Developments in optical diagnostics for combustion systems have been essential to the
recent improvements in efficiency and abatement of emissions that internal combustion engines
have undergone recently. Great emphasis has been placed in the measurement of quantities with
high temporal and spatial resolution, which has enabled the understanding of key physical and
chemical processes, but there remains a need for obtaining spatially integrated measurements to
understand how local events affect the overall behavior of the gases in a turbulent combustion
chamber. Strontium offers a potential avenue to provide these measurements. When present in
combustion it produces strontium monohydroxide, which spontaneously emits radiation in
several bands of the visible spectrum, and thus enables the determination of temperature
independently of species concentration through the Boltzmann distribution. Further, chemical
equilibrium calculations can relate equivalence ratio to the relative concentration strontium and
strontium monohydroxide, which could also be measured optically.
The potential of this technique was explored in this work. An optical engine was operated
under different conditions with a strontium-containing fuel and spectral measurements of the
radiation emitted from the chamber were performed. The temperature in the cylinder was
predicted by a one-dimensional thermodynamic model that used a two-zone model for flame
propagation. The relative spectrally resolved emission intensity of atomic strontium and
strontium monohydroxide was measured using a spectrometer coupled with camera, and the
collected signals were related to the conditions in the chamber. From the results the
mathematical formulation for the relationship of spectral intensity with temperature was found to
be adequate, and important insights for the application of the diagnostic in imaging experiments
were obtained. A universally applicable calibration was not attained due to experimental
limitations, however, but the key barriers to overcome were identified.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/153368/1/ivantib_1.pd
