The characteristic modes and structures of bluff-body stabilized flames in supersonic coflow air

Jiho Kim, Youngbin Yoon, Chul Woung Park, Jae Won Hahn

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The stability and structure of bluff-body stabilized hydrogen flames were investigated numerically and experimentally. The velocity of coflowing air was varied from subsonic velocity to a supersonic velocity of Mach 1.8. OH PLIF images and Schlieren images were used for analysis. Flame regimes were used to classify the characteristic flame modes according to the variation of the fuel-air velocity ratio, into jet-like flame, central-jet-dominated flame, and recirculation zone flame. Stability curves were drawn to find the blowout regimes and to show the improvement in flame stability with increasing lip thickness of the fuel tube, which acts as a bluff-body. These curves collapse to a single line when the blowout curves are normalized by the size of the bluff-body. The variation of flame length with the increase in air flow rate was also investigated. In the subsonic coflow condition, the flame length decreased significantly, but in the supersonic coflow condition, the flame length increased slowly and finally reached a near-constant value. This phenomenon is attributed to the air-entrainment of subsonic flow and the compressibility effect of supersonic flow. The closed-tip recirculation zone flames in supersonic coflow had a reacting core in the partially premixed zone, where the fuel jet lost its momentum due to the high-pressure zone and followed the recirculation zone; this behavior resulted in the long characteristic time for the fuel-air mixing.

Original languageEnglish
Pages (from-to)386-397
Number of pages12
JournalInternational Journal of Aeronautical and Space Sciences
Volume13
Issue number3
DOIs
Publication statusPublished - 2012 Oct 11

All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Materials Science(all)
  • Aerospace Engineering
  • Electrical and Electronic Engineering

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