scholarly journals Mixture fraction, soot volume fraction, and velocity imaging in the soot-inception region of a turbulent non-premixed jet flame

2017 ◽  
Vol 36 (1) ◽  
pp. 899-907 ◽  
Author(s):  
Okjoo Park ◽  
Ross A. Burns ◽  
Oliver R.H. Buxton ◽  
Noel T. Clemens
Keyword(s):  
Volume Fraction ◽  
Mixture Fraction ◽  
Soot Volume Fraction ◽  
Jet Flame ◽  
Velocity Imaging

Analytical Formulation-Based Soot Modelling in Ethylene Laminar Jet Diffusion Flames

2021 ◽  
Author(s):  
Amit Makhija ◽  
Krishna Sesha Giri
Keyword(s):  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Soot Volume Fraction ◽  
Smoke Point ◽  
Computational Time ◽  
Detailed Model ◽  
Conservation Equations ◽  
Oxidation Rates

Abstract Soot volume fraction predictions through simulations carried out on OpenFOAM® are reported in diffusion flames with ethylene fuel. A single-step global reaction mechanism for gas-phase species with an infinitely fast chemistry assumption is employed. Traditionally soot formation includes inception, nucleation, agglomeration, growth, and oxidation processes, and the individual rates are solved to determine soot levels. However, in the present work, the detailed model is replaced with the soot formation and oxidation rates, defined as analytical functions of mixture fraction and temperature, where the net soot formation rate can be defined as the sum of individual soot formation and oxidation rates. The soot formation/oxidation rates are modelled as surface area-independent processes. The flame is modelled by solving conservation equations for continuity, momentum, total energy, and species mass fractions. Additionally, separate conservation equations are solved to compute the mixture fraction and soot mass fraction consisting of source terms that are identical and account for the mixture fraction consumption/production due to soot. As a consequence, computational time can be reduced drastically. This is a quantitative approach that gives the principal soot formation regions depending on the combination of local mixture fraction and temperature. The implemented model is based on the smoke point height, an empirical method to predict the sooting propensity based on fuel stoichiometry. The model predicts better soot volume fraction in buoyant diffusion flames. It was also observed that the optimal fuel constants to evaluate soot formation rates for different fuels change with fuel stoichiometry. However, soot oxidation strictly occurs in a particular region in the flame; hence, they are independent of fuel. The numerical results are compared with the experimental measurements, showing an excellent agreement for the velocity and temperature. Qualitative agreements are observed for the soot volume fraction predictions. A close agreement was obtained in smoke point prediction for the overventilated flame. An established theory through simulations was also observed, which states that the amount of soot production is proportional to the fuel flow rate. Further validations underscore the predictive capabilities. Model improvements are also reported with better predictions of soot volume fractions through modifications to the model constants based on mixture fraction range.

Prediction of Soot Formation Trends in Turbulent Kerosene-Air Diffusion Jet Flames With Elevated Operating Pressure

2017 ◽  
Author(s):  
Pravin Nakod ◽  
Saurabh Patwardhan ◽  
Ishan Verma ◽  
Stefano Orsino
Keyword(s):  
Environmental Protection Agency ◽  
Volume Fraction ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Soot Volume Fraction ◽  
Operating Pressure ◽  
Jet Flames ◽  
Emission Standard ◽  
Radial Profiles ◽  
Air Diffusion

Emission standard agencies are coming up with more stringent regulations on soot, given its adverse effect on human health. It is expected that Environmental Protection Agency (EPA) will soon place stricter regulations on allowed levels of the size of soot particles from aircraft jet engines. Since, aircraft engines operate at varying operating pressure, temperature and air-fuel ratios, soot fraction changes from condition to condition. Computation Fluid Dynamics (CFD) simulations are playing a key role in understanding the complex mechanism of soot formation and the factors affecting it. In the present work, soot formation prediction from numerical analyses for turbulent kerosene-air diffusion jet flames at five different operating pressures in the range of 1 atm. to 7 atm. is presented. The geometrical and test conditions are obtained from Young’s thesis [1]. Coupled combustion-soot simulations are performed for all the flames using steady diffusion flamelet model for combustion and Mass-Brookes-Hall 2-equation model for soot with a 2D axisymmetric mesh. Combustion-Soot coupling is required to consider the effect of soot-radiation interaction. Simulation results in the form of axial and radial profiles of temperature, mixture fraction and soot volume fraction are compared with the corresponding experimental measured profiles. The results for temperature and mixture fraction compare well with the experimental profiles. Predicted order of magnitude and the profiles of the soot volume fraction also compare well with the experimental results. The correct trend of increasing the peak soot volume fraction with increasing the operating pressure is also captured.

Impact of Soot Radiative Properties, Pressure and Soot Volume Fraction on Radiative Heat Transfer in Turbulent Sooty Flames

2020 ◽  
Author(s):  
Kevin Torres Monclard ◽  
Olivier Gicquel ◽  
Ronan Vicquelin
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Turbulent Flames ◽  
Radiative Properties ◽  
Jet Flame ◽  
Soot Particles

Abstract The effect of soot radiation modeling, pressure, and level of soot volume fraction are investigated in two ethylene-air turbulent flames: a jet flame at atmospheric pressure studied at Sandia, and a confined pressurized flame studied at DLR. Both cases have previously been computed with large-eddy simulations coupled with thermal radiation. The present study aims at determining and analyzing the thermal radiation field for different models from these numerical results. A Monte-Carlo solver based on the Emission Reciprocity Method is used to solve the radiative transfer equation with detailed gas and soot properties in both configurations. The participating gases properties are described by an accurate narrowband ck model. Emission, absorption, and scattering from soot particles are accounted for. Two formulations of the soot refractive index are considered: a constant value and a wavelength formulation dependency. This is combined with different models for soot radiative properties: gray, Rayleigh theory, Rayleigh-Debye-Gans theory for fractal aggregates. The effects of soot radiative scattering is often neglected since their contribution is expected to be small. This contribution is determined quantitatively in different scenarios, showing great sensitivity to the soot particles morphology. For the same soot volume fraction, scattering from larger aggregates is found to modify the radiative heat transfer noticeably. Such a finding outlines the need for detailed information on soot particles. Finally, the role of soot volume fraction and pressure on radiative interactions between both solid and gaseous phases is investigated.

scholarly journals Effects of Fuel Molecular Weight on Emissions in a Jet Flame and a Model Gas Turbine Combustor

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Anandkumar Makwana ◽  
Suresh Iyer ◽  
Milton Linevsky ◽  
Robert Santoro ◽  
Thomas Litzinger ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Volume Fraction ◽  
Soot Formation ◽  
Premixed Flames ◽  
Soot Volume Fraction ◽  
Spatial Development ◽  
Gas Turbine Combustor ◽  
Jet Flames ◽  
Jet Flame ◽  
Model Gas Turbine Combustor

The objective of this study is to understand the effects of fuel volatility on soot emissions. This effect is investigated in two experimental configurations: a jet flame and a model gas turbine combustor. The jet flame provides information about the effects of fuel on the spatial development of aromatics and soot in an axisymmetric, co-flow, laminar flame. The data from the model gas turbine combustor illustrate the effect of fuel volatility on net soot production under conditions similar to an actual engine at cruise. Two fuels with different boiling points are investigated: n-heptane/n-dodecane mixture and n-hexadecane/n-dodecane mixture. The jet flames are nonpremixed and rich premixed flames in order to have fuel conditions similar to those in the primary zone of an aircraft engine combustor. The results from the jet flames indicate that the peak soot volume fraction produced in the n-hexadecane fuel is slightly higher as compared to the n-heptane fuel for both nonpremixed and premixed flames. Comparison of aromatics and soot volume fraction in nonpremixed and premixed flames shows significant differences in the spatial development of aromatics and soot along the downstream direction. The results from the model combustor indicate that, within experiment uncertainty, the net soot production is similar in both n-heptane and n-hexadecane fuel mixtures. Finally, we draw conclusions about important processes for soot formation in gas turbine combustor and what can be learned from laboratory-scale flames.

Effects of Fuel Molecular Weight on Emissions in a Jet Flame and a Model Gas Turbine Combustor

2017 ◽  
Author(s):  
Anandkumar Makwana ◽  
Suresh Iyer ◽  
Milton Linevsky ◽  
Robert Santoro ◽  
Thomas Litzinger ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Volume Fraction ◽  
Premixed Flames ◽  
Soot Volume Fraction ◽  
Spatial Development ◽  
Inlet Temperature ◽  
Gas Turbine Combustor ◽  
Jet Flames ◽  
Jet Flame ◽  
Model Gas Turbine Combustor

The objective of this study is to understand the effects of fuel volatility on soot emissions. The effect of fuel volatility on soot is investigated in two experimental configurations: a jet flame and a model gas turbine combustor. The jet flame experiment provides information about the effects of fuel on the spatial development of aromatics and soot in an axisymmetric, co-flow, laminar flame at atmospheric pressure. The data from the model gas turbine combustor illustrate the effect of fuel volatility on net soot production under conditions similar to an actual engine at cruise, operated at 5 atm, an inlet temperature of 560 K, and an inlet global equivalence ratio of 0.9 to 1.8. Two fuels with different boiling points are investigated: n-heptane/n-dodecane mixture and n-hexadecane/n-dodecane mixture. The n-hexadecane has a boiling point of 287° C as compared to 216° C for n-dodecane and 98° C for n-heptane. The jet flames investigated are non-premixed and premixed flames (jet equivalence ratios of 24 and 6) in order to have fuel rich conditions similar to those in the primary zone of an aircraft engine combustor. The results from the jet flames indicate that the peak soot volume fraction produced in the n-hexadecane fuel is slightly higher as compared to the n-heptane fuel for both non-premixed and premixed flames. The comparison of aromatics and soot volume fraction in non-premixed and premixed flames shows significant differences in the spatial development of aromatics and soot along the downstream direction. The results from the model combustor indicate that, within experiment uncertainty, the net soot production is similar in both n-heptane and n-hexadecane fuel mixtures. In comparing the results from these two burner configurations, we draw conclusions about important processes for soot formation in gas turbine combustors and what can be learned from laboratory-scale flames.

Deconvolution of Temperature and Soot Volume Fraction in a Turbulent Ethylene Flame by Inverse Spectral Radiation Analysis

Volume 4 ◽  
2004 ◽  
Author(s):  
Yuan Zheng ◽  
Jay P. Gore
Keyword(s):  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Turbulent Flames ◽  
Gradient Algorithm ◽  
Spectral Radiation ◽  
Jet Flame ◽  
Ethylene Flame ◽  
Simultaneous Reconstruction ◽  
Local Mean ◽  
Good Agreement

We report a new non-intrusive diagnostics technique for the simultaneous reconstruction of temperature (T) and soot volume fraction (fv) profiles in axi-symmetric turbulent luminous flames. Line-of-sight spectral radiation intensities (Iλ) for one diametric and nine chord-like radiation paths from a representative horizontal plane of a turbulent ethylene jet flame were measured by a fast infrared array spectrometer. By inverse analysis of the measured mean Iλ at four wavelengths where continuum radiation from soot particles dominates, four local scalar statistics, including mean and root-mean-square (rms) of T and fv, were de-convoluted. Powell’s conjugate-gradient algorithm and Brent’s line minimization algorithm were adopted in solving the present four-variable inverse problem. The calculated mean Iλ matched the experimental data very well within a 3% difference in general. The reconstructed local mean/rms T and fv distributions were in reasonably good agreement with sampling data from similar turbulent flames.

Coupling LES with soot model for the study of soot volume fraction in a turbulent diffusion jet flames at various Reynolds number configurations

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohamed Ibrahim N.H. ◽  
M. Udayakumar ◽  
Sivan Suresh ◽  
Suvanjan Bhattacharyya ◽  
Mohsen Sharifpur
Keyword(s):  
Reynolds Number ◽  
Nucleation Rate ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Surface Oxidation ◽  
Surface Growth ◽  
Nitrogen Diffusion ◽  
Coagulation Rate ◽  
Content Type ◽  
Jet Flame

Purpose This study aims to investigate the insights of soot formation such as rate of soot coagulation, rate of soot nucleation, rate of soot surface growth and soot surface oxidation in ethylene/hydrogen/nitrogen diffusion jet flame at standard atmospheric conditions, which is very challenging to capture even with highly sophisticated measuring systems such as Laser Induced Incandescence and Planar laser-induced fluorescence. The study also aims to investigate the volume of soot in the flame using soot volume fraction and to understand the global correlation effect in the formation of soot in ethylene/hydrogen/nitrogen diffusion jet flame. Design/methodology/approach A large eddy simulation (LES) was performed using box filtered subgrid-scale tensor. A filtered and residual component of the governing equations such as continuity, momentum, energy and species are resolved and modeled, respectively. All the filtered and residual components are numerically solved using the ILU method by considering PISO pressure–velocity solver. All the hyperbolic flux uses the QUICK algorithm, and an elliptic flux uses SOU to evaluate face values. In all the cases, Courant–Friedrichs–Lewy (CFL) conditions are maintained unity. Findings The findings are as follows: soot volume fraction (SVF) as a function of a flame-normalized length for three different Reynolds number configurations (Re = 15,000, Re = 8,000 and Re = 5,000) using LES; soot gas phase and particulate phase insights such as rate of soot nucleation, rate of soot coagulation, rate of soot surface growth and soot surface oxidation for three different Reynolds number configurations (Re = 15,000, Re = 8,000 and Re = 5,000); and soot global correction using total soot volume in the flame volume as a function of Reynolds number and Froude number. Originality/value The originality of this study includes the following: coupling LES turbulent model with chemical equilibrium diffusion combustion conjunction with semi-empirical Brookes Moss Hall (BMH) soot model by choosing C6H6 as a soot precursor kinetic pathway; insights of soot formations such as rate of soot nucleation, soot coagulation rate, soot surface growth rate and soot oxidation rate for ethylene/hydrogen/nitrogen co-flow flame; and SVF and its insights study for three inlet fuel port configurations having the three different Reynolds number (Re = 15,000, Re = 8,000 and Re = 5,000).

Simultaneous planar measurements of temperature and soot volume fraction in a turbulent non-premixed jet flame

2015 ◽  
Vol 35 (2) ◽  
pp. 1931-1938 ◽  
Author(s):  
S.M. Mahmoud ◽  
G.J. Nathan ◽  
P.R. Medwell ◽  
B.B. Dally ◽  
Z.T. Alwahabi
Keyword(s):  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Jet Flame

The Effect of a Mini-Scale Flame-Holder on Nano-Particulate Soot Aerosol Formation and CO/CO2 Emissions From a Jet Fuel Combustion Chamber

2015 ◽  
Author(s):  
Masoud Darbandi ◽  
Majid Ghafourizadeh ◽  
Gerry E. Schneider
Keyword(s):  
Combustion Chamber ◽  
Mass Fraction ◽  
Volume Fraction ◽  
Mixture Fraction ◽  
Radiation Heat Transfer ◽  
Soot Volume Fraction ◽  
Transport Equations ◽  
Flame Holder ◽  
Soot Aerosol ◽  
Mass Fractions

A combustion chamber, burning gaseous kerosene, is simulated to investigate the effects of mini-scale flame-holder geometry and its position on the combustion performance and the resulting nano-particulate soot aerosol, carbon monoxide, and carbon dioxide pollutions. To model the complex process of soot nanoparticle formation including the nucleation, coagulation, surface growth, and oxidation, we use a two-equation soot model to solve the soot mass fraction and soot number density transport equations. Considering a detailed chemical kinetic consisting of 121 species and 2613 elementary reactions, we construct the required flamelets library, i.e. the lookup table, and apply the flamelet combustion model, which solves the transport equations of mixture fraction and its variance. We take into account the turbulence-chemistry interaction using the presumed-shape probability density functions PDFs. Applying the two-equation κ-ε turbulence model with round-jet corrections and suitable wall functions, the transport equations of turbulence kinetic energy and its dissipation rate are solved to close the turbulence closure problem. Since it is required to impose the effects of radiation for the most important radiating species, we include the radiation heat transfer of soot and gases assuming the optically-thin flame consideration. In this regard, the radiation heat transfer is determined locally and only affected by the emissions. We evaluate the achieved solutions through our developed method comparing with the data documented in an experimental test, i.e. a gaseous-kerosene/air turbulent nonpremixed flame. The comparisons are provided for the achieved flame structure, i.e., the experimental data reported on the distributions of mixture fraction, temperature, and soot volume fraction. Next, we consider a disk-type mini-scale flame-holder inside the combustion chamber to study its effects on the flow pattern of reacting flow and the distributions of temperature, soot volume fraction, soot particles diameter, CO, and CO2 mass fractions. Our results show that the mounted flame-holder would increase the inside temperature while reduce the temperature, soot volume fraction, CO, and CO2 mass fractions of the exhaust gases. We also study the geometry and position of mini-scale flame-holder numerically in terms of the average values of temperature, soot volume fraction, soot particles diameter, CO mass fraction, and CO2 mass fraction at the outlet of combustion chamber. Our results indicate that increasing the radius of flame holder would lead to a reduction in carbonaceous emissions, i.e. black carbon, CO, and CO2, and the temperature of exhaust gases. Evidently, a maximum temperature increase inside the combustion chamber would augment the combustion performance. We also show that mounting the flame holder at the lower positions above the fuel nozzle exit would lead to the same consequences. The present study provides good informative advices to the researchers who investigate pollution in aero-engine combustion chambers.

scholarly journals Temperature, Oxygen, and Soot-Volume-Fraction Measurements in a Turbulent C2H4-Fueled Jet Flame

2015 ◽  
Author(s):  
Sean P. Kearney ◽  
Daniel Robert Guildenbecher ◽  
Caroline Winters ◽  
Paul Abraham Farias ◽  
Thomas W. Grasser ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Jet Flame
Sign in / Sign up

Export Citation Format

Share Document