And here is a chart showing the temperature, pressure and velocity of
   the gas flow in a turbine engine, the J79.

   Regards,

   Gordon.


   ******************************************
   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
--------------------------------------
   No signature so I had to cut and past Mark Waldron name ;)
   You guys are hard to train.

   There are no dumb questions. In fact that is an excellent question.
   Gases have velocity, mass and inertia, not shown in the diagram,
   that also explain their behavior.

   Ram jets and SCRAM jets work in exactly the same way.

   Paul Lamar ...No rotor no motor.

--------------------------------------
   Good question, Mark.

   As Paul mentioned, the reason the gas doesn't back up is because it
   has inertia due to its mass and velocity. In order to stop and
   reverse its flow back into the compressor, the pressure rise in the
   combustion chamber would have to be high enough to overcome the inertia.

   Another way of stating this is momentum. If you run down a football
   field you have a momentum equal to your mass times the speed you are
   going. Inertia is the tendency of wanting to keep going in the same
   direction and speed.

   You mentioned static and dynamic pressure. If you take a bicycle
   pump and pump up a tire you have increased the static pressure
   inside the tire. But there is no dynamic pressure because the air is
   not moving -- nor is there an object moving against the air.

   Now when you unscrew the valve, you release a jet of air which has
   dynamic pressure. If you put your hand against it you can feel a
   force. This force is the result of the momentum that the moving air
   imparts to your hand as it hits. This is what thrust is.

   Now think what it would take to make that stream of air coming out
   of the tire reverse course and flow back into the tire. The pressure
   in the chamber in which the tire is sitting would have to increase
   very quickly and dramatically in order to arrest that jet and force
   it back into its hole.

   So yes, you thought it out correctly that the dynamic pressure of
   the air flow inside that engine is what keeps it from flowing in
   reverse.


   Regards,

   Gordon.


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