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Uniflow design theory

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Steamchick

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Another clue to size of radiator... A flue tube boiler full of fire, after passing the steam through an engine, needs a condenser of similar size (heat exchanging surface area) to the boiler to get a suitable heat flow through the copper. But that allows for a boiler with hot gas average temp of 200 to 300 degrees C, versus cooling air of 20 to 30C. A flash boiler is much more compact, so don't compare size for size with a condenser!
K
 

Peter Twissell

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Worth having a look at percolating condensors, in which exhaust steam is fed into the bottom of a heat exchanger, so it comes into direct contact with water (condensate). The condensate is cooled by the heat exchanger. Liquid to copper heat transfer is far more efficient than gas to copper, so a relatively small condensor can handle a lot of exhaust steam.
The condensor on a Stanley steam car is a percolator and is about the same size as internal combustion car radiators of the same period.
 

Richard Hed

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So... while we're talking recompression and relief valves (or not), there's been passing reference to condensers. It make good sense to reduce exhaust port pressure to < atmosphere. I see in principle how this might work, but has anyone made one recently? Firstly, I'd like to know clever solutions to avoid lots of plumbing. As Stumpf says, it defeats the purpose to have any obstacles in the path of steam flow from port to condenser. (I feuded a free source for Stumpf 1922, link is in the designing steam engines thread.
I'm seeing a vessel with radiator fins or similar, with perhaps boiler feed water passing through to additionally cool the exhaust and so condensate can be recycled. Can anyone add details/design solutions? I've seen some images of 'jet' condensers but there doesn't seem to be much info, unless I'm missing the key search term.
thx!
Take a look at Jay Leno's Doble Steam engine vid on utub. It's not what you're asking for but it does have a condenser and the Doble put all the steam to use two or three times before condensing it. That car was BRILLIANT
 

Anatol

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50,00pm or maybe a factor of or 5 less... it was screaming! I çant remember, but the web will...
On condensers: for a small tug I used concentric copper tubes, steam and condensate outside, pond water drifting through the inside per outlet close to front of screw.very successful, as the pond had an adequate supply of cold.... (In Sunderland there is always an adequate supply of cold everywhere!).
But if you are pumping out a lot of kW of steam from your boiler, getting 1 or 2 kW from a high speed boat engine, then the rest (lots!) Of the kW need a Huge condenser... Look at steam tables for the heat in steam at 1 bar abs at 100C, versus water at 30C, based on the volume of water you boiler will use, and develop the heat flow required at the condenser.... Then look at the radiator on your car - which can take 10 or 15% of the power your engine can develop.... So if you have a 75 kW engine, the radiator can manage maybe 10 to 15 kW? It may give you a clue as to the size of radiator you could need, if you pro-rata size (areas) for your needs.
Does that help?
K
re 50,000 rpm
- what kind of valve works at that speed?

re (In Sunderland there is always an adequate supply of cold everywhere!).
- in LA not so much, we've got high 30s not 40s night and day at present

re It may give you a clue as to the size of radiator you could need,
Yikes. so getting vacuum on the exhaust ports that way seems difficult.
I'd already thought of running a vacuum pump, but that sounds like 'robbing Peter to pay Paul' as an old codger I knew used to say. So with the uniflow, not only do you have to contend with too much recompression, but you have to accept wasting a lot of perfectly useful steam in exhaust - it difficult to see how they made their mark as 'efficient' with these factors working against them. But then I saw a graph that showed the Newwcomen engine as 1`% efficient, so there was a lot of room for improvement ;), even 2% was doubling efficiency.

So what about that wasted steam? There were some compound uniflow, but its difficult to reconcile the exhaust needs .... unless of course the second cylinder sucked the exhaust out... would that work - with a long stroke to allow further expansion?

re Does that help?
- yes, thankyou
 

Anatol

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Worth having a look at percolating condensors, in which exhaust steam is fed into the bottom of a heat exchanger, so it comes into direct contact with water (condensate). The condensate is cooled by the heat exchanger. Liquid to copper heat transfer is far more efficient than gas to copper, so a relatively small condensor can handle a lot of exhaust steam.
The condensor on a Stanley steam car is a percolator and is about the same size as internal combustion car radiators of the same period.
fascinating. I'd thought of passing exhaust through feed water, but was still thinking that through. thanks!
 

Anatol

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I found some footage of Paul Windross's record holding hydroplane:
not a lot happens for the first 3 minutes...a couple of old geezers wading around up to their armpits in cold water in the drizzle. Not what I'd call a good time! But then that damn thing is scary fast. So - apropos of what? - bash uniflow? or 50,000rpm?
 

Steamchick

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Has anyone worked out how fast Paul Windross's engine goes when not in the water?I saw a demo at the Harrogate show about 5 years ago.... just running on the bench for a minute. Absolutely LOUD! The silencer on the side probably chops 20dBA or so, but compared to the voices, this must have been way over 90dBA on the water - note the changing tone due to Doppler shifting? (Reminded me of the 120+ dBA of Yamaha racing bikes in the mid-1970s!). Must have been doing 5000rpm Plus?
A quote from another site...
https://steamautomobile.com:8443/ForuM/read.php?1,22422
"These engines probably have steam at about 1000 psi and run around 10,000 rpm. The boiler tubes may get to 1500 degrees F. They are non condensing uniflow engines with 54 degrees of steam admission and 102 degrees exhaust duration. Plan to throttle the engine with a variable valve lift and timing to reduce the cut-off. The boiler is around 30 feet of 1/4 OD .028 wall 316 stainless steel tubing."
I reckon Paul's burners (3 off paraffin) must be well over 10kW each...(??) and the flash boiler - both fed by a pump on the end of the crankshaft. I think Paul's boiler has a lot of nickel alloy tubes - as he explained copper would fail at the pressures and temperatures achieved! - No idea what the superheat temp is, and pressure at the engine....
A great world record!
Well done Paul! (What next?).
K
 

Steamchick

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On one of my boats - using a tiny amount of steam compared to you - I use the exhaust back-pressure - from a Stuart and Turner Star engine - to push the condensate from the condenser to a reservoir - where the hot water mixes with the reserve and is then recycled back to the boiler. This isn't the "regular" use of a condenser to develop vacuum to improve efficiency, but the recirculated water enables prolonged running on the pond - which location makes re-watering by hand-pump a bit difficult. But that is only a simple pond-cooled condenser.
Maybe steam-car condensers are useful designs for you?
K
 

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