Transient Combustion Chamber

Description

This project simulates a combustion chamber in ANSYS Fluent using a transient, pressure-based solver with the effect of gravity included. This is fundamentally a reacting-flow problem: the flow field and the chemistry are coupled, so the simulation must resolve the chemical reaction, the heat it releases, and the transport of the resulting hot products together. Methane is burned with air inside the chamber, and the entire setup is built around capturing this reaction and the way the combustion products move through the geometry. The chamber comprises three main parts — the air inlet pipe, the burner section, and the outlet pipe — and contains a thin internal wall pierced by cavities of varying size. The small primary holes cool the chamber wall through a film-cooling layer of flow, while the larger holes help anchor the flame at the center of the chamber, a configuration typical of real combustor liners.

The geometry is three-dimensional and was created in Design Modeler. Meshing was performed in ANSYS Meshing using an unstructured triangular grid of 694,928 elements.

Methodology

Because the flow inside a combustor is complex and highly turbulent, the RNG k-ε turbulence model with standard wall functions is used. The combustion itself is represented through the Species Transport model, which lies at the heart of any reacting-flow simulation: it tracks each chemical constituent and the reactions that convert reactants into products while releasing energy. Air and fuel (CH₄) enter at mass flow rates of 0.02 kg/s and 0.0006 kg/s respectively, both at 300 K, and the chamber's outer wall is treated as adiabatic. The reaction is modeled as a two-step methane-air combustion involving six species — methane, oxygen, nitrogen, water vapor, carbon dioxide, and carbon monoxide — with the inlet air composed of oxygen and nitrogen at mass fractions of 0.23 and 0.77.

Conclusion

The results are presented as three-dimensional volume renderings and streamlines of velocity, pressure, temperature, density, and the mass fractions of the participating species, giving a detailed view of the combustion process. Air enters around the periphery and the methane-air mixture from the bottom surface, meeting to form the combustion region. There, temperature and pressure rise sharply as the reaction proceeds, and the heated flow accelerates toward the outlet — the central behavior the simulation sets out to capture.

As a study in reacting flow, the project demonstrates how a species-transport, multi-step reaction approach coupled with a transient solver can reproduce the tightly linked interaction of chemistry and fluid motion — flame stabilization, heat release, and the transport of combustion products — through a realistic combustor geometry.