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Old 06-09-2015, 10:52 PM   #1 (permalink)
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Centrifugal oxygen enrichment...

What's your take on this:

https://www.google.com/patents/US6363923

A 15 cm diameter cylinder, spinning at ~80,000 RPM or more, driven like a turbo off exhaust gasses, used to centrifugally separate out the nitrogen from the oxygen in air and feed the oxygen to the engine, thereby effectively increasing the engine's volumetric efficiency. A 15 cm cylinder at ~80,000 RPM can supposedly achieve 33% oxygen content. As the engine works harder, the cylinder spins faster, and increases the percentage of oxygen in the intake air... so the harder you work your engine, the more effective cubic inches you've got.

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Old 06-10-2015, 03:53 AM   #2 (permalink)
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I am sure there's some or other reason why more oxygen isn't necessarily a good thing.

And, if my car has a turbo, is it doing this already?
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Old 06-10-2015, 02:22 PM   #3 (permalink)
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If a real world centrifuge works as well as the calculated performance in the patent, then the oxygen enriched mixture would certainly make for better performance. Of course, the engine would need to be redesigned for the increased combustion temperature.

The centrifuge would need to run at a constant speed, so driving from an exhaust turbine would not work. A drum at 80,000 RPM is a gyroscope with high gyroscopic forces at every turn or bump. If it failed, it would explode like a hand grenade. It takes power to run, more than would be gained by any increased efficiency.

Other than all that, it's an interesting idea.
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Old 06-10-2015, 02:24 PM   #4 (permalink)
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The idea of increased oxygen for combustion . . .

. . . is an old one. Without the presence of the buffering nitrogen, the oxidation of any fuel would be very fast and would not suffer the side reactions that result in NOx pollutants.

However, flame speed is not just increased, but the flame temperature becomes exceedingly high. Parts longevity becomes a serious issue. If I recall, an Xprize entrant proposed to run an internal combustion engine with pure oxygen and fuel. Bottled O2 or the use of adsorption technology was to feed an engine with ceramic coatings. Even then, at high relative loads, the cutting torch heat produced by pure O2 and fuel would damage parts in short order. Discussion on the forums suggested steam as a buffering gas, but the now bulky fueling/concentrator system would be saddled by an even bulkier water tank and/or condenser.
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Old 06-10-2015, 06:55 PM   #5 (permalink)
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CAUTION -- Analogous 'Uni·corn' Humor follows (wink,wink):

I heard that if you sling a politician 'around' fast enough you can separate the LIGHT BS from the HEAVY BS; but (sadly) he will STILL be a politician.
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Old 06-11-2015, 03:08 PM   #6 (permalink)
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I don't see any reason why it shouldn't work in principle. After all, centrifuge enrichment of uranium hexafluoride gas is one way to separate the fissionable U-235 from the U-238. Whether the production rate would be high enough to be useful is another question.

One drawback, though, is that the enriched gas is going to contain a lot more argon and CO2, because they're heavier than oxygen.
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Old 06-11-2015, 03:22 PM   #7 (permalink)
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The two gases aren't that dissimilar in their molecular weight, nitrogen is about 88% of oxygen by weight.

I'm not very good at this advanced stuff so let me just play with the math on my back-of-the-envelope level.

80,000 rpm
15 cm diameter = 176 cm3 per cm of centrifuge length

Let's assume for the sake of charity that the centrifuge is 100cm long. That gives it a volume of 17,600 cm3.

Now let's assume a perfectly average 2-liter four-cylinder car being fed by this contraption.

Every revolution of the crank consumes (ideally) 1,000cm3 of air. So in 18 revs it uses the entire volume of the centrifuge.

Let's assume that engine runs at 3000rpm when cruising at 60mph. It's a little on the buzzy side for such a modest engine, but I'm trying to keep the math simple. In one second, it turns 50 revs. It consumes the entire volume of centrifuge three times.

Granted the centrifuge is generating over 53,000 G - and I'd be curious to know what they plan to make this out of, and whether they can make it lightly enough, plus its containment, that any benefit accorded by it isn't overshadowed by its own weight and support systems - but with the two gases so close in molecular mass, is it possible to achieve useful separation with that kind of throughput? The device has only one-third of a second to separate the two in a really short stack height, not a lot of room for stratification there.

And finally, any kind of harvesting system that pulls the separated gases must generate some turbulence that might well completely undo all the hard work of the separation in the first place.

With 53,000 G's to play with, I think this would be a LOT more useful as a plain ol' supercharger.

I'm kind of a hack at this stuff, if anyone can (gently) point out where I have gone horribly wrong I would be very interested to hear it.
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Old 09-24-2015, 04:09 AM   #8 (permalink)
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Now, such a device could be installed on one of those self-balancing motorcycles and do dual duty.
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Old 09-24-2015, 08:43 AM   #9 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
CAUTION -- Analogous 'Uni·corn' Humor follows (wink,wink):

I heard that if you sling a politician 'around' fast enough you can separate the LIGHT BS from the HEAVY BS; but (sadly) he will STILL be a politician.
I'll remember this one. Removing both BS masses would leave little left to consider.

regards
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