Effect of Coflow Air Velocity on Heat-loss-induced Self-excitation in Laminar Lifted Propane Coflow-Jet Flames Diluted with Nitrogen

질소로 희석된 프로판 동축류 층류 제트 부상화염에서 열손실에 의한 자기진동에 대한 동축류 속도 효과

  • 이원준 (부경대학교 기계공학과) ;
  • 윤성환 (부경대학교 친환경수송시스템연구소) ;
  • 박정 (부경대학교 기계공학과) ;
  • 권오붕 (부경대학교 기계공학과) ;
  • 박종호 (충남대학교 기계공학과) ;
  • 김태형 (한국전력연구원 수화력발전팀)
  • Received : 2012.02.21
  • Accepted : 2012.03.22
  • Published : 2012.03.30

Abstract

Laminar lifted propane coflow-jet flames diluted with nitrogen were experimentally investigated to determine heat-loss-related self-excitation regimes in the flame stability map and elucidate the individual flame characteristics. There exists a critical lift-off height over which flame-stabilizing effect becomes minor, thereby causing a normal heat-loss-induced self-excitation with O(0.01 Hz). Air-coflowing can suppress the normal heat-loss-induced self-excitation through increase of a Peclet number; meanwhile it can enhance the normal heat-lossinduced self-excitation through reducing fuel concentration gradient and thereby decreasing the reaction rate of trailing diffusion flame. Below the critical lift-off height. the effect of flame stabilization is superior, leading to a coflow-modulated heat-loss-induced self-excitation with O(0.001 Hz). Over the critical lift-off height, the effect of reducing fuel concentration gradient is pronounced, so that the normal heat-loss-induced self-excitation is restored. A newly found prompt self-excitation, observed prior to a heat-loss-induced flame blowout, is discussed. Heat-loss-related self-excitations, obtained laminar lifted propane coflow-jet flames diluted with nitrogen, were characterized by the functional dependency of Strouhal number on related parameters. The critical lift-off height was also reasonably characterized by Peclet number and fuel mole fraction.

Acknowledgement

Supported by : 한국연구재단

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