Quenching of Premixed Flames at Cold Walls: Effects on the Local Flow Field

Jainski, Christopher; Rißmann, Martin; Jakirlić, Suad; Böhm, Benjamin; Dreizler, Andreas

doi:10.1007/s10494-017-9836-8

Cited by 26 publications

(15 citation statements)

References 30 publications

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“…12, where the velocity component parallel to the cold wall is plotted along horizontal lines at specific and constant values of z − z 0 . While the 2D simulations overestimate the velocity locally, the results from the 3D simulation are closer to the PIV measurements, confirming previous studies (Jainski et al 2018).…”

Section: Flow Velocity and 2d Vs 3d Effectssupporting

confidence: 88%

“…However, regardless of the agreement between experimental and numerical flow fields, the flow field is fundamentally different in the 3D case compared Fig. 11 Field of the magnitude of the fluid velocity from PIV measurements (Jainski et al 2018) and the 2D and 3D simulations to the 2D case. Nonetheless, quenching distances are nearly unaffected so that the details of the flow field are an unlikely cause for the observed differences of the quenching distances.…”

Section: Flow Velocity and 2d Vs 3d Effectsmentioning

confidence: 97%

“…The main difference between the 2D and 3D setup is, that the bulk flow velocity at the inlet is reduced from 1.9 m/s for the 3D case to 1.52 m/s for the 2D case or 80% of the experimental setup, in order to achieve the same flame height between 2D simulation, 3D simulation and experiment. Figure 11 shows the velocity magnitude field from PIV measurements (Jainski et al 2018) as well as 2D and 3D simulations. It can be seen that the velocities in the 2D case are much higher due to the missing flow divergence in 2D.…”

Section: Flow Velocity and 2d Vs 3d Effectsmentioning

confidence: 99%

“…The authors determined quenching distances under various flame and wall conditions. Since then, extensive experimental (Lu et al 1991;Ezekoye et al 1992;Bellenoue et al 2003;Sotton et al 2005;Kim et al 2006;Boust et al 2007;Labuda et al 2011;Mann et al 2014;Dreizler and Böhm 2015;Suckart et al 2016;Rißmann et al 2017;Jainski et al 2017aJainski et al , b, 2018Kosaka et al 2018;Häber and Suntz 2018;Kosaka et al 2019) and numerical (Poinsot et al 1993;Bruneaux et al 1996;Popp and Baum 1997;Hasse et al 2000;Andrae et al 2002;Singh 2004;Chauvy et al 2010;Proch and Kempf 2015;Ganter et al 2017;Heinrich et al 2018a, b;Strassacker et al , 2019) studies on flame-wall interactions (FWI) have been carried out in recent years. Even though almost seven decades have been spent on the investigation of flame quenching near (cold) walls, which has improved the understanding of the flame-wall interaction substantially, one is far from having a quantitative understanding of the phenomena.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of Quenching Distances for Side-Wall Quenching Using Detailed Diffusion and Chemistry

Zirwes

Häber

Zhang

et al. 2020

Flow Turbulence Combust

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The numerical investigation of quenching distances in laminar flows is mainly concerned with two setups: head-on quenching (HOQ) and side-wall quenching (SWQ). While most of the numerical work has been conducted for HOQ with good agreement between simulation and experiment, far less analysis has been done for SWQ. Most of the SWQ simulations used simplified diffusion models or reduced chemistry and achieved reasonable agreement with experiments. However, it has been found that quenching distances for the SWQ setup differ from experimental results if detailed diffusion models and chemical reaction mechanisms are employed. Side-wall quenching is investigated numerically in this work with steady-state 2D and 3D simulations of an experimental flame setup. The simulations fully resolve the flame and employ detailed reaction mechanisms as well as molecular diffusion models. The goal is to provide data for the sensitivity of numerical quenching distances to different parameters. Quenching distances are determined based on different markers: chemiluminescent species, temperature and OH iso-surface. The quenching distances and heat fluxes at the cold wall from simulations and measurements agree well qualitatively. However, quenching distances from the simulations are lower than those from the experiments by a constant factor, which is the same for both methane and propane flames and also for a wide range of equivalence ratios and different markers. A systematic study of different influencing factors is performed: Changing the reaction mechanism in the simulation has little impact on the quenching distance, which has been tested with over 20 different reaction mechanisms. Detailed diffusion models like the mixture-averaged diffusion model and multi-component diffusion model with and without Soret effect yield the same quenching distances. By assuming a unity Lewis number, however, quenching distances increase significantly and have better agreement with measurements. This was validated by two different numerical codes (OpenFOAM and FASTEST) and also by 1D head-on quenching simulations (HOQ). Superimposing a fluctuation on the inlet velocity in the simulation also increases the quenching distance on average compared to the reference steady-state case. The inlet velocity profile, temperature boundary condition of the rod and radiation have a negligible effect. Finally, three dimensional simulations are necessary in order to obtain the correct velocity field in the SWQ computations. This however has only a negligible effect on quenching distances.

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Section: Flow Velocity and 2d Vs 3d Effectssupporting

confidence: 88%

Section: Flow Velocity and 2d Vs 3d Effectsmentioning

confidence: 97%

Section: Flow Velocity and 2d Vs 3d Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Numerical Study of Quenching Distances for Side-Wall Quenching Using Detailed Diffusion and Chemistry

Zirwes

Häber

Zhang

et al. 2020

Flow Turbulence Combust

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“…Recent analyses on turbulent premixed flame-wall interaction suggest that the decrease in dilatation rate either due to flame quenching as a result of wall heat loss or due to wall-induced confinement can have a significant influence on enstrophy (Lai et al 2017a), turbulent kinetic energy (Lai et al 2017b;Ahmed et al 2019c), turbulent scalar flux (Lai et al 2017c), scalar variance (Lai and Chakraborty 2016a) and reactive scalar gradient statistics (Sellmann et al 2017;Lai and Chakraborty 2016b, c, d;Ahmed et al 2020;Bruneaux et al 1997) in the near-wall region. Moreover, the usual log-law for mean velocity and temperature variations is often rendered invalid during turbulent premixed flame-wall interactions (Bruneaux et al 1997(Bruneaux et al , 1996Jainski et al 2018). The modelling of wall-bounded turbulent reacting flows is currently in a rudimentary state, and there is an urgent need to obtain fundamental physical information and develop high-fidelity closures for turbulent premixed flame-wall interactions.…”

Section: Final Remarks and Outlookmentioning

confidence: 99%

Influence of Thermal Expansion on Fluid Dynamics of Turbulent Premixed Combustion and Its Modelling Implications

Chakraborty

2021

Flow Turbulence Combust

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The purpose of this paper is to demonstrate the effects of thermal expansion, as a result of heat release arising from exothermic chemical reactions, on the underlying turbulent fluid dynamics and its modelling in the case of turbulent premixed combustion. The thermal expansion due to heat release gives rise to predominantly positive values of dilatation rate within turbulent premixed flames, which has been shown to have significant implications on the flow topology distributions, and turbulent kinetic energy and enstrophy evolutions. It has been demonstrated that the magnitude of predominantly positive dilatation rate provides the measure of the strength of thermal expansion. The influence of thermal expansion on fluid turbulence has been shown to strengthen with decreasing values of Karlovitz number and characteristic Lewis number, and with increasing density ratio between unburned and burned gases. This is reflected in the weakening of the contributions of flow topologies, which are obtained only for positive values of dilatation rate, with increasing Karlovitz number. The thermal expansion within premixed turbulent flames not only induces mostly positive dilatation rate but also induces a flame-induced pressure gradient due to flame normal acceleration. The correlation between the pressure and dilatation fluctuations, and the vector product between density and pressure gradients significantly affect the evolutions of turbulent kinetic energy and enstrophy within turbulent premixed flames through pressure-dilatation and baroclinic torque terms, respectively. The relative contributions of pressure-dilatation and baroclinic torque in comparison to the magnitudes of the other terms in the turbulent kinetic energy and enstrophy transport equations, respectively strengthen with decreasing values of Karlovitz and characteristic Lewis numbers. This leads to significant augmentations of turbulent kinetic energy and enstrophy within the flame brush for small values of Karlovitz and characteristic Lewis numbers, but both turbulent kinetic energy and enstrophy decay from the unburned to the burned gas side of the flame brush for large values of Karlovitz and characteristic Lewis numbers. The heat release within premixed flames also induces significant anisotropy of sub-grid stresses and affects their alignments with resolved strain rates. This anisotropy plays a key role in the modelling of sub-grid stresses and the explicit closure of the isotropic part of the sub-grid stress has been demonstrated to improve the performance of sub-grid stress and turbulent kinetic energy closures. Moreover, the usual dynamic modelling techniques, which are used for non-reacting turbulent flows, have been shown to not be suitable for turbulent premixed flames. Furthermore, the velocity increase across the flame due to flame normal acceleration may induce counter-gradient transport for turbulent kinetic energy, reactive scalars, scalar gradients and scalar variances in premixed turbulent flames under some conditions. The propensity of counter-gradient transport increases with decreasing values of root-mean-square turbulent velocity and characteristic Lewis number. It has been found that vorticity aligns predominantly with the intermediate principal strain rate eigendirection but the relative extents of alignment of vorticity with the most extensive and the most compressive principal strain rate eigendirections change in response to the strength of thermal expansion. It has been found that dilatation rate almost equates to the most extensive strain rate for small sub-unity Lewis numbers and for the combination of large Damköhler and small Karlovitz numbers, and under these conditions vorticity shows no alignment with the most extensive principal strain rate eigendirection but an increased collinear alignment with the most compressive principal strain rate eigendirection is obtained. By contrast, for the combination of high Karlovitz number and low Damköhler number in the flames with Lewis number close to unity, vorticity shows an increased collinear alignment with the most extensive principal direction in the reaction zone where the effects of heat release are strong. The strengthening of flame normal acceleration in comparison to turbulent straining with increasing values of density ratio, Damköhler number and decreasing Lewis number makes the reactive scalar gradient align preferentially with the most extensive principal strain rate eigendirection, which is in contrast to preferential collinear alignment of the passive scalar gradient with the most compressive principal strain rate eigendirection. For high Karlovitz number, the reactive scalar gradient alignment starts to resemble the behaviour observed in the case of passive scalar mixing. The influence of thermal expansion on the alignment characteristics of vorticity and reactive scalar gradient with local principal strain rate eigendirections dictates the statistics of vortex-stretching term in the enstrophy transport equation and normal strain rate contributions in the scalar dissipation rate and flame surface density transport equations, respectively. Based on the aforementioned fundamental physical information regarding the thermal expansion effects on fluid turbulence in premixed combustion, it has been argued that turbulence and combustion modelling are closely interlinked in turbulent premixed combustion. Therefore, it might be necessary to alter and adapt both turbulence and combustion modelling strategies while moving from one combustion regime to the other.

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Assessment and application of wavelet-based optical flow velocimetry (wOFV) to wall-bounded turbulent flows

et al. 2023

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The performance of a wavelet-based optical flow velocimetry (wOFV) algorithm in extracting high accuracy and high-resolution velocity fields from tracer particle images in wall-bounded turbulent flows is assessed. wOFV is first evaluated using synthetic particle images generated from a channel flow DNS of a turbulent boundary layer. The sensitivity of wOFV to the regularization parameter ($$\lambda$$ λ ) is quantified and results are compared to cross-correlation-based PIV. Results on synthetic particle images indicated different sensitivity to under-regularization or over-regularization depending on which region of the boundary layer is being analyzed. Nonetheless, tests on synthetic data revealed that wOFV can modestly outperform PIV in vector accuracy across a broad $$\lambda$$ λ range. wOFV showed clear advantages over PIV in resolving the viscous sublayer and obtaining highly accurate estimates of the wall shear stress and thus normalizing boundary layer variables. wOFV was also applied to experimental data of a developing turbulent boundary layer. Overall, wOFV revealed good agreement with both PIV and a combined PIV + PTV method. However, wOFV was able to successfully resolve the wall shear stress and correctly normalize the boundary layer streamwise velocity to wall units where PIV and PIV + PTV showed larger deviations. Analysis of the turbulent velocity fluctuations revealed spurious results for PIV in close proximity to the wall, leading to significantly exaggerated and non-physical turbulence intensity in the viscous sublayer region. PIV + PTV showed only a minor improvement in this aspect. wOFV did not exhibit this same effect, revealing that it is more accurate in capturing small-scale turbulent motion in the vicinity of boundaries. The enhanced vector resolution of wOFV enabled improved estimation of instantaneous derivative quantities and intricate flow structure both closer to the wall and more accurately than the other velocimetry methods. These aspects show that, within a reasonable $$\lambda$$ λ range that can be verified using physical principles, wOFV can provide improvements in diagnostics capability in resolving turbulent motion occurring in the vicinity of physical boundaries. Graphical abstract

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Quenching of Premixed Flames at Cold Walls: Effects on the Local Flow Field

Cited by 26 publications

References 30 publications

Numerical Study of Quenching Distances for Side-Wall Quenching Using Detailed Diffusion and Chemistry

Numerical Study of Quenching Distances for Side-Wall Quenching Using Detailed Diffusion and Chemistry

Influence of Thermal Expansion on Fluid Dynamics of Turbulent Premixed Combustion and Its Modelling Implications

Assessment and application of wavelet-based optical flow velocimetry (wOFV) to wall-bounded turbulent flows

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