06/03/03

During induction, it is necessary to get as much free hydrogen as possible for
combustion.  In a normal hydrocarbon, there is either a CH3 radical or a CH2
radical.  

The fate of a CH3 particle, particularly in a rich mixture, tends strongly to
join another CH3 and become ethane H3C-CH3.  It has a minor about 15%
probability of becoming CH4 and stable.

Methane CH4 has a probability of surviving combustion.  It shows up as a major
HC constituent in exhaust gases.  Its a bad thing - this cow fart stuff - must
be controlled.  Not involved in smog - who cares, we be the air coppers.  Not
involved in pollution - so what - gasoline is bad- and us enviro-whacko nazis
must punish you for it anyway.

Methane - present or formed, has a high octane ( 130 or so ), burns slowly and
very hotly.  And once formed, is basically stable through not only induction
but most of combustion.

Alcohols and nitromethane are slow burning fuels requiring a lot of energy
input to burn.  Why be that?  Methanal CH3OH scissions into CH3 and OH.  This
leaves the OH to form free hydrogen - and the OH tends to form stable water
and requires more energy to keep going.

CH3 becomes either CH4 or H3C-CH3 and ethane is similar in combustion to
methane. 

Nitromethane CH3NO2 scissions into CH3 and NO2.  Same as above - but no free
hydrogen.  Much more heat needed to break some free.  And the oxygen in the
NO2 radical? - its tightly bound till very late in the combustion.  Its saving
grace is when the scission occurs, there is a nice,large release of bond
energy to provide a lot of heat.

The only quickly usable source of hydrogen is the CH2 radicals.  The greater
the CH2's the faster the charge will combust.  If they CH2 are not in a ring
like benzene or naphthalene.  

In a normal hydrocarbon like non-oxygenated gasoline, most of the CH2 are not
in ring structures and become the source for most free hydrogen and free
radicals.

Note again and again - during induction and early combustion - carbon
reactions do not provide much of the energy and are basically inert dilutions.
Its all about the hydrogen.

Adding internal coolants such as water, methanal, acetone, ethanol, etc acts
to increase the heat sink and slow induction.  This is partially caused by the
weight of the charge increasing faster than the energy release, and because
the scissioning of these coolants leaves less reactable particles added to the
charge.

Adding oxo-hydrogen particles ( OH etc ) decreases the induction time as the
hydrogen is already in a free radical form.  Adding oxo-carbonates like CO
just add mass and may increase induction time.  They will not contribute till
late in the combustion cycle.  Bound nitro-oxygens like NO2 simply add mass
until late in the combustion cycle.