Small-scale superadiabatic combustors with a two-step chain-branching chemistry model: asymptotic models and the effect of two-dimensionality on lean mixtures burning

• Published in: Combustion and flame 2024-01, Vol.259, p.113127, Article 113127
• Main Authors: Bosch, Javier, Fernández-Galisteo, Daniel, Jiménez, Carmen, Kurdyumov, Vadim N.
• Format: Article
• Language: English
• Subjects: Intermediate chain-branching chemistry; Laminar premixed flame; Micro combustion; Narrow-channel approximation; Two-step kinetic model
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/j.combustflame.2023.113127

Small-sized super-adiabatic combustion devices consisting of countercurrent channels with heat-exchange segments are investigated for their ability to burn ultra-lean mixtures. The study is carried out numerically using a two-step chain-branching kinetic model in which the flammability limit appears explicitly. Various asymptotic approximations for modeling the process are considered, together with the solution of the two-dimensional conservation equations for species and temperature in the gas and the solid walls. The influence of the width of the channels and the separating walls properties on the efficiency of the device in burning mixtures below the flammability limit is investigated. The main goal of the study is to determine the applicability of the considered asymptotic models for the effective prediction of the operation of such combustion devices. In this work, the appearance of non-symmetric structures for diffusion combustion is investigated for the first time within the framework of the coupled Navier-Stokes and transport equations. In the considered configuration fuel and oxidizer are injected from a porous plug into a planar channel forming two edge flames. The simultaneous appearance of symmetrically and non-symmetrically situated edge flames is demonstrated, and the regions of existence of such structures are investigated.