Partially Premixed Combustion: Composition PDF Transport

Partially Premixed Combustion, Composition PDF Transport, ANSYS Fluent CFD Training

Description

This project simulates partially premixed combustion using Composition PDF Transport in ANSYS Fluent, examining a combustion chamber featuring three distinct inlet boundaries: a pure air inlet, a fuel-air mixture inlet, and a pilot inlet supplying combusted flow for activation energy. This configuration allows for detailed investigation of partially premixed combustion dynamics under conditions that closely mirror advanced industrial combustion systems.

The geometry was designed in Design Modeler and meshed in ANSYS Meshing using a structured grid totaling 2,352 elements.

Methodology

The simulation proceeded across three progressive phases. In the first phase, the Partially Premixed Combustion model was applied with a non-adiabatic energy treatment and a chemical equilibrium approach, using a pre-generated PDF table for efficient data storage and the Zimont model for turbulent flame speed calculation — establishing an initial baseline solution.

The second phase built on this foundation by enabling Composition PDF Transport for more detailed modeling, incorporating a Chemkin mechanism for comprehensive reaction chemistry. ISAT (In Situ Adaptive Tabulation) was implemented alongside chemistry agglomeration to balance simulation speed against acceptable error margins during this more computationally demanding stage.

The third and final phase refined the solution further by disabling chemistry agglomeration while continuing to draw on the ISAT table populated during the second phase — achieving a high-fidelity result capable of capturing the full complexity of the combustion dynamics involved. Throughout all three phases, the energy equation remained enabled to track temperature changes accurately, 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 this partially premixed, multi-inlet environment, how temperature evolves across different regions of the chamber, how species form and are consumed throughout the reaction, and specifically how the pilot inlet influences overall combustion dynamics.

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