Simulation of turbulent lifted methane jet flames: Effects of air-dilution and transient flame propagation

Chen, Zhi X.; Ruan, S.; Swaminathan, Nedunchezhian

doi:10.1016/j.combustflame.2014.09.010

Cited by 44 publications

(90 citation statements)

References 67 publications

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“…All the flames considered are located on a cylindrical pipe, discharging pure fuel vertically, in the absence of any pilot flame. The presence of cross winds [1] can reduce combustion efficiency, as can the presence of inert gas, such as nitrogen and carbon dioxide [2], as well as air [3,4]. A review of the extensive experimental data on jet flame heights and lift-off distances is presented in [5].…”

Section: Introductionmentioning

confidence: 99%

Generalised correlations of blow-off and flame quenching for sub-sonic and choked jet flames

Palacios

Bradley

2017

Combustion and Flame

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Dimensionless groups suggested by the mathematical modelling of subsonic fuel jet flames, and extensive experimental data, have been reasonably successsful in correlating dimensionles flame heights and flame lift-off distances in terms of a dimensionless flow number. This approach is extended to the more exacting correlations that define regimes of flame quenching, blow-off, and lifted flames.Experimental data from these diverse sources are analysed, and the bounds of these regimes are expressed in terms of the critical minimum jet pipe diameter to avoid blow-off, normalised by the laminar flame thickness for the maximum burning velocity mixture, and the flow number. The regimes extend from low Reynolds number laminar flows in hypodermic tubes to high Reynolds number choked flows, with supersonic shocks.Data are well corrrelated in the subsonic regime for a range of hydrocarbon gases, in which critical pipe diameters for the avoidance of blow-off increase with flow number. Matters are more complex in the extended choked flow regime, in which there are less data. This regime of supersonic flow and shock waves is one of improved fuel/air mixing and enhanced reactivity, to such an extent that the critical pipe diameter, after reaching a maximum, decreases. Data are presented in this regime, and indeed over the full range of conditions, for methane, propane and hydrogen jet flames. Hydrogen exhibits more reactive characteristics than the hydrocarbons. In terms of the correlating parameters, whereas laminar flame thickness is related to that of the non-reacting preheat zone, such a zone is difficult 2 to define with hydrogen, as a consequence of the upstream diffusion of H atoms, and this aspect is discusssed.

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Section: Introductionmentioning

confidence: 99%

Generalised correlations of blow-off and flame quenching for sub-sonic and choked jet flames

Palacios

Bradley

2017

Combustion and Flame

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“…Note that the two additional residual terms involving cross correlation between the temporal and spatial averaging procedures [10] are considered to be negligible for this study as in [11]. Previous RANS studies [7,8,12,13] showed that the total time-averaged correlation, {Z c }, is quite influential in partially premixed lifted flames. This was further confirmed in a recent experimental study by Barlow et al [5] showing a strong Z-c correlation in a partially premixed piloted jet flame.…”

Section: Introductionmentioning

confidence: 99%

“…In the Reynolds-averaged Navier-Stokes (RANS) context, the effect of this correlation has been assessed previously by Ruan et al [7] and Chen et al [8] using a presumed joint probability density function (JPDF) approach for turbulent lifted flames. The statistical correlation was included in the JPDF using a copula method [7,9].…”

Section: Introductionmentioning

confidence: 99%

A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

Chen

Doan

Ruan

et al. 2018

Combustion Theory and Modelling

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Subgrid correlation of mixture fraction, Z, and progress variable, c, is investigated using direct numerical dimulation (DNS) data of a hydrogen lifted jet flame. Joint subgrid behaviour of these two scalars are obtained using a Gaussian-type filter for a broad range of filter sizes. A joint probability density function (JPDF) constructed using single-snapshot DNS data is compared qualitatively with that computed using two independent β-PDFs and a copula method. Strong negative correlation observed at different streamwise locations in the flame is captured well by the copula method. The subgrid contribution to the Z-c correlation becomes important if the filter is of the size of the laminar flame thickness or larger. A priori assessment for the filtered reaction rate using the flamelet approach with independent β-PDFs and correlated JPDF is then performed. Comparison with the DNS data shows that both models provide reasonably good results for a range of filter sizes. However, the reaction rate computed using copula JPDF is found to have a better agreement with the DNS data for large filter sizes because the subgrid Z-c correlation effect is included.

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“…However, the prediction of blow-off, as the ultimate limiting condition of lift-off, when localised extinctions cause the flame to simultaneously leave the burner and extinguish, presents more severe modelling problems [5]. They include the development of oscillatory, non-linear phenomena.…”

Section: Introductionmentioning

confidence: 99%

“…There have been significant successes in the mathematical modelling of lift-off distances, L, and plume heights for pure fuel jet flames, and in the associated formulation of appropriate dimensionless groups for the correlation of experimental data [2][3][4][5][6]. The region between the exit plane of a fuel jet discharging into the atmosphere and the flame leading edge is one of intense mixing that generates high strain rates.…”

Section: Introductionmentioning

confidence: 99%

Lift-off and blow-off of methane and propane subsonic vertical jet flames, with and without diluent air

Palacios

Bradley

2016

Fuel

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The paper seeks to increase understanding of subsonic jet flame blow-off phenomena, through experimental studies that include the controlled introduction of air into the fuel jet. As the molar concentration of air in the jet flame gas, Aj, is increased the reaction zone becomes leaner, and the flame lift-off distance increases.Eventually, flame oscillations develop and are followed by flame blow-off. A jet mixing analysis enables the extent of the leaning-off of the mixture to be estimated. From this, the reduced mean flamelet burning velocity, ua, is found at the location of the pure fuel jet flame. The conditions for blow-off are correlated with the last measured stable values of the dimensionless flow number, Ub*, for methane and propane jet flames, with and without added air. Values of Ub* decline as the proportion of added air increases, more markedly so with methane. This is attributed to the leaning-off of the flame, and the associated decrease in the flame extinction stretch rate. As Ub* declines in value, with increasing air dilution, the emissions of unburned hydrocarbons just prior to blow-off increase. An underlying generality of the findings is revealed when ua is introduced into the expression for Ub*, and Aj is normalised by the moles of air required to burn a mole of fuel.

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Simulation of turbulent lifted methane jet flames: Effects of air-dilution and transient flame propagation

Cited by 44 publications

References 67 publications

Generalised correlations of blow-off and flame quenching for sub-sonic and choked jet flames

Generalised correlations of blow-off and flame quenching for sub-sonic and choked jet flames

A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames

Lift-off and blow-off of methane and propane subsonic vertical jet flames, with and without diluent air

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