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Topic: does oxygen spontaneously combust in high heat?  (Read 2859 times)

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Offline iScience

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does oxygen spontaneously combust in high heat?
« on: October 12, 2013, 07:43:46 PM »
at high temperatures in a combustion engine oxygen spontaneously combusts which limits the efficiency of an internal combustion engine. But i just wanted to be sure, is it the oxygen that's doing something with itself (spontaneously "combusting" by itself) or is it that the heat breaks apart the O-O bond and the single oxygen then reacts with the hydrocarbon?

Offline billnotgatez

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Re: does oxygen spontaneously combust in high heat?
« Reply #1 on: October 12, 2013, 08:02:24 PM »
can you post a link that says this

Offline iScience

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Re: does oxygen spontaneously combust in high heat?
« Reply #2 on: October 12, 2013, 09:34:19 PM »
what do you mean?

Offline billnotgatez

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Re: does oxygen spontaneously combust in high heat?
« Reply #3 on: October 12, 2013, 11:03:39 PM »
where did you get your information from
Quote
high temperatures in a combustion engine oxygen spontaneously combusts

Offline curiouscat

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Re: does oxygen spontaneously combust in high heat?
« Reply #4 on: October 12, 2013, 11:56:10 PM »
at high temperatures in a combustion engine oxygen spontaneously combusts which limits the efficiency of an internal combustion engine. But i just wanted to be sure, is it the oxygen that's doing something with itself (spontaneously "combusting" by itself) or is it that the heat breaks apart the O-O bond and the single oxygen then reacts with the hydrocarbon?

They probably mean knocking.

Combusts without a spark plug initiation.

Offline magician4

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Re: does oxygen spontaneously combust in high heat?
« Reply #5 on: October 13, 2013, 12:02:48 AM »
the thermal dissociation of oxygen will take place, yes
... starting at approx 3500 K , give or take, to be more precise

temperature in the combustion engine will reach approx . 2500 K max. (except of the initial plasma formed by the ignition plug: this is much hotter)


think


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Offline iScience

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Re: does oxygen spontaneously combust in high heat?
« Reply #6 on: October 13, 2013, 01:26:09 AM »
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where did you get your information from

my thermo class: we were talking about how the compression ratio affects the efficiency and how the compression ratio is limited by how hot the chamber is allowed to be before the oxygen spontaneously dissociates and leads to combustion

Offline Borek

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Re: does oxygen spontaneously combust in high heat?
« Reply #7 on: October 13, 2013, 03:13:05 AM »
Oxygen doesn't combust, period. What you mean is that the mixture of fuel with air (containing oxygen) spontaneously detonates when heated.
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Offline magician4

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Re: does oxygen spontaneously combust in high heat?
« Reply #8 on: October 13, 2013, 03:24:19 PM »
in addition:

depending on the very type of engine (i.e. the compression factor) , the compression will lead to temperatures in the ballpark of 300°C to 700°C before ignition. this is way beneath any relevant thermally triggered oxygen dissociation.

what happens however (with for example diesel engines) is, that oxygen will crash into an alkane , and abstract a hydrogen:
R-H + O2   :rarrow: R. + HOO.

... and these two radicals will start the chain reaction


regards

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There is a theory which states that if ever anybody discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.
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