Doug,
Sounds to me as though you are trying to tell me that I have misstated
the facts.
I am just giving you the info that I received from a person with
credentials on the subject. And I do still know that lean mixtures do
burn pistons. You haven't explained how that happens!
I have not and do not claim to be an expert on the subject. It is not my
intention to start a fight with anyone over this or any other subject.
Just fuel for discussion. Sorry, your wordy reply, although it sounds
very scientific, does not convince me that my original statements were
wrong!
Tom
dferguso@ebmail.gdeb.com wrote:
>
> Lean mixtures actually burn with less temperature, but because a lean
> mixture also burns slower, the heat is held to the piston for a longer
> period of time, hence "Melt Down."
> "lean mixtures actually burn with less temperature " - compared to what,
> an ideal perfect mix , yes, compared to a rich mix, not necessarily. in the
> first case the combustion process is starved of fuel, in the latter the
> process is starved of air, neither yields maximum thermal results. lets
> take a fresh look at whats happening inside the combustion chamber with
> burn rates. the fuel mixture starts burning from the time the spark plug
> discharges and may burn through the time the piston pushes this burning mix
> out the exhaust port. during this time the heat from combustion is
> transferred to the engine, including the piston dome. now lets consider a
> slow burning scenario first. the slow burning mix would ignite and burn in
> the chamber, and with the slow burn comes slowly increasing heat, the more
> fuel burned, the more heat liberated. so, consequently it takes a period of
> time for the combustion chamber to reach maximum temperature since it takes
> a period of time for all the fuel mix to get burned. in other words, the
> cylinder does not reach max temp quickly. in a fast burning scenario, the
> combustion chamber reaches max temp much more quickly since the burning
> fuel mix reaches max temp much more quickly since the fuel mix burns much
> more quickly. so in a fast burning scenario the cylinder is exposed to
> maximum temp for a longer period of time, and therefore causes more heat to
> be transferred to the engine, including the piston dome - i.e. the heat is
> held to the piston dome for a longer period of time in a quick burn, not a
> slow burn. another principle of household physics to observe is the ideal
> gas law ( gas as in "gaseous" not "gasoline" ) which states that pressure
> times volume divided by temperature is always constant. so in a fast
> burning scenario the liquid fuel portion of the mix is convertd to gaseous
> combustion products much more quickly,and with more gaseous combustion
> products crammed into the combustion chamber, cylinder pressure is
> increased and by the ideal gas law, if pressure increases, so must
> temperature in a fixed volume ( yes , the volume of the combustion chamber
> is always changing with crankshaft rotation, but it is comparitively the
> same for the same engine weather it has a slow burning or fast burning
> mix). so , pressure is held to the piston for a longer period of time also.
> as pressure goes up, temp goes up, piston temp goes up, margin to melting
> goes down.
>
> regards-
> doug@black radon
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