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Sriram Popuri July 13, 1999 20:07

Coal combustion with Fluent 4.5 or 5.0!
Hi! I have a very specific question about solving coal combustion problems using Fluent. I need to solve a coal combustion problem where the oxidizer (air) is coming through an inlet into the combustor; but the fuel is already inside the domain. The fuel (solid carbon or coal particles)is injected using the disperse phase model (DPM). The coal particles can be modeled as combusting particles in the DPM. I want to solve the problem with finite rate chemistry. I am having problems setting up the problem. The fuel combustion problems that are solved in tutorials (both liquid and solid fuels) have well defined inlets. Usually the fuel and oxidizer come from outside the domain. This brief introduction to the problem brings me to this very specific question: Should the fuel always be introduced through a well defined inlet? Or, can it be injected inside the domain (or combustor) using the DPM model? If someone could answer my question, I appreciate it. If you need me explain the problem in a little more detail, I could do that. thanks in advance!

Jin Wook LEE July 24, 1999 02:27

Re: Coal combustion with Fluent 4.5 or 5.0!
Dear Popuri

I am afraid that it might be poor answer.

As far as I know, you do not have any proble because Fluent allows that combusting particle(s) can be injected everywhere inside the domain. Fluent calculates heat and mass source from the initial position of particles. You should give the initial condition of coal particles such as temperature, velocity and so on. For the initial velocity, if solid loading ratio is small as usual in coal combustion, even zero might be enough because drag force of fluid is strong enough to entrain the particles within very short time.

I hope that it might be helpfule to you.

Though I am not a speialist for coal combustion, I have some experience for 2 phase combustion with Fluent, so that I would like to discuss everyone who is interested in two phase combustion problem.

Sincerely, Jin Wook LEE

Sriram Popuri July 24, 1999 11:34

Re: Coal combustion with Fluent 4.5 or 5.0!
Jin! Thanks for your reply. You were correct. I have figured out the disperse phase model (how to inject combusting carbon particles) in Fluent, well not entirely. I am dealing with a new set of troubles now. I cannot get good enough combustion inside my domain. "What physical parameters cotrol this" is what I am trying to figure out now. My particles are very small in size (much smaller than coal particles) and my mass flow is very small indeed; so it's almost like I am putting a micro heat source in my domain. Although, the oxidizer flow very much laminar, probably the convective losses could be pretty huge. If you are interested in knowing what my problem is, I will be happy to explain it to you. I am trying to get a good qualitative solution atleast. Thanks again for your reply.

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