JOINT MAE-CER SEMINAR

Direct Numerical Simulations of Turbulent Premixed Flames in Lean Methane/Air Mixtures

John Abraham, San Diego State University
November 2, 2016, 11:00am - 12:00pm, EBU-II 479

ABSTRACT:

Lean-burn natural gas engines are attractive because they generate lower carbon and nitric oxide emissions relative to more conventional engines. Cycle to cycle variability and the potential for engine misfire determine the lean limit of operation. CFD Models can assist in optimizing the engines, but the lack of robust turbulent combustion sub-models limits the fidelity of available CFD models. One input to some of the sub-models employed is the turbulent flame speed. But, the determination of the dependence of the premixed turbulent flame speed on the turbulent field and mixture properties remains a challenging problem. A computational approach to simulate turbulent premixed flame propagation in the frame of reference of the flame front itself, relying on an inflow/outflow configuration, is employed to carry out direct numerical simulations of turbulent premixed flames in lean methane/air mixtures under conditions of relevance to lean-burn natural gas engines. These conditions lie in the Thin Reaction Zone (TRZ) regime of turbulent premixed combustion. From the simulations, an expression for the normalized turbulent flame speed that is a function of the turbulent Reynolds number and the Karlovitz number is derived. Insights gained from the simulations are applied to propose improvements to the modeling of flame surface density evolution.

BIO:

Professor Abraham received his Ph.D. from the Department of Mechanical and Aerospace Engineering at Princeton University in 1986, held positions as a Research Staff Member at Princeton University, Senior Engineer at John Deere, the Richard and Barbara Nelson Assistant Professor in the Department of Mechanical Engineering at the University of Minnesota, and Associate Professor and Professor in the School of Mechanical Engineering at Purdue University. He joined the Department of Mechanical Engineering at San Diego State University as Professor and Chair in July 2015. His research interests include combustion, multiphase flows, sprays, fuel chemistry, computational fluid dynamics, and high-performance computing. His work has led to 3 patents, over 120 archival journal publications, over 160 additional publications in conference proceedings, and 3 invited book chapter contributions. Professor Abraham is a Fellow of the American Society of Mechanical Engineers and the Society of Automotive Engineers (SAE). He has won the Lloyd L. Withrow Distinguished Speaker award from the SAE, and the Harry Solberg Best Teacher award from the School of Mechanical Engineering at Purdue University. He is Associate Editor of Combustion Science and Technology and the ASME Journal of Fluids Engineering.