skip to main content

Recent Experimantal Reults on the Effects of High Turbulence of the Structure and Blowoff Behavior of Bluff-Body Stabilized Premixed Flames

  • April 3, 2017
  • 4:00 p.m.
  • 117A Surge Building
  • Dr. Baki Cetegen, University of Connecticut
  • Faculty Host:  Lin Ma

Abstract:

The structure of unconfined, lean premixed flames stabilized on an axisymmetric bluff body is studied for different levels of turbulence intensity in the approach flow. The mixture approach velocities range from 5 to 15 m/s while the mean turbulence intensity levels between 4 and 30 % are achieved by using suitable turbulence generation schemes. These conditions allow reaching turbulence Reynolds numbers, based on the fluctuating velocity and turbulence integral length scales, up to 8000.  Simultaneous diagnostics of OH and CH2O planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV) is performed for heat release and velocity measurements. The flame structure is observed to be strongly modified by the turbulent flow field. Formation of cusps and unburnt mixture fingers are observed as the turbulence intensity is increased from 4 to 14 %, but for these cases the heat release front remains continuous. For turbulent conditions higher than 14 % rms, localized extinctions occur along the flame surface creating isolated pockets of OH with heat release occurring along its boundary. Pockets of preheated reactants along with fresh reactants are also found inside the flame envelope. The overall flame shape was observed to change from symmetric (varicose) to asymmetric (sinuous) mode with increasing turbulence intensity due to the reduction of the bulk density ratio between the burnt and unburnt regions. The turbulent flame speed and flame front statistics – curvature, flame surface density, brush thickness, strain rate and turbulent to laminar flame area ratio have been evaluated to quantify the burning characteristics.  Lean flame blowoff equivalence ratio dependence on fuel type and turbulence conditions also reveals interesting results.  These experimental results in a canonical flame configuration can also be used for validation of LES and DNS simulations.

 

Bio:

Baki Cetegen received his B.S. (1978) in ME and Physics summa cum laude from Bosphorous University in Istanbul Turkey followed by M.S. (1979) in ME from UC Berkeley and Ph.D. (1982) in ME from Caltech.  After working several years in industry at Energy and Environmental Research Corporation as a research engineer and group leader and later as a postdoctoral research fellow at UC Irvine with Prof. William A. Sirignano, he joined the faculty of University of Connecticut where he is currently United Technologies Chair Professor.  He has published over 200 articles in topics ranging from turbulent combustion, detonations and rotating detonations, combustion and plasma synthesis of ceramic materials and coatings, buoyant flames and buoyancy induced instabilities, shock-induced and vortical mixing enhancement, among others.  He is a member of the Combustion Institute, a fellow of ASME and an elected member of the Connecticut Academy of Science and Engineering (CASE).  He was the chair of the Executive Board of Combustion Institute Eastern States Section (2009-2011).  He has served as the department head of Mechanical Engineering from 2006 to 2015.  He currently serves as Vice President and President-elect of Connecticut Academy of Science and Engineering.

Tags