Re: Whys and Hows of Water Injection on Jet Engines

From:         cpeters <cpeters@sparc1.castles.com>
Organization: North Bay Network, Inc. news server - not responsible for content
Date:         29 Feb 96 01:24:25 
References:   1
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According to Bill Gunston's book `Jet and Turbine Aero Engines', water
injection both cools the turbine gas temperature (thus allowing for
higher fuel flow which increases thrust) and increases air density, which
provides greater mass flow through the turbine, giving higher jetpipe
pressure, and thus augmenting thrust. Injection of water or a
water/methanol mix was either into the combustion chamber or before the
compressor. The advantage of combuster injection was greater water flow
rates.

Either way, this system is non-existent on most modern jet engines. It
was used when engines were more anemic (for a given weight), especially
on hot and high takeoffs. The bulk, cost, maintenance, weight, louder
noise, and efflux of black smoke are also reasons that lead to its
demise. Hope this helped.
Carl Peters