Hi Namasthe! I am new to this group. I am a student from canada. I work in fluent on a particular problem in which I face a difficulty. I hope any one from here will be able to help me.Here is the problem in which I work..

This is basically a combustion invloving species transport. This is a simulation of flow thru's a High Velocity Oxygen fuel (HVOF) process. We have a HVOF nozzle in which the coating particle is mixed with Nitrogen gas and fed in to the nozle by one port. In a another port propylene and air(Fuel) is fed. Combustion of propylene occurs and this accelerate the particle fed in another port to supersoni velocity at the nozle exit. To prevent over heating, nitrogen is fed as coolent in anotehr port.

In this problem, we consider 4 steps of chemical reactions, whose enthalpy of formation is very important. But selecting a species transport combustion modelling, I dont know where to enter the Enthalpy of each reaction.

If some one can tell me where I can enter the enthalpy of reaction, I will be happy. Also if the U think that the model I use is not correct, then pls suggest me an alternate one.

Srivatsan

In menu Define->materials

in "Material type" you choose "fluid"

then in "properties" you can get enthalpy

[sanmi]

I am working on the Carbonization of Biomass (Sawdust) using Numerical Simulation. I have tried several methods but not having a headway.

The objectives of the simulation are to monitor the thermal conversion during the carbonization process and also monitor mass fraction and fixed carbon of the biomass with time.

I am trying to use species transport to study the carbonization process but I am not getting any result. I had already done the hydrodynamics study but to proceed further to the thermal conversion of the biomass is a problem.

Please, on compassionate ground, could you please help me with steps that could be of help or detailed guidelines that I could follow to get the expected results.


I would be glad to hear from you.

Thank you.

[vinerm]

Carbonization is a reaction, hence, you need to enabled reactions along with Species Transport. The type of reaction model depends on the model being used to represent sawdust. If sawdust is being represented by a fluid, then you just need to enable Volumetric reactions for carbonization. If sawdust is packed as a bed, then you need to enable wall reactions. If sawdust is being represented as small particles then you need to enable particle surface reactions. All options are available within Species Transport.

[sanmi]

Thank you. I really appreciate those your suggestions. I will critically look at those options and check their suitabillities. Thank you.

[sanmi]

In the case of carbonization of biomass, what will be the reactant and product species?.

Secondly, whenever I choose a multiphase model, the coal calculator goes off. How do I implement my proximate and ultimate analysis?. and how do I get my stoichiometric coefficients?.

Finally, Pls how do I arrive at knowing the percentage mass yield of char, which is the most important in my project?.

Thank you

[vinerm]

You may not require a multiphase model for carbonization of sawdust. For products and reactants, I'd recommend you to study some literature. In terms of molecules, it would, of course, be hydrocarbons and oxygen as reactants with oxides of carbon and hydrogen as products. However, the reactions, their stoichiometric coefficients, reaction kinetics, etc. require literature survey or at least going through some book that explains reactions for carbonization of wood.

[sanmi]

Dear Mr. Vinerm

Thank you, sir. I really appreciate you.

I have done a lot of reading but have not seen literature that explains carbonization in the absence of Oxygen (not combustion). I will search more to see if I can get relevant literature, most importantly knowing the percentage yield of char or any other thing that could quantify or qualify the char.

If I have any breakthrough, I will inform you. Please, if there is any material that you think could help me or any further help you could render, kindly send it.

Thank you and God bless you.

[vinerm]

I also wrote carbonization in tune with you but it is not carbonization but oxidation. Sawdust is already carbon. You might find some relevant articles online.

https://www.tandfonline.com/doi/abs/...00102200302392

https://www.sciencedirect.com/scienc...55270117313417

[sanmi]

Thank you for those links you sent. I was able to download those papers and gather some important points. I really appreciate those journal papers.

God bless you.

[sanmi]

I tried initializing my problem and I keep receiving the message that "There must be more than one species on each phase". How do I go about the message?

[vinerm]

If there are heterogeneous reactions in the system, i.e., reactions across phases, then each phase must be composed of more than one component. E.g., if saw dust has to oxidize, then the phase containing saw dust must be made up of Carbon and something else. Similarly, the gas to which it oxidizes must have CO and/CO2 and something else. Each phase must have at least two components.

[sanmi]

Dear Friend,

Permit me to call you friend because you have been a friend, always responding to my question within a short time. I really appreciate your reply. I have not been able to solve the problem, could not able to figure out what I am not getting right as regards pyrolyzing or carbonizing sawdust in the absence of oxygen.

I am actually considering two phases. Nitrogen gas as phase 1 or gaseous phase and Sawdust as Phase 2. While I expect the reaction to give me volatile gases and char. Initializing the problem is a challenge. I do not know where I am to specify those species for respective phases as regards the error message. I have played around the setup but the error message keeps showing up whenever I am to initialize.

Thank you.

[vinerm]

If the volume fraction of sawdust is lesser than or around 10%, then use DPM model for dust. If gaseous phase is only Nitrogen, it will not allow any volatiles to enter because you have specified that the phase can contain only Nitrogen. E.g., if CO and H2 have to come out of the dust as volatiles, then the gaseous phase should have N2, H2, and CO as components and not just N2. During initialization, you could specify 0 mass fractions for H2 and CO but the species must be part of the phase. Secondly, with DPM, you have to use combusting particle type. You may also work with multicomponent type of the particle but combusting is more suitable. A combusting particle should also has multiple species. With DPM, you do not need to use Euler-Euler or VOF or Mixture model. Refer to this tutorial by Ansys

http://dl.mr-cfd.com/tutorials/ansys...ustion-ebu.pdf

[sanmi]

Thank you, Mr. Vinerm

I really appreciate your intelligent reply. Although I am considering not using the multiphase model anymore. If I am to continue with Euler-Euler model, where am I to specify different species contained in my phases.?. Secondly, how do I set up a fixed bed reactor (no-injection) using DPM, with the sawdust taking about 30% of the reactor?.

[vinerm]

If you want to setup a system with packed-bed, then Euler-Euler is the recommended way; so, you have to use multiphase. 30% volume fraction can be handled by DPM but you will have to use it along with DEM; in effect, involving Euler-Euler. So, Euler-Euler is the way to go.

First, you need to include all the components that expect to be present in the system such as, C, CO, CO2, O2, N2, etc. Then, create two mixtures, one with a few species that are part of dust and another one with the species that are included in the gas phase. Now, assign one mixture to phase-1 and other one to phase-2.

[sanmi]

Thank you. I never knew all these about the problem I am solving. I really appreciate your contributions. Let me go back to read and work on these suggestions. I will get back to you. God bless you, Sir.

[sanmi]

Originally Posted by vinerm

If you want to setup a system with packed-bed, then Euler-Euler is the recommended way; so, you have to use multiphase. 30% volume fraction can be handled by DPM but you will have to use it along with DEM; in effect, involving Euler-Euler. So, Euler-Euler is the way to go.

First, you need to include all the components that expect to be present in the system such as, C, CO, CO2, O2, N2, etc. Then, create two mixtures, one with a few species that are part of dust and another one with the species that are included in the gas phase. Now, assign one mixture to phase-1 and other one to phase-2.

Good day. Thank you for your previous assistance rendered. I discovered an article that explains using the DEM-DPM collision model as you suggested. It requires writing a file for parcel injection. I have been trying to write the file but not getting it neither am I able to download the file (92Kparcels.inj) used in the article. I have tried creating the injection by other means but file injection seems to be recommended to solve a packed bed problem.

My problem now is creating an injection file for DEM. I have been battling with this but no avail.


http://https://topic.alibabacloud.co..._31261540.html

[sanmi]

Dear All, How do I specify wood dust as phase material. I have the proximate and ultimate analysis result, so do I create my material as phase material for purpose of combustion.

Thank you.