A DNS study on the stabilization mechanism of a turbulent lifted ethylene jet flame in highly-heated coflow


Yoo, Chun Sang, Richardson, Edward S., Sankaran , Ramanan and Chen, Jacqueline H. (2011) A DNS study on the stabilization mechanism of a turbulent lifted ethylene jet flame in highly-heated coflow. Proceedings of the Combustion Institute, 33, (1), 1619-1627. (doi:10.1016/j.proci.2010.06.147).

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Description/Abstract

Direct numerical simulation (DNS) of the near-field of a three-dimensional spatially-developing turbulent ethylene jet flame in highly-heated coflow is performed with a reduced mechanism to determine the stabilization mechanism. The DNS was performed at a jet Reynolds number of 10,000 with over 1.29 billion grid points. The results show that auto-ignition in a fuel-lean mixture at the flame base is the main source of stabilization of the lifted jet flame. The Damko¨ hler number and chemical explosive mode (CEM) analysis also verify that auto-ignition occurs at the flame base. In addition to auto-ignition, Lagrangian tracking of the flame base reveals the passage of large-scale flow structures and their correlation with the fluctuations of the flame base similar to a previous study (Yoo et al., J. Fluid Mech. 640 (2009) 53–481) with hydrogen/air jet flames. It is also observed that the present lifted flame base exhibits a cyclic ‘saw-tooth’ shaped movement marked by rapid movement upstream and slower movement downstream.
This is a consequence of the lifted flame being stabilized by a balance between consecutive auto-ignition events in hot fuel-lean mixtures and convection induced by the high-speed jet and coflow velocities. This is confirmed by Lagrangian tracking of key variables including the flame-normal velocity, displacement speed, scalar dissipation rate, and mixture fraction at the stabilization point.

Item Type: Article
ISSNs: 1540-7489 (print)
Keywords: direct numerical simulation (dns), auto-ignition, turbulent lifted flame, ethylene, reduced mechanism
Subjects: Q Science > QA Mathematics
T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TL Motor vehicles. Aeronautics. Astronautics
Divisions: Faculty of Engineering and the Environment > Engineering Sciences
ePrint ID: 203171
Date Deposited: 14 Nov 2011 11:57
Last Modified: 27 Mar 2014 19:47
URI: http://eprints.soton.ac.uk/id/eprint/203171

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