Catalytic Combustion problems

yellow-stuff · August 28, 2009, 05:46

hello everybody,

I am trying to simulate the catalytic combustion of propane in a channel. The wall surface of the channel is coated with Platinum.
I have written an UDF to describe the wall surface reaction rate and hooked it up to Fluent. The reaction takes place, but my temperature increases with every iteration above 5000K, which is way too high.
If I increase the heat loss through the outer wall to absurd values (150w/m2-k) the temperature decreases.
What can be the problem of the increasing temperature?
I am using the pressure based solver and transport+reaction species model with wall surface reactions, inlet diffusion, thermal diffusion and heat of surface reactions enabled. The specific heat of the species is calculated via a piecewise-polynomial function, of propane/air mixture via mixing law.

Thanks and regards

ps. This is my first time I deal with Fluent.

yellow-stuff · September 3, 2009, 01:02

Well, I created a new mesh and the problem of the increasing temperature doesn't occur anymore.
But now I have some convergence problems with my setup. There are in the majority of cases fluctuations in the residuals of continuity and I don't think I have convergence because there is no flattening of the monitored variables.
Mass flow rate at the outlet and maximum values of temperature on wall and symmetry are monitored.

What can I do to get convergence and improve my solution?
Any recommendations?

Thanks a lot.
Regards

August 28, 2009, 05:46	Catalytic Combustion problems	#1
yellow-stuff New Member Gerhard Selle Join Date: Aug 2009 Posts: 6 Rep Power: 5	hello everybody, I am trying to simulate the catalytic combustion of propane in a channel. The wall surface of the channel is coated with Platinum. I have written an UDF to describe the wall surface reaction rate and hooked it up to Fluent. The reaction takes place, but my temperature increases with every iteration above 5000K, which is way too high. If I increase the heat loss through the outer wall to absurd values (150w/m2-k) the temperature decreases. What can be the problem of the increasing temperature? I am using the pressure based solver and transport+reaction species model with wall surface reactions, inlet diffusion, thermal diffusion and heat of surface reactions enabled. The specific heat of the species is calculated via a piecewise-polynomial function, of propane/air mixture via mixing law. Thanks and regards ps. This is my first time I deal with Fluent.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Problems in combustion of char	Cleiton	CFX	2	December 12, 2008 11:35
Dimensionless Problems Combustion	Pedro Pacheco	Main CFD Forum	1	September 17, 2007 16:05
IC engine Spray-EBU combustion model problems	deisler	CD-adapco	0	May 14, 2007 05:45
Catalytic combustion	CPRL	CD-adapco	3	March 1, 2006 20:44
Combustion Convergence problems	Art Stretton	Phoenics	5	April 2, 2002 04:59

September 3, 2009, 01:02		#2
yellow-stuff New Member Gerhard Selle Join Date: Aug 2009 Posts: 6 Rep Power: 5	Well, I created a new mesh and the problem of the increasing temperature doesn't occur anymore. But now I have some convergence problems with my setup. There are in the majority of cases fluctuations in the residuals of continuity and I don't think I have convergence because there is no flattening of the monitored variables. Mass flow rate at the outlet and maximum values of temperature on wall and symmetry are monitored. What can I do to get convergence and improve my solution? Any recommendations? Thanks a lot. Regards