scholarly journals Influence of Pressure on Near Nozzle Flow Field and Soot Formation in Laminar Co-Flow Diffusion Flames

2021 ◽  
Author(s):  
A. Mansouria ◽  
N.A. Eaves ◽  
M.J. Thomson Thomson ◽  
S.B. Dworkin
Keyword(s):  
Flow Field ◽  
Diffusion Flame ◽  
Atmospheric Pressure ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Environmental Concern ◽  
Large Mass ◽  
Effect Of Pressure ◽  
Recirculation Zones ◽  
Fuel Tube

Soot formation from combustion devices, which tend to operate at high pressure, is a health and environmental concern, thus investigating the effect of pressure on soot formation is important. While most fundamental studies have utilized the coflow laminar diffusion flame configuration to study the effect of pressure on soot, there is a lack of investigations into the effect of pressure on the flow field of diffusion flames and the resultant influence on soot formation. A recent work has displayed that recirculation zones can form along the centreline of atmospheric pressure diffusion flames. This present work seeks to investigate whether these zones can form due to higher pressure as well, which has never been explored experimentally or numerically. The CoFlame code, which models co-flow laminar, sooting, diffusion flames, is validated for the prediction of recirculation zones using experimental flow field data for a set of atmospheric pressure flames. The code is subsequently utilized to model ethane-air diffusion flames from 2 to 33 atm. Above 10 atm, recirculation zones are predicted to form. The reason for the formation of the zones is determined to be due to increasing shear between the air and fuel steams, with the air stream having higher velocities in the vicinity of the fuel tube tip than the fuel stream. This increase in shear is shown to be the cause of the recirculation zones formed in previously investigated atmospheric flames as well. Finally, the recirculation zone is determined as a probable cause of the experimentally observed formation of a large mass of soot covering the entire fuel tube exit for an ethane diffusion flame at 36.5 atm. Previously, no adequate explanation for the formation of the large mass of soot existed.

scholarly journals Influence of Pressure on Near Nozzle Flow Field and Soot Formation in Laminar Co-Flow Diffusion Flames

2021 ◽  
Author(s):  
A. Mansouria ◽  
N.A. Eaves ◽  
M.J. Thomson Thomson ◽  
S.B. Dworkin
Keyword(s):  
Flow Field ◽  
Diffusion Flame ◽  
Atmospheric Pressure ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Environmental Concern ◽  
Large Mass ◽  
Effect Of Pressure ◽  
Recirculation Zones ◽  
Fuel Tube

Soot formation from combustion devices, which tend to operate at high pressure, is a health and environmental concern, thus investigating the effect of pressure on soot formation is important. While most fundamental studies have utilized the coflow laminar diffusion flame configuration to study the effect of pressure on soot, there is a lack of investigations into the effect of pressure on the flow field of diffusion flames and the resultant influence on soot formation. A recent work has displayed that recirculation zones can form along the centreline of atmospheric pressure diffusion flames. This present work seeks to investigate whether these zones can form due to higher pressure as well, which has never been explored experimentally or numerically. The CoFlame code, which models co-flow laminar, sooting, diffusion flames, is validated for the prediction of recirculation zones using experimental flow field data for a set of atmospheric pressure flames. The code is subsequently utilized to model ethane-air diffusion flames from 2 to 33 atm. Above 10 atm, recirculation zones are predicted to form. The reason for the formation of the zones is determined to be due to increasing shear between the air and fuel steams, with the air stream having higher velocities in the vicinity of the fuel tube tip than the fuel stream. This increase in shear is shown to be the cause of the recirculation zones formed in previously investigated atmospheric flames as well. Finally, the recirculation zone is determined as a probable cause of the experimentally observed formation of a large mass of soot covering the entire fuel tube exit for an ethane diffusion flame at 36.5 atm. Previously, no adequate explanation for the formation of the large mass of soot existed.

A Numerical Study of the Influence of Hydrogen Addition on Soot Formation in a Laminar Counterflow Ethylene/Oxygen/Nitrogen Diffusion Flame

2004 ◽  
Author(s):  
Hongsheng Guo ◽  
Fengshan Liu ◽  
Gregory J. Smallwood
Keyword(s):  
Diffusion Flame ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Soot Volume Fraction ◽  
Phase Reaction ◽  
Nitrogen Diffusion ◽  
Atom Concentration ◽  
Hydrogen Addition

The influence of hydrogen addition to the fuel on soot formation in an ethylene/oxygen/nitrogen diffusion flame was numerically studied by simulation of three counterflow laminar diffusion flames at atmosphere pressure. The fuel mixtures for the three flames are pure ethylene, ethylene/hydrogen and ethylene/helium, respectively, while the oxidant is a mixture of oxygen and nitrogen. A detailed gas phase reaction mechanism including species up to benzene and complex thermal and transport properties were used. The soot inception and surface growth rates were, respectively, calculated based on benzene and HACA (H-abstraction and C2H2-addition) mechanisms. The predicted results for the three flames were compared and analyzed. It is indicated that although the addition of either hydrogen or helium to the fuel can reduce the soot volume fraction, the addition of hydrogen is more efficient. While the addition of helium reduces soot formation only through dilution, the addition of hydrogen suppresses soot formation through both dilution and chemical reaction effects. This conclusion is qualitatively consistent with available experiments. The simulations revel that the chemically inhibiting effect is caused by the decrease of hydrogen atom concentration in soot formation region, due to the displacement of the primary reaction zone, when hydrogen is added to the fuel.

scholarly journals Influence of pressure on near nozzle flow field and soot formation in laminar co-flow diffusion flames

2018 ◽  
Vol 23 (3) ◽  
pp. 536-548 ◽  
Author(s):  
Amin Mansouri ◽  
Nick A. Eaves ◽  
Murray J. Thomson ◽  
Seth B. Dworkin
Keyword(s):  
Flow Field ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Nozzle Flow

Numerical simulation of soot formation in a turbulent diffusion flame: comparison among three soot formation models

2011 ◽  
Vol 226 (5) ◽  
pp. 1290-1301 ◽  
Author(s):  
R Sarlak ◽  
M Shams ◽  
R Ebrahimi
Keyword(s):  
Diffusion Flame ◽  
Turbulent Diffusion ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Radiation Heat Transfer ◽  
Soot Volume Fraction ◽  
Suitable Model ◽  
Turbulent Diffusion Flame ◽  
Turbulent Diffusion Flames

Combustion and soot formation in a turbulent diffusion flame are simulated. Chemistry of combustion is treated with a detailed reaction mechanism that employs 49 species and 277 reactions. Turbulence is taken into account via the corrected k–ε model. Radiation heat transfer from flame is modelled by the P-1 model. An empirical model proposed by Khan and Greeves and two semi-empirical models proposed by Tesner and Lindstedt are used to simulate the soot formation in the flame. Khan and Greeves model showed to underpredict the maximum soot volume fraction. Nevertheless, the main shortcoming of Khan and Greeves model which undermines the applicability of this model to prediction of soot formation in turbulent diffusion flames is the inability to locate the highly sooting regions of the flame properly. Tesner model underpredicts the soot formation significantly, although the predicted shapes of the soot profiles are in accordance with the experimental measurements. Lindstedt model performs well in predicting both the maximum soot formation and the soot profile shapes in the chamber. Therefore, Lindstedt model can be considered as the most suitable model for the prediction of soot formation in turbulent diffusion flames.

scholarly journals Influence of a Standing Wave Flow-Field on the Dynamics of a Spray Diffusion Flame

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 27
Author(s):  
J. Barry Greenberg ◽  
David Katoshevski
Keyword(s):  
Liquid Phase ◽  
Flow Field ◽  
Standing Wave ◽  
Diffusion Flame ◽  
Stokes Number ◽  
Flame Height ◽  
Wave Flow ◽  
Two Dimensional ◽  
Governing Equations ◽  
First Time

A theoretical investigation of the influence of a standing wave flow-field on the dynamics of a laminar two-dimensional spray diffusion flame is presented for the first time. The mathematical analysis permits mild slip between the droplets and their host surroundings. For the liquid phase, the use of a small Stokes number as the perturbation parameater enables a solution of the governing equations to be developed. Influence of the standing wave flow-field on droplet grouping is described by a specially constructed modification of the vaporization Damkohler number. Instantaneous flame front shapes are found via a solution for the usual Schwab–Zeldovitch parameter. Numerical results obtained from the analytical solution uncover the strong bearing that droplet grouping, induced by the standing wave flow-field, can have on flame height, shape, and type (over- or under-ventilated) and on the existence of multiple flame fronts.

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.

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