h a l f b a k e r yGo ahead. Stick a fork in it.
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Start with cool, low pressure water.
Use a pump to simultaneously increase the water's pressure, and move it into the heater.
Inside the heater, the water's temperature increases, but *not* above it's boiling point.
The hot water then moves into a cylinder with a piston in it.
As the water
is transferred into the cylinder, it pushes on the piston, producing a certain amount of hydraulic power.
After the cylinder's intake valve closes, the pressure inside the cylinder will drop, and due to it's high temperature, the water spontaneously boils. Not all of it will boil, of course -- some will remain liquid.
When the piston has reached it's furthest point, and the volume in the cylinder is at it's highest, then the exhaust valve is opened, and the mix of steam and water is expelled into the condenser.
After going through the condenser, the H2O will be liquid once again, and the cycle is repeated.
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what exactly are we looking at here....
We put hot water into a hot piston. It boils. WHEEEEEE!!!! |
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This way you can achieve pressures lower than 1 atmosphere. Your engine won't work, unless you keep your cylinder with the piston in vaccuum or a low pressure environment. |
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But in order to create vacuum you needs energy in the first place. |
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[Inyuki] //Your engine won't work, unless you keep your
cylinder with the piston in vaccuum // So, a steam engine
for use in outer space? [+] |
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//After the cylinder's intake valve closes, the pressure inside the cylinder will drop// |
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This makes no sense whatsoever. (-) |
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[ldischler], perhaps [goldbb] means temperature, not pressure... |
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[morrison_rm], anyway, I don't see any advantages of such closed system to ordinary steam engine where you can simply keep the 300'C water in under pressure (as it is in some type of nuclear plants), then let it into a cylinder to push a piston, and then collect the lower temperature steam to condense it back to liquid water to be heated... or, is it what the [goldbb] meant in the first place? |
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//[ldischler], perhaps [goldbb] means temperature, not pressure... // |
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No, he obviously means pressure. The only way this could work would be if you reduced the working load after closing the intake valve, or used some sort of latching mechanism. |
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What are you people talking about? This idea as stated is simple and would work. Take water and heat it in a boiler so that it gets hot but doesn't boil in the high pressure. Next release some of the superheated water into a piston at high pressure. As long as the water pressure is greater than the mechanical resistance, the water will boil into steam as the piston is pushed down. |
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The reason this is not used is water in it's liquid state is a bitch to deal with. The release of the water into the piston would be like a water cutter. Even tiny water droplets pummel steam turbine blades. Also because we are only dealing with water we have to stay below the triple point of water (660C?) so the hot and cold side can't have that much temperature differential so the power is low. |
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// The reason this is not used is water in it's liquid state is a bitch to deal with. // |
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Perhaps one could use a reducer valve, just like for a gas cylinder, to avoid the "water cutter" effect, but it seems that the whole system then has to operate in higher temperature to avoid the quick cooling and condensation of the released water gas. |
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"water in it's liquid state is a bitch to deal with" |
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//Perhaps one could use a reducer valve, just like for a gas cylinder//
You can't use a pressure reducer as the pressure is the only thing that is keeping the water from vaporizing and that pressure is the only thing that drives the piston. A pressure reducer would turn this into a straight steam engine, so let me change my statement, you can, but not within the realm of this idea. |
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I think there is an advantage to having the phase change happen in the piston as it would occur isothermally, so inline with the Carnot ideal. |
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[MisterQED], sorry for thinking outside the scope of this idea. |
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How about having an array of sufficiently narrow tulbe-like cylinders with electrically heated walls and heated pistons, so that if you inject any water with tiny droplets, it would quickly evaporate due to proximity to the hot walls of cylinders wall and this way push the piston? ... Maybe it could help to avoid the water-cutter effects. |
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MisterQED, why would the release of water into the piston be like a water cutter? |
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I know that *droplets* of water, moving at very high speed, through steam or air, will be damaging to whatever surface they impinge on, but since there's no steam mixed with the very hot water until after it goes into the piston and the intake valve closes, I don't think that should be a problem. |
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//What are you people talking about? This idea as stated is simple and would work. Take water and heat it in a boiler so that it gets hot but doesn't boil in the high pressure. Next release some of the superheated water into a piston at high pressure. As long as the water pressure is greater than the mechanical resistance, the water will boil into steam as the piston is pushed down.// |
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If this is the idea, then it's a cylinder using 0% quality steam, and the pump isn't necessary. The idea has no particular advantage unless you want to waste energy.
In operation, liquid would flash into steam as soon as you opened the inlet valve, and, with the valve closed, the delivered force would drop as the cylinder shaft extended against the load (unlike a hydraulic or pneumatic system where the working pressure remains constant). The volume of water draining from the system represents a tremendous amount of wasted heat, as water is hundreds of times denser than steam. |
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[morrison_rm] Did you mean the Newcomen engine? |
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Won't work. The pressure won't drop in the cylinder just because the inlet valve closes. Assuming the pressure does change for no reason, very little water will flash, maybe 10% since the latent heat of vaporisation of water is so large it will rapidly sub cool the water. Also it would be virtually impossible to pump saturated water into anything without it flashing on the way (due to pressure drop and any vena contractors that get in the way). Also, since the steam is constantly saturated you would be unable to get any expansive work out of it because as it expands, it cools and would then condense. [MisterQED] mentioned the difficulties wet steam in a turbine, this is less of a problem in reciprocating engines because the speeds are reduced (steam engine usually has a lower rpm but also a turbine can be 2m in diameter so the blades on the outer edge can approach sonic speeds) |
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