Strategies for UV Nitric Oxide LIF Imaging in High-Pressure Combustion Systems

TONGHUN LEE

Department of Mechanical Engineering, Michigan State University

The unique properties of laser light enable selective, non-intrusive and quantitative probing of physical (e.g., pressure, temperature, flow-structure, gas-velocity, etc.) and chemical (e.g., species concentration, reaction kinetics, etc.) parameters with high temporal and spatial resolution. This talk will focus on developing practical diagnostic strategies for detection of temperature and nitric oxide (NO) formation in high pressure (p<60bar) combustion systems using laser-induced-fluorescence (LIF) of nitric oxide as well as alternative laser diagnostics strategies for high-pressure combustion applications.

Laser-induced fluorescence (LIF), is a versatile and powerful tool for selective probing of chemical species and capable of providing 2D imaging. However, High-pressure combustion environments pose a unique set of challenges in the application of NO-LIF as increased collision between molecules impact the photochemistry and the overall signal. In order to develop a robust imaging strategy, the following four issues will be investigated.

• First, excitation strategies are optimized for high-pressure applications in the A−X bands of NO. This allows the user to select specific laser wavelength, power and beam quality.

• Second, carbon dioxide (CO2) LIF is discussed as it impacts all UV laser diagnostics in high-pressure combustion and is of particular importance in NO imaging.

• Third, an accurate temperature measurement technique for steady, high-pressure flames is proposed and demonstrated.

• Finally, detection strategies are optimized for high-pressure applications. This allows the user to predict signal purity and also design the detection setup.

The discussion and demonstrations reported in this study provide a practical guideline for application of instantaneous 1-D or 2-D NO-LIF imaging in high-pressure combustion systems.

Tonghun Lee joined the Department of mechanical Engineering at Michigan State University as an assistant professor in 2006. He has received his PhD ('06) and MS ('02) in mechanical engineering from Stanford University and his BS ('00) in mechanical engineering from Yonsei University in South Korea. His research interests include laser spectroscopic imaging of advanced propulsion and energy conversion systems. (webpage: http://www.egr.msu.edu/~tonghun)