The steam feed to the injector doesn't need to be higher pressure than the pressure than the boiler. Exhaust steam from the cylinders can be used rather than live steam from the boiler.
See
No, majorly different.
A bolier feedwater injector is fed with steam at boiler pressure, entrains some cold water and then delivers the whole lot through a check valve at _higher_ than boiler pressure.
Engine driven pump. If they were standing for some time, then engine had to run up and down a little, just to give the pumps a workout.
Later they used injectors, worked by complex thermodynamics and nozzles. Some also retained crosshead-driven pumps, a very few used separate steam driven pumps (as did most stationary or marine engines
- search for "Weir pump"). Later still they managed to make injectors work using the low pressure _exhaust_ steam from the engine.
Almost never used - couple of late American locos did, mostly turbines (turbines benefit even more from working into a vacuum).
This was done in a few desert locations, and on underground railways to avoid steam exhaust. They usually used jet condensers to save weight.
Not much point really. If you're going to preheat, preheat the feedwater. About the only one that preheated the combustion feed air was the LNER's experimental 10000 , with the water-tube Yarrow boiler. The air inlet was an ugly letterbox at the front end, then air went down either side between the brick-built firebox and the outer casing, mostly to stop the pant burning off the casing.
Shipped from England. Cosmetics, haberdashery and marriageable women were some of the most profitable export cargoes around, particularly to Australia.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember dave saying something like:
Overnight Water Pixies, of course.
Actually, in those days in the middle of nowhere, hand pumping was used from an adjacent well or borehole. Basic hand pumps are very effective and if labour is cheap, it's not really a problem.
to click on at the bottom when I have a free moment!)
J.
Ond[ul]ine?
Hydraulic Ram Pump?
Not usually, as hydraulic rams need plentiful supplies of water and a hillside. America (the bit we're discussing) was largely flat and dry instead, so wind pumps were preferred. They did develop pretty good borehole drilling kit by the mid 19th C. Also train services were infrequent at this time, so pump speed wasn't a limitation.
Not really. That device is more akin to an ejector. Unfortunately Wikipedia makes a poor job of differenciating between an injector and an ejector.
On my toy mamod it was - the steam pipe looped under the boiler to pick up some extra heat from the burner before it went to the cylinders.
Pete
On Tue, 21 Jul 2009 23:44:16 +0100, Pete Verdon had this to say:
Superheated steam.. well known efficiency booster. Now have you ever seen a flash steam model hydroplane..blowlamp heats coil of copper tube red hot, water from a pump is on the engine feeds it, prime with a few drops, let go and WHOOSH.
Ah. Good old YouTube
Don't think there's anything to understand. I think you just accidentally cropped the first youtube URL you gave.
Tim
Yes, well known efficiency booster. But it does _not_ increase the pressure - how could it when the tube is open at both ends? What it _does_ do is raise the temperature, hence the volume of the steam - which means there is less water to make the same volume of steam. This probably doesn't matter on your Mamod, but matters quite a lot on real systems.
I suspect it's also pretty important to be sure the steam doesn't condense back out to water as the pressure drops during the power stroke!
Andy
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