Thanks a lot for responding, Uncle Al!
I'm a complete newbie at usenet. I've never needed it much in my line of
work.
Phil wrote:> > Hi!
Post by PhilThis is my first time posting here (5 newsgroups).
I sure would appreciate some advice on a couple of things.
First, what volumetric ratio is the optimal mixture for combustion of butane
with air at STP?
Depends what you want out. For raw temperature, a stoichiometric mix
in pure oxygen. If you wnat to get work out of it in a real world
engine, other considerations intrude.
I want a rapid increase in pressure within a vessel whose volume won't
change
much at first. But it's not a bomb, though it sounds a lot like one. The hot
gas is
to escape through a small opening a fraction of a second later.
Post by PhilWhat temperature is required to initiate the combustion reaction?
Not temp necessarily, energy input. Look up sparks and explosions. A
little Pt catalyst may set it off spontaneously. It is a free radical
chain - exponentiation chugs along.
I had been under the impression that some small bit of the unstable mixture
had
to absorb enough energy to effectively achieve a threshold temp in order to
trigger combustion in the neighboring bits and so on, regardless of what
source
that energy comes from: electrical arc, localized catalytic reaction,
adiabatic
heating, etc.
If one were to insert into the mixture an electrical filament and slowly
increase
it's temp, at what point would it trigger the reaction? Or within about 10 C
anyway.
Post by PhilAt what rate would a combustion front propagate through this mixture?
Depends. Confined or unconfined? Shape? Surface/volume ratio?
Deflagration, explosion, or detonation?
Locally. What I mean is, neglecting any movement caused by the pressure
wave emitted by earlier parts of the reaction, ignoring any overall pressure
and
temperature changes caused by it, and assuming that the reaction front is
not
dramatically curved or distorted.
Well, actually a general rough average with a precision of about 2 sig dig
would
be fine for my purposes.
Butane burning in air starting at standard temp and pressure would be
deflagration, wouldn't it? Could it produce a strong enough shock wave to
act
as a true explosive?
Post by PhilIf volume is held constant before and after combustion, by what amount will
the temperature of the mixture have increased after the reaction?
Finally, if the mixture is made leaner, will the temperature increase be
reduced roughly proportionally to the amount of fuel present?
Doesn't that sound like a poorly stated p-chem homework problem,
folks?
Uh, ya. I suppose it kind of does...
I'm not a chemist, just a guy that builds cars.
I meant something like: Half the fuel, therefore half the energy distributed
through the same amount of air would have half the effect, wouldn't it? I'm
guessing...
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
Thank you again for taking the time to reply to me.
Phil.