Numerical investigation of the effects of different injection parameters on Damköhler number in the natural gas MILD combustion

Zhang, Zewu; Liu, Xiaoshan; Zhang, Liqi; Luo, Cong; Mao, Zhihui; Xu, Yongqing; Liu, Ji; Liu, Gaocheng; Chen, Zheng

doi:10.1016/j.fuel.2018.09.133

Cited by 45 publications

(16 citation statements)

References 40 publications

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“…are enclosed by using a Reynolds Averaged Navier–Stokes (RANS) approach. A realizable k- ε model is adopted to describe the turbulent flow, and a discrete ordinate (DO) model and a weight-sum-gray-gas (WSGG) model are used to resolve the radiative heat transfer equation. , The particle radiation interaction is considered, and the emissivity and scattering factor are 0.9 and 0.6, respectively. , The Eddy dissipation concept (EDC) model assumes that the turbulent flow consists of the “fine structure eddies” and the “surrounding fluids”, and the chemical reactions occurs in “fine structure eddies”, which is similar to the feature of the dispersed MILD combustion. , …”

Section: Methodsmentioning

confidence: 99%

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH₃ under Moderate or Intense Low-Oxygen Dilution Combustion Mode

et al. 2022

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Cocombustion technology of pulverized coal blending with NH 3 has a promising use in large-scale CO 2 reduced emission. However, the unstable flame and high NOx emissions during the cocombustion process retard its wide application. In order to overcome these limits, a new scheme of advanced moderate or intense low-oxygen dilution (MILD) combustion technology implemented in pulverized coal/NH 3 cocombustion is proposed in this work, and a numerical study on cocombustion characteristics of pulverized coal blending with different NH 3 proportions (0% ∼ 50% NH 3 , by caloric) is performed. Results show that the achievement of a pulverized coal/NH 3 MILD combustion regime is preferred at a high NH 3 case. As NH 3 proportions increase from 0 to 50%, the furnace temperatures are decreased due to the enhancement of heat transfer between flue gas and the furnace wall. The ignition time and temperature of coal particles are decreased by 52.1 and 33.0%, respectively, while the particle burnout time is prolonged by 52.3% and the char consumption rate decreases linearly. In addition, MILD combustion shows a good potential to reduce NOx conversion during pulverized coal/NH 3 cofiring. Although the proportion of NH 3 reaches up to 50%, NOx conversion ratio is only 2.1%. These results are expected to provide several new insights into stable flame and low NOx emissions of pulverized coal/NH 3 cocombustion.

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Section: Methodsmentioning

confidence: 99%

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH₃ under Moderate or Intense Low-Oxygen Dilution Combustion Mode

et al. 2022

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“…Meanwhile, the temperature and velocity at the outlet plane are monitored. When the variations are within 1 K and 0.1 m/s, respectively, they are regarded as another criterion for solution convergence …”

Section: Numerical Methods and Grid Independencymentioning

confidence: 99%

“…When the variations are within 1 K and 0.1 m/s, respectively, they are regarded as another criterion for solution convergence. 52 4.2. Grid Independency.…”

Section: Computational Domain and Conditionsmentioning

confidence: 99%

Numerical Simulation of Turbulent Non-premixed Combustion Processes for Methane and Dimethyl Ether Binary Fuels

Yuan

et al. 2021

ACS Omega

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The C 1ε = 1.6 standard k – ε equation combined with the steady flamelet model was applied to a methane/dimethyl ether swirl combustion field, and the effects of the dimethyl ether (DME) blending ratio and operating pressure on the flame behavior, including species variation, reaction zone behavior, and flame entrainment, were investigated. The results demonstrated that selected models could better reproduce the trends of the experimental measurements. The downstream reaction zone achieved better calculation accuracy than the outer shear layer of the first recirculation zone. The addition of DME accelerated the accumulation process of H 2 , O, H, and OH radicals. The intermediate radical CH 2 O was rapidly developed by the influence of the H extraction rate under a constant fuel volume flow rate. The reaction zone dimensions were approximately linearly and positively correlated with the DME blending ratio, whereas flame entrainment expressed a lower DME concentration dependence in the high-DME mass-dominated system. The operating pressure significantly impacted the distribution of reactive radicals in the turbulent flame; meanwhile, the flame and reaction zone length showed nonlinear inverse behavior with pressure variation, while the thickness of the reaction zone was always linearly and negatively correlated with pressure. Moreover, the peak flame entrainment rate also experienced a nonlinear decline with pressure elevation; however, the peak positions were not sensitive to pressure fluctuation. Concurrently, the response surface functions for the reaction zone dimensions were established covering the range of 0–1 for the DME blending ratio and 1–5 atm operating pressure, which could provide assistance for combustion condition optimization and combustion chamber design.

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“…Figure 13, showing the chemical flame occupation degree (RF), suggests that the CRT scale up had 6.6%, while the base case and the CV prototype had 4.7%. MILD combustion possesses the magnitude of flow time scale being comparable to that of chemical time scale (Wang et al, 2018) or the former was one order of magnitude larger (Zhang et al, 2019). Damköhler number is the ratio of flow time scale (τf) to reaction time scale (τc) (Da = τf/τc).…”

Section: Scale Effect On Mild Combustion Regimementioning

confidence: 99%

“…There have been several studies on MILD combustion, both experimentally and numerically, such as; effects of geometry and operating condition, the effect of burner configuration (Nada et al, 2015;Lee et al, 2019a), furnace chamber configuration (Schaffel-Mancini et al, 2010;Tu et al, 2015a), jet velocity of reactant (Mi et al, 2011;Veríssimo et al, 2013), reactant temperature (Khoshhal et al, 2011;Huang et al, 2014), chemical composition of fuel and oxidizer (Dally et al, 2004;Tu et al, 2015b;Lee et al, 2019b), on NOx formation and reduction (Wünning and Wünning, 1997;Mancini et al, 2002) and microscopic characteristics (Jin and Zhou, 2015;Zhang et al, 2019;).…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the effect of constant velocity and constant residence time scaling criteria on the natural gas MILD combustion

Suksam

Charoensuk

2019

JTST

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This paper concerns with effect of scaling on performance of MILD combustor when increasing its geometry and thermal throughput from the 0.58 MW prototype to its scaled-up versions of 5.8 MW. The constant velocity (CV) and constant residence time (CRT) scaling approaches were used in this work. Their performances were simulated with a numerical model for MILD combustion which was thoroughly validated against existing experimental data. It was found that despite MILD condition could be successfully maintained with both scaling approaches up to the scaling factor of 10, the effect of CV scaling could lead to elevated NOx emission due to increase in flow retention time in hot environment. The results were also discussed in term of Damköhler number. Despite of promising technology of MILD combustion for low-NOx emission, care must be taken on NOx emission level when scaling up with large scale factor under the CV criteria. As for the CRT criteria with increasing inlet velocity with the scale factor, the fuel and air supply pressure should be considered as a constrain when scaling up with large scale factor.

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Numerical investigation of the effects of different injection parameters on Damköhler number in the natural gas MILD combustion

Cited by 45 publications

References 40 publications

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH₃ under Moderate or Intense Low-Oxygen Dilution Combustion Mode

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH₃ under Moderate or Intense Low-Oxygen Dilution Combustion Mode

Numerical Simulation of Turbulent Non-premixed Combustion Processes for Methane and Dimethyl Ether Binary Fuels

Numerical investigation of the effect of constant velocity and constant residence time scaling criteria on the natural gas MILD combustion

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Numerical investigation of the effects of different injection parameters on Damköhler number in the natural gas MILD combustion

Cited by 45 publications

References 40 publications

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH3 under Moderate or Intense Low-Oxygen Dilution Combustion Mode

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH3 under Moderate or Intense Low-Oxygen Dilution Combustion Mode

Numerical Simulation of Turbulent Non-premixed Combustion Processes for Methane and Dimethyl Ether Binary Fuels

Numerical investigation of the effect of constant velocity and constant residence time scaling criteria on the natural gas MILD combustion

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Product

Resources

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Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH₃ under Moderate or Intense Low-Oxygen Dilution Combustion Mode

Computational Study on Cocombustion Characteristics of Pulverized Coal Blending with NH₃ under Moderate or Intense Low-Oxygen Dilution Combustion Mode