Vortex merging events during amplitude switching in mixed-mode pressure oscillations in a partially premixed backward facing combustor

Modeling Unsteady Flow of a Lean Partially Premixed Flame on a Dry Low NOx Combustion System

Volume 1B: Combustion, Fuels and Emissions ◽

10.1115/gt2013-94969 ◽

2013 ◽

Author(s):

Salvatore Matarazzo ◽

Hannes Laget ◽

Evert Vanderhaegen ◽

Jim B. W. Kok

Keyword(s):

Gas Turbine ◽

Limit Cycle ◽

Gas Turbines ◽

Premixed Flame ◽

Computational Domain ◽

Pressure Oscillations ◽

Combustion Dynamics ◽

Partially Premixed ◽

Partially Premixed Flame ◽

Limit Cycle Behavior

The phenomenon of combustion dynamics (CD) is one of the most important operational challenges facing the gas turbine (GT) industry today. The Limousine project, a Marie Curie Initial Training network funded by the European Commission, focuses on the understanding of the limit cycle behavior of unstable pressure oscillations in gas turbines, and on the resulting mechanical vibrations and materials fatigue. In the framework of this project, a full transient CFD analysis for a Dry Low NOx combustor in a heavy duty gas turbine has been performed. The goal is to gain insight on the thermo-acoustic instability development mechanisms and limit cycle oscillations. The possibility to use numerical codes for complex industrial cases involving fuel staging, fluid-structure interaction, fuel quality variation and flexible operations has been also addressed. The unsteady U-RANS approach used to describe the high-swirled lean partially premixed flame is presented and the results on the flow characteristics as vortex core generation, vortex shedding, flame pulsation are commented on with respect to monitored parameters during operations of the GT units at Electrabel/GDF-SUEZ sites. The time domain pressure oscillations show limit cycle behavior. By means of Fourier analysis, the coupling frequencies caused by the thermo-acoustic feedback between the acoustic resonances of the chamber and the flame heat release has been detected. The possibility to reduce the computational domain to speed up computations, as done in other works in literature, has been investigated.

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Combustion Instabilities With Different Degrees of Premixedness in a Separated Dual-Swirl Burner

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4047182 ◽

2020 ◽

Vol 142 (6) ◽

Cited By ~ 1

Author(s):

Xinyao Wang ◽

Xiao Han ◽

Heng Song ◽

Chi Zhang ◽

Jianchen Wang ◽

...

Keyword(s):

Equivalence Ratio ◽

Large Scale ◽

Convective Motion ◽

Flame Surface ◽

Mode Transition ◽

Combustion Instabilities ◽

Pressure Oscillations ◽

Flame Response ◽

Partially Premixed ◽

Phase Angles

Abstract The effects of premixedness degrees on combustion instabilities of separated dual-swirl flames have been investigated experimentally in the Beihang Axial Swirler Independently Stratified (BASIS) burner. The degree of premixedness is modulated by the fuel split between two injection positions in the outer stream. In the spectra of pressure oscillations, both the frequency and amplitude are positively correlated with fuel split ratios under partially premixed conditions, and the mode transition between perfectly and partially premixed conditions has been observed. The location of perfectly premixed flames shows no obvious variation at different phase angles, only with a slightly wrinkling of the flame surface along the shear layer. Under partially premixed conditions, however, the flame is found to feature a large-scale periodic convective motion, accompanied by the obvious variation of heat releases due to the equivalence ratio oscillations. The local Rayleigh index map compares the thermoacoustic driving factors under perfectly and partially premixed conditions. The development of above convective motions under partially premixed conditions is explained by combining the variations of pressure oscillations and heat releases. An analysis of the thermoacoustic network and convective path is applied to explain the cause of the mode transition. The results show that the appearance of equivalence ratio oscillations and the elongated convective path under partially premixed conditions brings a longer delay time of the flame response, which could be the reason for the mode transition.

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The modality effect as an interaction between the auditory and visual systems in a mixed mode situation.

PsycEXTRA Dataset ◽

10.1037/e432362004-001 ◽

1982 ◽

Author(s):

Kjell Ohlsson ◽

Jerker Roennberg

Keyword(s):

Mixed Mode ◽

Modality Effect ◽

Visual Systems

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“To Corrupt a Man in the Midst of a Verse”: Ben Jonson and the Prose of the World

Ben Jonson Journal ◽

10.3366/bjj.2017.0179 ◽

2017 ◽

Vol 24 (1) ◽

pp. 46-72

Author(s):

Jacob Tootalian

Keyword(s):

Mixed Mode ◽

Ben Jonson ◽

Digital Analysis ◽

Interactive Engagement ◽

Sentence Level ◽

Linguistic Patterns ◽

The World ◽

Selection Of ◽

Bartholomew Fair

Ben Jonson's early plays show a marked interest in prose as a counterpoint to the blank verse norm of the Renaissance stage. This essay presents a digital analysis of Jonson's early mixed-mode plays and his two later full-prose comedies. It examines this selection of the Jonsonian corpus using DocuScope, a piece of software that catalogs sentence-level features of texts according to a series of rhetorical categories, highlighting the distinctive linguistic patterns associated with Jonson's verse and prose. Verse tends to employ abstract, morally and emotionally charged language, while prose is more often characterized by expressions that are socially explicit, interrogative, and interactive. In the satirical economy of these plays, Jonson's characters usually adopt verse when they articulate censorious judgements, descending into prose when they wade into the intractable banter of the vicious world. Surprisingly, the prosaic signature that Jonson fashioned in his earlier drama persisted in the two later full-prose comedies. The essay presents readings of Every Man Out of his Humour and Bartholomew Fair, illustrating how the tension between verse and prose that motivated the satirical dynamics of the mixed-mode plays was released in the full-prose comedies. Jonson's final experiments with theatrical prose dramatize the exhaustion of the satirical impulse by submerging his characters almost entirely in the prosaic world of interactive engagement.

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