Direct comparison of self-excited instabilities in mesoscale multinozzle flames and conventional large-scale swirl-stabilized flames

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The present experimental investigation demonstrates important trends and offers physical insights into self-excited combustion instabilities in mesoscale multinozzle flames composed of sixty small injectors. Here we focus on the response of a prototypical micromixer-type injector assembly, fabricated using an additive manufacturing technique, in comparison with the behavior of conventional large-scale swirl-stabilized flames. Our results highlight that the development of self-excited instabilities in unconventional mesoscale flames is fundamentally different from that in large-scale swirl flames, in terms of the onset of instabilities, nonlinear modal dynamics, and amplitude/frequency of limit cycle oscillations under the same operating conditions. These differences are attributable to the alteration in local flow/flame structures and the resulting flameto-flame/flame-wall interaction mechanisms. An integrated analysis of large datasets reveals that the two interacting swirl-stabilized flames tend to couple strongly with a low-frequency L1 mode at about 220 Hz, whereas the sixty-injector small-scale flames are capable of triggering multiple higher-frequency instabilities at 310, 470, and 600 Hz. That is, the use of the micromixer-type injector assembly in a lean-premixed system causes the occurrence of combustion instabilities to shift toward a higher equivalence ratio. However, due to the absence of a large recirculation zone near the primary reaction region, the combustion system equipped with the small-scale multinozzle injectors was found to suffer from lean blowoff phenomena at low equivalence ratio.
Publisher
ELSEVIER SCIENCE INC
Issue Date
2021-04
Language
English
Article Type
Article
Citation

PROCEEDINGS OF THE COMBUSTION INSTITUTE, v.38, no.4, pp.6005 - 6013

ISSN
1540-7489
DOI
10.1016/j.proci.2020.05.049
URI
http://hdl.handle.net/10203/276854
Appears in Collection
AE-Journal Papers(저널논문)
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