Heat release and flame structure measurements of self-excited acoustically-driven premixed methane flames

Journal Article · Thu Oct 15 04:00:00 EDT 2009 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2009.06.018· OSTI ID:21227400

Kopp-Vaughan, Kristin M; Tuttle, Steven G; Renfro, Michael W ^[1]; King, Galen B ^[2]

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1. Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Rd, U-3139, Storrs, CT 06269 (United States)
2. School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)

An open-open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane-air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re = 1780-4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube combustor. This coupling creates sustainable self-excited oscillations in flame front area and shape. The period of the oscillations occur at the resonant frequency of the combustion chamber when the flame is placed {proportional_to}1/4 of the distance from the bottom of the tube. In this investigation, the shape of these acoustically-driven flames is measured by employing both OH planar laser-induced fluorescence (PLIF) and chemiluminescence imaging and the images are correlated to simultaneously measured pressure in the combustor. Past research on acoustically perturbed flames has focused on qualitative flame area and heat release relationships under imposed velocity perturbations at imposed frequencies. This study reports quantitative empirical fits with respect to pressure or phase angle in a self-generated pressure oscillation. The OH-PLIF images were single temporal shots and the chemiluminescence images were phase averaged on chip, such that 15 exposures were used to create one image. Thus, both measurements were time resolved during the flame oscillation. Phase-resolved area and heat release variations throughout the pressure oscillation were computed. A relation between flame area and the phase angle before the pressure maximum was derived for all flames in order to quantitatively show that the Rayleigh criterion was satisfied in the combustor. Qualitative trends in oscillating flame area were found with respect to feed tube flow rates. A logarithmic relation was found between the RMS pressure and both the normalized average area and heat release rate for all flames. (author)

• OSTI ID: 21227400
• Journal Information: Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 10 Vol. 156; ISSN CBFMAO; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AIR
BURNERS
COMBUSTION CHAMBERS
COMBUSTION KINETICS
CONES
COUPLING
DISTANCE
DISTURBANCES
FLAMES
FLOW RATE
HEAT TRANSFER
METHANE
OSCILLATIONS
PRESSURE DEPENDENCE
Phase-resolved imaging
Rijke tubes
SHAPE
SOUND WAVES
TIME RESOLUTION
TUBES
Thermoacoustic interactions
VARIATIONS
VELOCITY