| Summary: | Natural gas is the primary fuel used in industrial gas turbines for power generation. Hydrocarbon blends
of methane, ethane, and propane make up a large portion of natural gas and it has been shown that
dimethyl ether can be used as a supplement or in its pure form for gas turbine combustion. Because of
this, a fundamental understanding of the physical characteristics such as the laminar flame speed is
necessary, especially at elevated pressures to have the most relevance to the gas turbine industry. This
thesis discusses the equations governing premixed laminar flames, historical methods used to measure the
laminar flame speed, the experimental device used in this study, the procedure for converting the
measured data into the flame speed, the results of the measurements, and a discussion of the results. The
results presented in this thesis include the flame speeds for binary blends of methane, ethane, propane,
and dimethyl ether performed at elevated pressures, up to 10-atm initial pressure, using a spherically
expanding flame in a constant-volume vessel. Also included in this thesis is a comparison between the
experimental measurements and four chemical kinetic models. The C4 mechanism, developed in part
through collaboration between the National University of Ireland Galway and Texas A&M, was improved
using the data presented herein, showing good agreement for all cases. The effect of blending ethane,
propane, and dimethyl ether with methane in binary form is emphasized in this study, with the resulting
Markstein length, Lewis number (Le), and flame stability characterized and discussed. It was noticed in
this study, as well as in other studies, that the critical radius of the flame typically decreased as the Le
decreased, and that the critical radius of the flame increased as the Le increased. Also, a rigorous uncertainty analysis has been performed, showing a range of 0.3 cm/s to 3.5 cm/s depending on
equivalence ratio and initial pressure.
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