Burning Pure Oxygen vs. "Air"

[euromodder]

Originally Posted by jeff88

An oxygen concentrator draws air from behind the radiator (or wherever you want)
Some issues:

Main issue : Volume, or rather lack of it.

Calculate how much air goes through a car engine per hour @ 14.7:1 ... it's a lot, and not the kind of volume you'd get out of one of those.

[RedDevil]

Originally Posted by jeff88

Are you saying this scenario could potentially turn your engine into a thermal lance? What if we used ceramic, would that resolve that issue (take the iron out of that equation)?

If you would try this in an unmodified and otherwise normally aspirated engine, yes there is the risk (or near certainty) of a total meltdown. Ceramics would help - need to be able to take the heat though.

Originally Posted by jeff88

Lean burn means more efficient engine, right? How would oxygen end up being unused and how would it be a risk, explosion? How would pumping losses occur if the oxygen is DI? Obviously, there is an issue with exhaust still.

Direct injection is the way to go, and quite handy if it is stored under high pressure anyway. No pumping losses, no need for the first half of the Otto cycle at all. Just inject at the end of the exhaust stroke, and it will immediateliy ignite and start the next work stroke.

If you precisey match oxygen and fuel you will not get perfect combustion. Some of the oxygen will remain and some of the fuel will be unburnt or halfburnt (carbon monoxide), like in a normally aspirated engine. The cat will burn the last of the fuel with the scraps of oxygen.
Lean burn means adding slightly more oxygen, so all the fuel gets burned while obviously some oxygen remains. Since there is no nitrogen there are no nitrogen oxides in the exhaust gas, and because of the total burn there is no carbon monoxide. You would not need a cat and still have clean exhaust gas. The exhaust will have to be rust prrof though, as the hot oxygen remains would be all too happy to bond with any free metal.

[gone-ot]

A "mechanically cycling rocket engine" is what you're describing.

[Occasionally6]

About 20 years ago there was an aircraft used either for a distance record or high altitude atmospheric observation that used cooled, recycled exhaust gas as the working fluid, with O2 tank storage to enable the combustion of the fuel. The excess exhaust gas was bled off. That was done to maintain the engine power output in a low pressure atmosphere.

I understand that some submarines use something similar when submerged.

[jeff88]

Originally Posted by Allch Chcar

You should look into oxygenated fuels before you look at direct injecting oxygen. Specifically, alcohols like Ethanol and Methanol. Not only are they cleaner and more efficient than Gasoline but they make more power. Their biggest disadvantages are less energy in a gallon and cold starting problems with early FFVs. Newer higher compression engines work even better and current FFVs have special startup routines in addition to more Gasoline content in the winter. The earliest FFVs were designed to run on Gasoline, E85, or even M85.

Methanol has an octane value of 112 while Ethanol has an octane value of 110. But it drops to about 96 octane in E85, M85 is unknown.

I appreciate the insight. I haven't decided what fuel to use in this experiment yet, but would definitely anticipate an "Earth-friendly" fuel, especially a renewable one if possible. Can you explain further how E & M are more efficient and make more power even though they have less energy content?

In terms of compression within the cylinder, what is the difference between 112 octane vs. 110 octane? How much more compression can a 112 take compared to a 110?

This table was helpful for me: Fuel Comparison Chart

Originally Posted by RedDevil

The exhaust will have to be rust proof though, as the hot oxygen remains would be all too happy to bond with any free metal.

What would be a good material to use? Ceramic exhaust, stainless steel? I would think ceramic would be best, especially if we use it in the cylinder itself.

Originally Posted by Occasionally6

About 20 years ago there was an aircraft used either for a distance record or high altitude atmospheric observation that used cooled, recycled exhaust gas as the working fluid, with O2 tank storage to enable the combustion of the fuel. The excess exhaust gas was bled off. That was done to maintain the engine power output in a low pressure atmosphere.

I understand that some submarines use something similar when submerged.

I was working on that exact thought when you posted. I'll attach the diagrams I came up with.

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What do you guys think about these? I *think* I have everything figured out, except how to "create" enough oxygen on-demand. I don't have any intention of using a medical device, rather the idea of using a "filter" like zeolites to increase the oxygen content.