Mechanical and Civil Engineering Seminar

Turbulent combustion processes currently account for the majority of the world's energy usage and will continue to do so for the foreseeable future. Applications, which range from power generation to transportation, will rely on advancements in combustion systems that simultaneously increase efficiency, decrease harmful emissions, and offer increased fuel flexibility through the use of alternative fuels. However, such advancements are quite challenging due to the complex nature of turbulent combustion environments found in modern energy-conversion systems. Turbulent flows are inherently time-varying, multi-dimensional phenomena, and when coupled to chemical reactions, create a highly dynamic physicochemical system occurring on multiple length and time scales. In this seminar, I will discuss the targeted development and application of advanced laser diagnostic methods for examining and understanding flow turbulence, mixing, and turbulence-chemistry interaction in turbulent and reacting flow environments. The first part of the seminar will describe the scientific challenges (and requirements) of quantitative measurements in turbulent combustion systems. A primary focus concerns acquiring and interpreting data that is useful for both understanding the governing physical and chemical processes and providing benchmark data for combustion model assessment. I will also discuss the tremendous opportunity for unprecedented insight into turbulent combustion physics through the use of high-speed laser-based imaging. I will focus on recent advances made in my research group in the application of multi-kHz-rate planar laser-induced fluorescence (PLIF), Rayleigh scattering, and Raman scattering imaging in turbulent and reacting flows. I will describe the development of our unique high-energy pulse burst laser system, which has provided new opportunities to investigate turbulence and combustion dynamics. Examples include the investigation of large-scale mixing dynamics in turbulent jets and non-premixed flames and the role of temperature, mixture fraction, and scalar dissipation rate on the auto-ignition of transient fuel injection into hot, vitiated oxidizer streams.