The Effects of Fuel Mixtures in Nonpremixed Combustion for a Bluff-Body Flame

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Lu Chen ◽  
Francine Battaglia
Keyword(s):  
Bluff Body ◽  
Turbulence Models ◽  
Industrial Applications ◽  
Oh Radicals ◽  
No Production ◽  
Nonpremixed Flames ◽  
No Emission ◽  
Nonpremixed Combustion ◽  
Turbulent Nonpremixed ◽  
Fuel Mixtures

A numerical investigation is presented assessing the effects of hydrogen compositions and nonflammable diluent mixtures on the combustion and NO emission characteristics of syngas nonpremixed flames for a bluff-body burner. An assessment of turbulent nonpremixed modeling techniques is presented and is compared with the experiments of Correa and Gulati (1992, “Measurements and Modeling of a Bluff Body Stabilized Flame,” Combust. Flame, 89(2), pp. 195–213). The realizable k–ε and the Reynolds stress (RSM) turbulence models were found to perform the best. As a result, increased hydrogen content caused the radial velocity and strain rate to decrease, which was important for mixing whereby NO production decreased. Also, the effectiveness of nonflammable diluent mixtures of N2, CO2, and H2O was characterized in terms of the ability to reduce NO emission in syngas nonpremixed flames. Results indicated that CO2 was the most effective diluent to reduce NO emission and H2O was more effective than N2. CO2 produced low levels of OH radical, which made CO2 the most effective diluent. Although H2O increased OH radicals, it was still effective to reduce thermal NO because of its high specific heat. It will be numerically shown that hydrogen concentration in the H2/CO/N2 flame does not significantly affect temperature but dramatically decreases NO emission, which is important for industrial applications that can use hydrogen in syngas flames.

The Effects of Fuel and Air Mixtures in Non-Premixed Combustion for a Bluff-Body Flame

2015 ◽  
Author(s):  
Lu Chen ◽  
Francine Battaglia
Keyword(s):  
Bluff Body ◽  
Numerical Study ◽  
Premixed Flames ◽  
Turbulence Models ◽  
Premixed Combustion ◽  
Oh Radicals ◽  
No Emission ◽  
Combustion Modeling ◽  
High Specific Heat ◽  
Low Levels

The bluff-body stabilized flame is used in a numerical study of the non-premixed flames. This paper shows numerical investigations on the effects of hydrogen compositions and nonflammable diluent mixtures on the combustion and NO emission characteristics of syngas non-premixed flames for a bluff-body burner. The assessment of turbulent non-premixed combustion modeling techniques is presented and discussed. The simulations study the predictive capabilities of five turbulence models and are compared with the experiments of Correa and Gulati [1] for a non-premixed flame of 27.5%CO/32.3%H2/40.2%N2 and air. The Realizable k-ε and the Reynolds Stress (RSM) models were found to perform the best. Based on this, a numerical study to assess the effects of hydrogen component on syngas non-premixed combustion was performed. As a result, hydrogen addition caused the radial velocity and strain rate to decrease, which was important for mixing to decrease NO. Also, the effectiveness of nonflammable diluent mixtures, including N2, CO2 and H2O, were characterized in terms of the ability to reduce NO emission in syngas non-premixed flames. Results indicated that CO2 was the most effective diluent to reduce NO emission and H2O was more effective than N2. CO2 diluent produced low levels of OH radical, which makes CO2 the most effective diluent. Although H2O increased OH radicals, it was still effective to decrease the thermal NO because of its high specific heat.

Effects of Fuel-Side N2, CO2, H2O Dilution on Combustion Characteristics and NOx Formation of Syngas Turbulent Nonpremixed Jet Flames

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Liying Zhuo ◽  
Yong Jiang ◽  
Rong Qiu ◽  
Jiangtao An ◽  
Wu Xu
Keyword(s):  
International Workshop ◽  
Flame Structure ◽  
Flame Temperature ◽  
Nonpremixed Flames ◽  
Nox Formation ◽  
Extinction Process ◽  
Turbulent Nonpremixed ◽  
Fuel Mixtures ◽  
The One ◽  
Good Agreement

The effects of the three fuel-side diluents N2, CO2, and H2O on the accurate flame structure and NOx formation characteristics of the turbulent syngas nonpremixed flames are investigated using the one-dimensional-turbulence (ODT) model. For nonpremixed flames, the fuel mixtures consist of H2, CO and three diluents: N2, H2O, and CO2. The proportion of diluents is varied from 10% to 30% while the H2/CO ratio is kept as a constant at 0.75 all the time. Mass fraction of main species and temperature of 30% N2 basic dilution case predicted by the ODT model are compared with the tests measuring results obtained by International Workshop on Measurements and Computation of Turbulent Nonpremixed Flames, and it is found that the results are in good agreement. Numerical results indicate that the CO2 diluted flames have the largest reduction on flame temperature as well as the NOx emission, while H2O is more effective than N2. For CO2 and H2O dilution flames, flame structure becomes unstable with an obvious lift phenomenon. Since ODT captures the flame extinction process, flames added with CO2 and H2O not only have a lower extinction temperature but also the reignition process is slower.

Drag on a Confined Cylinder in Axial Flow

2004 ◽  
Author(s):  
H. P. Kritzinger ◽  
C. R. Kleijn ◽  
H. E. A. Van den Akker
Keyword(s):  
Bluff Body ◽  
Transport Model ◽  
Axial Flow ◽  
Turbulence Models ◽  
Industrial Applications ◽  
General Interest ◽  
Mean Velocity ◽  
Drag Forces ◽  
Reynolds Stress Transport Model ◽  
Typical Configuration

Bluff body drag prediction remains a challenging subject for numerical investigators, with important industrial applications in aero- and hydrodynamics. A typical configuration of general interest is that of a confined axial cylinder. Experimental data for this geometry is scarce. In this paper, drag forces on this configuration were investigated using the commercial CFD solver Fluent 6. The work includes results with various mesh densities and different Reynolds numbers. Several common turbulence models as available in Fluent were applied. Good agreement to experiments was obtained with the realizable k-ε model and with the Reynolds stress transport model. The standard k-ε model was found to be inappropriate. Increased blockage (confinement) of the cylinder resulted in a corresponding increase in the drag force. This increase is shown to be a function of the mean velocity at the smallest cross-section of the channel.

A test of a flamelet model for turbulent nonpremixed combustion☆

1994 ◽  
Vol 96 (1-2) ◽  
pp. 104-120 ◽  
Author(s):  
Y BURIKO ◽  
V KUZNETSOV ◽  
D VOLKOV ◽  
S ZAITSEV ◽  
A URYVSKY
Keyword(s):  
Flamelet Model ◽  
Nonpremixed Combustion ◽  
Turbulent Nonpremixed

scholarly journals Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in Sahel rangeland (Mali)

2015 ◽  
Vol 12 (2) ◽  
pp. 1155-1203
Author(s):  
C. Delon ◽  
E. Mougin ◽  
D. Serça ◽  
M. Grippa ◽  
P. Hiernaux ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Litter Decomposition ◽  
Litter Production ◽  
No Production ◽  
Emission Model ◽  
No Emission ◽  
Yearly Average ◽  
No Release ◽  
Emission Fluxes ◽  
Sahel Region

Abstract. This work is an attempt to provide seasonal variation of biogenic NO emission fluxes in a sahelian rangeland in Mali (Agoufou, 15.34° N, 1.48° W) for years 2004–2008. Indeed, NO is one of the most important precursor for tropospheric ozone, and the contribution of the Sahel region in emitting NO is no more considered as negligible. The link between NO production in the soil and NO release to the atmosphere is investigated in this study, by taking into account vegetation litter production and degradation, microbial processes in the soil, emission fluxes, and environmental variables influencing these processes, using a coupled vegetation-litter decomposition-emission model. This model includes the Sahelian-Transpiration-Evaporation-Productivity (STEP) model for the simulation of herbaceous, tree leaf and fecal masses, the GENDEC model (GENeral DEComposition) for the simulation of the buried litter decomposition and microbial dynamics, and the NO emission model (NOFlux) for the simulation of the NO release to the atmosphere. Physical parameters (soil moisture and temperature, wind speed, sand percentage) which affect substrate diffusion and oxygen supply in the soil and influence the microbial activity, and biogeochemical parameters (pH and fertilization rate related to N content) are necessary to simulate the NO flux. The reliability of the simulated parameters is checked, in order to assess the robustness of the simulated NO flux. Simulated yearly average of NO flux ranges from 0.66 to 0.96 kg(N) ha-1 yr-1, and wet season average ranges from 1.06 to 1.73 kg(N) ha-1 yr-1. These results are in the same order as previous measurements made in several sites where the vegetation and the soil are comparable to the ones in Agoufou. This coupled vegetation-litter decomposition-emission model could be generalized at the scale of the Sahel region, and provide information where little data is available.

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