Optical Diagnostics in Energy Conversion Processes
Författare
Summary, in English
This thesis presents development in optical diagnostics for studies of energy conversion processes. Work has been done in characterization of electrode wear in spark plugs, multi-species high-speed tomographic laser-induced fluorescence, high-speed diagnostics in lab-scale gas turbine burners, and surface temperature measurements on gas turbine burner injection nozzles.
A new method of monitoring erosion of the electrodes in spark plugs made from nickel has been established, based on the emission of Ni atoms in the 339~360 nm spectral range. Spectral study revealed the spectral range in which high intensity of Ni atomic emission can be observed while low intensity of background emission is present. An excitation scan has shown that laser excitation at Ni’s 336.957 nm absorption line can induce the most optimum signal-to-noise ratio in the desired detection window. The fluorescence lifetime of the found excitation scheme has been measured, reporting an effective fluorescence lifetime of approximately 1.1 ns, which was not seen to be changing as the spark discharge plasma decays. It has been further established that the integrated fluorescence intensity of the current excitation scheme is proportional to the Ni atom number density. Such findings have created a solid foundation for further 2D studies on the generation of Ni atoms from the spark discharge and erosion of the electrodes.
The construction of an injection seeded OPO producing signal wavelength at 609 nm pumped by a high-speed burst mode laser system has been described. A routine of alignment of the OPO cavity has been established and described in detail in the thesis. Using the same laser system, quasi-simultaneous 10 kHz tomographic LIF measurement of anisole and formaldehyde has been successfully performed, where only two sets of high-speed CMOS and image intensifier were used for acquisition of 8 views from different angles thanks to the application of an improved sensor splitting strategy. The eight acquired views were successfully placed on the same horizontal plane also due to the improved strategy. A novel imaging timing design succeeded in the quasi-simultaneous acquisition of fluorescence signal from two species on the same imaging sensor.
High-speed formaldehyde planar laser-induced fluorescence measurements have shown insufficient droplet breakup and evaporation in a Triple Annular Research Swirler burner using ethanol as fuel. High amount of ethanol droplets has been observed in the LIF sequences. In addition, it has been shown that excess formaldehyde was trapped in the outer recirculation zone. The averaged flow structure in the outer recirculation zone has been demonstrated by optical flow estimation performed on the acquired formaldehyde LIF sequence.
Finally, a study on the injection nozzle surface temperature of a lab-scaled gas turbine burner has been presented. A galvo system was used for automated temperature measurement on a 2D array of points on the burner surface. It was found that the surface temperature of the injection nozzle was affected by the cooling from the supplied fresh gas and heating from the flame. Specifically, increased heating could be observed when a flame attached to the injection nozzle.
A new method of monitoring erosion of the electrodes in spark plugs made from nickel has been established, based on the emission of Ni atoms in the 339~360 nm spectral range. Spectral study revealed the spectral range in which high intensity of Ni atomic emission can be observed while low intensity of background emission is present. An excitation scan has shown that laser excitation at Ni’s 336.957 nm absorption line can induce the most optimum signal-to-noise ratio in the desired detection window. The fluorescence lifetime of the found excitation scheme has been measured, reporting an effective fluorescence lifetime of approximately 1.1 ns, which was not seen to be changing as the spark discharge plasma decays. It has been further established that the integrated fluorescence intensity of the current excitation scheme is proportional to the Ni atom number density. Such findings have created a solid foundation for further 2D studies on the generation of Ni atoms from the spark discharge and erosion of the electrodes.
The construction of an injection seeded OPO producing signal wavelength at 609 nm pumped by a high-speed burst mode laser system has been described. A routine of alignment of the OPO cavity has been established and described in detail in the thesis. Using the same laser system, quasi-simultaneous 10 kHz tomographic LIF measurement of anisole and formaldehyde has been successfully performed, where only two sets of high-speed CMOS and image intensifier were used for acquisition of 8 views from different angles thanks to the application of an improved sensor splitting strategy. The eight acquired views were successfully placed on the same horizontal plane also due to the improved strategy. A novel imaging timing design succeeded in the quasi-simultaneous acquisition of fluorescence signal from two species on the same imaging sensor.
High-speed formaldehyde planar laser-induced fluorescence measurements have shown insufficient droplet breakup and evaporation in a Triple Annular Research Swirler burner using ethanol as fuel. High amount of ethanol droplets has been observed in the LIF sequences. In addition, it has been shown that excess formaldehyde was trapped in the outer recirculation zone. The averaged flow structure in the outer recirculation zone has been demonstrated by optical flow estimation performed on the acquired formaldehyde LIF sequence.
Finally, a study on the injection nozzle surface temperature of a lab-scaled gas turbine burner has been presented. A galvo system was used for automated temperature measurement on a 2D array of points on the burner surface. It was found that the surface temperature of the injection nozzle was affected by the cooling from the supplied fresh gas and heating from the flame. Specifically, increased heating could be observed when a flame attached to the injection nozzle.
Avdelning/ar
Publiceringsår
2024-09-27
Språk
Engelska
Issue
256
Fulltext
- Available as PDF - 11 MB
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Dokumenttyp
Doktorsavhandling
Förlag
Division of Combustion Physics, Department of Physics, Lund University
Ämne
- Atom and Molecular Physics and Optics
Nyckelord
- Laser Diagnostics
- Combuston Diagnostics
- High-speed Imaging
- Laser-induced Fluoresence
- Fluorescene Lifetime
- Burst-mode Laser
Aktiv
Published
Handledare
ISBN/ISSN/Övrigt
- ISSN: 1102-8718
- ISBN: 978-91-8104-118-7
- ISBN: 978-91-8104-117-0
Försvarsdatum
27 september 2024
Försvarstid
09:15
Försvarsplats
Lecture Hall Rydbergsalen, Department of Physics, Professorsgatan 1, Faculty of Engineering LTH, Lund University, Lund.
Opponent
- Mikhail Slipchenko (Prof.)