Abstract: This presentation will aim at highlighting and discussing the following important peculiarity of combustion of lean hydrogen-air mixtures. High molecular diffusivity of hydrogen can result in significant local variations in mixture composition, temperature, fuel consumption and heat release rates due to imbalance of molecular fluxes of chemical and thermal energies to and from stretched reaction zones. Under laminar conditions, such differential diffusion effects cause diffusional-thermal instability of premixed flames. In turbulent flows, the effects manifest themselves in a significant increase in burning rate. Classical experimental and recent Direct Numerical Simulation (DNS) data that show importance of such phenomena will be discussed, various approaches to modeling differential diffusion effects in lean hydrogen-air turbulent flames will be critically analyzed using DNS data, results of a few relevant validation studies will be presented, and remaining gaps in contemporary fundamental knowledge on such effects will be emphasized.

Bio: Professor Andrei Lipatnikov received his Ph.D. in Molecular and Chemical Physics from Moscow Institute of Physics and Technology in 1987. Subsequently, he was employed by that Institute until he was invited to join Department of Thermo- and Fluid Dynamics at Chalmers University of Technology as a guest scientist in 1996. In May 1998, he was permanently employed as a researcher at the same department. In August 2000, the School of Mechanical and Vehicular Engineering accepted Dr. Lipatnikov as a docent. In July 2017, he got appointment of a research professor. His academic activities have been concerned with modeling of burning of gaseous mixtures in turbulent and laminar flows, pollutant formation in flames, autoignition of premixed reactants, thermo-acoustic instabilities, fuel sprays, as well as numerical simulations of turbulent flames in laboratory burners and internal combustion engines. He has authored a monograph and about 325 scientific contributions, including 148 original journal papers and five invited review articles published by Progress in Energy and Combustion Science and Annual Review of Fluid Mechanics.