🚀 go-pugleaf

Phil wrote:
> Hi!
> This 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?
> What temperature is required to initiate the combustion reaction?
> At what rate would a combustion front propagate through this mixture?
> If 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?
> 
> Thanks.
> Phil.

Phil wrote:
> 
> Hi!
> This 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.

> What 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.

> At what rate would a combustion front propagate through this mixture?

Depends.  Confined or unconfined?  Shape?  Surface/volume ratio? 
Deflagration, explosion, or detonation?

> If 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?

-- 
Uncle Al
http://www.mazepath.com/uncleal/
 (Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

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.



"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:41B8A5AD.80E06D51@hate.spam.net...

> Phil wrote:> > Hi!
> > This 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.


> > What 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.


> > At 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?


> > If 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.

Phil wrote:
> 
> 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.
> 
> "Uncle Al" <UncleAl0@hate.spam.net> wrote in message
> news:41B8A5AD.80E06D51@hate.spam.net...
> 
> > Phil wrote:> > Hi!
> > > This 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.

hand gun, rifle; pressure vessel with frangible disk.  "escape through
a small opening a fraction of a second later" may be very optimistic.
 
> > > What 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.

Spark plug.  This stuff has been exhaustively addressed in gasoline
and diesel engines, including dwell angle.  The hardware and its
dynamic tuning have been refined to a fare-thee-well.

> 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. 

[snip]

> 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?

Gas-air bomb.  Yeah.

> > > If volume is held constant before and after combustion, by what amount
> will
> > > the temperature of the mixture have increased after the reaction?

/_\H reaction and specific heat (Cv !!) of the mix is a good start.

> > > 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...

If Detroit can design an engine anybody can do it with the same
$billion.  Wouldn't it be best to go into the literature and see what
has been documented, theory and practice?  The thermodynamics and
hydrodynamics of an engine are immensely complex.  There are guys who
make a fat living minutely sculpting the interiors of race car intake
and exhaust manifolds to balance pressure along length and lessen
turbulence, respectively.  The watershed improvement in high
performance engines was to locate valve lifters at nodes so vibration
didn't eat them and their operation.

-- 
Uncle Al
http://www.mazepath.com/uncleal/
 (Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

Thanks for the help!
I think I have some redesigning to do...

Phil.


"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:41B9CACC.B9F9FE78@hate.spam.net...
> Phil wrote:
> >
> > 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.
> >
> > "Uncle Al" <UncleAl0@hate.spam.net> wrote in message
> > news:41B8A5AD.80E06D51@hate.spam.net...
> >
> > > Phil wrote:> > Hi!
> > > > This is my first time posting here (5 newsgroups).

[snip]

>  The watershed improvement in high
> performance engines was to locate valve lifters at nodes so vibration
> didn't eat them and their operation.
>
> -- 
> Uncle Al
> http://www.mazepath.com/uncleal/
>  (Toxic URL! Unsafe for children and most mammals)
> http://www.mazepath.com/uncleal/qz.pdf