DIMENSIONLESS GENERAL TRANSIENT MODELING FOR SMOLDERING COMBUSTION REACTORS
Nome: RUAN SCHULTZ RIGUETTI
Data de publicação: 28/11/2025
Banca:
Nome |
Papel |
|---|---|
| FLÁVIO LOPES FRANCISCO BITTENCOURT | Coorientador |
| MARCELO RISSO ERRERA | Examinador Externo |
| MARCIO FERREIRA MARTINS | Presidente |
| MARCO AURELIO BAZELATTO ZANONI | Examinador Externo |
| MIRIAM SUELY KLIPPEL | Examinador Interno |
Resumo: Smoldering combustion is a slow, flameless process that occurs at relatively low temperatures and reaction rates, typically under limited oxygen conditions. Beyond its scientific interest, this process offers environmental, technological, and social benefits, which make it relevant for both industrial applications and sustainable development. In this context, the present research
develops and applies a general dimensionless numerical model for smoldering combustion reactors, aiming to simulate the phenomenon on a small scale. The approach relies on a 2D axisymmetric model implemented in COMSOL Multiphysics (v5.4) using the Local Thermal Non-Equilibrium (LTNE) consideration, which allows separate treatment of the solid and fluid phases. Conservation equations for mass, momentum, energy, and species transport were implemented in a dimensionless form and enable a comprehensive and generalized analysis of the physical and chemical processes involved. Novel dimensional and dimensionless groups emerged during the non-dimensionalization process, associated with the effects of particle-bed burning and the interstitial chemical kinetic dynamics. Classical numbers such as Prandtl, Grashof, Darcy, Schmidt, and Peclet numbers also appeared. The model proposed in the methodology was validated through three case studies. The first involved combustion at the fluid–porous interface, highlighting the influence of natural convection. In this case, the model reproduced the same recirculation patterns reported in the reference study and also allowed investigation of how the velocity profile was distorted by these recirculations.
The second case addressed the cooling of a porous bed and was used to calibrate convective heat transfer under transient conditions. The results showed that the model is capable of simulating studies without a reactive porous bed, although a maximum discrepancy of 25% was observed in the temperature profiles when comparing the simulations with the experimental
data. The third case consisted of a full simulation of smoldering combustion, which included the ignition process through a heat source, propagation of the combustion front, and coupled interactions between heat and mass. This case allows analysis of solid fuel consumption over time and comparison of temperature profiles with experimental data obtained at different axial positions
of the reactor. In general, the results demonstrate that the model created is capable of capturing the main behaviors with good agreement compared to the experimental data and the results from the literature. Therefore, the proposed methodology provides a reliable model that allows one to understand smoldering dynamics.
