This thesis explores the effects of operating parameters on the location and shape of lifted
flames in a Low Swirl Burner (LSB). In addition, it details the development and analysis of
a CH PLIF imaging system for visualizing flames in lean combustion systems. The LSB is
studied at atmospheric pressure using LDV and CH PLIF. CH* chemiluminescence is used
for high pressure flame imaging.
A four-level model of the fluorescing CH system is developed to predict the signal intensity
in hydrocarbon flames. Results from imaging an atmospheric pressure laminar flame are used
to validate the behavior of the signal intensity as predicted by the model. The results show
that the fluorescence signal is greatly reduced at high pressure due to the decreased number
of CH molecules and the increased collisional quenching rate. This restricts the use of this
technique to increasingly narrow equivalence ratio ranges at high pressures. The limitation
is somewhat alleviated by increasing the preheat temperature of the reactant mixture. The
signal levels from high hydrogen-content syngas mixtures doped with methane are found to
be high enough to make CH PLIF a feasible diagnostic to study such flames. Finally, the
model predicts that signal levels are unlikely to be significantly affected by the presence of
strain in the flow field, as long as the flames are not close to extinction.
The results from the LSB flame investigation reveal that combustor provides reasonably
robust flame stabilization at low and moderate values of combustor pressure and reference
velocities. However, at very high velocities and pressures, the balance between the reactant
velocity and the turbulent flame speed shifts in favor of the former resulting in the flame
moving downstream. The extent of this movement is small, but indicates a tendency towards
blow off at higher pressures and velocities that may be encountered in real world gas turbine
applications. There is an increased tendency of relatively fuel-rich flames to behave like
attached flames at high pressure. These results raise interesting questions about turbulent
combustion at high pressure as well as provide usable data to gas turbine combustor designers
by highlighting potential problems.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/45828 |
| Date | 27 August 2012 |
| Creators | Periagaram, Karthik Balasubramanian |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Detected Language | English |
| Type | Dissertation |
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