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-   -   High velocity error (http://www.cfd-online.com/Forums/phoenics/117305-high-velocity-error.html)

romulo May 6, 2013 11:02

High velocity error
 
I am trying to study spray charactersitics from a nozzle using phoenics ( similar to gas turbine combustion chamber set-up). Using KE Turbulence model, I am getting velocity in the region of 54000m/s. I know it is incorrect as I am expecting to see something in the region of 10-25 m/s (velocity at exit of nozzle).

Initially i was not getting convergence, but this was resolved by tweaking SARAH. start from ambient is off, and I have given pressure=500 psi and tem=120 deg c as initialisation. still the velocity is high. I am kind-of run out of ideas.

any ideas or suggestions are much appreciated. Thanks.

Nozzle exit dia=0.00044m
Nozzle Inlet dia=0.00762m
mass flow rate at fuel inlet=2.9kg/s
density of fuel=750kg/m3
temp of fuel=120 deg c

Air inlet mass flow rate=10kg/s
temp of air=400 deg C
density of air=0.5 kg/m3

http://i40.tinypic.com/5yxafb.gif[/IMG]

Savio102 May 30, 2013 08:10

Romulo,

the mass flow rate is seems to be a bit to much for the diameters you gave. A GT will have that king of flow rate but not for a single nozzle. i suggest you divide the mass flow rate with the number of nozzles in the combustor becayse the 2.9kg/s is what the combustor feels from multiple nozzle, not a single nozzle. I also suggest that you run each part at a time i.e only one inlet and air, and than proceed from there. All the best.


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