Settle a bet

Composition and transformation of substance.

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Settle a bet

#1  Postby lucek » Apr 25, 2012 7:29 pm

Does gasoline vapor at the proper air fuel mix explode of deflagrate?
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Re: Settle a bet

#2  Postby Matt8819 » Apr 25, 2012 7:32 pm

lucek wrote:Does gasoline vapor at the proper air fuel mix explode of deflagrate?


I don't think it can be an explosion...it doesn't burn fast enough to technically be an explosion. I think, anyway

Although I may be confusing explosion with detonation. Either way, in open air, gasoline vapours burn, to the best of my knowledge, not explode.
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Re: Settle a bet

#3  Postby Weaver » Apr 25, 2012 7:52 pm

Yeah, gas vapor doesn't detonate - the shock wave isn't supersonic.
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Re: Settle a bet

#4  Postby lucek » Apr 25, 2012 11:11 pm

Looks like I won my bet. Thanks.
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Re: Settle a bet

#5  Postby klazmon » Apr 26, 2012 12:00 am

I think it depends on the definition of explode. As someone already said, detonation usually refers to burning with a supersonic shock and deflagration with subsonic combustion wave. Both are commonly called explosions. A wiki article differentiates the two via the terms high explosion and low explosion. In astrophysics, a type 1a supernova is mostly deflagration (the jury is still out on whether there is any change over to detonation when the thermonuclear flame gets close the to surface of the white dwarf) but I don't think anyone would say it is not an explosion ;)
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Re: Settle a bet

#6  Postby Weaver » Apr 26, 2012 5:10 am

Well, I would describe them more accurately as high-order and low-order explosions - again, based on detonation velocity.

Deflagration is a low-order explosion.

http://en.wikipedia.org/wiki/Explosive_ ... l#Chemical
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Re: Settle a bet

#7  Postby Ultimate » Apr 26, 2012 5:16 am

I think its theoretically possible, unless you're talking about at atmospheric pressure. Its a holy grail of engine building to create supersonic explosions to drive the engine. It would create a massive boost in efficiency. http://en.wikipedia.org/wiki/Pulse_detonation_engine

At atmospheric pressure its going to deflagrate, at much higher pressures you can get a sonic detonation (this is what happens in your standard internal combustion engine. Super sonic is possible but damn hard to achieve. We're still working on it.
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Re: Settle a bet

#8  Postby lucek » Apr 26, 2012 12:13 pm

klazmon wrote:I think it depends on the definition of explode. As someone already said, detonation usually refers to burning with a supersonic shock and deflagration with subsonic combustion wave. Both are commonly called explosions. A wiki article differentiates the two via the terms high explosion and low explosion. In astrophysics, a type 1a supernova is mostly deflagration (the jury is still out on whether there is any change over to detonation when the thermonuclear flame gets close the to surface of the white dwarf) but I don't think anyone would say it is not an explosion ;)

Perhaps then we have to account for the speed of sound in the medium.
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