Author Topic: Stuart No1 centrifugal pump  (Read 2981 times)

Offline Dan Rowe

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Re: Stuart No1 centrifugal pump
« Reply #15 on: November 28, 2021, 03:24:21 PM »
Checking on the history of centrifugal pumps led to a couple of interesting links.

https://archive.commercialmotor.com/article/25th-july-1912/8/the-history-and-development-of-the-turbine-pump

"John Gwynne, who in the year 1851, took out a patent (No. 13,577)"

https://wikimili.com/en/Gwynnes_Limited

I failed to find the patent drawing but the early pumps were low head drainage pumps driven by a steam engine. I was surprised to learn how early the patent date is it predates the Worthington duplex steam pump by a few years.

Cheers Dan
« Last Edit: November 29, 2021, 07:05:29 PM by Dan Rowe »
ShaylocoDan

Offline MJM460

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Re: Stuart No1 centrifugal pump
« Reply #16 on: November 29, 2021, 10:35:06 AM »
Interesting that the centrifugal pump was patented so early, compared with the Worthington pump.  The Worthington was just a combination of two known technologies, so one might expect it to have come earlier, while the centrifugal pump had no direct hand driven equivalent, but it’s simplicity is no doubt the reason it took off, once recognised.  The same basic principle and arrangement is common to most pumps today.  One moving part and one simple to seal shaft exit, what’s not to like?  Especially, once the bearings were placed outside the seal so not subject to corrosion from the pumped fluid.  Also, can handle reasonable size entrained solids as long as they will fit through the passages.  Compare that with the jack pump that Toby has been building and shown in his excellent build log.  But I also know which one is more interesting on a model display!

Regarding the blade angle, forwards leaning, backwards leaning and straight radial are all used.  As John said earlier, it mainly just changes the curve shape.   Forward leaning gives a curve that, starting from closed discharge valve, has a rising discharge head before it starts to fall with increasing flow.  Commonly seen in large fire pumps, where the pressure is a little easier to handle if you only need one hose, but more pressure is available as flow increases, when you need all the water you can get.

Backwards leaning gives a head  curve that falls continuously with increasing flow from shutoff.  It is preferred in applications involving pumps operating in parallel for more flow. 

The radial ones I have seen most commonly are in very high speed pumps giving very high head in one stage.  But I don’t know how common they are in other applications.  They have an obvious advantage in simplicity for manufacture.

The casing also comes with subtle differences.  The concentric volute, (the casing passage around the impeller) only allows flow for part of the impeller at a time as Charles already mentioned, which clearly limits the design to lower flow applications.  More commonly the flow area in the volute increases around the periphery of the impeller to the outlet passage, allowing flow through the whole area of the impeller.    For simplicity of manufacture this was often designed as three or more curves of slightly different radius with centre’s placed to approximate a gradually increasing radius.  This casing volute form is called full emission, while the close fitting concentric casing used with straight radial blades is called partial emission.  The outlet nozzle itself is also designed as a divergent passage, which increases the kinetic energy recovery in the most efficient pumps.

I hope that helps clarify some of the puzzle.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #17 on: November 29, 2021, 03:17:40 PM »
From what has been said ST knew what they were doing when they designed this pump, one feature I have never seen is the holes through the impeller, it only has 0.002” clearance from the casing round the outer edge so no meaningful quantity of water would travel behind it,it also has a 0.031” gap behind it, so is there a reason for the holes?

Online Jo

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Re: Stuart No1 centrifugal pump
« Reply #18 on: November 29, 2021, 04:48:32 PM »
From what has been said ST knew what they were doing when they designed this pump, one feature I have never seen is the holes through the impeller, it only has 0.002” clearance from the casing round the outer edge so no meaningful quantity of water would travel behind it,it also has a 0.031” gap behind it, so is there a reason for the holes?

Mechanically it would act as a "pressure limit" on the output: If the water couldn't get out the higher pressure would build up down the vane until it reached those holes, then the excess water would go though the holes which would prevent the pressure effect going higher.

Jo
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Offline astroud

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Re: Stuart No1 centrifugal pump
« Reply #19 on: November 29, 2021, 05:11:06 PM »
Wondering if the holes are in fact to relieve pressure at the back of the impeller that might cause leakage across any seal and into the bearing.

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #20 on: November 29, 2021, 06:09:00 PM »
The purpose of the holes is to equalise the pressure on the impeller faces to minimise axial load. A well designed pump can create a very considerable vacuum, which tries to pull the impeller out through the inlet.
« Last Edit: November 29, 2021, 06:16:03 PM by Charles Lamont »

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #21 on: November 29, 2021, 08:17:13 PM »
Thanks for the explanation, there is no thrust bearing so the holes would make sense.

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #22 on: December 02, 2021, 08:48:09 PM »
Pushing on with more progress the, cover has come out well except a little blow hole that won’t make a difference, the mounting bracket was straight forward.
I have made a small base for it to bring it up to the height of the D10 crankshaft just need to mount them together on something appropriate.
Next a coat of paint to match
« Last Edit: December 02, 2021, 08:52:36 PM by Steamingandy »

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #23 on: December 02, 2021, 10:41:42 PM »
Nice job.

(If it were mine and I was making this a permanent pairing, I think I would remove the redundant reversing gear from the engine.)

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #24 on: December 06, 2021, 07:40:52 PM »
Pump painted and mounted with the D10, flow looks adequate for both condensers, has been suggested using a gearbox to reduce the reves of the D10, I might have a go there should be enough power.
<a href="https://www.youtube.com/watch?v=VF96ZQuXK6k" target="_blank">http://www.youtube.com/watch?v=VF96ZQuXK6k</a>
« Last Edit: December 06, 2021, 09:20:04 PM by Steamingandy »

Offline crueby

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Re: Stuart No1 centrifugal pump
« Reply #25 on: December 06, 2021, 07:49:04 PM »
Very well done!

Offline Admiral_dk

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Re: Stuart No1 centrifugal pump
« Reply #26 on: December 06, 2021, 09:11:48 PM »
Great result - both as pump and looks  :ThumbsUp:

Online Kim

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Re: Stuart No1 centrifugal pump
« Reply #27 on: December 06, 2021, 09:37:34 PM »
That's cool!  I love seeing model engines doing real work!  Your pump is working great!

Kim

Offline propforward

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Re: Stuart No1 centrifugal pump
« Reply #28 on: December 06, 2021, 10:22:54 PM »
Fantastic - really nice result and great to see it pumping like that.
Stuart

Forging ahead regardless.

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #29 on: December 08, 2021, 03:58:23 PM »
After a suggestion I tried a gearbox looks like I will be making another base, the D10 handles the set up with ease
<a href="https://www.youtube.com/watch?v=-NAeV2GzZ9g" target="_blank">http://www.youtube.com/watch?v=-NAeV2GzZ9g</a>