Effect of slit pattern on the structure of premixed flames issuing from perforated burners in domestic condensing boilers

Abstract

Domestic condensing boilers are equipped with perforated burners ensuring short-length premixed flames issues from a series of circular holes and slits. Despite some efforts that have been devoted to understanding the effect of hole diameter, pattern, and hole-to-hole distance on the resulting flames, very little is known about the flames from a series of slits. In this work 3-dimensional numerical simulations with skeletal kinetic mechanisms are performed to determine the structure of premixed methane-air flames issuing from two-slits patterns, often recurring in practical burner designs, i.e. several equally-spaced slits and a group of four slits. The arrangement of the slits greatly influences the resulting flames. A significant change in the flame behaviour occurs depending on the inlet velocity; at low speeds, the flames issuing from the slits present a flat region, while increasing the speed they assume a conical shape along the slit length. Neighbour flames are distinct from each other at low speeds, while they interact strongly with increasing the velocity. Interestingly, a series of several slits produce a single long wedge-shaped flame, while the group of four slits generates a single conical flame.

Keywords:

• laminar premixed flame
• laminar flame propagation
• combustion process
• multi-slit
• condensing boilers
• computational fluid dynamics

Acknowledgments

The authors thank Polidoro S.p.A. (Italy) for sharing the burners images.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The present work was supported by the POR FESR 2014–2020 ‘HyPOWERED’ project, funded by Regione Emilia-Romagna Italy and by the Ministry of University and Research (MUR) as part of the PON 2014–2020 ‘Research and Innovation’ resources – Green/Innovation Action DM MUR 1062/2021.