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Pressure BC for combustion chamber

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Old   August 19, 2009, 12:29
Default Pressure BC for combustion chamber
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Giuki Cael
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Dear all,

I have some trouble understanding all the parameters for setting up pressure boundary conditions in Fluent.

I have a combustion chamber with annulus to simulate. At this stage cold flow is considered. I'm using velocity inlet or mass flow inlet at the moment under standard operating conditions.

I would like to simulate the chamber under the right pressure. Which would mean the flow entering the annulus at my inlet BC should be under a pressure of approx. 41.6 bar. I want to achieve a pressure drop between 4-5% over my chamber. Let's say for now a pressure drop of 2 bar.

So now in Fluent I can change:

Operating pressure
Pressure inlet: Gauge pressure
Initial/supersonic gauge pressure
Pressure outlet: Gauge pressure

I know that the total pressure is equal to the gauge pressure added with operating pressure. And that by initial/supersonic pressure the static pressure is meant. But that doesn't help me much in setting the right values.

I've tried setting operating pressure at 39.6 bar and setting the Gauge pressure at my inlet at 2 bar and 0 gauge at my exit BC. I have doubts whether this represents the physical situation. Does anybody has an idea how I should set them right and why?

Thank you!
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Old   July 19, 2011, 11:35
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Hi Giuki,

I am stuck with the same kind of problem...

My settings for the combustion chamber (simple cylinder) :

Air inlet BC: mass flow inlet
gas inlet BC: mass flow inlet
outlet: pressure outlet, gauge pressure = 0.
the operating pressure was set to 5 bar (its the air inlet pressure)
steady state, species transport, cold flow ...

with the above settings fluent gives out following results for Absolute pressure:
outlet: 5bar
Air inlet: 4,6 bar
Gas inlet: 4,7 bar... as u can see the outlet pressure is higher than the inlet pressure..

Could u help me ...
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