Dr. Shengkai WangStanford University
Development of modern internal combustion and propulsion engines of better performance, efficiency and reliability requires accurate knowledge of key properties (e.g. temperature, pressure, velocity and composition) of the high-temperature combustion gas. Laser absorption sensors have great potential for such applications because they can provide real-time quantitative measurements of these properties without intruding the combustion processes. However, the need to resolve trace amount of critical species, the demand for high measurement speed, and the presence of non-absorption losses such as particular scattering and beam steering, have posed certain challenges to conventional laser absorption sensors.
This talk will present two strategies that have overcome these challenges and allowed for accurate measurements of small absorption signals in transient and noisy environments: (1) use of cavity-enhanced absorption spectroscopy (CEAS) to improve detection sensitivity; (2) use of wavelength/frequency modulation spectroscopy (WMS/FMS) to minimize noise. Example applications of these strategies for detecting various gas species in the UV, visible and IR spectral regions, which significantly improved their detection limits by a few orders of magnitude, will also be demonstrated. The talk will be concluded with an outlook of future research plans exploring the broad applicability of these precision sensing methodologies.
Dr. Shengkai Wang works on thermal fluids and optical diagnostics research at Stanford University’s High Temperature Gasdynamics Laboratory (HTGL), where his research entails development and application of ultra-sensitive laser absorption diagnostic methods for studying high-temperature chemical kinetics and gasdynamics. He received his Ph.D. in Mechanical Engineering and Ph.D. Minor in Electrical Engineering from Stanford University in 2017, M.S. in Mechanical Engineering from Stanford University in 2012, and B.S. in Mechanical Engineering from Peking University in 2010. He was awarded the Bernard Lewis Fellowship in 2016 for advancing measurement of cavity-enhanced absorption to shock tubes kinetics and leading shock tube studies of important elementary combustion reactions.
Host: Dr. Kenneth Brezinsky
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