Re: Water injection ?

From:         bradg@io.org (Brad Gillies)
Organization: Internex Online, Toronto, Ontario, Canada (416 363 3783)
Date:         31 Oct 95 00:31:26 
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In article <airliners.1995.1636@ohare.Chicago.COM>,
   gernot@vmars.tuwien.ac.at (Gernot Auer (Prak 1 Gerhard)) wrote:

>Is there anyone who can support clues how 'water injection' in any way could
>effectively increase engine power?
>
>We were discussing about how water as material itself could increase
>the quantity of boost generated by the engines in first place, and thus
>increasing the overall power. Any possibility this theory could make
>it ?

Water injection is used quite widely for aircraft operating from high hot
runways.
There are 2 reasons this works

1)Water injected into the combustion chamber inlet as a liquid is quickly
turned into steam from the heat. This causes increased pressure in the
combustion chamber and therefore more power.

2) Water injected into the combustion chamber inlet cools the combustion
gasses enough to allow more fuel to be added for increased power.

This is because the single limiting factor to turbine engine operation is the
turbine inlet temperature.  more fuel creates more heat energy and the
turbines cannot absorb it all and they fail. The water cools the gasses enough
that more energy can be added to the airflow while keeping the temperature
within limits.

Any turbine engine book should have a chapter on this subject.

--
Brad Gillies     Bradg@io.org
WWW: http://www.io.org/~bradg/
A&P, AME (Canada), PPASEL (Canada)
Leading Edge Aviation Services