An Optical Analysis of the Blowoff Behavior for Bluff Body-Stabilized Flames in Vitiated Flow

<p>In bluff body-stabilized flames, a variety of physical phenomena contribute to the flame destabilization as lean blowoff is approached. These effects include increased strain on the flame shear layers, decreased attenuation of Bénard-von Kármán vortex shedding, and the presence of thermoacoustic instabilities. Lean, bluff body-stabilized flames were studied in an enclosed rectangular-duct, turbulent combustion rig with a triangular flame holder under vitiated conditions with both symmetric and asymmetric fuel distributions. Air and fuel flows within the rig were characterized using a PIV system and a continuous emissions gas analyzer, respectively. </p> <p>High-speed videos of these flames undergoing blowoff were taken to serve as the primary data source for analysis. To examine the effects of Bénard-von Kármán vortex instabilities and local strain-induced extinctions on the lean blowoff process, proper orthogonal decomposition (POD) algorithms were applied to the frames of the high-speed videos. POD mode shapes representing each of these phenomena were extracted and the relative contributions of these mode shapes were plotted over time as the flame approaches blowoff. Time-series analysis was also performed on a trace of the pressure oscillations and POD mode coefficients for a preliminary examination of the relevant acoustic influence on the blowoff event. </p> <p>For future application to the turbulent combustion rig, a tunable diode laser absorption spectroscopy (TDLAS) system was developed. A TDL with a center wavelength in the near infrared region was simultaneously scanned across absorption lines of H₂O and CO₂ to obtain temperature and species concentration data. A McKenna Flat Flame burner was used to create a calibration environment for these measurements. Both direct and wavelength-modulated spectroscopy methods are examined, and their respective viability for use in the combustion rig is discussed.</p>

Name thesis:degree_name

Master of Science

Discipline thesis:degree_discipline

Mechanical Engineering

Year dc:date.available

2011

Author dc:creator

• Jensen, Trevor

Contributors dc:contributor

• Baki Cetegen, Thomas Barber
• Michael Renfro

• Bluff body
• Combustion
• POD
• TDLAS
• turbulent flame

Repository record dc:identifier

https://digitalcommons.lib.uconn.edu/gs_theses/141

OAI identifier oai:identifier

oai:digitalcommons.lib.uconn.edu:gs_theses-1188