scholarly journals Study of Extinction Properties in Dimethyl Ether Diffusion Flames (1st Report, Effects of Equilibrium Flame Temperature and Flame Structure on Extinction Properties)

2008 ◽  
Vol 74 (746) ◽  
pp. 2236-2243
Author(s):  
Kimitoshi TANOUE ◽  
Shuho MORI ◽  
Takayuki TAJIRI ◽  
Fumio SHIMADA
Keyword(s):  
Dimethyl Ether ◽  
Diffusion Flames ◽  
Flame Structure ◽  
Flame Temperature

Reduction of NOx Formation by Water Sprays in Strained Two-Stage Flames

1997 ◽  
Vol 119 (4) ◽  
pp. 836-843 ◽  
Author(s):  
S. C. Li ◽  
N. Ilincic ◽  
F. A. Williams
Keyword(s):  
Diffusion Flames ◽  
Laser Sheet ◽  
Flame Structure ◽  
Flame Temperature ◽  
Temperature Fields ◽  
Two Stage ◽  
Two Phase ◽  
Nox Formation ◽  
Numerical Predictions ◽  
Water Sprays

Staged combustion can be employed to reduce the formation of CO and NOx, stabilize the flame, decrease the flame temperature, and create better working conditions in gas turbine combustors. To help understand influences of partial premixing and addition of water on NOx formation, we study two-stage flames in a counterflow spray burner. This paper reports experimental and theoretical results concerning two-stage combustion in which one feed stream is composed of a fuel-rich mixture of methane and air and the other is air. Water sprays are added to the air stream. This two-phase laminar counterflow configuration exhibits a green premixed flame, a blue diffusion flame, and a vaporization plane. All three are flat and parallel. The separation distances between them decrease with increasing equivalence ratio and strain rate. Flow visualization is provided through illumination by an argon ion laser sheet, velocity fields and spray structure are measured by a phase-doppler particle analyzer, concentration fields of major stable species are measured by gas chromatography of samples withdrawn from the flame, and temperature fields are measured by a thermocouple. Numerical integrations that employ a recent chemical-kinetic data base are performed to model the flame structure and NOx formation. Comparisons of experimental results with numerical predictions are made to test agreement. This work provides information on hydrocarbon combustion in both premixed flames and diffusion flames, indicates how NOx is formed in fuel-rich flames, and suggests how the pollutants can be reduced.

scholarly journals Reduction of NOx Formation by Water Sprays in Strained Two-Stage Flames

1996 ◽  
Author(s):  
S. C. Li ◽  
N. Ilincic ◽  
F. A. Williams
Keyword(s):  
Diffusion Flames ◽  
Laser Sheet ◽  
Flame Structure ◽  
Flame Temperature ◽  
Temperature Fields ◽  
Two Stage ◽  
Two Phase ◽  
Nox Formation ◽  
Numerical Predictions ◽  
Water Sprays

Staged combustion can be employed to reduce the formation of CO and NOx, stabilize the flame, decrease the flame temperature and create better working conditions in gas turbine combustors. To help understand influences of partial premixing and addition of water on NOx formation, we study two-stage flames in a counterflow spray burner. This paper reports experimental and theoretical results concerning two-stage combustion in which one feed stream is composed of a fuel-rich mixture of methane and air and the other is air. Water sprays are added to the air stream. This two-phase laminar counterflow configuration exhibits a green premixed flame, a blue diffusion flame and a vaporization plane. All three are flat and parallel. The separation distances between them decrease with increasing equivalence ratio and strain rate. Flow visualization is provided through illumination by an argon ion laser sheet, velocity fields and spray structure are measured by a phase-doppler particle analyzer, concentration fields of major stable species are measured by gas chromatography of samples withdrawn from the flame, and temperature fields are measured by a thermocouple. Numerical integrations which employ a recent chemical-kinetic data base are performed to model the flame structure and NOx formation. Comparisons of experimental results with numerical predictions are made to test agreement. This work provides information on hydrocarbon combustion in both premixed flames and diffusion flames, indicates how NOx is formed in fuel-rich flames and suggests how the pollutants can be reduced.

Study on flame structure and extinction mechanism of dimethyl ether spherical diffusion flames

Energy ◽  
2020 ◽  
Vol 193 ◽  
pp. 116786 ◽  
Author(s):  
Yinhu Kang ◽  
Qiang Wang ◽  
Pengyuan Zhang ◽  
Congcong Liu ◽  
Xiaofeng Lu ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
Diffusion Flames ◽  
Flame Structure ◽  
Spherical Diffusion

scholarly journals Investigation of Thermal Radiation from Soot Particles and Gases in Oxy-Combustion Counter-Flow Flames

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1756
Author(s):  
Chaoyang Wang ◽  
Guangtong Tang ◽  
Huibo Yan ◽  
Lujiang Li ◽  
Xiaopei Yan ◽  
...  
Keyword(s):  
Thermal Radiation ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Flame Temperature ◽  
Stoichiometric Mixture ◽  
Particle Radiation ◽  
Mixture Ratio ◽  
Soot Particles

Oxy-combustion with high flame temperature, low heat loss, high combustion efficiency, and low NOx emissions is being extensively studied. The thermal radiation from soot particles and gases in oxy-combustion accounts for the vast majority of the total heat transfer. Based on a detailed chemical reaction mechanism coupled with the soot particle dynamics model and optically thin radiation model, the influence of the flame structure and temperature distribution on the thermal radiation in oxygen-enriched counterflow diffusion flames was studied in this paper. The results revealed that reasonable assignment of total recycled flue gas and the degree of dilution of fuel and oxidant were critical, which can be used to adjust the overall radiation situation of the flame. At the same adiabatic flame temperature, as the fuel concentration decreased and the oxidant concentration increased (the stoichiometric mixture ratio is from 0.3 to 0.6), the soot formation decreased, which led to the particle radiation disappearing while the main radiation zone of gases moved 0.04 cm toward the fuel side. At the same stoichiometric mixture fraction (0.4), the radiation area was broadened and the radiation of soot particles was gradually enhanced with the adiabatic flame increasing from 2300 K to 2700 K.

scholarly journals Effect of the Preheated Oxidizer Temperature on Soot Formation and Flame Structure in Turbulent Methane-Air Diffusion Flames at 1 and 3 atm: A CFD Investigation

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3671
Author(s):  
Subrat Garnayak ◽  
Subhankar Mohapatra ◽  
Sukanta K. Dash ◽  
Bok Jik Lee ◽  
V. Mahendra Reddy
Keyword(s):  
Mole Fraction ◽  
Air Temperature ◽  
Reaction Rate ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Flame Structure ◽  
Soot Volume Fraction ◽  
Computational Domain ◽  
Pressure Elevation

This article presents the results of computations on pilot-based turbulent methane/air co-flow diffusion flames under the influence of the preheated oxidizer temperature ranging from 293 to 723 K at two operating pressures of 1 and 3 atm. The focus is on investigating the soot formation and flame structure under the influence of both the preheated air and combustor pressure. The computations were conducted in a 2D axisymmetric computational domain by solving the Favre averaged governing equation using the finite volume-based CFD code Ansys Fluent 19.2. A steady laminar flamelet model in combination with GRI Mech 3.0 was considered for combustion modeling. A semi-empirical acetylene-based soot model proposed by Brookes and Moss was adopted to predict soot. A careful validation was initially carried out with the measurements by Brookes and Moss at 1 and 3 atm with the temperature of both fuel and air at 290 K before carrying out further simulation using preheated air. The results by the present computation demonstrated that the flame peak temperature increased with air temperature for both 1 and 3 atm, while it reduced with pressure elevation. The OH mole fraction, signifying reaction rate, increased with a rise in the oxidizer temperature at the two operating pressures of 1 and 3 atm. However, a reduced value of OH mole fraction was observed at 3 atm when compared with 1 atm. The soot volume fraction increased with air temperature as well as pressure. The reaction rate by soot surface growth, soot mass-nucleation, and soot-oxidation rate increased with an increase in both air temperature and pressure. Finally, the fuel consumption rate showed a decreasing trend with air temperature and an increasing trend with pressure elevation.

scholarly journals Effects of strain rate and CO2 on no formation in CH4/N2/O2 counter-flow diffusion flames

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 769-776
Author(s):  
Fei Ren ◽  
Longkai Xiang ◽  
Huaqiang Chu ◽  
Weiwei Han
Keyword(s):  
Strain Rate ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Flame Temperature ◽  
Co2 Concentration ◽  
No Production ◽  
Counter Flow ◽  
Detailed Chemistry ◽  
No Formation ◽  
Key Factor

The reduction of nitrogen oxides in the high temperature flame is the key factor affecting the oxygen-enriched combustion performance. A numerical study using an OPPDIF code with detailed chemistry mechanism GRI 3.0 was carried out to focus on the effect of strain rate (25-130 s?1) and CO2 addition (0-0.59) on the oxidizer side on NO emission in CH4 / N2 / O2 counter-flow diffusion flame. The mole fraction profiles of flame structures, NO, NO2 and some selected radicals (H, O, OH) and the sensitivity of the dominant reactions contributing to NO formation in the counter-flow diffusion flames of CH4\/ N2 /O2 and CH4 / N2 / O2 / CO2 were obtained. The results indicated that the flame temperature and the amount of NO were reduced while the sensitivity of reactions to the prompt NO formation was gradually increased with the increasing strain rate. Furthermore, it is shown that with the increasing CO2 concentration in oxidizer, CO2 was directly involved in the reaction of NO consumption. The flame temperature and NO production were decreased dramatically and the mechanism of NO production was transformed from the thermal to prompt route.

scholarly journals Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

2019 ◽  
Vol 9 (19) ◽  
pp. 3989 ◽  
Author(s):  
Cheng Wang ◽  
Anthony Chun Yin Yuen ◽  
Qing Nian Chan ◽  
Timothy Bo Yuan Chen ◽  
Qian Chen ◽  
...  
Keyword(s):  
Flame Structure ◽  
Flame Temperature ◽  
Combustion Process ◽  
Flame Height ◽  
Reacting Flow ◽  
Detailed Chemistry ◽  
Eddy Generation ◽  
Fire Whirl ◽  
Generation Mechanisms ◽  
The Impact

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5   m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

Theoretical Assessment of Convective and Radiative Heat Losses in a One-Dimensional Multiregion Premixed Flame With Counter-Flow Design Crossing Through Biofuel Particles

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Mehdi Bidabadi ◽  
Saman Hosseinzadeh ◽  
Sadegh Sadeghi ◽  
Mostafa Setareh
Keyword(s):  
Temperature Profile ◽  
Radiative Heat ◽  
Flame Structure ◽  
Flame Temperature ◽  
Heat Losses ◽  
Flame Velocity ◽  
Mass Fractions ◽  
Interface Matching ◽  
Energy Balances ◽  
Stagnation Plane

Due to perspective of biomass usage as a viable source of energy, this paper suggests a potential theoretical approach for studying multiregion nonadiabatic premixed flames with counterflow design crossing through the mixture of air (oxidizer) and lycopodium particles (biofuel). In this research, convective and radiative heat losses are analytically described. Due to the properties of lycopodium, roles of drying and vaporization are included so that the flame structure is created from preheating, drying, vaporization, reaction, and postflame regions. To follow temperature profile and mass fraction of the biofuel in solid and gaseous phases, dimensionalized and nondimensionalized forms of mass and energy balances are expressed. To ensure the continuity and calculate the positions of drying, vaporization, and flame fronts, interface matching conditions are derived employing matlab and mathematica software. For validation purpose, results for temperature profile is compared with those provided in a previous research study and an appropriate is observed under the same conditions. Finally, changes in flame velocity, flame temperature, solid and gaseous fuel mass fractions, and particle size with position measured from the position of stagnation plane, strain rate, and heat transfer coefficient in the presence/absence of losses are evaluated.

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