Partially Premixed Combustion: Non-Adiabatic Chemical Equilibrium

Partially Premixed Combustion, Non-Adiabatic, Chemical Equilibrium, ANSYS Fluent CFD Training

Description

This project simulates partially premixed combustion under non-adiabatic conditions inside a two-dimensional combustion chamber using ANSYS Fluent, focusing on the chemical equilibrium approach applied to a unique configuration where pure air and a fuel-air mixture interact directly within the chamber — a scenario commonly found in advanced combustion systems.

The geometry was designed in Design Modeler and meshed in ANSYS Meshing using a structured grid totaling 4,700 elements.

Methodology

The Partially Premixed Combustion model was used to represent the combustion process, applying a non-adiabatic energy treatment to realistically capture heat transfer effects, alongside a chemical equilibrium approach for predicting species concentrations. Separate inlets for pure air and the fuel-air mixture allow this setup to closely mirror advanced real-world combustion configurations.

A pre-generated Probability Density Function (PDF) table stored temperature variation, mixture density, and species mass fraction data ahead of the main simulation, improving computational efficiency while supporting the chemical equilibrium calculations throughout. Turbulent flame propagation was captured using the Zimont turbulent flame speed model, which accounts for the interaction between turbulence and chemical reactions.

The simulation proceeded in two stages: an initial cold flow simulation to establish baseline flow patterns without combustion, followed by the combustion simulation itself, enabling the combustion equations and using the patch option to initialize the progress variable. The energy equation was enabled throughout to accurately track temperature changes, with turbulence modeled using the standard k-epsilon model.

Conclusion

Results include temperature distribution contours, velocity profiles throughout the chamber, mass fractions for the various chemical species, and streamlines revealing the resulting flow and mixing patterns. These results offer insight into how combustion progresses within a partially premixed environment, how non-adiabatic conditions shape temperature evolution, how species form and are consumed throughout the reaction, and how secondary flow structures enhance mixing and overall combustion efficiency.

These insights are directly applicable to designing advanced gas turbine combustors, optimizing dual-fuel engine systems, and improving combustion efficiency in industrial furnaces relying on partially premixed combustion behavior.