Hypersonic Combustion in Scramjet with Viscous Heating, CFD Simulation ANSYS Fluent TrainingDescriptionHydrogen combustion inside a scramjet engine at hypersonic speed represents one of the most demanding reacting-flow problems in CFD, coupling supersonic compressible flow, finite-rate chemistry, and wall heating within a single transient case.A scramjet (supersonic-combustion ramjet) has no moving parts — it relies entirely on engine geometry to compress incoming air, inject and burn fuel, and expand the combustion products for thrust. This distinguishes it from a conventional ramjet, which decelerates flow to subsonic conditions before combustion occurs; a scramjet instead sustains supersonic combustion throughout, enabling flight above Mach 5.The 2D geometry consists of two sections — a lower preheating region and an upper stable-burn region — built in Design Modeler and meshed in ANSYS Meshing using a structured grid of 16,320 cells. Inlet air enters at Mach 6, with the domain initialized at 300 K. At the mid-nozzle location, where the flow decelerates to Mach 1, hydrogen is injected supersonically, triggering combustion within the nozzle.MethodologyCombustion is modeled using the Species Transport model with its volumetric reaction sub-model, with air treated as an ideal gas so that density responds correctly to the steep temperature rise generated during burning. Turbulence is captured using the standard k-ε model, and the case is solved as transient to resolve the developing flow field and flame structure.Given the numerically stiff nature of hypersonic reacting flows, first-order discretization schemes and reduced under-relaxation factors are deliberately applied to maintain stable convergence throughout the solution process.ConclusionResults include 2D contours and vector fields for pressure, temperature, velocity, Mach number, density, and turbulence intensity. The flow physics follows a clear progression: air enters the domain, decelerates to Mach 1 at the combustion section, then re-accelerates toward the outlet. Combustion drives temperatures beyond 4000 K, with viscous heating clearly visible in the near-wall elements, where high-speed shear converts kinetic energy into heat at the wall surface.

DescriptionThis project simulates combustion in the presence of an electrohydrodynamic (EHD) field using ANSYS Fluent. A simple combustion chamber is designed, into which airflow and fuel enter axially. The fuel, C₁₀H₂₂ (decane), enters through the central section, with the airflow surrounding it.The study is carried out in two stages. First, ordinary combustion between air and fuel is investigated; then the same combustion is performed in the presence of an EHD field. Applying EHD causes the fluid to become electrically charged, and the motion of the ionized particles or molecules — together with their interaction with the electric field and the surrounding fluid — is studied. The combustion reaction is modeled using the Species Transport model, with C₁₀H₂₂ and O₂ defined as reactants and CO₂ and H₂O as products.Airflow enters the chamber at 447 K with a velocity of 5 m/s, while fuel enters at 300 K with a velocity of 0.01 m/s. The EHD model is used to impose the effect of the electric field on the chamber's performance: a current density of 40 A/m² is applied at the inlet and outlet boundaries, with a positive charge defined on the inlet boundary and a negative charge on the outlet boundary.Geometry & MeshThe geometry was created as a 3D model in Design Modeler. The computational domain is a horizontal cylindrical combustion chamber; fuel enters through a narrow inner tube, and airflow enters around this tube. Meshing was performed in ANSYS Meshing using an unstructured grid, producing 1,000,658 cells.Setup & SolutionSeveral assumptions underpin the simulation: a pressure-based solver is used, the simulation is steady, and the effect of gravity is neglected.Viscous model — standard k-epsilon with standard wall functionsSpecies — Species Transport with 5 volumetric species (C₁₀H₂₂, O₂, CO₂, H₂O, N₂) and volumetric reactionsEnergy — enabledPotential (electric field) — enabledBoundary conditions — Inlet-Air: velocity inlet at 5 m/s, 447 K, O₂ mass fraction 0.21, current density −40 A/m²; Inlet-Fuel: velocity inlet at 0.01 m/s, 300 K, C₁₀H₂₂ mass fraction 1, current density 0 A/m²; Outlet: pressure outlet at 0 Pa gauge, current density 40 A/m²; Inner Wall: stationary, coupled thermal condition; Outer Wall: stationary, zero heat flux, current density 0 A/m²Methods — Coupled pressure-velocity coupling; second-order for pressure; second-order upwind for momentum, species mass fraction, and energy; first-order upwind for turbulent kinetic energy and turbulent dissipation rateInitialization — standard method, with 0 Pa gauge pressure, O₂ mass fraction 0.21, velocity 5 m/s, temperature 447 K, and potential 0ConclusionOn completion of the solution, 2D and 3D contours of temperature, velocity, pressure, and the mass fraction of each species (CO₂, C₁₀H₂₂, O₂, N₂, and H₂O) were obtained. These results are presented in two modes — without EHD and with EHD — so that the effect of the electric field can be assessed through direct comparison. The contours show that when EHD is applied to the combustion chamber, more energy is delivered to the species, producing higher product temperatures. This rise in the temperature of the reacting species accelerates the combustion reaction. Furthermore, examination of the reaction products indicates that combustion in the presence of EHD proceeds with higher quality, demonstrating how the electric field can be used to enhance combustion performance.

Premixed Combustion, Species Transport, Eddy Dissipation, ANSYS Fluent CFD TrainingDescriptionThis project simulates premixed combustion inside a combustion chamber using ANSYS Fluent, with fuel and air assumed to enter the chamber already premixed through a single boundary. The 2D geometry was designed in Design Modeler and meshed in ANSYS Meshing using a structured mesh totaling 86,002 elements.MethodologyThe Species Transport model is used to represent the combustion process, applying a single-step methane-air reaction with the volumetric option enabled to capture combustion throughout the chamber. Turbulence-chemistry interaction is handled using the Eddy Dissipation model, which bypasses detailed reaction kinetics and instead accounts for combustion behavior based purely on the effect of turbulent mixing. The energy equation is enabled to capture temperature changes driven by combustion, with turbulence modeled using the standard k-epsilon model.ConclusionThe simulation results include contours of temperature, velocity, mass fractions of the various species, and streamlines. The temperature contour shows a clear rise within the chamber, confirming that combustion has taken place. The streamlines also reveal secondary flow structures forming within the chamber — these secondary flows enhance the mixing between fuel and air, thereby improving the overall combustion process.

Premixed Combustion, Eddy Dissipation/Finite Rate Model, ANSYS Fluent CFD Simulation TrainingDescriptionThis project simulates premixed combustion inside a combustion chamber using ANSYS Fluent, with fuel and air assumed to enter the chamber already premixed through a single boundary.The Eddy Dissipation/Finite Rate model combines two distinct approaches to reaction rate calculation: the Eddy Dissipation model, which assumes combustion is limited purely by turbulent mixing, and the Finite Rate model, which calculates reaction rates directly from Arrhenius chemical kinetics. At each computational cell, the model takes the smaller of the two calculated rates — meaning the reaction proceeds at whichever rate is the limiting factor, mixing or chemistry. This makes the model particularly useful for cases where reaction kinetics may become locally significant (such as near flame ignition points or in regions of low turbulence), rather than assuming mixing is always the sole limiting process, as the standalone Eddy Dissipation model does.The 2D geometry was designed in Design Modeler and meshed in ANSYS Meshing using a structured mesh totaling 86,002 elements.MethodologyThe Species Transport model is used to represent the combustion process, applying a single-step methane-air reaction with the volumetric option enabled to capture combustion throughout the chamber.Turbulence-chemistry interaction is handled using the Eddy Dissipation/Finite Rate model, evaluating both the turbulent-mixing-limited rate and the kinetics-limited rate at each point in the domain and applying the smaller of the two. The energy equation is enabled to capture temperature changes driven by combustion, with turbulence modeled using the standard k-epsilon model.ConclusionThe simulation results include contours of temperature, velocity, mass fractions of the various species, and streamlines. The temperature contour shows a clear rise within the chamber, confirming that combustion has taken place.The streamlines also reveal secondary flow structures forming within the chamber — these secondary flows enhance the mixing between fuel and air, thereby improving the overall combustion process. Because the model accounts for finite-rate kinetics alongside mixing, this simulation can also capture combustion behavior in regions where reaction rates are not purely mixing-controlled, offering a more complete picture of the flame structure than a mixing-only approach would provide.

Non-Premixed Combustion, Eddy Dissipation, ANSYS Fluent CFD TrainingDescriptionThis project simulates non-premixed combustion inside a combustion chamber using ANSYS Fluent, with fuel and air entering the chamber through two separate boundaries — meeting and mixing only within the chamber itself, consistent with non-premixed combustion behavior. The 2D geometry was designed in Design Modeler and meshed in ANSYS Meshing using a structured mesh totaling 63,280 elements.MethodologyThe Species Transport model is used to represent the combustion process, applying a single-step methane-air reaction with the volumetric option enabled to capture combustion throughout the chamber. Turbulence-chemistry interaction is handled using the Eddy Dissipation model. The energy equation is enabled to capture temperature changes driven by combustion, with turbulence modeled using the standard k-epsilon model.ConclusionThe simulation results include contours of temperature, velocity, mass fractions of the various species, and streamlines. The temperature contour shows a clear rise within the chamber, confirming that combustion has taken place. The streamlines also reveal secondary flow structures forming within the chamber — these secondary flows enhance the mixing between fuel and air, thereby improving the overall combustion process.

Two Stream Combustion, CFD Simulation ANSYS Fluent TrainingDescriptionCombustion reactions occur when air combines with hydrocarbon fuel, converting fuel energy into heat energy. In some applications, two separate fuel streams are used to carry out this reaction — a configuration known as two-stream combustion, where two fuel streams react with a common oxidizer. This project models a horizontal cylindrical combustion chamber using methane (CH₄) and diesel (C₁₂H₂₃) as fuels, combined with an oxidizer stream to produce combustion. The chamber includes four separate inlets: one each for the primary fuel, secondary fuel, and oxidizing stream. The CH₄ stream enters at a flow rate of 0.02 kg/s and 810 K, the C₁₂H₂₃ stream at 0.02 kg/s and 530 K, and the oxidizer at 1.2 kg/s and 723 K.The Species model was used to define the combustion reaction, configured in non-premixed combustion mode — meaning fuel and oxidizer enter the reaction zone through separate paths without mixing beforehand. This model relies on a mixture fraction representing the mass fraction derived from the fuel stream. Since a secondary fuel is present, the secondary stream option was also activated. The 3D geometry was built in SpaceClaim, representing the interior of a horizontal cylindrical combustion chamber with four inlets for primary fuel, secondary fuel, and airflow. The domain was meshed in ANSYS Meshing using an unstructured mesh totaling 689,854 cells.MethodologyThe simulation was run under steady-state conditions using a pressure-based solver, with gravitational effects excluded.Key model settings included:Turbulence model: Realizable k-epsilon with standard wall functionsSpecies model: Non-premixed combustion with non-adiabatic energy treatment and secondary stream enabledSpecies definitions: Fuel as CH₄, oxidizer as 0.79 N₂/0.21 O₂, secondary stream as C₁₂H₂₃Boundary conditions: Mass flow inlets for fuel (0.02 kg/s, 810 K, mean mixture fraction 1), oxidizer (1.2 kg/s, 723 K, mean mixture fraction 0), and secondary fuel (0.02 kg/s, 530 K, secondary mean mixture fraction 1); pressure outlet at 0 Pa gauge; stationary walls with zero heat fluxSolution methods: SIMPLE pressure-velocity coupling, standard pressure discretization, and first-order upwind schemes applied across momentum, turbulence, mixture fraction, and energy equationsInitialization: Hybrid methodConclusionResults include 2D and 3D contours of pressure, velocity, temperature, and species mass fractions (CH₄, CO₂, C₁₂H₂₃, O₂, H₂O, H₂, CO), along with water-liquid and water-vapor volume fractions. Temperature rises significantly within the reaction zone, where the primary and secondary fuel streams combine with the oxidizing stream inside the chamber, releasing substantial thermal energy. Near the chamber inlet, reactant mass fractions (CH₄, C₁₂H₂₃, and O₂) decrease, while reaction product concentrations (CO₂, CO, H₂O, and others) correspondingly increase — confirming that the combustion reaction proceeds correctly, converting fuel and oxidizer into combustion products.

Diesel-Air Mixture Flow with Fuel Droplet Evaporation, CFD TrainingDescriptionThis project investigates the complex dynamics of a diesel-air mixture using ANSYS Fluent, focusing on the interaction between dispersed fuel droplets and the continuous air phase, along with the impact of droplet evaporation on the resulting flow field — analysis directly relevant to engine combustion and fuel spray characterization. The 3D geometry represents a simplified cylindrical combustion chamber, built in SpaceClaim, and meshed in ANSYS Meshing using a grid of over 2 million elements to ensure sufficient resolution for capturing the complex flow phenomena involved.MethodologyA pressure-based, transient solver was used, with the standard k-epsilon turbulence model and standard wall functions applied to capture the flow's turbulent behavior. The energy equation was enabled to resolve the temperature field. The Species Transport model with Eddy-Dissipation for turbulence-chemistry interaction was used to model the mixing of diesel and air. The Discrete Phase Model (DPM) simulated the movement and evaporation of fuel droplets as discrete entities, with two-way coupling enabled to capture the interaction between the dispersed phase (droplets) and the continuous phase (air). Temperature-dependent latent heat effects were also included to account for the energy consumed during droplet evaporation.Droplet evaporation was permitted throughout the domain, capturing the associated mass transfer process. Diesel fuel was injected from the center of the inlet, with air entering from the surrounding region, and the simulation ran for 5 seconds to capture the mixture's transient behavior.ConclusionThe simulation results provide detailed insight into the diesel-air mixture's flow behavior: Density contours show higher mixture density near the injection point, decreasing as the diesel jet spreads and mixes with the surrounding air — reflecting diesel's higher density relative to air. Mass fraction contours for diesel (C10) show the fuel jet extending into the chamber, with concentration progressively decreasing as mixing occurs, while nitrogen mass fraction contours show a corresponding decrease near the injection point as the diesel jet displaces the surrounding air.Static temperature contours reveal a significant temperature rise where the diesel jet interacts with the air, indicating heat release associated with combustion. Turbulence intensity is elevated near the jet, reflecting strong mixing activity, while velocity magnitude contours show peak velocity at the jet core, gradually decreasing as the jet spreads — illustrating momentum transfer from the injected diesel. Particle trajectories from the DPM model illustrate the dispersion and evaporation of individual fuel droplets within the chamber, with smaller droplets evaporating faster and exhibiting shorter residence times. Particle residence time visualizations further show how time spent within the domain varies depending on droplet size and injection location.

Lime Kiln Combustion CFD Simulation by ANSYS Fluent, TutorialDescriptionThis project simulates the combustion process of methane gas within a vertical lime kiln using ANSYS Fluent. The 3D geometry was designed in Design Modeler as a semi-modeled vertical furnace, leveraging the structure's symmetry to reduce computational cost. The model includes four fuel inlets positioned around the middle of the kiln's side surface, a fifth fuel inlet at the furnace center, a primary air inlet at the center of the kiln, a secondary air inlet in the furnace's lower section, an outlet for reaction products in the lower section, and a dedicated outlet for gas discharge at the top of the furnace. The domain was meshed in ANSYS Meshing, totaling 2,219,550 elements.MethodologyA vertical lime kiln consists of two main functional zones: the combustion zone and the preheating zone. Fuel and air enter through the middle of the kiln and undergo a combustion reaction, releasing substantial heat and raising the internal temperature. Separately, calcium carbonate (limestone) is introduced from the upper section of the kiln. As it absorbs heat generated by the combustion process, it undergoes a distinct thermal decomposition reaction, releasing carbon dioxide and producing calcium oxide (quicklime). This project focuses specifically on modeling the combustion reaction itself within the kiln, rather than the limestone decomposition process.The combustion reaction models a chemical interaction between air and methane, represented using the Species Transport model with its volumetric reaction sub-model. Flow entering through the four side inlets and the central inlet consists of 0.9 methane (CH₄) and 0.1 nitrogen (N₂), entering at 1.357 m/s and 300 K, alongside a simultaneous airflow entering from the central region.The model includes two outlets: reaction products exit through the bottom outlet at atmospheric pressure, while excess gases are drawn out through a separate suction-fan-driven outlet. Porous media was incorporated within the kiln, modeled as aluminum with a porosity coefficient of 0.3, an inertial resistance of 907.4 1/m, and a viscous resistance of 1,100,000 1/m². The standard k-epsilon turbulence model and the energy equation were used to solve the turbulent flow field and capture temperature variation throughout the domain.ConclusionResults include 2D and 3D contours of pressure, temperature, velocity, and mass fractions for O₂, CH₄, H₂O, CO₂, N₂, and CaCO₃. The results confirm that reaction products — including carbon dioxide and water vapor — form as a result of the combustion reaction between methane fuel and air, releasing significant heat in the process. This generated heat is precisely what drives the subsequent dissociation of calcium carbonate into quicklime, linking the combustion process directly to the kiln's primary industrial function.

Premixed Combustion in a Porous Zone, CFD Simulation ANSYS Fluent TrainingDescriptionThis project simulates premixed combustion within a porous zone using ANSYS Fluent, examining how the presence of porous media affects combustion behavior. Porous media combustion, often implemented through matrix-stabilized burners, works by allowing the flame to propagate through the solid matrix of a porous material rather than in free space. The solid matrix absorbs and redistributes heat through conduction and radiation, which tends to broaden the reaction zone, lower peak flame temperatures, and improve flame stability compared to conventional open-flame combustion. This approach is widely used in industrial burners and heating applications where more uniform heat distribution, reduced thermal peaks, and extended operational stability are desired — making the comparison between porous and non-porous combustion a valuable way to quantify these effects. The 3D geometry was designed in Design Modeler, consisting of two sections: a lower preheating region and an upper stable-burn region. The domain was meshed in ANSYS Meshing using a structured grid totaling 8,700 cells.MethodologyThis simulation models a simple premixed combustion case within a porous zone, examining how the porous structure influences combustion temperature and helps stabilize the flame — configured as a matrix-stabilized burner. Results were compared against an equivalent premixed combustion case without porosity to isolate the effect of the porous medium. The Species Transport model was used to represent the combustion process, with the incoming mixture flow set at a methane mass fraction of 0.23 and an oxygen mass fraction of 0.77. Combustion was initiated using the ignition spark sub-model. Gravitational effects were included at -9.81 m/s² along the y-axis, and turbulence was resolved using the SST k-omega model.ConclusionResults include 3D velocity fields, air and water volume fraction contours, and simulation animation. The findings show that the porous zone reduces static temperature within the combustion region and promotes a more uniform, stable combustion process compared to an equivalent case without porosity — consistent with the general behavior expected of matrix-stabilized porous burners, where the solid matrix's heat redistribution moderates and stabilizes the reaction zone.

Radiation Heat Transfer in Combustion Chamber, ANSYS Fluent TrainingDescriptionThis project investigates the steady combustion of methane and air within a simple extended cubical combustion chamber using ANSYS Fluent, with particular attention to radiation heat transfer — a critical consideration given the extremely high temperatures involved in combustion chambers. The 3D geometry was designed in Design Modeler and meshed in ANSYS Meshing, totaling 384,112 elements.MethodologyThe simulation captures a mixture static temperature reaching a maximum of 3500 K within the chamber. Methane and air enter the domain through separate inlets — methane through a single inlet, while airflow enters through two inlets to promote a more uniform fuel-air mixture. Air and fuel enter at mass flow rates of 0.00468 kg/s and 0.000205 kg/s, respectively.The chemical reaction between methane and air produces CO₂ and H₂O; since the combustion is air-rich, oxygen and nitrogen remain unconsumed at the end of the reaction. The Species Transport model was activated to simulate combustion, with volumetric reactions enabled.Given the high temperatures generated within the chamber, radiation heat transfer required explicit modeling, so the Discrete Ordinates (DO) model was also enabled. Turbulence was resolved using the RNG k-epsilon model, chosen for its ability to more accurately capture intense heat flux generation within the domain compared to other k-epsilon variants.ConclusionResults include 2D contours of temperature, velocity, species mass fraction, streamlines, and velocity vectors throughout the combustion chamber, with an outlet mixture mass flow rate of 0.004885042 kg/s. The primary combustion process occurs within the chamber itself, clearly visible in the temperature and reaction heat contours, which show the maximum temperature gradient and peak reaction heat concentrated in this region. The combustion process is similarly evident in the species mass fraction contours — the CO₂ mass fraction, for instance, shows a sharp increase corresponding directly to the combustion reaction taking place.