"Arfa Daily" wrote in message
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"Arfa Daily" wrote in message
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"Captain Midnight" wrote in message
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"**THE-RFI-EMI-GUY**" wrote in message
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I assume the can is open on one end like a soup can, not a coke can. I
think the water is there to provide an airtight, frictionless seal for
more effect. Keeping the firercracker dry is tricky. This looks like a
good use for the hundreds of firecrackers I have left over!
What he is simulating is the explosion that happens in one of your cars
engine cylinders. A car engine operates on a series of small controlled
explosions. In your car, the explosive force drives a piston down,
pushing a connecting rod which in turn rotates a crankshaft. A car
engine has 4 to 8 cylinders which fire sequentially and smoothly. The
links below illustrate this with a single cylinder like a lawnmower
engine. These are "internal combustion engines".
My sister did a similar science project years ago with a coffee can
fitted with a spark plug and filled with a very small amount of
gasoline
or ether. A plastic lid was placed on top and an ignition coil made a
spark which blew the plastic lid off. Not as dramatic as a fire
cracker.
http://www.keveney.com/otto.html
http://en.wikipedia.org/wiki/Four-stroke_cycle
Dumb_Blonde wrote:
Thank you in advance for your time. I found a neat project to do with
my 14 year old son, but would like to know the science behind it so it
will be educational.
Here is the video link.
http://www.metacafe.com/watch/470767...ct_experiment/
It is a fire cracker experiment, and I know he will love it, but I am
clueless as to how this makes my car run.
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©
Their is no explosion in a properly operating internal combustion
engine.
The fuel merely heats the air. The expansion of the air pushes the
piston.
An explosion called detonation or knock can put a hole in the piston.
Some
engines require higher octane fuel to keep knock from occurring.
That seems to me to be a misleading description of the principles of an
internal combustion engine. The fuel is mixed with the air in a very
carefully controlled ratio, highly compressed, and is then set light to,
either by a spark in the case of a gasoline engine, or by self ignition
from the rapid heating of the mixture during compression, in the case of
a diesel. It burns or combusts, and what comes out of the exhaust, after
the burning, is not air, but a fully reduced residue of the burning
process. The burning of the mixture under such intense pressure, in what
is essentially a fully contained space, takes place at such speed, it
would usually be considered to be representative of a controlled
explosion. Detonation knock is normally as a result of the timing of the
ignition source not being ideal for the engine in question. The
detonation process should be started just before the piston reaches top
dead centre, so that by the time the burning has spread fully from the
initiating point - ie the spark plug - through the entire mixture, and is
thus at its fiercest, the piston has rolled over past its point of being
momentarily stationary, and is just beginning on its way back down the
cylinder. The rapidly burning ( exploding ? ) mixture will then deliver
maximum thrust to the piston, driving it down the cylinder bore. If the
mixture starts to burn too early, it will reach maximum energy output
before the piston has reached the top, so will oppose the upward movement
of the piston, which is still occuring, leading to the pre-detonation
knock.
Maybe it is just semantics, and some may disagree, but that has always
been my take on how an engine works, ever since I was first rebuilding
them as a kid, because I couldn't afford repair shop prices !!
Arfa
Just as a matter of interest, I just looked up the word " explosion " at
http://dictionary.reference.com/browse/explosion
and interestingly, the first result, 5th definition, specifically mentions
the internal combustion engine. The third result, definition 1a also seems
to cover it neatly, as does the twelfth
Arfa
Ah, it could be a question of semantics ! It's just occured to me what you
were saying. It is the pressure wave from the burning ( although I still
think " exploding " covers it also ) mixture that drives the piston down,
and not the actual burning mixture ( flame front is it called ? ), which
should not actually touch the top of the piston before it burns out, and can
cause damage, if it does. Yep ! that's it I reckon. We're both on the same
page now. Sorry ...
Arfa