Acoustic parametric instability, its suppression and a beating instability in a mesoscale combustion tube

Ajit Kumar Dubey, Yoichiro Koyama, Nozomu Hashimoto, Osamu Fujita

Research output: Contribution to journalArticlepeer-review

Abstract

The present work reports thermo-acoustic instability in a mesoscale tube of diameter 8 mm (> quenching diameter) and length 702 mm. Mixtures with Lewis number, Le~ 0.8 (rich C2H4/O2/CO2), 1.05 (lean C2H4/O2/CO2) and 1.34 (lean C2H4/O2/N2) are used. Several new flame responses are observed. For lower burning velocity mixtures, flame extinction is observed due to heat loss when primary instability transforms to secondary instability for all Le mixtures. However, parametric cellular structures which are characteristic of parametric instability are observed only for Le of 0.8. It is proposed based on calculations and experiments that parametric structures will be observed only when diameter of tube is two times larger than the characteristic wavelength of parametric instability. If the tube diameter doesn't allow formation of parametric structure whirling and counter-rotating flames are observed instead of parametric structures. Suppression of acoustic parametric instability is observed for higher burning velocity mixtures with Le>1 and its mechanism is discussed. For a range of SL, a beating instability is observed for CO2 diluted mixtures of Le>1, where pressure oscillation and flame motion show beating oscillations of frequency around 15 Hz. This beating instability is believed to be caused by non-linear interaction of acoustic instability with pulsating instability of flame front which is caused due to combined radiative and convective heat loss. Due to CO2 dilution, the radiative heat losses could play a significant role in inducing pulsating instability.

Original languageEnglish
Pages (from-to)277-291
Number of pages15
JournalCombustion and Flame
Volume228
DOIs
Publication statusPublished - 2021 Jun

Keywords

  • Beating instability
  • Combustion tube
  • Mesoscale combustion
  • Parametric instability
  • Pulsating instability

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Physics and Astronomy(all)

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