Unsteady ultra-lean combustion of methane and biogas in a porous burner – An experimental study

Habiba, R., Yadollahia, B., Saeed, A. , Doranehgard, M. H., Li, L. K. B. and Karimi, N. (2020) Unsteady ultra-lean combustion of methane and biogas in a porous burner – An experimental study. Applied Thermal Engineering, 182, 116099. (doi: 10.1016/j.applthermaleng.2020.116099)

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Abstract

The response of ultra-lean flames, stabilised in a porous burner, to the fluctuations imposed on the fuel flow rate is investigated experimentally. The study is motivated by the likelihood of small biogas generators to produce fuels with temporal variations in their flow rate and chemical composition. The employed porous burner includes layers of silicon carbide porous foam placed inside a quartz tube. The burner is equipped with a series of axially arranged thermocouples and is imaged by a digital camera. Methane and a blend of methane and carbon dioxide (mimicking biogas) are mixed with air and then fed to the burner at equivalence ratios below 0.3. The fuel flow rate is modulated with a programmable mass flow controller by imposing a sinusoidal wave with variable amplitude and frequency on the steady fuel flow. Through analysis of the flame images and collected temperature traces, it is shown that the imposed disturbances result in motion of the flame inside the burner. Such motion is found to qualitatively follow the temporal variation in the fuel flow for both methane and biogas. Nonetheless, the amplitude of the flame oscillations for methane is found to be higher than that for biogas. Further, it is observed that exposure of the burner to the fuel fluctuations for a long time (180 s) eventually results in flame destabilisation. However, stabilised combustion was achieved for methane mixtures at amplitudes between 0 and 30% of steady values over a period of 60 s. This study reveals the strong effects of unsteady heat transfer in porous media upon the fluctuations in flame position.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Karimi, Dr Nader and Saeed, Mr Ali
Authors: Habiba, R., Yadollahia, B., Saeed, A., Doranehgard, M. H., Li, L. K. B., and Karimi, N.
College/School:College of Science and Engineering > School of Engineering
Journal Name:Applied Thermal Engineering
Publisher:Elsevier
ISSN:1359-4311
ISSN (Online):1359-4311
Published Online:28 September 2020
Copyright Holders:Copyright © 2020 The Authors
First Published:First published in Applied Thermal Engineering 182:116099
Publisher Policy:Reproduced under a Creative Commons License

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