" and ask themselves why the heck i am interested in some power station in the state of Washington. So in conclusion let me forward that! Why the heck are you? --Kharon (talk) 17:28, 21 September 2018 (UTC)

I can't find any sources to support the general idea that the water flow is pulsed in Pelton designs. The flow can be increased or decreased depending on output demand, but everything I've seen is that it's essentially held constant at any given time. Sounds like a possible confusion of the idea of pulse vs impulse (physics)? DMacks (talk) 17:31, 21 September 2018 (UTC)

The transfer of water flow from each bucket to the next one of a Pelton wheel is modelled by design to minimise turbulence which represents wasted energy and vibration; note the shaped leading edges of the buckets here. The idea of externally interrupting the flow between buckets invites causing Water hammer, an extremely dangerous phenomenon at the high levels of kinetic energy involved in hydropower stations; witness the devastation in the 2009 Sayano–Shushenskaya power station accident. DroneB (talk) 17:06, 23 September 2018 (UTC)

• The idea of pulsed flow in water turbines (including Pelton wheels) is nonsense. Andy Dingley (talk) 22:03, 23 September 2018 (UTC)