steamyman
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would a model injector work on 10 to 20 psianyone know 
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Les
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You can get low pressure injectors, not sure how low, try contacting an model engineering supplier, but the injector can be very fickle.
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steamyman
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ok. thanks. 
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IndianaRog
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Just curious...WHAT is a model injector????
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Les
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It is a device for putting cold water into a boiler using steam from the boiler.
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IndianaRog
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Thanks Les...learn something new everyday!
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steamyjim
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An injector is quite a complicated thing Rog...
Basicly there are a series of nozels which steam is blasted through. The steam is then at high speed and when water is dropped in from above it is blasted along on the steam and into the boiler 
Thats how i think it works anyway-anyone who knows exactly please tell me 
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MTA
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| steamyjim wrote: | An injector is quite a complicated thing Rog...
Basicly there are a series of nozels which steam is blasted through. The steam is then at high speed and when water is dropped in from above it is blasted along on the steam and into the boiler
Thats how i think it works anyway-anyone who knows exactly please tell me |
I have a newsletter somewhere explaining how it works.
Interestingly enough, in theory they should not work. Although they do! 
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Bogstandard
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I very much doubt it.
I couldn't get the smallest one available to fire enough to recharge a boiler and that was at 40psi. They really do need the high pressure steam of larger engines.
On low pressure, an engine driven water pump, bypass valve and clack valve is the way to go.
John
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Titan
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It all boils down to the law of physics which says that energy cannot be destroyed.
Take steam at high pressure in a wide pipe moving slowly. It has high Potential Energy (P.E.) due to the pressure, but low Kinetic Energy (K.E.) due to moving slowly.
If you have a small hole at the end of the pipe, the steam has to travel much faster in order to get the same amount of steam through the small hole as is moving slowly through the large pipe.
This means that the K.E. of the steam is much increased. As you can not create or destroy energy, this has to come from somewhere - and since (ignoring the thermodynamics or heat side of things for now) the only source of energy is the Pressure or P.E. of the steam, then this is proportionately reduced, ie the pressure drops. Get the ratio of large pipe to small hole right, and you can even drop the pressure right down to a vacuum. (As a side note this is how steam engines create a vacuum for operating brakes - a vacuum ejector is pretty well half of an injector)
So if on the other side of the small hole we have a chamber that we also connect to the water tank, it will create a vacuum in it and actually suck up water!
Now supposing we have another small hole in the other side of the chamber that this fast moving jet of low pressure steam/water mix is directed at, by using the same principle in reverse, the steam and water is slowed down as it goes from small hole to big pipe and the pressure goes up. And if it is going more slowly than the steam in the big pipe that you started it all with, then it will miraculously have a higher pressure than you started with, and therefore be able to force itself in to the boiler!
Now if you are still with me, the small hole/large pipe scenario outlined above are actually the 'cones' of the injector, and there is a bit more physics involved with thermodynamics and the steam condensing in to water, which are also important contributers to the energy required for the process, but what I have tried to outline above is somewhere near the basic principle.
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Florian
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This picture may help some of you to have an idea of how an injector is designed:
The Injector uses the mass inertia and also the special design of the cones. In combination with the venturi design and volume expansion of the steam, the steam reaches very high velocities and carries along the water. Because the water has some mass (-> mass inertia) it flows trough the third cone and trough the check valve after the injector. (And there is no way back because of the check valve).
I think it also is important that the steam becomes water again when mixed with the water. (volume decreases)
This is all I knowabout and it's just a crude description of how it works;
Florian
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Les
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Don't forget that you are using steam to inject cold water into the boiler and therefore the pressure drops.
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Florian
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| Les Marsh wrote: | | Don't forget that you are using steam to inject cold water into the boiler and therefore the pressure drops. |
Yes but the pressure doesn't matter anymore if the steam gets together with the water; from this point its the kinetic energy that matters. (the steam heats up the feeding water)
Florian
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Les
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| Florian wrote: | | Les Marsh wrote: | | Don't forget that you are using steam to inject cold water into the boiler and therefore the pressure drops. |
Yes but the pressure doesn't matter anymore if the steam gets together with the water; from this point its the kinetic energy that matters. (the steam heats up the feeding water)
Florian |
But when the boiler pressure gets low enough the injector will stop working.
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Florian
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That, of course is a fact, because then the kinetic energy is to low and the water won't go trough the check valve anymore.
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Dampfzauberer
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Hehehe....
I can tell you all it is possible, although i do not have a clou how that stuff works.
So how can i know?
Easy, just took a look in my Battenberg collectors catalogue:
In 1913 Marklin made for Gamage a vertical steam engine with attached steam injector.
Book says it's the only known toy engine fitted with this thing!
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