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-   -   diffusion flames (http://www.cfd-online.com/Forums/openfoam/76057-diffusion-flames.html)

elisabet May 12, 2010 16:17

diffusion flames
 
Hi everybody,

I need to know if a furnace combustion can be modeled by OF. This is not my research subject so I'm a little bit lost.

From Luca Mangani's PhD thesis I've learn that it should be modeled as a diffusion flame. I've done a quick overview on the implemented OF combustion solvers and I conclude that possibly the unique manner to model it is by reactingFoam.

1. Should we need anything else?
2. Any code modification?
3. What about the fuel definition?

I would really thank any help on it!

elisabet

elisabet May 13, 2010 10:39

What about fireFoam from OF1.6.x?

any suggestion?

elisabet

skarnani May 23, 2010 01:08

I think it would be possible. I'm still pretty new at this, could you include some additional details about the flow environment?

elisabet May 25, 2010 04:59

Thanks for the interest Skarnani!

The ones that asked me if OF can deal with such flows are interested in modeling a biomass kitchen. The system would be a cavity with a chimney. Wood could be the fuel. Fresh air would enter the cavity by a corner and hot air, combustion products and ashes would leave the system through the chimney by natural convection. Radiation has to be included in the modeling, at least under the non-participating media assumption. The phenomenon could be modeled first considering steady state.

Thanks for any suggestion!

elisabet

l_r_mcglashan May 25, 2010 05:18

I guess some things to think about are:

1) Is your flow laminar/turbulent.

2) How are you going to model the reaction (i.e. how important is the prediction of the product concentrations)? I've simulated laminar diffusion flames by coupling our own flamelet library to openfoam, and by using a lagrangian style tracking of the flamelet.

Have you done a literature survey yet? What are the standard modelling practices for this type of problem?

elisabet May 25, 2010 06:04

It's not my research field so I'm not really into it. The one that is going to do the simulation is not involved in CFD at all, nor any type of simulation. So I just wanted to know if it was somehow stright forward to simulate it in OF. If so, I would guide him a little bit, but I don't have much time now...

The final goal of the ongoing project is to get a code to provide to the ones that carry out the experimental part of this biomass kitchens in Peru (I guess), in order to improve the kitchen design. The ones that would use it are not involved in CFD simulations. Hence, it is probably more interesting to develop a simple code, with just convection + reaction as a first step.
However, if OF is really able to deal with the full pehomenon, it could be nice to validate the simple code with OF, as for example, to know how rellevant is radiation for this specific case, how important is to solve in detail the combustion, etc.

For the moment, I think that the bibliographic step has not been done yet so I can not answer your first question. As mentioned above, I would say the reaction is not needed to be modeled in detail, just its effects on heat sources and density variations.

Thanks.

elisabet

francescomarra May 26, 2010 12:10

Dear Elisabet,

I have some experience in modelling similar problems for a different appliance, an enclosed wood stove burning wood bricks.
At the time I have done these simulations I was not using OpenFOAM yet, but probably general observations can be equally applied.

The simulation of the full process is not a trivial task. Wood combustion is a very complex phenomena involving multiphase processes. Nevertheless the simulation required can be simplified if it is clear the objective of the simulation.

In my case it was the optimization of the heat recovery from the stove. With this respect you can assume the amount of heat released without taking care too much of the combustion process itself. Depending on the geometry of the furnace, you could also assume a very simple heat and mass sources in proper places instead of modelling the combustion process. In this way, the major difficulty is probably the proper account of the radiative heat transfer that strongly depend, in turn, from the local composition of burnt gases and the presence of soot.
The proper inclusion of a combustion model is really important if the objective of simulations is to improve pollutant emissions from the kitchen.

The observations of mcglashan are also important: the flow regime and the combustion model have to be considered when you have to establish if your simulations will be affordable with your computational resources.

Regards,

Franco

elisabet May 26, 2010 16:03

Thanks Franco!

Do you have any article with your work? It could be very useful. Or even a reference bibliography for these kind of systems?

elisabet

francescomarra May 27, 2010 13:06

Dear Elisabet,

Yes, I have some articles. I am sending you a private message to know an e-mail address to which send in attach these papers.

Regards,
Franco


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