Hi Anirudh Singh,

The difference between the "species transport model" and the "non premixed model" has been explained clearly in the "Theory Manual of Fluent". It seems to me that you did not check the "Theory Manual and User manual" of Fluent in a careful manner.

However, let's assume that you would like to simulate "CH4-Air non-premixed combustion" event in a domain of your interest by employing the "detailed reaction mechanism" of GRI-Mech 3.0. (http://combustion.berkeley.edu/gri-mech/version30/text30.html).

In this reaction mechanism, 53 species are involved! So, in order to predict the transport of all species (53) and their consumption/production in the combustion zone, technically, you have to solve the conservation equation of all Chemical species involved in your system (in this example, it is 53). If you want to do so, then you have to use the "Species transport model" in Fluent. And due to this feature, the "Species transport model" of Fluent is widely used in the field of non-premixed combustion. However, to solve the transport of all species in the combustion system, it is very expensive in terms of CPU time and Computing resources depending on "type of Calculation/Domain"!!

On the other hand, the "Non-premixed combustion model" of Fluent, which does not solve the conservation equation for individual species during the simulation of the "non-premixed combustion" event in the combustors. Instead, the concentration of individual species (and the associated issues with the chemical species) involved in the combustion system is estimated from the predicted "mixture fraction fields". After this point, naturally, a question would arise in your mind: What is the mixture fraction field? It can be addressed here (!), but I am not going to address it here as it is available in the open literature of Combustion. If you are really interested in this topic, then please take a look at the books on "Combustion" (any book of Combustion will be fine!). Anyway, all the best for your research.

Solving any problem in mass fraction uses Species model For example multiphase

Hi Anirudh Singh,

The difference between the "species transport model" and the "non premixed model" has been explained clearly in the "Theory Manual of Fluent". It seems to me that you did not check the "Theory Manual and User manual" of Fluent in a careful manner.

However, let's assume that you would like to simulate "CH4-Air non-premixed combustion" event in a domain of your interest by employing the "detailed reaction mechanism" of GRI-Mech 3.0. (http://combustion.berkeley.edu/gri-mech/version30/text30.html).

In this reaction mechanism, 53 species are involved! So, in order to predict the transport of all species (53) and their consumption/production in the combustion zone, technically, you have to solve the conservation equation of all Chemical species involved in your system (in this example, it is 53). If you want to do so, then you have to use the "Species transport model" in Fluent. And due to this feature, the "Species transport model" of Fluent is widely used in the field of non-premixed combustion. However, to solve the transport of all species in the combustion system, it is very expensive in terms of CPU time and Computing resources depending on "type of Calculation/Domain"!!

On the other hand, the "Non-premixed combustion model" of Fluent, which does not solve the conservation equation for individual species during the simulation of the "non-premixed combustion" event in the combustors. Instead, the concentration of individual species (and the associated issues with the chemical species) involved in the combustion system is estimated from the predicted "mixture fraction fields". After this point, naturally, a question would arise in your mind: What is the mixture fraction field? It can be addressed here (!), but I am not going to address it here as it is available in the open literature of Combustion. If you are really interested in this topic, then please take a look at the books on "Combustion" (any book of Combustion will be fine!). Anyway, all the best for your research.

Thank You sir , that was a great help

Just adding what I understood after using species transport model.

We can perform many types or any type of chemical reactions in STM. Just we have to know the kinetics of the reactions. In non premixed we have to only specify the species' mass fraction and we cant control reactions.

Suggestions appreciated.

Hi Anirudh Singh,

Yes, it is possible to control the reactions under species transport model of Fluent. So, please check the user manual of Fluent in this regard.

Akter Hossain Sir, I am working on a species transport model for reduction reaction in fluent.Will you Please guide me how I can solve this simulation.

Hello Mr. Prashant C. Jikar,

The quasi steady state approximation (or QSSA) is a standard, and one of the popular procedures, which is widely used for the reduction of a detailed reaction kinetics model. It actually allows the elimination of evolution of the species having a short time of existence with respect to the typical time of reaction chain. However, you will find further information regarding this topic once you put this key word in any search engine (Google). After reducing your targeted reaction, then you will be able to use it in ANSYS Fluent Platform. In ANSYS, no option is available for reduction; so you have to use other schemes such as Chemkin Software, and it is convenient in handling the detailed reaction Scheme. So, select the right Method for reduction and the right software. Hope you will find your solution.

Hi!

Can we use ansys fluent for non-combustion process like fischer - tropsch synthesis? If yes, why does the mixture tab only shows air weith some other components?

The species transport model does not have any reactions or combustion but in the partially premixed combustion model you are transporting a mixture fraction. kindly refer to :

https://www.cfd-online.com/Forums/fluent/215897-exact-differenc-between-partially-premixed-combustion-species-transport-fluent.html