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Adi March 26, 2001 01:13

fixed bed combustion
Hi, For 3D gasification modeling I am using pdf method for the reaction chemistry. But I find difficulties to get the correct result, such as the distribution temperature in the fixed bed combustor are not comparable with the experimental result. The lower portion in the combustor should have higher temperature compared to the upper portion/zone.

Is there anybody can assist me to solve my problem?


Greg Perkins March 26, 2001 19:54

Re: fixed bed combustion
What models are you ising and Fluent version? How do you model the solid phase, if at all?


Adi March 29, 2001 01:16

Re: fixed bed combustion
Hi, Thanks for the asking. I use Fluent 5.4 Version. The reaction model is pdf method (2 stream non adiabatic method). The flow of biomass particles is modeled using discrete phase model. Injection type: cone with customs laws: Devolatilization (4th law), surface reaction (5th law),inert heating (1st law) and the rest are inactives.

For boundary condition; inlet air-velocity: 2m/s, temperature 1000 K, turbulence int:10, turb. length scale :0.001m.

Are there any information which you still wants to know?

Thank you Adi

Greg Perkins March 29, 2001 19:27

Re: fixed bed combustion
If you're using the lagrangian method then I assume you are modelling a dilute flow of particles - such as in a pf boiler or entrained flow gasifier.

To me, fixed bed combustion, refers to a dense solid phase which may have a volume fraction of >0.3 in which case the lagrangian treatment is not valid. In this case the solids velocity is very low - almost zero.

Between the too there is fluidised beds where there are strong coupling between the gas and solid phases - and again the loading is such that a lagrangian treatment is generally not valid.



Adi April 17, 2001 15:01

Re: fixed bed combustion
Hi Greg, So which method will you prefer?

Regards Adi

Greg Perkins April 17, 2001 20:06

Re: fixed bed combustion
Eulerian models are appropriate for fixed bed combustion but Fluent doesn't have these inbuilt.


Adi April 18, 2001 23:24

Re: fixed bed combustion
Dear Greg, Thank you for your reply. So, does it means an UDF shoud be built to support the fix bed combustion?

Cheers Adi

Greg Perkins April 19, 2001 01:20

Re: fixed bed combustion
Well that's what I'm doing, but its been a major headache to be honest. I wouldn't advise it again, to be honest. Write your own code.


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