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 Damköhler 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) 453-481) 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.
| Original language | English |
|---|---|
| Pages (from-to) | 1619-1627 |
| Number of pages | 9 |
| Journal | Proceedings of the Combustion Institute |
| Volume | 33 |
| Issue number | 1 |
| DOIs | |
| State | Published - 2011 |
Funding
The work at Ulsan National Institute of Science and Technology (UNIST) was supported by the 2009 Research Fund of UNIST . The work at Sandia National Laboratories (SNL) was supported by the US Department of Energy, the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, and Office of Advanced Scientific Computing Research. JHC was supported as part of the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001198. Figures 1, 3 and 4 were provided by Dr. L. Pickett, Dr. H. Yu at SNL, and Prof. T. Lu at the University of Connecticut, respectively.
Keywords
- Auto-ignition
- Direct numerical simulation (DNS)
- Ethylene
- Reduced mechanism
- Turbulent lifted flame