SUMMARY

For the past several decades, increasingly stringent pollution and emission controls have caused a rise in the use of combustors operating under lean, premixed conditions. Operating lean (excess air) lowers the level of nitrous oxides (NOx) emitted to the environment. In addition, concerns over climate change due to increased carbon dioxide (CO2) emissions and the need for energy independence in the United States have spurred interest in developing combustors capable of operating with a wide range of fuel compositions. One method to decrease the carbon footprint of modern combustors is the use of high hydrogen content (HHC) fuels. While these fuels offer the opportunity to reduce emissions, their burning characteristics are not well understood; one parameter that is important to the understanding of burning characteristics is the turbulent flame speed. For these HHC fuels, the very low molecular weight of hydrogen introduces non-unity Lewis number and differential diffusion effects. The coupling of these effects with turbulence and the overall effect on flame propagation is a complex problem that requires further research. The objective of this research is to develop tools and models that capture these physics in order to measure and predict turbulent flame speeds over conditions realistic to the environment of gas turbine combustors.

This study introduces a turbulent flame speed scaling law developed from leading point concepts for turbulent premixed flames that is used to collapse turbulent flame speed data over a wide range of conditions. I will define the turbulent flame speed and how it is measured, discuss the novel method by which turbulence is generated in our facility, and introduce the low swirl burner (LSB). Next I will present an overview of the current results obtained for my research. These results include detailed velocity characterizations of the turbulence generator in order to understand the turbulent flow field of the burner and initial particle image velocimetry (PIV) experiments on the LSB to obtain measurements of the turbulent flame speed. Finally, I present an overview of my proposed work, which includes measurements of the flame speed over a broader range of conditions and simultaneous flow and flame measurements in order to experimentally investigate the leading points model.