# Combustion engines

## Main Question or Discussion Point

Can pure oxygen be used in internal combusion gas or diesel engines?
If no, what percentage could be used?

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mgb_phys
Homework Helper
Yes - but don't try it at home!

russ_watters
Mentor
"How much" is 1/5 the volume of air it normally gets, since that's the fraction of oxygen in air.

Pure oxygen would be impossible (edit: without designing the engine specifically for the task), as even if you injected 1/5 the volume it would totally screw up the mixing process (not enough volume of gas to volume fuel) resulting in a rich burn overall.

If you inject 100% O2 you need 5x the fuel otherwise you are just getting a lean burn, but if you had stoichiometric FAR with 100% O2 the temperatures and pressures are increasing to silly levels which would then screw up the flame speeds. Either way you are looking at nuking the engine.

Now you can increase the oxygen content slightly (which is essentially what nitrous does) and fuel more heavily, this is fine but will be component limited. This method keeps the volume of gas pretty much the same, but increases the o2 concentration.

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mgb_phys
Homework Helper
The Swedes (IIRC) have a diesel engine sub that runs on diesel and liquid oxygen. The LOX is stored in tanks outside the hull so they can run the diesel submerged.

But as you said - the engine is rather special!

You could make it run on hho. and have noexternal air at all. its the perfect stochiometric ratio for it to burn. I beleive ive created an efficient one but haven't finished my design. got the plates done but not the pump. I think the probelm is everyones trying to wire the plates in series in the water only way this is possible is to have the plates in completely different containers otherwise there connected everywhere. My design is two 2 foot by 2 foot plates bolted together with a small gap dont remember the number off the top of my head right now. when i hooked it up it hummed like a transformer on a telephone pole and dropped the power of a battery down to 55% in 10 mins the designs like the ones off the internet i saw that i built would run for a few hours and the battery would only be down to 85% i haven't shared this with anyone yet because i wasn't sure how i wanted to present it to the world to a car company and get rich or give it to the people and stick it to the man. well i'm giving it to the people and sticking it to the man so here you go all you need is 2 big plates and a pump this is the part i haven't gotten yet to force the water through and it will also keep it cool. i know the hotter it is the better it runs but get so hot and your just producing steam and that's pretty easy to accomplish in a shorted circuit and that's pretty much what this is. Actualy i'm going outside to work on it right now i need to get a video and put it on youtube.

I really dont want to burst your bubble mate as I think innovation and indiviudals such as yourself are vital in this day and age. As much as I dont want to tread on you:

But HHO is a crock of **** as far as running a car goes. It takes more energy to make the gas than you get from burning it, so its useless as a fuel source. Also ask yourself how are you making the HHO, its commonly touted as an alternative to fossil fuels... yet is made by electrolysis of water. And where does the majority of our electricity come from...

Even assuming 100% efficieny all the energy released is exactly what it took to break the H2O apart in the first place. Leaving you with no net gain. Hydrogen is an energy carrier not an energy source.

There is a reason why there are no water powered cars, its becuase they would break the laws of phyiscs which as we all know not even Scotty can do.

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"Can pure oxygen be used in internal combusion gas or diesel engines?"

An engine is only 20% efficient due to the air ratios, so theoretically adding more oxygen to a combustion chamber would increase the efficiency of that engine. However the nitrogen acts as a cooling agent in the chamber and reacts at combustion temperature levels of 2400K to produce NOx - without the nitrogen i think not even ceramic exhaust ports could withstand the temperatures.

Possibly a bit late - but hey!!!

"Can pure oxygen be used in internal combusion gas or diesel engines?"

An engine is only 20% efficient due to the air ratios, so theoretically adding more oxygen to a combustion chamber would increase the efficiency of that engine.
In a word - no.

However the nitrogen acts as a cooling agent in the chamber and reacts at combustion temperature levels of 2400K to produce NOx - without the nitrogen i think not even ceramic exhaust ports could withstand the temperatures.
Nitrogen plays another important part in the IC engine; it expands while absorbing that heat.