An experimental investigation of thermoacoustic instabilities in a premixed swirl-stabilized flame

Journal Article · Mon Oct 15 04:00:00 EDT 2007 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2007.05.012· OSTI ID:20961955

Fritsche, D; Fueri, M; Boulouchos, K ^[1]

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1. ETH Swiss Federal Institute of Technology, Institute of Energy Technology, Aerothermochemistry and Combustion Systems Laboratory, Sonneggstrasse 3, CH-8092 Zurich (Switzerland)

Modern gas turbines use lean premixed combustion to achieve the best compromise between pollutant emissions and efficiency. This type of combustion increases the flame receptivity to external perturbations, thereby promoting the onset of large-amplitude pressure oscillations called thermoacoustic instabilities (often referred to as combustion noise). To improve our understanding of stability properties in such complex systems, encountered in many industrial applications, the flame structure of an atmospheric swirl-stabilized burner of 30 to 75 kW was systematically investigated for various inlet temperatures and air-fuel ratios. This investigation revealed the existence of two stable flame types (one lean and one rich) separated by a region of unstable flames characterized by very distinct flame shapes, flame pressure drops, and dynamic pressure oscillations. The lean transition from stable to unstable flames has been associated with a critical flame temperature at the edge of two different flame-stabilizing mechanisms, while the rich transition from unstable to stable flames has been attributed to a critical ratio of hydrodynamic to combustion times in terms of Damkoehler number. In this noise island, the mechanism for instability is due to the nonmonotonic behavior of flame pressure drop as the air-fuel ratio is changed, the maximum pressure drop across the flame coinciding with the maximum dynamic pressure. Finally, the frequency analysis of the dynamic pressure revealed the coupling with the acoustic eigenmodes of the combustion chamber for the dominant mode and with the plenum for secondary ones the frequency of which did not change with flame temperature. (author)

• OSTI ID: 20961955
• Journal Information: Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 1-2 Vol. 151; ISSN CBFMAO; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
42 ENGINEERING
BURNERS
COMBUSTION
COMBUSTION KINETICS
COUPLING
DISTURBANCES
FLAMES
FREQUENCY ANALYSIS
FUEL-AIR RATIO
GAS TURBINES
HEAT
INSTABILITY
NOISE
OSCILLATIONS
POWER RANGE 10-100 KW
PRESSURE DROP
SHAPE
STABILITY
TEMPERATURE DEPENDENCE