Species Transport

What is Species?

Ansys Fluent can simulate the mixing and transport of chemical species by resolving conservation equations defining the convection, diffusion, and reaction sources for each component species. It is possible to explain many simultaneous chemical reactions that take place in the fluid phase (volumetric reactions), on wall or particle surfaces, and/or in the porous zone. This section describes the modeling capabilities for species transport, both with and without reactions.

Fluent can model species transport and reaction using several independent models.

• Species Transport and Finite-Rate Chemistry Approach
• Non-Premixed Combustion Approach
• Premixed Combustion Approach
• Partially Premixed Combustion Approach
• Composition PDF Transport Approach

Species Transport Approach

Convection, diffusion, and reaction sources conservation equations for many component species are solved using this method. Multiple chemical processes that occur in the bulk flow, at wall or particle surfaces, or in the porous zone can all be specified by the user for modeling at the same time.

Multicomponent transport inevitably introduces several important physical effects into the system, such as temperature gradients, enthalpy transmission, and diffusion. The reaction rate R_i may be specified as:

• Finite-Rate model (Arrhenius kinetics)

General finite-rate chemistry directly determines reaction rates by ignoring the impact of turbulent fluctuations on kinetics rates.

• Eddy-dissipation model

To avoid costly Arrhenius chemical kinetic calculations, reaction rates are believed to be controlled by turbulence while neglecting the impact of chemistry timeframes. The model is computationally cheap, but only one or two-step heat-release mechanisms should be utilized for realistic results. This strategy should only be applied when the chemistry timescales of interest are known to be quick compared to the domain’s turbulence timescales.

• Eddy-dissipation-concept model

Turbulent flames can incorporate complicated chemical kinetics while considering turbulence and kinetics timescales. It should be noted that detailed simulations of chemical kinetics might be computationally expensive.

Diffusion- or kinetics-limited surface reactions are also possible; in the second case, surface coverage may also be important. In this situation, Fluent can monitor the molar concentrations of species that have adsorption to walls. Modeling of particle surface reactions is also possible.

Non-Premixed Combustion Approach

Instead of writing and solving transport equations for individual species, this method writes and solves them for mixed fractions. The resulting mixture fraction field is used to compute the species concentrations.

The non-premixed combustion approach is predicated on the idea that you are simulating a diffuser or pulverized fuel flame, all combustion systems having separate fuel and oxidizer inlets.

The foundation of the non-premixed combustion model is the idea that a fluid’s current thermochemical state can be connected to a conserved scalar variable.

Premixed Combustion Approach

Before ignition, fuel and oxidizer are molecularly combined in premixed combustion. A flame front spreading into the unburned reactants causes combustion to happen.

During premixed combustion, a thin, spreading flame moves over the (potentially turbulent) boundary. Non-premixed combustion is often a mixing issue in a contract. Tracking the turbulent flame speed as a function of the laminar flame speed and the turbulence at the interface is the main issue for premixed combustion.

Partially Premixed Combustion Approach

The Partially Premixed Combustion model is based on the non-premixed combustion and the premixed combustion models.

Systems that use partially premixed combustion produce flames with irregular fuel-oxidizer mixes with equivalence ratios. These flames include imperfectly premixed inlets, lean premixed combustors with diffusion pilot flames and cooling air jets, and premixed jets discharging into a still atmosphere.

Composition PDF Transport Approach

A probability density function (PDF) can be used by ANSYS Fluent software to explain finite-rate chemical kinetics in turbulent reacting flows. This method, for instance, can be used to model effects like flame extinction and ignition of species like NOx. Even though it requires complicated computation, this model has the advantage of sometimes accurately accounting for turbulent flow.

Many CFD projects about Species applications in different devices are simulated by the MR-CFD team.

An example is the Vortex Combustion Chamber simulation. In this CFD Analysis, the combustion inside a Vortex Combustion Chamber, which helps to cool and increase the mixing of propulsion components in the combustion chamber and makes complete combustion in smaller volume chambers, is carried out using ANSYS Fluent software by our experts.

Also, the pollution existence in indoor and outdoor places can be modeled by the Species method. In another CFD project, the performance of Jet Fans in a Tunnel in the presence of pollution generated by cars is investigated by ANSYS Fluent software. In this simulation, the exact movement of pollution under the influence of the fan is visible.

MR-CFD, an Expert in the Field of Species Simulations

With several years of experience in simulating various problems in different CFD fields using ANSYS Fluent software, the MR-CFD Company is ready to offer extensive modeling, meshing, and simulation services. Our simulation Services for Species simulations are categorized as follows:

• Simulation and analysis of Virus Spread due to different phenomena and places.
• HVAC CFD Simulation in the operating room, smoking room, etc.
• Modeling of Combustion inside Storage Tank, Combustion Chamber, boiler, etc.
• Simulation of Providing Indoor and Outdoor Locations Thermal Comfort.
• Analysis of different Species applications in a fluidized bed, packed bed, etc.
• CFD Simulation of material decomposition.
• Analysis of Food Processing in case of drying, Refrigeration, etc.
• …

You may find the related products to the Species simulation category in Training Shop.

Our services are not limited to the mentioned subjects, and the MR-CFD is ready to undertake different and challenging projects in the Species Engineering modeling field ordered by our customers. We even accept carrying out CFD simulation for any abstract or concept design you have in your mind to turn them into reality and even help you reach the best design for what you may have imagined. You can benefit from MR-CFD expert consultation for free and then order your project to be simulated and trained.

By outsourcing your project to the MR-CFD as a CFD simulation freelancer, you will not only receive the related project’s resource files (Geometry, Mesh, Case & Data, …), but also you will be provided with an extensive tutorial video demonstrating how you can create the geometry, mesh, and define the needed settings(pre-processing, processing and post-processing) in the ANSYS Fluent software all by yourself. Additionally, post-technical support is available to clarify issues and ambiguities.