10/07/2003

Combustion and Dihydrogen Monoxide


In Glassman's world, atoms is atoms.

Looking at combustion, it is important to understand that there is no atomic
history.  Sufficient energy to cause combustion will release enough energy so
that virtually all atoms are dissociated to the atomic level.

Once this occurs during the creation and passage of the flame front, only the
atomic reactions will be involved in creating the combustion products.

With the exception of oxidation, all of the contained energy in the fuel and
the air will be released prior to dissociation and with the passage of the
flame front.  The total is the total - whether it comes from latent heat of
vaporization, bond breakage, heat of formation or whatever.

The energy release of oxidation requires both fuel and oxidizer.  When there
is the exact amount of fuel and oxidizer present to completely consume each,
that is the stoichemic mixture.  Fuels in excess of stoichemic are simply
mass.  Since there is no more oxidizer, there is no more energy release from
oxidation no matter what.  The blather about tossing some alcohol in with
water injection for some heat energy is strictly HRM blather by uninformed
journalist swine.  Conversely, when the fuel is exhausted, if there is excess
oxygen, it too is simply mass.

Without considering dissociation, the highest temperature is at stoichemic as
the greatest amount of energy is released with the least amount of total
atomic mass.

Because hydrogen tends to burn faster and hotter than carbon, there is a
tendency for hydrogen to be burned instead of carbon in a rich mixture,
somewhat raising the energy.  There is, however, La Chatiliers principle,
which states that as pressure goes up, dissociation goes down.  At about 4.5
to one compression ratio, peak temperature is reached around 15% rich.  About
6.5 to 7.0 compression ratio, peak temperature is reached about 5-10% rich and
by 10 to 1 or so, only an RCH off stoic.   There is also a temperature issue,
in that below a certain temperature, combustion cannot be sustained in an
engine.  This is about 1450 kelvin for 1 atmosphere rising to about 1900 to
1950 kelvin at 50 atmospheres.  Cummins research.  Further, as the mass
increases with respect to the energy release, higher temperatures are needed
to sustain combustion.  It is critical to understand that in a spark ignition
engine, firing a spark into less that critical temperature WILL NOT IGNITE the
charge.  The temperature must already be above critical from compression and
early combustion or there will be no ignition.  Again, cummins research.

With the pressure and the mass taken care of mentally, we need to deal with
CHON.  Carbon Hydrogen Oxygen Nitrogen.  There are three driving ratio's.
Equivalence or Fuel Air, Hydrogen to Carbon and Oxygen to Nitrogen.

Hydrogen to Carbon.  The more Hydrogen there is with respect to carbon, the
higher the temperature the flame will be and the faster it will burn.

Oxygen to nitrogen.  One mole airborne oxygen atomic or molar, has 3.78 moles
of nitrogen associated with it.  Fuel born oxygen may have little or no
nitrogen associated with it.  It is the combined air and fuel borne oxygen
ratio to nitrogen that counts.  Nosssssss has 2 nitrogen to 1 oxygen for
example and thus, combined with the air will result in significantly hotter
and faster burning ( because of the close availability of oxygen and the
reduce inert gas ).  

Mixture - again - stoichemic is the highest temperature.

KEY CONCEPT.  Once dissociated, the combustion result will be the result of
the various gasses without a regard to their history.  Atoms is atoms.

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Previously we discussed that atoms is atoms and the combustion result depended
only on the energy released, the atomic mass and the atomic ratio ( CHON ).

Now let us consider Dihydrogen Monoxide.  First, equivalence ratio is exactly
stoichemic.  Two hydrogen, one oxygen.  Perfectly stoichemic.  Further, the
more Dihydrogen Monoxide we add with respect to the baseline fuel, the closer
to stoichemic the mixture becomes REGARDLESS of the original mixture - rich or
lean!!!!!!!!

As we are adding mass faster than we are adding energy, the overall
temperature of the charge will fall.

The Hydrogen to Carbon ratio, will however increase, tending to raise the
temperature relationships of the fuel, and more hydrogen will be consumed
because of the rate preference of hydrogen combustion.

The Oxygen to Nitrogen ratio will increase, tending again to raise the
temperature relationships of the oxidizer.

In fact, save for the increase in mass for approximately the same energy, all
of the ratios of combustion move to higher temperature.

Naca established that power increased on a test engine up to 1.6 lbs of water
per pound of fuel, and that power increased far beyond what a fuel only engine
could achive.  Further, 1.6 is not a hard limit, but the point on a hard
chrome lined cylinder that sufficient blow by existed to cause water to form
in the oil.

But, water did not work with a Car Craft Nissan, so obviously it won't work
even if you actually have a clue of what you are doing - right?

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Atoms is atoms.  

At oxidation, only those fuel atoms having atomic sex with oxygen atoms will
release energy.  Any excess of fuel or oxygen becomes simply atomic mass.

Both air and fuel absorb heat from the engine.  This heat is released at
combustion.  With all fuels, there is a lower and upper heat of combustion.
The difference between the two, is that the formed water in the upper or
higher heat of combustion is reduced to a liquid state.  Mercedes in an engine
paper on alcohol, states that if the fuel is fully vaporized, the energy
released at combustion will be that of the higher heat of combustion.  The
difference between the two is the heat of vaporization of the fuel.

Thus energy taken from a previous cycle is added to the current cycle to
increase the available heat of combustion.

Which brings us back to Dihydrogen Monoxide.  It takes energy to break the
bonds and dissociate an H2O molecule.  This is significant.  The more energy
we can add to the Dihydrogen Monoxide molecule from absorbing "wasted" heat
from the metal and the air, the greater the heat release will be at
combustion.

So far, so good, but the dissociation takes a crapload more energy than the
particle picks up from the heat of vaporization.  This energy is pulled from
combustion and "slows" combustion.  But, once dissociated, the hydrogen and
oxygen burn violently at much hotter than hydrocarbon combustion temperatures
and return a bunch of energy.  In an ideal world, the oxidation energy would
exactly balance the dissociation energy, and there would be no penalty for
combusting Dihydrogen Monoxide.

But then the Laws of Thermodynamics and TANSTAAFL get involved.  The end
result of adding Dihydrogen Monoxide is a small loss of energy.  But this loss
of energy is nowhere near as significant as the increase in effective octane
allowing more fuel and higher pressures to be achieved.

Thus beware the myth that adding Dihydrogen Monoxide will kill combustion.