Special Issue "Numerical Simulations of Turbulent Combustion"

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (15 June 2019).

Special Issue Editor

Guest Editor
Prof. Dr. Andrei Lipatnikov

Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Göteborg 412 96, Sweden
Website | E-Mail
Interests: premixed turbulent flames; laminar flames; pollutant formation; gas mixture autoignition

Special Issue Information

Dear Colleagues,

Turbulent burning of gaseous fuels is widely used for energy conversion in stationary power generation, e.g. gas turbines, land transportation, e.g. piston engines, and aviation, e.g. aero-engine afterburners. Nevertheless, fundamental understanding of turbulent combustion is still limited, because it is a highly non-linear and multiscale process that involves various local phenomena and thousands (e.g. for gasoline-air mixtures) of chemical reactions between hundreds of species, including a number of reactions that control emissions from flames. Therefore, there is a strong need for elaborating high fidelity, advanced numerical models and methods that will catch the governing physical mechanisms of flame-turbulence interaction and, consequently, will make turbulent combustion computations an efficient predictive tool for applied research and, in particular, for development of a new generation of ultra clean and highly efficient internal combustion engines that will allow the society to properly respond to current environmental and efficiency challenges. Accordingly, this Special Issue seeks papers aimed at (i) contributing to fundamental understanding of flame-turbulence interaction by analyzing results of unsteady multi-dimensional numerical simulations and (ii) developing and validating high fidelity models and efficient numerical methods for Computational Fluid Dynamics research into turbulent combustion in laboratory burners and in engines.

Prof. Andrei Lipatnikov
Guest Editor

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Keywords

  • turbulence
  • combustion
  • flame
  • reacting flow
  • numerical modeling
  • direct numerical simulation
  • large eddy simulation
  • computational fluid dynamics

Published Papers (4 papers)

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Research

Open AccessArticle
Closure Relations for Fluxes of Flame Surface Density and Scalar Dissipation Rate in Turbulent Premixed Flames
Received: 11 February 2019 / Revised: 26 February 2019 / Accepted: 4 March 2019 / Published: 7 March 2019
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Abstract
In this study, closure relations for total and turbulent convection fluxes of flame surface density and scalar dissipation rate were developed (i) by placing the focus of consideration on the flow velocity conditioned to the instantaneous flame within the mean flame brush and [...] Read more.
In this study, closure relations for total and turbulent convection fluxes of flame surface density and scalar dissipation rate were developed (i) by placing the focus of consideration on the flow velocity conditioned to the instantaneous flame within the mean flame brush and (ii) by considering the limiting behavior of this velocity at the leading and trailing edges of the flame brush. The model was tested against direct numerical simulation (DNS) data obtained from three statistically stationary, one-dimensional, planar, premixed turbulent flames associated with the flamelet regime of turbulent burning. While turbulent fluxes of flame surface density and scalar dissipation rate, obtained in the DNSs, showed the countergradient behavior, the model predicted the total fluxes reasonably well without using any tuning parameter. The model predictions were also compared with results computed using an alternative closure relation for the flame-conditioned velocity. Full article
(This article belongs to the Special Issue Numerical Simulations of Turbulent Combustion)
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Open AccessArticle
DNS Study of the Bending Effect Due to Smoothing Mechanism
Received: 28 January 2019 / Revised: 14 February 2019 / Accepted: 15 February 2019 / Published: 19 February 2019
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Abstract
Propagation of either an infinitely thin interface or a reaction wave of a nonzero thickness in forced, constant-density, statistically stationary, homogeneous, isotropic turbulence is simulated by solving unsteady 3D Navier–Stokes equations and either a level set (G) or a reaction-diffusion equation, respectively, with [...] Read more.
Propagation of either an infinitely thin interface or a reaction wave of a nonzero thickness in forced, constant-density, statistically stationary, homogeneous, isotropic turbulence is simulated by solving unsteady 3D Navier–Stokes equations and either a level set (G) or a reaction-diffusion equation, respectively, with all other things being equal. In the case of the interface, the fully developed bulk consumption velocity normalized using the laminar-wave speed SL depends linearly on the normalized rms velocity u′/SL. In the case of the reaction wave of a nonzero thickness, dependencies of the normalized bulk consumption velocity on u′/SL show bending, with the effect being increased by a ratio of the laminar-wave thickness to the turbulence length scale. The obtained bending effect is controlled by a decrease in the rate of an increase δAF in the reaction-zone-surface area with increasing u′/SL. In its turn, the bending of the δAF(u′/SL)-curves stems from inefficiency of small-scale turbulent eddies in wrinkling the reaction-zone surface, because such small-scale wrinkles characterized by a high local curvature are smoothed out by molecular transport within the reaction wave. Full article
(This article belongs to the Special Issue Numerical Simulations of Turbulent Combustion)
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Open AccessArticle
Effects of Lewis Number on the Evolution of Curvature in Spherically Expanding Turbulent Premixed Flames
Received: 30 November 2018 / Revised: 7 January 2019 / Accepted: 11 January 2019 / Published: 16 January 2019
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Abstract
The effects of Lewis number on the physical mechanisms pertinent to the curvature evolution have been investigated using three-dimensional Direct Numerical Simulation (DNS) of spherically expanding turbulent premixed flames with characteristic Lewis number of Le=0.8, 1.0 and 1.2. It [...] Read more.
The effects of Lewis number on the physical mechanisms pertinent to the curvature evolution have been investigated using three-dimensional Direct Numerical Simulation (DNS) of spherically expanding turbulent premixed flames with characteristic Lewis number of L e = 0.8 , 1.0 and 1.2. It has been found that the overall burning rate and the extent of flame wrinkling increase with decreasing Lewis number L e , and this tendency is particularly prevalent for the sub-unity Lewis number (e.g., L e = 0.8 ) case due to the occurrence of the thermo-diffusive instability. Accordingly, the L e = 0.8 case has been found to exhibit higher probability of finding saddle topologies with large magnitude negative curvatures in comparison to the corresponding L e = 1.0 and 1.2 cases. It has been found that the terms in the curvature transport equation due to normal strain rate gradients and curl of vorticity arising from both fluid flow and flame normal propagation play pivotal roles in the curvature evolution in all cases considered here. The net contribution of the source/sink terms of the curvature transport equation tends to increase the concavity and convexity of the flame surface in the negatively and positively curved locations, respectively for the L e = 0.8 case. This along with the occurrence of high and low temperature (and burning rate) values at the positively and negatively curved zones, respectively acts to augment positive and negative curved wrinkles induced by turbulence in the L e = 0.8 case, which is indicative of thermo-diffusive instability. By contrast, flame propagation effects tend to weakly promote the concavity of the negatively curved cusps, and act to decrease the convexity of the highly positively curved bulges in the L e = 1.0 and 1.2 cases, which are eventually smoothed out due to high and low values of displacement speed S d at negatively and positively curved locations, respectively. Thus, flame propagation tends to smoothen the flame surface in the L e = 1.0 and 1.2 cases. Full article
(This article belongs to the Special Issue Numerical Simulations of Turbulent Combustion)
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Open AccessArticle
Investigation of the Turbulent Near Wall Flame Behavior for a Sidewall Quenching Burner by Means of a Large Eddy Simulation and Tabulated Chemistry
Received: 25 July 2018 / Revised: 22 August 2018 / Accepted: 3 September 2018 / Published: 6 September 2018
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Abstract
Combustion will play a major part in fulfilling the world’s energy demand in the next 20 years. Therefore, it is necessary to understand the fundamentals of the flame–wall interaction (FWI), which takes place in internal combustion engines or gas turbines. The FWI can [...] Read more.
Combustion will play a major part in fulfilling the world’s energy demand in the next 20 years. Therefore, it is necessary to understand the fundamentals of the flame–wall interaction (FWI), which takes place in internal combustion engines or gas turbines. The FWI can increase heat losses, increase pollutant formations and lowers efficiencies. In this work, a Large Eddy Simulation combined with a tabulated chemistry approach is used to investigate the transient near wall behavior of a turbulent premixed stoichiometric methane flame. This sidewall quenching configuration is based on an experimental burner with non-homogeneous turbulence and an actively cooled wall. The burner was used in a previous study for validation purposes. The transient behavior of the movement of the flame tip is analyzed by categorizing it into three different scenarios: an upstream, a downstream and a jump-like upstream movement. The distributions of the wall heat flux, the quenching distance or the detachment of the maximum heat flux and the quenching point are strongly dependent on this movement. The highest heat fluxes appear mostly at the jump-like movement because the flame behaves locally like a head-on quenching flame. Full article
(This article belongs to the Special Issue Numerical Simulations of Turbulent Combustion)
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