scholarly journals A Computational Study of Pressure Effects on Pollutants Generation in Gas Turbine Combustors

1995 ◽  
Author(s):  
E. M. Amin ◽  
G. E. Andrews ◽  
M. Pourkashnian ◽  
A. Williams ◽  
R. A. Yetter
Keyword(s):  
Gas Turbine ◽  
Mass Fraction ◽  
Soot Formation ◽  
Numerical Study ◽  
Computational Study ◽  
Mixture Fraction ◽  
Gaussian Function ◽  
Soot Oxidation ◽  
Major Effect ◽  
Pressure Effects

A numerical study of the effect of pressure on the formation of NOx and soot in an axisymmetric 30° counter rotating axial swirler lean low NOx gas turbine combustor has been conducted. This has previously been studied experimentally and this CFD investigation was undertaken to explain the higher than expected NOx emissions. The combustion conditions selected for the present study were 300 deg K inlet air, 0.4 overall equivalence ratio, and pressures of 1 and 10 bar. The numerical model used here involved the solution of time-averaged governing equations using an elliptic flow-field solver. The turbulence was modelled using algebraic stress modelling (ASM), The Thermo-chemical model was based on the laminar flamelet formulation. The conserved scalar/assumed pdf approach was used to model the turbulence chemistry interaction. The study was for two pressure cases at 1 and 10 bar. The turbulence-chemistry interaction is closed by assumption of a Clipped Gaussian function form for the fluctuations in the mixture fraction. The kinetic calculations were done separately from the flowfield solver using an opposed laminar diffusion flame code of SANDIA. The temperature and species profiles were made available to the computations through look-up tables. The pollutants studied in this work were soot and NO for which three more additional transport equations are required namely; averaged soot mass fraction, averaged soot particle number density, and finally averaged NO mass fraction. Soot oxidation was modelled using molecular oxygen only and a strong influence of pressure was predicted. Pressure was shown to have a major effect on soot formation.

A Computational Study of Pressure Effects on Pollutant Generation in Gas Turbine Combustors

1997 ◽  
Vol 119 (1) ◽  
pp. 76-83 ◽  
Author(s):  
E. M. Amin ◽  
G. E. Andrews ◽  
M. Pourkashnian ◽  
A. Williams ◽  
R. A. Yetter
Keyword(s):  
Gas Turbine ◽  
Mass Fraction ◽  
Soot Formation ◽  
Laminar Flame ◽  
Numerical Study ◽  
Computational Study ◽  
Mixture Fraction ◽  
Gaussian Function ◽  
Soot Oxidation ◽  
Pressure Effects

A numerical study of the effect of pressure on the formation of NOx and soot in an axisymmetric 30 deg counterrotating axial swirler lean low-NOx gas turbine combustor has been conducted. This has previously been studied experimentally and this CFD investigation was undertaken to explain the higher than expected NOx emissions. The combustion conditions selected for the present study were 300 K inlet air, 0.4 overall equivalence ratio, and pressures of 1 and 10 bar. The numerical model used here involved the solution of time-averaged governing equations using an elliptic flow-field solver. The turbulence was modeled using algebraic stress modeling (ASM). The thermochemical model was based on the laminar flame let formulation. The conserved scalar/assumed pdf approach was used to model the turbulence chemistry interaction. The study was for two pressure cases at 1 and 10 bar. The turbulence–chemistry interaction is closed by assumption of a clipped Gaussian function form for the fluctuations in the mixture fraction. The kinetic calculations were done separately from the flowfield solver using an opposed laminar diffusion flame code of SANDIA. The temperature and species profiles were made available to the computations through look-up tables. The pollutants studied in this work were soot and NO for which three more additional transport equations are required, namely: averaged soot mass fraction, averaged soot particle number density, and finally averaged NO mass fraction. Soot oxidation was modeled using molecular oxygen only and a strong influence of pressure was predicted. Pressure was shown to have a major effect on soot formation.

PAHs and Soot Emissions in Oxygenated Ethylene Diffusion Flames at Elevated Pressures

2018 ◽  
Author(s):  
Krishna C. Kalvakala ◽  
Suresh K. Aggarwal
Keyword(s):  
Diffusion Flames ◽  
Soot Formation ◽  
Computational Study ◽  
Mixture Fraction ◽  
Flame Temperature ◽  
Primary Objective ◽  
Soot Emission ◽  
Elevated Pressures ◽  
Polycyclic Aromatic ◽  
Soot Emissions

Operating combustion systems at elevated pressures has the advantage of improved thermal efficiency and system compactness. However, it also leads to increased soot emission. We report herein a computational study to characterize the effect of oxygenation on PAHs (Polycyclic Aromatic Hydrocarbons) and soot emissions in ethylene diffusion flames at pressures 1–8atm. Laminar oxygenated flames are established in a counterflow configuration by using N2 diluted fuel stream along with O2 enriched oxidizer stream such that the stoichiometric mixture fraction (ζst) is varied, but the adiabatic flame temperature is not materially changed. Simulations are performed using a validated fuel chemistry model and a detailed soot model. The primary objective of the study was to expand the fundamental understanding of PAH and soot formation in oxygenated flames at elevated pressures. At a given pressure, as the level of oxygenation (ζst) is increased, we observe a significant reduction in PAHs (benzene and pyrene) and consequently in soot formation. Further, at a fixed ζst, as pressure is increased, it leads to increased benzene and pyrene formation, and thus increased soot emission. The reaction path analysis indicates that this can be attributed to the fact that at higher pressures, the C2/C4 path becomes more significant for benzene formation compared to the propargyl recombination path.

scholarly journals A computational study of soot formation and flame structure of coflow laminar methane/air diffusion flames under microgravity and normal gravity

2021 ◽  
Author(s):  
Armin Veshkini ◽  
Seth B. Dworkin
Keyword(s):  
Normal Gravity ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Computational Study ◽  
Flame Structure ◽  
Chemical Kinetic ◽  
Surface Growth ◽  
Rate Of Increase

A numerical study is conducted of methane-air coflow diffusion flames at microgravity (μg) and normal gravity (lg), and comparisons are made with experimental data in the literature. The model employed uses a detailed gas phase chemical kinetic mechanism that includes PAH formation and growth, and is coupled to a sectional soot particle dynamics model. The model is able to accurately predict the trends observed experimentally with reduction of gravity without any tuning of the model for different flames. The microgravity sooting flames were found to have lower temperatures and higher volume fraction than their normal gravity counterparts. In the absence of gravity, the flame radii increase due to elimination of buoyance forces and reduction of flow velocity, which is consistent with experimental observations. Soot formation along the wings is seen to be surface growth dominated, while PAH condensation plays a more major role on centerline soot formation. Surface growth and PAH growth increase in microgravity primarily due to increases in the residence time inside the flame. The rate of increase of surface growth is more significant compared to PAH growth, which causes soot distribution to shift from the centerline of the flame to the wings in microgravity. Keywords: laminar diffusion flame,methane-air,microgravity, soot formation, numerical modelling

scholarly journals Numerical Analysis of Turbulent Combustion in a Model Swirl Gas Turbine Combustor

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Ali Cemal Benim ◽  
Sohail Iqbal ◽  
Franz Joos ◽  
Alexander Wiedermann
Keyword(s):  
Experimental Data ◽  
Natural Gas ◽  
Gas Turbine ◽  
Turbulence Model ◽  
Flue Gas ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Gas Turbine Combustor ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

Turbulent reacting flows in a generic swirl gas turbine combustor are investigated numerically. Turbulence is modelled by a URANS formulation in combination with the SST turbulence model, as the basic modelling approach. For comparison, URANS is applied also in combination with the RSM turbulence model to one of the investigated cases. For this case, LES is also used for turbulence modelling. For modelling turbulence-chemistry interaction, a laminar flamelet model is used, which is based on the mixture fraction and the reaction progress variable. This model is implemented in the open source CFD code OpenFOAM, which has been used as the basis for the present investigation. For validation purposes, predictions are compared with the measurements for a natural gas flame with external flue gas recirculation. A good agreement with the experimental data is observed. Subsequently, the numerical study is extended to syngas, for comparing its combustion behavior with that of natural gas. Here, the analysis is carried out for cases without external flue gas recirculation. The computational model is observed to provide a fair prediction of the experimental data and predict the increased flashback propensity of syngas.

scholarly journals Soot Modeling in Gas Turbine Combustors

1997 ◽  
Author(s):  
Anil K. Tolpadi ◽  
Allen M. Danis ◽  
Hukam C. Mongia ◽  
R. Peter Lindstedt
Keyword(s):  
Gas Turbine ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Three Dimensional ◽  
Rate Coefficients ◽  
Combustion Model ◽  
Model Parameters ◽  
Production Term ◽  
Gas Turbine Combustors ◽  
Soot Model

A method is presented for predicting soot in gas turbine combustors. A soot formation/oxidation model due to Fairweather et al [1992] has been employed. This model has been implemented in the CONCERT code which is a fully elliptic three-dimensional (3-D) body-fitted computational fluid dynamics (CFD) code based on pressure correction techniques. The combustion model used here is based on an assumed probability density function (PDF) parameterized by the mean and variance of the mixture fraction and a β-PDF shape. In the soot modeling, two additional transport equations corresponding to the soot mass fraction and the soot number density are solved. As an initial validation, calculations were performed in a simple propane jet diffusion flame for which experimental soot concentration measurements along the centerline and along the radius at various axial downstream stations were available from the literature. Soot predictions were compared with measured data which showed reasonable agreement. Next, soot predictions were made in a 3-D model of a CF6-80LEC engine single annular combustor over a range of operating pressures and temperatures. Although the fuel in the combustor is Jet-A, the soot computations assumed propane to be the surrogate fuel. To account for this fuel change, the soot production term was increased by a factor of 10X. In addition, the oxidation term was increased by a factor of 4X to account for uncertainties in the assumed collision frequencies. The soot model was also tested against two other combustors, a CF6-80C and a CFM56-5B. Comparison of the predicted scot concentrations with measured smoke numbers showed fairly good correlation within the range of the soot model parameters studied. More work has to be performed to address several modeling issues including sensitivity to oxidation rate coefficients and scalar diffusion.

Numerical Study of Inlet Turbulators Effect on the Thermal Characteristics of a Jet Propulsion-Fueled Combustor and Its Hazardous Pollutants Emission

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Masoud Darbandi ◽  
Majid Ghafourizadeh
Keyword(s):  
Thermal Behavior ◽  
Soot Formation ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Transport Equations ◽  
Lookup Table ◽  
Chemical Mechanism ◽  
Jet Propulsion ◽  
Pollutants Emission ◽  
Polycyclic Aromatic

This work numerically studies the effects of inlet air and fuel turbulators on the thermal behavior of a combustor burning the jet propulsion (JP) (kerosene-surrogate) fuel and its resulting pollutants emission including the nanoparticulate soot aerosols and aromatic compounds. To model the soot formation, the method employs a semi-empirical two-equation model, in which the transport equations for soot mass fraction and soot number density are solved considering soot nanoparticles evolutionary process. The soot nucleation is described using the phenyl route in which the soot is formed from the polycyclic aromatic hydrocarbons. Incorporating a detailed chemical mechanism described by 200 species and 6907 elementary reactions, the flamelets and their lookup table library are precomputed and used in the context of steady laminar flamelet model (SLFM). Thus, the current finite-volume method solves the transport equations for the mean mixture fraction and its variance and considers the chemistry–turbulence interaction using the presumed-shape probability density functions (PDFs). To validate the utilized models, a benchmark combustor is first simulated, and the results are compared with the measurements. Second, the numerical method is used to investigate the effects of embedding different inflow turbulators on the resulting flame structure and the combustor pollutants emission. The chosen turbulators produce mild to severe turbulence intensity (TI) effects at the air and fuel inlets. Generally, the results of current study indicate that the use of suitable turbulators can considerably affect the thermal behavior of a JP-fueled combustor. Additionally, it also reduces the combustor polycyclic aromatic hydrocarbon (PAH) pollutants emission.

A computational study of soot formation and flame structure of coflow laminar methane/air diffusion flames under microgravity and normal gravity

2021 ◽  
Author(s):  
Armin Veshkini ◽  
Seth B. Dworkin
Keyword(s):  
Normal Gravity ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Computational Study ◽  
Flame Structure ◽  
Chemical Kinetic ◽  
Surface Growth ◽  
Rate Of Increase

A numerical study is conducted of methane-air coflow diffusion flames at microgravity (μg) and normal gravity (lg), and comparisons are made with experimental data in the literature. The model employed uses a detailed gas phase chemical kinetic mechanism that includes PAH formation and growth, and is coupled to a sectional soot particle dynamics model. The model is able to accurately predict the trends observed experimentally with reduction of gravity without any tuning of the model for different flames. The microgravity sooting flames were found to have lower temperatures and higher volume fraction than their normal gravity counterparts. In the absence of gravity, the flame radii increase due to elimination of buoyance forces and reduction of flow velocity, which is consistent with experimental observations. Soot formation along the wings is seen to be surface growth dominated, while PAH condensation plays a more major role on centerline soot formation. Surface growth and PAH growth increase in microgravity primarily due to increases in the residence time inside the flame. The rate of increase of surface growth is more significant compared to PAH growth, which causes soot distribution to shift from the centerline of the flame to the wings in microgravity. Keywords: laminar diffusion flame,methane-air,microgravity, soot formation, numerical modelling

scholarly journals A computational study of soot formation and flame structure of coflow laminar methane/air diffusion flames under microgravity and normal gravity

2021 ◽  
Author(s):  
Armin Veshkini ◽  
Seth B. Dworkin
Keyword(s):  
Normal Gravity ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Computational Study ◽  
Flame Structure ◽  
Chemical Kinetic ◽  
Surface Growth ◽  
Rate Of Increase

A numerical study is conducted of methane-air coflow diffusion flames at microgravity (μg) and normal gravity (lg), and comparisons are made with experimental data in the literature. The model employed uses a detailed gas phase chemical kinetic mechanism that includes PAH formation and growth, and is coupled to a sectional soot particle dynamics model. The model is able to accurately predict the trends observed experimentally with reduction of gravity without any tuning of the model for different flames. The microgravity sooting flames were found to have lower temperatures and higher volume fraction than their normal gravity counterparts. In the absence of gravity, the flame radii increase due to elimination of buoyance forces and reduction of flow velocity, which is consistent with experimental observations. Soot formation along the wings is seen to be surface growth dominated, while PAH condensation plays a more major role on centerline soot formation. Surface growth and PAH growth increase in microgravity primarily due to increases in the residence time inside the flame. The rate of increase of surface growth is more significant compared to PAH growth, which causes soot distribution to shift from the centerline of the flame to the wings in microgravity. Keywords: laminar diffusion flame,methane-air,microgravity, soot formation, numerical modelling

scholarly journals Numerical Investigation of Soot Formation in Turbulent Diffusion Flame With Strong Turbulence–Chemistry Interaction

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
B. Manedhar Reddy ◽  
Ashoke De ◽  
Rakesh Yadav
Keyword(s):  
Mass Fraction ◽  
Volume Fraction ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Soot Volume Fraction ◽  
Turbulent Diffusion Flame ◽  
Flamelet Model ◽  
Soot Mass ◽  
One Step ◽  
Gas Flame

The present work is aimed at examining the ability of different models in predicting soot formation in “Delft flame III,” which is a nonpremixed pilot stabilized natural gas flame. The turbulence–chemistry interactions are modeled using a steady laminar flamelet model (SLFM). One-step and two-step models are used to describe the formation, growth, and oxidation of soot particles. One-step is an empirical model which solves the soot mass fraction equation. The two-step models are semi-empirical models, where the soot formation is modeled by solving the governing transport equations for the soot mass fraction and normalized radical nuclei concentration. The effect of radiative heat transfer due to gas and soot particulates is included using P1 approximation. The absorption coefficient of the mixture is modeled using the weighted sum of gray gases model (WSGGM). The turbulence–chemistry interaction effects on soot formation are studied using a single-variable probability density function (PDF) in terms of a normalized temperature or mixture fraction. The results shown in this work clearly elucidate the effect of radiation and turbulence–chemistry interaction on soot formation. The soot volume fraction decreases with the introduction of radiation interactions, which is consistence with the theoretical predictions. It has also been observed in the current work that the soot volume fraction is sensitive to the variable used in the PDF to incorporate the turbulence interactions.

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