Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

A direct numerical simulation study of flame structure and stabilization of an experimental high Ka CH4/air premixed jet flame

Journal Article · · Combustion and Flame
 [1];  [1];  [2]
  1. The Univ. of New South Wales, NSW (Australia)
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
In the present work, a direct numerical simulation (DNS) of an experimental high Karlovitz number (Ka) CH4/air piloted premixed flame was analyzed to study the inner structure and the stabilization mechanism of the turbulent flame. A reduced chemical mechanism for premixed CH4/air combustion with NOx based on GRI-Mech3.0 was used, including 268 elementary reactions and 28 transported species. The evolution of the stretch factor, I0, indicates that the burning rate per unit flame surface area is considerably reduced in the near field and exhibits a minimum at x/D = 8. Downstream, the burning rate gradually increases. The stretch factor is different between different species, suggesting the quenching of some reactions but not others. Comparison between the turbulent flame and strained laminar flames indicates that certain aspects of the mean flame structure can be represented surprisingly well by flamelets if changes in boundary conditions are accounted for and the strain rate of the mean flow is employed; however, the thickening of the flame due to turbulence is not captured. The spatial development of displacement speeds is studied at higher Ka than previous DNS. In contrast to almost all previous studies, the mean displacement speed conditioned on the flame front is negative in the near field, and the dominant contribution to the displacement speed is normal diffusion with the reaction contribution being secondary. Further downstream, reaction overtakes normal diffusion, contributing to a positive displacement speed. The negative displacement speed in the near field implies that the flame front situates itself in the pilot region where the inner structure of the turbulent flame is affected significantly, and the flame stabilizes in balance with the inward flow. Notably, in the upstream region of the turbulent flame, the main reaction contributing to the production of OH, H+O2⇌O+OH (R35), is weak. Moreover, oxidation reactions, H2+OH⇌H+H2O (R79) and CO+OH⇌CO2+H (R94), are influenced by H2O and CO2 from the pilot and are completely quenched. Hence, the entire radical pool of OH, H and O is affected. Furthermore, the fuel consumption layer remains comparably active and generates heat, mainly via the reaction CH4+OH⇌CH3+H2O (R93).
Research Organization:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Organization:
USDOE; USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
AC04-94AL85000
OSTI ID:
1361216
Alternate ID(s):
OSTI ID: 1419138
Report Number(s):
SAND--2017-2196J; PII: S001021801730069X
Journal Information:
Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: C Vol. 180; ISSN 0010-2180
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (57)

The asymptotic structure of stoichiometric methaneair flames journal May 1987
Response and flamelet structure of stretched premixed methaneair flames journal July 1988
The inner structure of methaneair flames journal August 1990
Unsteady strain rate and curvature effects in turbulent premixed methane-air flames journal July 1996
Several new numerical methods for compressible shear-layer simulations journal June 1994
Dynamic behavior of premixed flame fronts in laminar and turbulent flows journal January 1985
Preferential diffusion effects on the burning rate of interacting turbulent premixed hydrogen-air flames journal November 2002
Premixed flame response to unsteady strain rate and curvature journal July 1997
Analysis of the contribution of curvature to premixed flame propagation journal July 1999
Stretch effects on the burning velocity of turbulent premixed hydrogen/air flames journal January 2000
Effects of flow transients on the burning velocity of laminar hydrogen/air premixed flames journal January 2000
Dynamics and structure of unsteady, strained, laminar premixed flames journal January 1994
Negative flame speed in an unsteady 2-D premixed flame: A computational study journal January 1996
Investigation of scalar mixing in the thin reaction zones regime using a simultaneous CH-LIF/Rayleigh laser technique journal January 1998
Correlation of flame speed with stretch in turbulent premixed methane/air flames journal January 1998
Low-storage, explicit Runge–Kutta schemes for the compressible Navier–Stokes equations journal November 2000
Progress in knowledge of flamelet structure and extinction journal August 2000
Unsteady effects of strain rate and curvature on turbulent premixed flames in an inflow–outflow configuration journal April 2004
Direct numerical simulation of hydrogen-enriched lean premixed methane–air flames journal August 2004
Comparison of direct numerical simulation of lean premixed methane–air flames with strained laminar flame calculations journal January 2006
A new piloted premixed jet burner to study strong finite-rate chemistry effects journal October 2007
A criterion based on computational singular perturbation for the identification of quasi steady state species: A reduced mechanism for methane oxidation with NO chemistry journal September 2008
Strained flamelets for turbulent premixed flames, I: Formulation and planar flame results journal May 2010
Turbulence and combustion interaction: High resolution local flame front structure visualization using simultaneous single-shot PLIF imaging of CH, OH, and CH2O in a piloted premixed jet flame journal June 2010
Effect of the composition of the hot product stream in the quasi-steady extinction of strained premixed flames journal November 2010
From Large-Eddy Simulation to Direct Numerical Simulation of a lean premixed swirl flame: Filtered laminar flame-PDF modeling journal July 2011
Effects of preferential transport in turbulent bluff-body-stabilized lean premixed CH4/air flames journal August 2012
A petascale direct numerical simulation study of the modelling of flame wrinkling for large-eddy simulations in intense turbulence journal August 2012
On the fractal characteristics of low Damköhler number flames journal November 2013
Effects of strain rate, turbulence, reactant stoichiometry and heat losses on the interaction of turbulent premixed flames with stoichiometric counterflowing combustion products journal November 2013
LES of a premixed jet flame DNS using a strained flamelet model journal December 2013
Distributed reactions in highly turbulent premixed methane/air flames journal July 2015
Response of flame thickness and propagation speed under intense turbulence in spatially developing lean premixed methane–air jet flames journal September 2015
Differential diffusion effects, distributed burning, and local extinctions in high Karlovitz premixed flames journal September 2015
Impact of multi-component diffusion in turbulent combustion using direct numerical simulations journal November 2015
Turbulent premixed combustion: Flamelet structure and its effect on turbulent burning velocities journal February 2008
Structure of a spatially developing turbulent lean methane–air Bunsen flame journal January 2007
Experimental measurements of geometric properties of turbulent stratified flames journal January 2009
Effect of quenching of the oxidation layer in highly turbulent counterflow premixed flames journal January 2011
Petascale direct numerical simulation of turbulent combustion—fundamental insights towards predictive models journal January 2011
Premixed flame propagation in turbulent flow by means of stereoscopic PIV and dual-plane OH-PLIF at sustained kHz repetition rates journal January 2013
Flame structure analysis for categorization of lean premixed CH4/air and H2/air flames at high Karlovitz numbers: Direct numerical simulation studies journal January 2015
A comparison between direct numerical simulation and experiment of the turbulent burning velocity-related statistics in a turbulent methane-air premixed jet flame at high Karlovitz number journal January 2017
Turbulent burning velocity measurements: Extended to extreme levels of turbulence journal January 2017
Direct numerical simulation of H 2 /O 2 /N 2 flames with complex chemistry in two-dimensional turbulent flows journal December 1994
The evolution equation for the flame surface density in turbulent premixed combustion journal November 1994
The turbulent burning velocity for large-scale and small-scale turbulence journal April 1999
Turbulence–flame interactions in lean premixed hydrogen: transition to the distributed burning regime journal May 2011
Direct numerical simulations of a high Karlovitz number laboratory premixed jet flame – an analysis of flame stretch and flame thickening journal February 2017
Interactions between turbulence and flames in premixed reacting flows journal December 2011
Turbulence-flame interactions in DNS of a laboratory high Karlovitz premixed turbulent jet flame journal September 2016
Strain Characteristics Near the Flame Attachment Point in a Swirling Flow journal April 2011
Strained Premixed Laminar Flames Under Nonadiabatic Conditions journal March 1983
Extinction of Strained Premixed Propane-air Flames with Complex Chemistry journal August 1988
Terascale direct numerical simulations of turbulent combustion using S3D journal January 2009
Fuel Flexibility Influences on Premixed Combustor Blowout, Flashback, Autoignition, and Stability journal January 2008
High Resolution PIV and CH-PLIF Measurements and Analysis of a Shear Layer Stabilized Flame conference June 2015

Cited By (1)

Vitiated High Karlovitz n-decane/air Turbulent Flames: Scaling Laws and Micro-mixing Modeling Analysis journal July 2018