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Title: DIRECT NUMERICAL SIMULATION OF TURBULENT LIFTED HYDROGEN/AIR JET FLAME IN HEATED COFLOW

Abstract

No abstract prepared.

Authors:
 [1];  [2];  [2]
  1. ORNL
  2. Sandia National Laboratories (SNL)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Computational Sciences
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931857
DOE Contract Number:
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: Eccomas computational combustion, Delft, netherlands, 20070718, 20070718
Country of Publication:
United States
Language:
English

Citation Formats

Sankaran, Ramanan, Chen, Jacqueline H, and Yoo, Chun S. DIRECT NUMERICAL SIMULATION OF TURBULENT LIFTED HYDROGEN/AIR JET FLAME IN HEATED COFLOW. United States: N. p., 2007. Web.
Sankaran, Ramanan, Chen, Jacqueline H, & Yoo, Chun S. DIRECT NUMERICAL SIMULATION OF TURBULENT LIFTED HYDROGEN/AIR JET FLAME IN HEATED COFLOW. United States.
Sankaran, Ramanan, Chen, Jacqueline H, and Yoo, Chun S. Mon . "DIRECT NUMERICAL SIMULATION OF TURBULENT LIFTED HYDROGEN/AIR JET FLAME IN HEATED COFLOW". United States. doi:.
@article{osti_931857,
title = {DIRECT NUMERICAL SIMULATION OF TURBULENT LIFTED HYDROGEN/AIR JET FLAME IN HEATED COFLOW},
author = {Sankaran, Ramanan and Chen, Jacqueline H and Yoo, Chun S},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Abstract not provided.
  • Direct numerical simulation (DNS) of the near field of a three-dimensional spatially developing turbulent lifted hydrogen jet flame in heated coflow is performed with a detailed mechanism to determine the stabilization mechanism and the flame structure. The DNS was performed at a jet Reynolds number of 11,000 with over 940 million 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. A chemical flux analysis shows the occurrence of near-isothermal chemical chain branching preceding thermal runaway upstream of the stabilization point, indicative of hydrogenmore » auto-ignition in the second limit. The Damkoehler number and key intermediate-species behaviour near the leading edge of the lifted flame also verify that auto-ignition occurs at the flame base. At the lifted-flame base, it is found that heat release occurs predominantly through ignition in which the gradients of reactants are opposed. Downstream of the flame base, both rich-premixed and non-premixed flames develop and coexist with auto-ignition. 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. In particular, the relative position of the flame base and the coherent flow structure induces a cyclic motion of the flame base in the transverse and axial directions about a mean lift-off height. This is confirmed by Lagrangian tracking of key scalars, heat release rate and velocity at the stabilization point.« less
  • 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 Damkoehler 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 themore » 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.« less