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Toward Accurate Combustion Simulations with Stiff Chemistry

Title: Toward Accurate Combustion Simulations with Stiff Chemistry

Lecturer: Tianfeng Lu, Associate Professor, Department of Mechanical Engineering, University of Connecticut

Time: June 24, from 10:00 am

Place: Lectuer Hall, Department of Thermal Engineering

Abstract:
Practical combustion systems involve complex and stiff chemistry that is difficult to simulate, particularly when strong chemistry-turbulence interactions are present. Accurate resolution of chemistry and its response to flow variation is key to create a predicting power for chemically reacting flows, and it requires efficient and accurate methods for mechanism reduction, stiff chemistry solver, direct flame simulations, computational diagnostics, and combustion modeling, etc. This presentation will show our effort on theoretical and numerical development in response to these challenges. Specifically, reduced mechanisms were obtained for gasoline, diesel, kerosene, and renewable fuels, such as ethanol and biodiesel, using systematic approaches of directed relation graph (DRG), analytically solved linearized quasi steady state approximations, and dynamic chemical stiffness removal. New integration schemes will be introduced for efficiently solving stiff chemistry coupled with transport when conventional solvers are not applicable. For computational diagnostics, a chemical explosive mode analysis (CEMA) will be presented for systematic identification of critical flame features in complex flow fields, such as local ignition/extinction, flame instabilities, and flame fronts. Results from collaborative efforts on direct numerical simulation (DNS) with the nonstiff reduced mechanisms and CEMA will be shown for turbulent jet flames and homogeneous charge compression ignition combustion.

Biographical Sketch:
Dr. Lu received his B.S. and M.S. in Engineering Mechanics from Tsinghua University in 1994 and 1997, respectively, and Ph.D in Mechanical and Aerospace Engineering from Princeton University in 2004. Since then he has been a postdoctoral fellow and a research staff at Princeton. He joined the Department of Mechanical Engineering in the University of Connecticut as faculty member in 2008. Lu’s primary research interest is in combustion and computational fluid dynamics with special interests in mechanism reduction, stiff chemistry solver, and computational flame diagnostics. He is a member of the Combustion Institute, Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA), and the recipient of the inaugural Irvin Glassman young investigator award from the Eastern States Section of the Combustion Institute.

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