purging system of fired furncae

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Last Post 04 December 2018

bwadoud31 posted this 29 November 2018 - Last edited 30 November 2018

Hi all,
I am trying to simulate an existing ejector used to purge an fired furnace, but the issue is how we must define the boundary conditions. I tried the boundary conditions below: Reference pressure: 1 atm
Inlet of ejector: static pressure 7 bar and velocity 48 m/s
In the bottom of the furnace I tried 2 options:
1 inlet of furnace with a static pressure 0 atm
2 as opening with a static pressure 0atm
Out of the furnace I tried 2 options:
1 outlet of furnace with a static pressure 0 atm
2 as opening with a static pressure 0atm
The simulation did not converge.
NB: the geometry and the conditions is like the site (real case).
I need your help and your advice; after trying a lot of different setups, it seems that I need some help with the boundary conditions of my problem. I'm looking for a stable (steady state?) solution
I am using ANSYS CFX 14.5.
thanks, I am very grateful

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rwoolhou posted this 30 November 2018

Please can you post images in line: as staff we can't open attachments. Is the flow compressible?

Also, check the mesh and update to the current version.

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bwadoud31 posted this 01 December 2018

Hi dear rwoolhoo, how can I chek the mesh.

thank you for the advice, about the choice of boundary conditions, I try this simulation to know the mass flow rate of air at the bottom in the furnace, I used the knonw boundary conditions wich are:

1 the speed, mass flow rate and the pressure at the inlet of the ejector.
2 at the bottom of the furmace (atmospheric openning), we have only the atmospheric pressur, normaly is the inlet of atmospheric air.
3 at th top (duct) of furnace is the same (atmospheric openning), normaly is the exit (out).

at the end of this simulation we must confirm the mass flow rate at the bottom;