09/16/2003

Volumetric Heat

Volumetric heat is an older term you will run across in engineering manuals.
It means the heat "contained" within a certain volume of gas.  This is an
important concept as it directly relates to the internal or specific energy of
a gas.  A higher volumetric heat means simply more heat is retained in the gas
compared to a standard.  CO2 has the highest of the normal combustion gasses
of volumetric heat - which means that in a given quantity of heat ( energy ),
the CO2 molecule will have the greatest internal energy and the least sensible
energy.  Sensible energy - energy that can be measured as pressure - is what
drives the piston down.

Nitrogen, Oxygen, Carbon Monoxide all have about the same volumetric heat
within a small percentage at combustion temperature values from 500c thru
3000c.  Hydrogen is just a RCH (Red C*nt Hair) less than the above.  

By 3000 degrees, however, Dihydrogen-monoxide has 50% greater Volumetric Heat
than the above, and Carbon Dioxide has about 80% greater Volumetric Heat.

A short summary - the higher the Volumetric heat of a gas, the lower the
available energy for sensible energy for any given energy release ( combustion
).  Thus, we want the lowest Volumetric heat of any working gases.

In combustion, we generate dissociation of the gases based on chemical
equilibrium.  The greater the percentage of dissociated gas, the lower the
Volumetric heat.  We can do this by temperature or by mixture.  By mixture, a
rich mixture prefers hydrogen combustion over carbon production.  Dihydrogen
Monoxide has significantly less Volumetric heat than Carbon Dioxide, so we get
more free energy for expansion.  Carbon Monoxide vs Carbon Dioxide has
approaching half the Volumetric Heat of CO2.  

Thus, as the mixture becomes richer, the Volumetric Heat drops rapidly.  There
is a point rich that the dissociation products and the reduced Volumetric Heat
produce the greatest temperature followed shortly richer by a point of
greatest pressure.  Life is good.

Then, we have reports that thousands of hours of dyno testing by one of
members, Tom, reveals that greatest temperature and pressure is in the close
vicinity of stoic.  Life is not good - we have a disparity of fact.

Being a believer in the original pre Eviro-Nazi Whackoo scientific method -
I.E. facts are facts and you adjust theory to account for them vs the New
Methodology of Theory is Good - Facts are just adjustable data needed to prove
the wonderment of your most holy and highest theory of the Wackoo.  Phuck
anything environment - its all a religion of the left to dominate the world.

Pye reports peak temperatures around 15-20% rich.  Later, Obert and Lichty
report peak temperatures around 5-10% rich, and Tom reports peak temperatures
at closely stoic.  

Pyes engines were running 4.5 to 5.5 compression ratio.  Obert and Lichty
engines were running 6.5 to 8.0 compression ratio.  Toms engines routinely run
in the vicinity of 10 compression ratio.

Enter La Chatiliers principle - which states that as pressure goes up,
dissociation goes down almost to the point of holding temperature constant.
Higher compression pressures - lower dissociation Ergo, the constant movement
of peak pressure ( power ) and temperature to closely approaching
stoichiometric.

Life is good.  Facts match Theory.  Time out to go commiserate over doctor
findings with several young senoritas.  But arms flaying and "I'm the *sshole"
interfere.

If peak power is near stoichemic why is Dr Bruce finding improved economy
rich?  Head hurts.

Same data applies.  Assume that the VE is fixed ( its not! ) at low air flow.
If we take the manifold pressure times an arbitrary fixed compression ratio
and arbitrary VE, we can approximate the effective compression ratio.  All
testing and recording was done at full throttle with the various compression
ratio's.

If we set our mixture 15% excess fuel at about 4.5 to one or so, about 10%
excess at 6.5 to 7.0 or so, 5% at about 8.0 or so, and stoic approaching 10 to
1, we would be making the lowest volumetric heat thus the most temperature
available for pressure.  Verify using an egt.

Since the flame speed increases with richness, less advance is needed.  Thus
Bruces experience with adding fuel and reducing spark works in theory.  And
would explain why at differing manifold pressures, more or less fuel is
desired.

Remember that this works by lowering the Volumetric heat of the combustion.
We can also lower the volumetric heat by adding excess air.  With proper spark
adjustment, it would not be unexpected to see maximum milage either at some
point rich or weak and if the Volumetric Heat of the combustion gases were
calculated, the heats would be closely similar.

Bruce prefers the rich side and shortened advance - because the power on
response from that side is significantly quicker than what he has experienced
on the other side.  Remember - multiple engine cycles to make happy.

Now if he would only put a Khrysler Air Valve in his exhaust manifold or two,
his turbo lag issue would start to diminish.  See, his mixture is rich, and if
he added air, there would be afterburning that would help spool up his turbos
and the grin factor would increase.  All they basically are is a one way reed
type valve that when the manifold pressure is less than ambient atmospheric
pressure, to allow air to enter the manifold.  Once the turbo has spooled up,
and the manifold pressure is always above ambient they no longer admit air.
Something this simple and stupid can only work on K-crap thou.  Bruce would
never consider that.

Off to the Doctors.  Got a crapload of tests today, and several thumpy thump
tests to delineate how bad of a leaking valve I have and if surgery will be
needed soon.  I hope not.  This time, I may elect to pass on it and let nature
take its course.  But - one things for sure - pain will not be an issue - I
doubt that it could get worse.