Turbulent premixed flames in a model gas turbine combustor: fuel sensitivity and flame dynamics
Author
Summary, in English
is to provide a comprehensive understanding of the complex combustion processes associated with these alternative fuels. The propagation of turbulent premixed flames under different density ratio conditions is investigated
using direct numerical simulation (DNS). The displacement speed, which characterizes the self-propagation of an isosurface defined based on a reaction progress variable in a turbulent premixed flame, has gained significant interest in the scientific community for flame modeling purposes. In this thesis, a set of new transport equations for dilation and curvature-induced flame stretch rate is derived. Based on the set of evolution equations for displacement speed that takes into account the effects of curvature, normal diffusion, and reactions, this thesis analyzes the thermal expansion effect on the correlation between these quantities. The results reveal four scenarios of flame self-acceleration. The findings provide valuable insights into the understanding of the complex dynamics of turbulent premixed flames. A newly improved gas turbine model combustor, known as CeCOST burner, is the focus of an experimental
campaign that involves laser-based diagnostics techniques, including simultaneous OH-/CH2O planar laser induced fluorescence (PLIF), simultaneous OH-PLIF, particle imaging velocimetry (PIV), and phosphor thermometry for surface temperature measurements. High-speed OH* chemiluminescence and exhaust gas measurements are also utilized. The results of the study reveal that hydrogen-enrichment can significantly extend the operation of methane/air to ultra-lean mixtures, resulting in low NOx emissions. The structures of the flame and the flow show significant variations with hydrogen-enrichment. Isolated flame pockets are identified in lean hydrogen-enriched methane/air flames, as well as in syngas flames where a substantial amount of hydrogen is present. The vortex breakdown structure is found to be strongly coupled with the location of the reaction zones. Furthermore, it is observed that pilot flames can enhance flame stabilization by producing hot gas and radicals that aid in anchoring the flames in the outer recirculation zone of the combustor. The findings of this study provide valuable insights into the combustion characteristics of methane/air, hydrogen-enriched methane/air, and syngas/air flames in the CeCOST burner, as well as the influence of pilot flames on flame and flow structures. These insights contribute to the development of more efficient and environmentally friendly gas turbine combustor designs.
Department/s
Publishing year
2023
Language
English
Full text
- Available as PDF - 49 MB
- Download statistics
Document type
Dissertation
Publisher
Department of Energy Sciences, Lund University
Topic
- Energy Engineering
- Fluid Mechanics and Acoustics
Keywords
- Fuel flexibility
- Premixed turbulent combustion
- DNS
- Optical diagnostic
Status
Published
ISBN/ISSN/Other
- ISBN: 978-91-8039-733-9
- ISBN: 978-91-8039-734-6
Defence date
2 June 2023
Defence time
10:00
Defence place
Lecture Hall KC:A, Kemicentrum, Naturvetarvägen 14, Faculty of Engineering LTH, Lund University, Lund
Opponent
- Markus Klein (Prof.)