Investigation of a turbulent premixed combustion flame in a backward-facing step combustor; effect of equivalence ratio

Nemitallah, Medhat A.; Kewlani, Gaurav; Hong, Seunghyuck; Shanbhogue, Santosh J.; Habib, Mohamed A.; Ghoniem, Ahmed F.

doi:10.1016/j.energy.2015.12.010

Cited by 36 publications

(7 citation statements)

References 27 publications

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“…For all the fuels, one clockwise‐spinning eddy is observed in the ORZ irrespective of the Φ. Similar eddy formation in the ORZ was reported in an investigation of propane air combustion in a backward‐facing step combustor 72 . High aspect ratio between the inlet diameter and the diameter of quartz tube (combustion chamber) makes the IRZ more dominant compared with ORZ.…”

Section: Resultssupporting

confidence: 79%

“…71 In the studied cases, flame is dominated by the IRZ resulting in the mixing of burned and unburned species, which reduces the reaction consequently reducing the OH concentration and temperature (temperature distribution discussed in the following section) in the IRZ. 72 The recirculation in the combustion chamber can be observed from the velocity streamlines (in Figure 8) and vorticity distribution (in Figure 9) below.…”

Section: Resultsmentioning

confidence: 99%

“…Similar eddy formation in the ORZ was reported in an investigation of propane air combustion in a backward-facing step combustor. 72 High aspect ratio between the inlet diameter and the diameter of quartz tube (combustion chamber) makes the IRZ more dominant compared with ORZ. However, the formation and recirculation in ORZ is case sensitive for a fixed combustor design and is also a vital parameter for the flame stability.…”

Section: Temperature Profiles and Flow Field Structurementioning

confidence: 99%

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Analysis of methane, propane, and syngas oxy‐flames in a fuel‐flex gas turbine combustor for carbon capture

Haque

Nemitallah

Abdelhafez

et al. 2022

Intl J of Energy Research

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Premixed oxy-combustion flames of methane, syngas (CH 4 :CO:H 2 with the molar ratio of 2:1:1), and propane in CO 2 -diluted environment (for carbon capture) are examined in a swirl-stabilized combustor using large eddy simulations (LES) in three-dimensional (3-D) domain. The flame and emission characteristics are examined for the different fuels over a range of equivalence ratios (Φ: 0.34, 0.39, and 0.42), at 60% oxygen fraction (OF), and 2.5 m/s bulk inlet velocity under atmospheric conditions. The results indicate increments in several characteristic parameters that are of special importance for gas turbine combustion applications, including adiabatic flame temperature (T ad ), laminar flame speed (LFS), power density (PD), product formation rate (PFR), Damköhler number (Da), and CO emission, with the increase of Φ whatever the type of fuel. Alternatively, flame thickness (δ) decreases with the increase in Φ for the three fuels. Characteristic "V" shape with almost identical outer recirculation zone (ORZ) is also observed for the three fuels. Among the studied fuels, oxy-methane flames demonstrate highest flame thicknesses, least uniform temperature distribution (highest pattern factor) at combustor outlet, and lowest CO emission level. Oxy-syngas flames show more uniform temperature distribution (lowest pattern factor) at combustor outlet and highest CO emission as compared with the oxy-methane and oxy-propane flames. The oxy-propane flames have higher values of T ad , LFS, PD, PFR, Da, and thermal power (TP) along with lowest flame thickness compared with methane and syngas counterparts. Highlights• Increasing equivalence ratio improves the flame characteristics but increases CO emission.• Fuel type has insignificant effects on shape/size of the outer recirculation zone (ORZ).• Oxy-methane flames showed highest flame thicknesses and pattern factor and lowest CO.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Temperature Profiles and Flow Field Structurementioning

confidence: 99%

See 1 more Smart Citation

Analysis of methane, propane, and syngas oxy‐flames in a fuel‐flex gas turbine combustor for carbon capture

Haque

Nemitallah

Abdelhafez

et al. 2022

Intl J of Energy Research

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“…Therefore, the eddy in ORZ can be regulated by controlling the value of operating Φ, similar to what was concluded in a study of air-propane combustion in a backward-facing step combustor. 57 The intense eddy formation aides in improving turbulent mixing of the species; as a result, the reaction rate also improves leading to thicker and stronger reaction zone. 58 Furthermore, the probability density function (PDF) approach, incorporated in the simulations, plays a vital role in modeling the interaction between the turbulence and chemistry of the reacting flow.…”

Section: Flow-field Structure Of C 3 H 8 /O 2 /Co 2 Flamesmentioning

confidence: 99%

Numerical analysis supported with experimental measurements of premixed oxy‐propane flames in a fuel‐flex gas turbine combustor

et al. 2021

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The combustion, exhaust-gas concentrations, and stability characteristics of premixed CO 2 -diluted oxy-propane (C 3 H 8 /O 2 /CO 2 ) flames were investigated computationally using large eddy simulations (LES) in a swirl-stabilized model gas-turbine combustor. The simulations were carried out for ranges of equivalence ratio (Φ: 0.26-0.80) and oxygen fraction (OF: 35%-60%) at a fixed bulk inlet velocity of 5.2 m/s. The results indicate that the reaction rates increase with the increase of Φ and OF. Flames of the same adiabatic flame temperature (T ad ) show similar macro-and flowfield-structures, in terms of flame shape, flow circulation, and temperature, and species distributions, irrespective of the values of Φ and OF. At higher T ad , the flames were observed to be more compact with reduced flame thickness and higher Damkohler number (Da). In all cases, Da > 1 were observed, indicating the dominance of reaction rate in oxy-propane flames than the diffusion rate. A secondary IRZ was also observed near the outlet of the combustor. Mixture composition and combustion temperature influence the CO concentration at the combustor exit. The highest CO emission was observed at 0.17 ppm for the flame with highest Φ and T ad , meanwhile no CO emission was seen for flames with high OF and low Φ among the studied cases. Highlights 1. Adiabatic flame temperature is a quantifying parameter for flame

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“…They highlighted that the most representative way to report flame macrostructures is the OH radical molar concentration within the combustor domain. Nemitallah et al studied lean premixed propane–air flame stability in a backward-step facing combustor using the large eddy simulation (LES) turbulent scheme. They reported that the flame stabilizes strongly on the back-step side of the combustor at a higher equivalence ratio and, at a lower equivalence ratio, the flame lifts off the step point and the lift-off distance increases while reducing the equivalence ratio.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigations of Structure and Stability of Premixed Swirl-Stabilized CH₄/O₂/CO₂ Flames in a Model Gas Turbine Combustor

2019

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Premixed CH 4 /O 2 /CO 2 flames were studied experimentally and numerically in a swirl-stabilized combustor. The bulk throat velocity of the incoming combustible mixture was maintained constant at 5.2 m/s. The oxygen fraction of the O 2 / CO 2 oxidizer was kept constant at 60 vol %, while the effect of the equivalence ratio was examined from the blowout limit to the flashback one. The LES computational model was successfully validated through comparisons with experimental data in terms of axial and radial temperature profiles, as well as predicted OH* concentration maps versus visual flame appearance. Three different flame structures were observed while varying the equivalence ratio, namely, (I) double conical flame, (II) cornerstabilized flame, and (III) swirl-stabilized (V-shaped) flame. The double conical flame is observed at low equivalence ratios near the blowout limit. This flame stabilizes within both the inner and outer shear layers and has two distinct reaction zones with two inner recirculation zones (IRZs) separated by a colder, reaction-free corner recirculation zone (CRZ). The corner-stabilized flame is observed at higher equivalence ratios. The downstream reaction zone diminishes and merges with the upstream one to form a flame that stabilizes within a reacting CRZ. Increasing the equivalence ratio further induces a transition to the typical Vshape of swirl-stabilized flames with significantly stronger IRZ and weaker CRZ. This flame is thus stabilized by its IRZ. The Vshape prevails until flashback occurs when the hot reaction zone moves closest to the burner throat.

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Investigation of a turbulent premixed combustion flame in a backward-facing step combustor; effect of equivalence ratio

Abstract: 12In the present study, large-eddy simulation (LES) is utilized to analyze lean-premixed propane-

Cited by 36 publications

References 27 publications

Analysis of methane, propane, and syngas oxy‐flames in a fuel‐flex gas turbine combustor for carbon capture

Analysis of methane, propane, and syngas oxy‐flames in a fuel‐flex gas turbine combustor for carbon capture

Numerical analysis supported with experimental measurements of premixed oxy‐propane flames in a fuel‐flex gas turbine combustor

Experimental and Numerical Investigations of Structure and Stability of Premixed Swirl-Stabilized CH₄/O₂/CO₂ Flames in a Model Gas Turbine Combustor

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Investigation of a turbulent premixed combustion flame in a backward-facing step combustor; effect of equivalence ratio

Abstract: 12In the present study, large-eddy simulation (LES) is utilized to analyze lean-premixed propane-

Cited by 36 publications

References 27 publications

Analysis of methane, propane, and syngas oxy‐flames in a fuel‐flex gas turbine combustor for carbon capture

Analysis of methane, propane, and syngas oxy‐flames in a fuel‐flex gas turbine combustor for carbon capture

Numerical analysis supported with experimental measurements of premixed oxy‐propane flames in a fuel‐flex gas turbine combustor

Experimental and Numerical Investigations of Structure and Stability of Premixed Swirl-Stabilized CH4/O2/CO2 Flames in a Model Gas Turbine Combustor

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Experimental and Numerical Investigations of Structure and Stability of Premixed Swirl-Stabilized CH₄/O₂/CO₂ Flames in a Model Gas Turbine Combustor