Re: Surge on GE90

From: (Simon Craig)
Organization: OzEmail Pty Ltd - Australia
Date:         21 Jun 95 02:57:00 
References:   1
Followups:    1
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> I have a question... When an engine such as the GE90
> is starting, what controls which direction the combusted
> material is expelled from the combustion chamber?  I guess
> the fan is electrically spun-up with "starter", but when
> ignition first takes place as in any "explosion", how do
> you control which direction the expanded gases are expelled
> from the engine?  Is there some sort of mecahanism which
> governs the fan & compressor from turning in one direction
> only?

The engine is pun up by the starter through the gearbox, which is directly
driving the high speed turbine/compressor shaft.  This generates airflow
through the engine.  The engine must be motoring at a particular speed
before fuel is introduced (if one bothers to observe the correct starting
procedures).  The air flowing through the turbine is directed onto the
turbine blades, causing the turbine to spin in one direction only.  Most
large gas turbine, incidently have air driven starters not electric, and
they in themselves are small turbines.

> Also, are there any books available to the general public
> regaarding how the modern turbo-fan engines work.  I've been
> to the Nat'l Air and Space Museum in DC but there just wasn't
> enough information available other than the generic diagrams
> indicating what takes place in the various engine stages (fan,
> compressors, combustion chamber, etc).

The Rolls Royce publication called "the Jet Engine" is a very good book,
with lots of very clear diagrams and explanations in it.  I think Rolls
Royce publish it themselves, though.