> ******************************************
     > Okay, here's a basic (probably dumb) question: Notice that the
     > pressure in
     > the middle of the combustion section is higher than the pressure
     > at the
     > entry of the combustion section. Given this, why doesn't the gas flow
     > forward (to a section of lower pressure) to the compressor section?
     > Is it
     > maybe the fact that "pressure" shown in the chart is "static
     > pressure" and
     > that the static pressure PLUS the dynamic pressure of the gas
     > moving aft
     > into the combustion section is higher than the static pressure in the
     > combustion section, thus the gas keeps moving aft?
     >
     > Mark Waldron

I think they have considered the diffuser part of the combustion chamber
(structurally they often are) so the Px rise you see on the graph attributed
to combustion is really the Px rise in the diffuser (The J79 had a longer
diverging duct style diffuser than a modern dump differ would have).

You will alway have a pressure loss across a gas turbine combustor. Your CC
liner film cooling would not work without that pressure gradient.

Minimizing that pressure loss across the combustion section is one of the
design goals. It is a nasty tradeoff between mechanical guys begging for
more Px to make the cooling job easier, the performance guys not wanting to
give them any.

Mark W.


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