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Using a pressure swing absorption device, separate oxygen from the atmosphere. Using an injector, mix a mist of water droplets with the oxygen. Then, mix hydrogen (most of which will come from the fuel tank) with the oxygen and water, achieving a slightly fuel-rich mixture.
The purpose of the water
water that is added to the oxygen is to prevent spontaneous combustion of the oxyhydrogen mixture before it enters the engine.
Feed the mix into a four stroke diesel engine; specifically an engine whose fuel injection system has been modified to inject water. During the intake stroke, a precisely controlled amount of water is sprayed into the oxyhydrogen. The purpose of the water added at this point is to control ignition timing.
The compression stroke raises the temperature of the oxygen / hydrogen / water mix such that autoignition occurs. After autoignition, more water is injected -- this decreases the gas's temperature, increases it's pressure and results in more engine power.
The steam / hydrogen mix then goes to the condenser. The steam turns to water, while the hydrogen remains a gas. The water and hydrogen go through a gas/liquid separator.
The water is removed from the separator by a pump; some of the water will be recycled, the rest will be sprayed on the outside of the condenser.
The hydrogen is removed from the condenser by a vacuum pump, and fed back into the intake.
Engine power can be modulated in either of two ways:
A) By making the oxyhydrogen more hydrogen rich, so that less of the hydrogen burns. This of course produces less heat and less power. The hydrogen isn't wasted of course; it is recovered from the condenser.
B) By using a variable amount of exhaust gas recirculation (EGR). This recirculated gas is mostly steam, with a bit of hydrogen; it dilutes the intake charge, and, like option A, reduces the amount of hydrogen that is combusted.
Enriched_20Atmosphe...CE_20Steam_20Engine
uses water on the cylinder walls for direct cooling and lubrication as well as motive charge. [FlyingToaster, Feb 02 2010, last modified Feb 03 2010]
Reverse PSA Engine
Reverse_20PSA_20Engine
[goldbb, Feb 03 2010]
[link]
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pressure swing aDsorption will take more energy than you get out of the combustion process. |
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It's impossible to get a consistent, exact, stochiometric mix... if we tried, sometimes it would be just a tad fuel-rich, and sometimes it would be just a tad oxygen-rich. |
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When the mix is oxygen-rich, the combustion event will produce an oxidizing flame, which could, in turn, oxidize the inside of the engine cylinders. |
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By making the mix just a tiny bit fuel-rich, we avoid having an oxidizing flame. |
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Also, hydrogen has much better thermal expansion properties than oxygen. Theoretically, we could get more efficiency by making the engine's input very hydrogen-rich, but doing so would encourage hydrogen embrittlement, and furthermore would interfere with the operation of the condenser. |
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WcW, you've got a partial point -- PSA will consume a lot of energy, but I don't think it will consume more than the engine produces. |
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no, did some maths and you are right, but its still a lot more
energy than you could possibly re-gain with more efficient
combustion. |
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It's not merely about more efficient combustion -- although it is of course about that, too. |
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It's also a more efficient steam engine, since the combustion byproduct (steam) is in direct contact with the water being boiled (which was sprayed in that steam as a mist). |
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And, did I forget to mention, that if there is no nitrogen in the engine's intake, then there will be no nitrogen oxides in the engine's exhaust. |
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Specifically, the engine's exhaust will consist of two streams of gas: cool oxygen-reduced air coming out of the PSA device, and warm air that was used to cool the condenser. |
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An internal combustion burning hydrogen and air, on the other hand, is quite capable of producing NOx in it's exhaust. |
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Well... an engine that consumes say .3L of O2 per power stroke @ 2K RPM predictably uses 300 litres of O2 a minute... or 5L a second. |
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A PSA that produces 300 litres of O2 a minute would be how big, how heavy and use how much energy ? |
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