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THREE-DIMENSIONAL DNS OF METHANE-AIR TURBULENT PREMIXED FLAMES WITH REALISTIC REDUCED KINETIC MECHANISM

Mamoru Tanahashi
Department of Mechanical and Aerospace Engineering Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan

Satoshi Kikuta
Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8850, Japan

Nobuhiro Shiwaku
Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8850, Japan

Toshio Miyauchi
Dept. Mechanical and Aerospace Eng., Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan; Organization for the Strategic Coordination of Research and Intellectual Properties Meiji University 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa, Japan

Yuzuru Nada
Department of Mechano-Aerospace Engineering, Tokyo Institute of Technology Ookayama, Meguro-ku, Tokyo 152-8552; Faculty of Risk and Crisis Management, Chiba Institute of Science 3 Shiomi-cho, Choshi-city, Chiba 288-0025, Japan

Abstract

Three-dimensional direct numerical simulations (DNS) of methane-air turbulent premixed flames with a realistic reduced kinetic mechanism have been conducted to investigate effects of turbulence characteristics on the local flame structure. The reduced kinetic mechanism (MeCH-19), which is constructed based on GRI Mech. 2.11, is verified by comparing with two detailed kinetic mechanisms; GRI Mech. 2.11 and Miller & Bowman through the two-dimensional DNS. Important properties such as temperature, heat release rate and turbulent burning velocity obtained from detailed and reduced kinetic mechanisms are compared and they show good agreements with each other. Since the availability of MeCH-19 is verified by two-dimensional DNS, three-dimensional DNS is conducted using MeCH-19. Numerical conditions of the DNS can be classified into thin reaction zones. Different from our previous DNSs of hydrogen-air turbulent premixed flames, the distributions of temperature and heat release rate do not coincide and quite low heat release rate regions corresponding to the local extinction are observed. In the vicinities of these regions, flame elements are strongly stretching into two tangential directions. The local extinction mechanism was clarified by introducing lifetime of reactive species relative to eddy turnover time of strong coherent fine scale eddies in turbulence.