Applied Combustion Engineering
This is documented proof that these Volvo engineers found by including water
in the combustion chamber of their engine it would run on "reduced fuel and still get the same power output".
[Reformatted slightly for readability, but otherwise as posted.]
From: Robert Harris <bob@bobthecomputerguy.com>
To:
DIY_EFI@lists.diy-efi.org
Subject: Water and its effect on combustion.
Date: Mon, 10 Jul 2000 10:24:08 -0700
Message-ID:
<9ptjms0uu4oe292mpk6a6vhm2hn8bu9h1j@4ax.com>
Let us take a quick look at ignition. Those who have a Heywood
can look it up
- mines on loan so going by memory. The first thing that happens is a plasma
cloud is formed by
the arc consisting of super heated electron stripped atoms.
When this cloud "explodes" a ball of high energy particles
is shot outward.
The highest energy particles are the hydrogen atoms - and they penetrate the
charge about
5 times as far as the rest of the particles. As they lose energy
and return to normal temps - about 5000 k - they
begin to react chemically
with any surrounding fuel and oxygen particles. The effectiveness of spark
ignition
is directly related to the availability of free hydrogen. Molecules
containing tightly bound hydrogen such as methanol,
nitromethane, and methane
are far more difficult to ignite than those with less bonds.
During combustion - water
- H2O ( present and formed ) is extremely active in
the oxidation of the hydrocarbon. The predominate reaction is
the following:
OH + H ==> H2O
H2O + O ==> H2O2
H2O2
==> OH + OH
Loop to top and repeat.
The OH radical is the most effective at stripping hydrogen
from the HC
molecule in most ranges of combustion temperature.
Another predominate process is the HOO radical.
It is more active at lower
temperatures and is competitive with the H2O2 at higher temps.
OO
+ H ==> HOO
HOO + H ==> H2O2
H2O2 ==> OH + OH
This mechanism
is very active at both stripping hydrogen from the HC and for
getting O2 into usable combustion reactions.
Next
consider the combustion of CO. Virtually no C ==> CO2. Its a two step
process. C+O ==> CO.
CO virtually drops out of early mid combustion as the O
H reactions are significantly faster and effectively compete for
the available
oxygen.
Then consider that pure CO and pure O2 burns very slowly if at all. Virtually
the
only mechanism to complete the oxidization ( Glassman - Combustion Third
Edition ) of CO ==> CO2 is the "water method".
CO + OH ==> CO2 + H
H + OH ==> H20
H2O + O ==> H2O2
H2O2 ==> OH + OH
goto to top and repeat.
This simple reaction
accounts for 99% + of the conversion of CO to CO2. It is important in that fully two thirds of the energy of carbon
combustion is
released in the CO ==> CO2 process and that this process occurs slow and late in the combustion
of the fuel. Excess water can and does speed this conversion - by actively entering
into the conversion process thru the above mechanism.
The peak flame temperature is determined by three
factors alone - the energy
present and released, the total atomic mass, and the atomic ratio - commonly
called CHON
for Carbon, Hydrogen, Oxygen, and Nitrogen. The chemical
reactions in combustion leading to peak temperature are
supremely indifferent
to pressure. The temperatures and rates of normal IC
combustion are
sufficient to cause most of the fuel and water present to be dissociated and
enter into
the flame.
As
can be seen above, water is most definitily not only not inert but is a
very active and important
player in the combustion of hydrocarbon fuel.
Ricardo and others have documented that under certain conditions ( normally
supercharged
) water can replace fuel up to about 50% and develop the same power output, or that the power output can be increased by up
to 50% [with the] addition of water.
These conditions were investigated by NACA and others for piston
aircraft engines.
It is important to note that these improvements came at the upper
end of the power range where sufficient fuel and air was available to have an excess of energy that could not be converted
to usable pressure in a timely manner.
As a side note - Volvo recently released some SAE papers
documenting the use
of cooled EGR to both reduce detonation and return to a stoic
mixture under
boost in the 15 psi range - while maintaining approximately the same power
output. Notice - they reduced fuel and still get the same power output.
When
you consider that EGR consists primarily of nitrogen, CO2, and water ( to
the tune of about two gallons formed from each
gallon of water burned ), you
might draw the conclusion that it also was not "inert". They peaked their
tests at about 18% cooled EGR - which would work out to about 36% water
injection
and got about the same results under similar conditions that the
early NACA research got.
