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Old   June 20, 2007, 02:41
Default combustion of wood
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Özer AYDIN
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hi,

A certain mass of that is a cylndirical combustion chamber. The whole volume of combustion chamber is filled with wood shaving.The combustion air is sent in the direction of the combustion chamber axis.Which models are chosen? (Especially, the values relation with wood shavings in order to amount of wood volatiles are decreased by combustion. Thanks

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Old   June 20, 2007, 09:17
Default Re: combustion of wood
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Allan Walsh
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Why are you modeling this? If you answer that, you will be part of the way to your solution. Do you want temperatures, gas composition, wood burning rate? The first two can be done reasonably well in Fluent. For the last one, you would likely have to make your own model.
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Old   June 20, 2007, 10:06
Default combustion of wood
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Özer AYDIN
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Hi,Thanks for the asking.I study on smoldering combustion. I have some experimental results. I want to compare these results with numerical solution. I want to temperatures, gas composition, wood burning rate. What is your advise for modelling smoldering combustion. Wood shaving is burnt in a fixed bed. Fixed bed is cylindircal and full of wood shaving. How should I introduce this fuel to Fluent

Thank you Allan
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Old   June 21, 2007, 11:55
Default Re: combustion of wood
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Allan Walsh
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As a starting point, I would introduce the fuel from a surface representing the top of the fuel pile. Set a mass flux of water, volatiles (based on the fuel composition), and CO or CO2 from char combustion.

Then you need to add heat sink terms for water evaporated and heat source terms for char burned. And O2 sink terms for char combustion.

What are you trying to do? Model the combustion as a function of temperature, O2 concentration, and velocities (mass fluxes)? Of course, there is nothing built into Fluent to account for these things. You would have make your own stand-alone model or implement it into Fluent via a UDF. You would probably be looking at a year or two of work.
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Old   June 25, 2007, 03:11
Default Re: combustion of wood
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Özer AYDIN
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Hi,Thanks for the asking.I think I forgot to explain the physical model of the problem.In my case, wood sawings is in a cylindirical volume and is not moved or transported by air flow. Air is blowed from bottom of the cylinder. Air passes thorugh the wood sawing.At the experimental setup wood is ignited by electircal heater.The energy for ignition is given for a few minutes. Meanwhile air is blowed through the wood. Then heater is shut down and air is blowed continously.The combustion zone propagated to the upper part of the cylinder.This a unsteady problem.It can be solved as a unsteady problem or a steady problem.As a steady problem, the combustion front propagation front velocity will not be output. If it is solved a steady problem, I think wood mass flux should be given as a data.As an unsteady problem, a certain amount of wood sawing must be in the cylindrical volume and the propagation of combustion should be modelled.For us the best is the unsteady solution.So we have problem to choose the proper models for both steady and unsteady solution.If you give some advises for modelling, it will bie very helpful.Thank you very much.

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