Fw: Water injection (tech refs)

[Bruce Plecan]

>From another list,
just thought some folks might like to get the real info., about H2O
injection.
Personally, the Harry Ricardo book had enough detail to satisfy me....
Bruce

| > If you try to cool compressed air by injecting water, you
| > are cooling the intake but displacing oxygen molecules with
| > water molecules.  Does this actually result in a net
| > increase in oxygen for combustion?  I would inject the
| > water into the intake ports to get liquid water into the
| > combustion chamber, not water vapor.
| The main purpose of water injection is to avoid detonation,
| which allows for more spark advance and/or more boost.  But
| water injection can also improve volumetric efficiency, so
| yes there is actually a net increase in oxygen (up to a
| certain rate of water injection, approx 50% to 100% of fuel).

| From:

| OK, here are my references on water injection:
IThere is some really nice water injection data in A. R. Rogowski's
| textbook "Elements of Internal Combustion Engines", McGraw-Hill, 1953,
| ISBN 07-053575-2, pages 106-109 (unfortunately out of print last time I
| checked).  He shows 50% improvement in detonation-limited IMEP (basically
| torque) at stoichiometry, and 28% under more typical fuel-rich conditions,
| using water flow at 50% of fuel flow.  He showed that you get about 2/3 of
| the benefit using water flow at 25% of fuel flow.  It's not clear from the
| text, but I think these benefits were from increasing boost.  The data is
| referenced from Rowe and Ladd, Journal of the SAE volume 54, no. 1, Jan.
| 1946, which is more widely available than the textbook.
|
| SAE paper 690018 "Inlet manifold water injection for control of nitrogen
| oxides - theory and experiment", by Nicholls, El-Messiri, and Newhall,
| 1969.  Mostly part throttle, but does show 12% benefit in max torque with
| water flow at 50% of fuel flow (naturally aspirated).  [Oops, that was
| model results, actual data showed much less benefit.]
|
| A good history and practical tips are available in "Turbochargers" by Hugh
| MacInnes, HPBooks (a division of Price Stern Sloan Inc.), 1984.
|
| Sir Harry Ricardo did extensive experiments with water injection in the
| 1920's, which are described in his textbook "The High-Speed Internal
| Combustion Engine", 1958, pages 36-40.  He concluded that water injection
| enabled a compression ratio increase from 4:1 to 5:1 with very low octane
| fuel, for about 10% fuel economy improvement.
|
| Water injection is rather briefly described in the classic textbook by
| Charles F. Taylor "The Internal-Combustion Engine in Theory and Practice"
| (1968, 1985) Volume 2, page 70.  He recommends water flow at 50% of fuel
| flow.
|
| There is quite a literature on water injection for piston aircraft engines
| from the 1940's, but they are not widely available.  Some examples are
| Rothrock et al., "The induction of water to the inlet air as a means of
| internal cooling in aircraft-engine cylinders", NACA TR 756, 1943; and
| Bellman and Evvard "Knock-limited performance of several internal
| coolants", NACA TR 812 (ARR), 1945.  Note that NACA was the precursor to
| NASA.


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