• Invited

Direct numerical simulations of premixed and stratified flame propagation in turbulent channel flow

Andrea Gruber, Edward S. Richardson, Konduri Aditya, and Jacqueline H. Chen
Phys. Rev. Fluids 3, 110507 – Published 21 November 2018
An article within the collection: 2018 Invited Papers

Abstract

Direct numerical simulations are performed to investigate the transient upstream flame propagation (flashback) through homogeneous and fuel-stratified hydrogen-air mixtures transported in fully developed turbulent channel flows. Results indicate that, for both cases, the flame maintains steady propagation against the bulk flow direction, and the global flame shape and the local flame characteristics are both affected by the occurrence of fuel stratification. Globally, the mean flame shape undergoes an abrupt change when the approaching reactants transition from an homogeneous to a stratified mixing configuration. A V-shaped flame surface, whose leading-edge is located in the near-wall region, characterizes the nonstratified, homogeneous mixture case, while a U-shaped flame surface, whose leading edge propagates upstream at the channel centerline, distinguishes the case with fuel stratification (fuel-lean in the near-wall region and fuel-rich away from the wall). The characteristic thickness, wrinkling, and displacement speed of the turbulent flame brush are subject to considerable changes across the channel due to the dependence of the turbulence and mixture properties on the distance from the channel walls. More specifically, the flame transitions from a moderately wrinkled, thin-flamelet combustion regime in the homogeneous mixture case to a strongly wrinkled flame brush more representative of a thickened-flame combustion regime in the near-wall region of the fuel-stratified case. The combustion regime may be related to the Karlovitz number, and it is shown that a nominal channel-flow Karlovitz number, Kainch, based on the wall-normal variation of canonical turbulence (tη=(ν/ε)1/2) and chemistry (tl=δl/Sl) timescales in fully developed channel flow, compares well with an effective Karlovitz number, Kaflch, extracted from the present DNS datasets using conditionally sampled values of tη and tl in the immediate vicinity of the flame (0.1<C<0.3).

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  • Received 16 August 2018

DOI:https://doi.org/10.1103/PhysRevFluids.3.110507

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Collections

This article appears in the following collection:

2018 Invited Papers

Physical Review Fluids publishes a collection of papers associated with the invited talks presented at the 70th Annual Meeting of the APS Division of Fluid Dynamics.

Authors & Affiliations

Andrea Gruber*

  • SINTEF Energy Research, Thermal Energy Department, 7465 Trondheim, Norway and Norwegian University of Science and Technology, Department of Energy and Process Engineering, 7491 Trondheim, Norway

Edward S. Richardson

  • University of Southampton, SO17 1BJ Southampton, United Kingdom

Konduri Aditya and Jacqueline H. Chen

  • Sandia National Laboratories, Livermore, California 94550, USA

  • *andrea.gruber@sintef.no

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Issue

Vol. 3, Iss. 11 — November 2018

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