Computation of Nitric Oxide and Soot Emissions From Turbulent Diffusion Flames

1985 ◽  
Vol 107 (1) ◽  
pp. 48-53 ◽  
Author(s):  
T. Ahmad ◽  
S. L. Plee ◽  
J. P. Myers
Keyword(s):  
Diffusion Flames ◽  
Soot Oxidation ◽  
Air Entrainment ◽  
Reaction Rates ◽  
Gas Jet ◽  
Maximum Temperature ◽  
Injection Velocity ◽  
Soot Emission ◽  
No Emission ◽  
Jet Flame

An existing steady-state, locally homogeneous flow model of turbulent spray combustion was modified to predict NO emission from a spray flame and soot emission from a gas-jet flame. The effect of turbulent fluctuations on the reaction rates was accounted for. The predicted NO emission from an n-pentane spray with a changing injection velocity could be correlated with the convective time scale of the flow. Calculation of soot emission from a burning turbulent gas jet indicated that the centerline soot concentration reaches a peak upstream of the maximum temperature location and then decreases due to soot oxidation and dilution by air entrainment.

A numerical study of the effect of radial confinement on the characteristics of laminar co-flow methane–oxygen diffusion flames

2011 ◽  
Vol 225 (5) ◽  
pp. 1213-1228 ◽  
Author(s):  
K Bhadraiah ◽  
V Raghavan
Keyword(s):  
Numerical Model ◽  
Oxygen Diffusion ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Air Entrainment ◽  
Maximum Temperature ◽  
Low Oxygen ◽  
Numerical Predictions ◽  
Effect Of Oxygen ◽  
Different Diameters

A numerical investigation of the characteristics of laminar co-flow methane–oxygen diffusion flames has been carried out. The temperature and nitric oxide (NO) distributions in unconfined and partly confined flames are studied in detail. Radial confinements of different diameters and with a length of 150 times the fuel jet diameter have been considered to allow atmospheric nitrogen entry only from the top. A numerical model with a 43-step chemical kinetics mechanism and an optically thin radiation sub-model is employed to carry out simulations. The numerical model has been validated using the experimental data available in the literature. The effect of oxygen flowrate on temperature distributions is studied thoroughly. Confined flame extents are compared with the corresponding unconfined flame extents with the help of OH contours. The effect of confinement diameter on temperature and NO distributions is analysed in detail. At low oxygen flowrates, the extents of confined flames are higher than those of an unconfined flame. At a higher oxygen flowrate, the extent of unconfined flame becomes higher. The confined flames are in general hotter than the unconfined flames. However, at the highest oxygen flowrate and for an intermediate confinement diameter, the flame has the lowest maximum temperature. The amount of NO produced in confined flames is higher than the unconfined flames, due to air entrainment from the top of the confining tube, which increases the residence time for nitrogen transport and its oxidation. At the highest oxygen flowrate considered, numerical predictions show that for a given confinement length, there is an optimum confinement diameter which results in a minimum net production of NO among all the flames.

scholarly journals Numerical Study of the Structure and NO Emission Characteristics of N2- and CO2-Diluted Tubular Diffusion Flames

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1490
Author(s):  
Harshini Devathi ◽  
Carl A. Hall ◽  
Robert W. Pitz
Keyword(s):  
Diffusion Flames ◽  
Numerical Study ◽  
Reaction Pathway ◽  
Flame Structure ◽  
Reaction Rates ◽  
No Production ◽  
Emission Characteristics ◽  
No Emission ◽  
Nitrogen Radicals ◽  
Lower Temperature

The structure of methane/air tubular diffusion flames with 65 % fuel dilution by either CO2 or N2 is numerically investigated as a function of pressure. As pressure is increased, the reaction zone thickness reduces due to decrease in diffusivities with pressure. The flame with CO2-diluted fuel exhibits much lower nitrogen radicals (N, NH, HCN, NCO) and lower temperature than its N2-diluted counterpart. In addition to flame structure, NO emission characteristics are studied using analysis of reaction rates and quantitative reaction pathway diagrams (QRPDs). Four different routes, namely the thermal route, Fenimore prompt route, N2O route, and NNH route, are examined and it is observed that the Fenimore prompt route is the most dominant for both CO2- and N2-diuted cases at all values of pressure followed by NNH route, thermal route, and N2O route. This is due to low temperatures (below 1900 K) found in these highly diluted, stretched, and curved flames. Further, due to lower availability of N2 and nitrogen bearing radicals for the CO2-diluted cases, the reaction rates are orders of magnitude lower than their N2-diluted counterparts. This results in lower NO production for the CO2-diluted flame cases.

Non-buoyant diffusion flames with oscillatory air entrainment

1997 ◽  
Author(s):  
U. Hegde ◽  
D. Stocker ◽  
M. Bahadori ◽  
D. Stocker ◽  
M. Bahadori ◽  
...  
Keyword(s):  
Diffusion Flames ◽  
Air Entrainment ◽  
Buoyant Diffusion Flames

Synthesis of YFeO3-δ and LaFeO3-δ Perovskites with High Catalytic Activity in Carbon Oxidation Reactions

2021 ◽  
Vol 316 ◽  
pp. 105-109
Author(s):  
Evgeny A. Kirichenko ◽  
Pavel G. Chigrin ◽  
Anton A. Gnidenko
Keyword(s):  
Oxidation Mechanism ◽  
Soot Oxidation ◽  
Complex Oxide ◽  
Maximum Temperature ◽  
High Catalytic Activity ◽  
Carbon Oxidation ◽  
Oxidation Reactions ◽  
Oxide Systems ◽  
Reduction Of Metal Oxides ◽  
Catalytic Reaction Mechanism

YFeO3-δ (δ = 0.26) and LaFeO3-δ (δ = 0.5) perovskites with a high specific surface and oxygen non-stoichiometry was firstly synthesized by pyrolysis of polymer-salt compositions. It was shown that the catalytic oxidation of carbon in the presence of these complex oxide systems proceeds in the range of 400 - 700 °С, with a maximum temperature at 556 °С for YFeO3-δ; and 380 - 620 °С ,with a maximum temperature at 501 °С for LaFeO3-δ, in one-stage mode for both. By means of thermal analysis and diffractometry, it was shown that there is no contribution to the soot oxidation mechanism by cyclic perovskite surface transformations, due to the reduction of metal oxides by the soot and their subsequent reoxidation. It has been established that the basis of the catalytic reaction mechanism for both perovskites is the presence of oxygen vacancies on the surface of complex oxides.

A Numerical Simulation of Gas Jet Diffusion Flames Enveloped by a Cascade of Venturis

1999 ◽  
Author(s):  
Ala R. Qubbaj ◽  
S. R. Gollahalli
Keyword(s):  
Diffusion Flames ◽  
Co2 Concentration ◽  
Reaction Model ◽  
Numerical Results ◽  
Pollutant Emissions ◽  
Gas Jet ◽  
University Of Oklahoma ◽  
Burner Exit ◽  
Baseline Case ◽  
O2 Concentration

Abstract “Venturi-cascading” technique has been developed in the Combustion Laboratory at the University of Oklahoma. The goal was to control the pollutant emissions of diffusion flames by modifying the air infusion rate into the flame. The modification was achieved by installing a cascade of venturis around the burning gas jet. The basic idea behind this technique is controlling the stoichiometry of the flame through changing the flow dynamics and rates of mixing in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The thermal and composition fields of the baseline and venturi-cascaded flames were numerically simulated using CFD-ACE+, an advanced computational environment software package. The instantaneous chemistry model was used as the reaction model. The concentration of NO was determined through CFD-POST, a post processing utility program for CFD-ACE+. The numerical results showed that, in the near-burner, mid-flame and far-burner regions, the venturi-cascaded flame had lower temperature by an average of 13%, 19% and 17%, respectively, and lower CO2 concentration by 35%, 37%. and 32%, respectively, than the baseline flame. An opposite trend was noticed for O2 concentration; the cascaded flame has higher O2 concentration by 7%, 26% and 44%, in average values, in the near-burner, mid-flame and far-burner regions, respectively, than in the baseline case. The results also showed that, in the near-burner, mid-flame, and far-burner regions, the venturi-cascaded flame has lower NO concentrations by 89%, 70% and 70%, in average values, respectively, compared to the baseline case. The simulated results were compared with the experimental data. Good agreement was found in the near-burner region. However, the agreement was poor in the downstream regions. The numerical results substantiate the conclusion, which was drawn in the experimental part of this study, that venturi-cascading is a feasible method for controlling the pollutant emissions of a burning gas jet. In addition, the numerical results were useful to interpret the experimental measurements and understand the thermo-chemical processes involved. The results showed that the prompt-NO mechanism plays an important role besides the conventional thermal-NO mechanism.

A Numerical Investigation on Mixing Characteristics of Natural Gas Jets With High-Pressure Injection

2021 ◽  
Author(s):  
Long Liu ◽  
Tianyang Dai ◽  
Qian Xiong ◽  
Yuehua Qian ◽  
Bo Liu
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Air Entrainment ◽  
Gas Jet ◽  
Swirl Ratio ◽  
Marine Engine ◽  
Low Speed ◽  
Pressure Injection ◽  
Mixing Characteristics ◽  
High Pressure Injection

Abstract With increasingly stringent emissions limitation of greenhouse gas and atmospheric pollutants for ship, the direct injection of natural gas on the cylinder head with high-pressure injection is an effective method to make a high power output and decrease harmful gas emissions in marine natural gas dual fuel engines. However, the effects on mixing characteristics of high-pressure natural gas underexpanded jet have not been fully understood. Especially, the injection pressure is up to 30 MPa with large injection quantity and critical surrounding gas conditions for the low-speed two-stroke marine engine. Therefore, this research is focused on the flow and mixing process of the natural gas jet with high-pressure injection under the in-cylinder conditions of low-speed two-stroke marine engine. The gas jet penetration, the distribution of velocity and density, the equivalence ratio and air entrainment have been analyzed under different nozzle hole diameters by numerical simulation. The effects of surrounding gas conditions including pressure, temperature and swirl ratio on air entrainment and equivalence ratio distribution were studied in detail. From the numerical simulation, it is found that the mixing characteristics of natural gas jet can be improved under in-cylinder conditions of higher ambient temperature and swirl ratio, which is relevant to the low-speed two-stroke marine engine.

Effect of crossflow on the air entrainment of propane jet diffusion flames and a modified Froude number

Fuel ◽  
2018 ◽  
Vol 233 ◽  
pp. 454-460 ◽  
Author(s):  
Jingwu Wang ◽  
Jun Fang ◽  
Jinfu Guan ◽  
Yongming Zhang ◽  
Jinhua Sun
Keyword(s):  
Froude Number ◽  
Diffusion Flames ◽  
Air Entrainment ◽  
Jet Diffusion Flames
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