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    An Experimental Investigation on the Dynamics of Lean Premixed Swirl Flames

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    An Experimental Investigation on the Dynamics of Lean Premixed Swirl Flames_PhD Thesis_Francesco Di Sabatino_final version.pdf
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    34.19Mb
    Format:
    PDF
    Description:
    Dissertation - Francesco
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    Type
    Dissertation
    Authors
    Di Sabatino, Francesco cc
    Advisors
    Lacoste, Deanna cc
    Committee members
    Roberts, William Lafayette
    Knio, Omar cc
    worth, nicolas
    Program
    Mechanical Engineering
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2020-04
    Permanent link to this record
    http://hdl.handle.net/10754/662752
    
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    Abstract
    Gas turbine engines are an efficient and flexible way of power generation and aircraft propulsion. Even though different combustion systems can be implemented in these engines, more stringent regulations on pollutant emissions have been imposed throughout the years, especially in regard to nitrogen oxides (NOx). A very promising technology to reduce NOx emissions is lean premixed combustion (LPC), however, it is plagued by intense flame dynamics. Thermoacoustic instabilities, lean blow-off and lean instabilities are examples of dynamical phenomena that are detrimental to the gas turbines. In view of this, the present thesis presents the experimental investigation of the response of lean premixed swirl flames to acoustic perturbations at atmospheric and elevated pressures. The results of this investigation may be used to understand the thermoacoustic instabilities and further could be helpful in their prediction. Moreover, this work addresses the effects of non-thermal plasma discharges on the lean blow-off and stability limits of premixed swirl flames at elevated pressures. For the analysis of the flame response to acoustic fluctuations, the flame transfer functions, the flame dynamics, phase-locked velocity fields, and phase-locked measurements of flame curvature are collected through heat release and velocity fluctuations measurements, phase-locked images of the flame, particle image velocimetry, and planar laser-induced fluorescence, respectively. For the analysis of the effects of plasma discharges on the stability limits, electrical measurements and direct imaging of the flame are performed. The results include the development of an empirical relation based on the laminar burning velocity and on the circulation of the acoustically generated vortex to predict the response of the flame to acoustic fluctuations in different operating conditions. Moreover, the results show that the pressure has a strong impact on the response of lean premixed swirl flames to acoustic oscillations and on the flame-plasma interactions. Therefore, extrapolating results obtained at atmospheric conditions to elevated pressures may result in erroneous conclusions. Furthermore, it is shown that non-thermal plasma discharges can effectively extend the stability limits of lean premixed swirl flames at elevated pressures, underlining the potential of these discharges at conditions relevant for gas turbines.
    Citation
    Di Sabatino, F. (2020). An Experimental Investigation on the Dynamics of Lean Premixed Swirl Flames. KAUST Research Repository. https://doi.org/10.25781/KAUST-1Z090
    DOI
    10.25781/KAUST-1Z090
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-1Z090
    Scopus Count
    Collections
    Dissertations; Physical Science and Engineering (PSE) Division; Mechanical Engineering Program

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