Development of a Multiphase Flamelet Generated Manifold for Spray Combustion Simulations

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Xu Zhang ◽  
Ran Yi ◽  
C. P. Chen
Keyword(s):  
Mixture Fraction ◽  
Diffusion Reaction ◽  
Spray Combustion ◽  
Interphase Heat Transfer ◽  
Similarity Reduction ◽  
Spray Flame ◽  
Flamelet Generated Manifold ◽  
Mass Fractions ◽  
Combustion Processes ◽  
Reaction Processes

Abstract In this study, a model flame of quasi-one-dimensional (1D) counterflow spray flame has been developed. The two-dimensional (2D) multiphase convection-diffusion-reaction equations have been simplified to one dimension using similarity reduction under the Eulerian framework. This model flame is able to directly account for nonadiabatic heat loss, preferential evaporation, as well as multiple combustion regimes present in realistic spray combustion processes. A spray flamelet library was generated based on the model flame. To retrieve data from the spray flamelet library, the enthalpy was used as an additional controlling variable to represent the interphase heat transfer, while the mixing and chemical reaction processes were mapped to the mixture fraction and the progress variable. The spray flamelet generated manifolds (SFGM) approach was validated against the results from the direct integration of finite rate chemistry as a benchmark. The SFGM approach was found to give a better performance in terms of predictions of temperature and species mass fractions.

Development of a Multi-Phase Flamelet Generated Manifold for Spray Combustion Simulations

2020 ◽  
Author(s):  
Xu Zhang ◽  
Ran Yi ◽  
C. P. Chen
Keyword(s):  
Mixture Fraction ◽  
Diffusion Reaction ◽  
Spray Combustion ◽  
Direct Integration ◽  
Interphase Heat Transfer ◽  
Similarity Reduction ◽  
Progress Variable ◽  
Flamelet Generated Manifold ◽  
Significant Difference ◽  
Mass Fractions

Abstract In this study, a model flame of quasi-1D counterflow spray flame has been developed. The two-dimensional multiphase convection-diffusion-reaction (CDR) equations have been simplified to one dimension using similarity reduction under the Eulerian framework. This model flame is able to directly account for non-adiabatic heat loss as well as multiple combustion regimes present in realistic spray combustion processes. A spray flamelet library was generated based on the model flame. To retrieve data from the spray flamelet library, the enthalpy was used as an additional controlling variable to represent the interphase heat transfer, while the mixing and chemical reaction processes were mapped to the mixture fraction and the progress variable. The spray-flamelet/progress-variable (SFPV) approach was validated against the results from the direct integration of finite-rate chemistry as a benchmark. The SFPV approach gave a better performance in terms of temperature predictions, while the conventional gas-phase flamelet/progress-variable (FPV) approach over-predicted by nearly 20%. In terms of species mass fractions, there was no significant difference between the two, both showing good agreements with the direct integration of chemistry (DIC) model.

The Application of Flamelet-Generated Manifold in the Modeling of Stratified Premixed Cooled Flames

2014 ◽  
Author(s):  
Andrea Donini ◽  
Robert J. M. Bastiaans ◽  
Jeroen A. van Oijen ◽  
L. Philip H. de Goey
Keyword(s):  
Heat Loss ◽  
Mixture Fraction ◽  
Control Variable ◽  
Full Detail ◽  
Detailed Chemistry ◽  
Air Inlet ◽  
Flamelet Generated Manifold ◽  
Partially Premixed ◽  
Cost Efficient ◽  
Combustion Processes

CFD predictions of flame position, stability and emissions are essential in order to obtain optimized combustor designs in a cost efficient way. However, the numerical modeling of practical combustion systems is a very challenging task. As a matter of fact, the use of detailed reaction mechanisms is necessary for such reliable predictions. Unfortunately, the modeling of the full detail of practical combustion equipment is currently prohibited by the limitations in computing power, given the large number of species and reactions involved. The Flamelet-Generated Manifold (FGM) method reduces these computational costs by several orders of magnitude without loosing too much accuracy. Hereby FGM enables the application of reliable chemistry mechanisms in CFD simulations of combustion processes. In the present paper a computational analysis of partially premixed non-adiabatic flames is presented. In this scope, chemistry is reduced by the use of the FGM method. In the FGM technique the progress of the flame is generally described by a few control variables. For each control variable a transport equation is solved during run-time. The flamelet system is computed in a pre-processing stage, and a manifold with all the information about combustion is stored in a tabulated form. This research applies the FGM chemistry reduction method to describe partially premixed flames in combination with heat loss, which is a relevant condition for stationary gas turbine combustors. In order to take this into account, in the present implementation the reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the local equivalence ratio effect on the reaction is represented by the mixture fraction. A series of test simulations is performed for a two dimensional geometry, characterized by a distinctive stratified methane/air inlet, and compared with detailed chemistry simulations. The results indicate that detailed simulations are reproduced in an excellent way with FGM.

Comparison of Temperature Fields and Emissions Predictions Using Both an FGM Combustion Model, With Detailed Chemistry, and a Simple Eddy Dissipation Combustion Model With Simple Global Chemistry

2017 ◽  
Author(s):  
Pierre Q. Gauthier
Keyword(s):  
Mixture Fraction ◽  
Temperature Fields ◽  
Combustion Model ◽  
Detailed Chemistry ◽  
Combustion Modeling ◽  
Flamelet Generated Manifold ◽  
Wide Range ◽  
Turbulence Effects ◽  
Air Chemistry ◽  
Dissipation Model

The detailed modeling of the turbulence-chemistry interactions occurring in industrial flames has always been the leading challenge in combustion Computational Fluid Dynamics (CFD). The wide range of flame types found in Industrial Gas Turbine Combustion systems has exacerbated these difficulties greatly, since the combustion modeling approach must be able to predict the flames behavior from regions of fast chemistry, where turbulence has no significant impact on the reactions, to regions where turbulence effects play a significant role within the flame. One of these combustion models, that is being used more and more in industry today, is the Flamelet Generated Manifold (FGM) model, in which the flame properties are parametrized and tabulated based on mixture fraction and flame progress variables. This paper compares the results obtained using an FGM model, with a GRI-3.0 methane-air chemistry mechanism, against the more traditional Industrial work-horse, Finite-Rate Eddy Dissipation Model (FREDM), with a global 2-step Westbrook and Dryer methane-air mechanism. Both models were used to predict the temperature distributions, as well as emissions (NOx and CO) for a conventional, non-premixed, Industrial RB211 combustion system. The object of this work is to: (i) identify any significant differences in the predictive capabilities of each model and (ii) discuss the strengths and weakness of both approaches.

A Generalized FGM Progress Variable Weight Optimization Using HEEDS

2017 ◽  
Author(s):  
Graham Goldin ◽  
Yongzhe Zhang
Keyword(s):  
Constant Pressure ◽  
Operating Conditions ◽  
Weighted Sum ◽  
Weight Optimization ◽  
Reaction Progress ◽  
Optimization Software ◽  
Progress Variable ◽  
Flamelet Generated Manifold ◽  
Variable Weight ◽  
Mass Fractions

The Flamelet Generated Manifold (FGM) model requires a reaction progress variable which is usually defined as a weighted sum of species mass fractions. This progress variable should increase monotonically as flamelet states progress from unburnt to chemical equilibrium. A favorable attribute of the progress variable is that the flamelet species should change gradually with the progress variable, which reduces sensitivity of these species to any predicted errors in the progress variable. Previous publications have presented optimization algorithms for specific flamelet operating conditions, including fuel and oxidizer compositions and temperatures, and pressures. This work applies the HEEDS optimization software to find optimal species weights for a range of fuels and operating conditions. The fuels included are methane, methane-hydrogen, n-dodecane and n-heptane, at fuel-oxidizer temperatures of 293K and 1000K, and pressures of 1 and 30 atmospheres. For manifolds modeled by constant pressure ignition reactors, the optimal progress variable weights using four species weights are {αCO2 = 1, αCO = 0.91, αH2O = 0.52, αH2 = 1}, and for eight species weights are {αCO2 = 1, αCO = 0.91, αH2O = 0.51, αH2 = 1, αC2H2 = 0.16, αOH = −0.66, αH = −0.38, αO = 0.4}.

Scaling spray combustion processes in marine low-speed diesel engines

Fuel ◽  
2019 ◽  
Vol 258 ◽  
pp. 116133 ◽  
Author(s):  
Xinyi Zhou ◽  
Tie Li ◽  
Yijie Wei ◽  
Sichen Wu
Keyword(s):  
Diesel Engines ◽  
Spray Combustion ◽  
Low Speed ◽  
Combustion Processes

Impact of Combustion Models on Emissions Predictions From a Piloted Methane-Air Diffusion Flame

2019 ◽  
Author(s):  
Chitralkumar V. Naik ◽  
Hossam Elasrag ◽  
Rakesh Yadav ◽  
Ahad Validi ◽  
Ellen Meeks
Keyword(s):  
Mixture Fraction ◽  
Flame Structure ◽  
Direct Integration ◽  
Finite Rate ◽  
Modeling Approaches ◽  
Combustion Models ◽  
Eddy Simulation ◽  
Flamelet Generated Manifold ◽  
Simulation Results ◽  
Detailed Kinetics

Abstract Combustion models can have a significant impact on flame simulations. While solving finite rate chemistry typically yields more accurate predictions, they depend significantly on the detailed kinetics mechanism used. To demonstrate the effect, Large Eddy Simulation (LES) of Sandia Flame D [1] has been performed using various combustion models. Four different detailed kinetics mechanisms have been considered. They include DRM mechanism with 22 species, GRI-mech 2.11 with 49 species, GRI-mech 3.0 with 53 species [2], and Model Fuel Library (MFL) mechanism with 29 species [3]. In addition to the mechanisms, two modeling approaches considered are direct integration of finite rate kinetics (FR) and Flamelet Generated Manifold (FGM). The performance is compared between combinations of the mechanisms and combustion-modeling approaches for prediction of the flame structure and pollutants, including NO and CO. The mesh contains about half a million hexahedral cells and LES statistics were collected over ten flow throughs. Advanced solvers including dynamic cell clustering using the Chemkin-CFD solver in Fluent have been used for faster simulation time. Based on comparison of simulation results to the measurements at various axial and radial positions, we find that the results using the FGM approach were comparable to those using direct integration of FR chemistry, except for NO. In general, the simulation results are in good agreement with the experiment in terms of aerodynamics, mixture fraction and temperature profiles. However, kinetics mechanisms were found to have the most pronounced effect on emissions predictions. NO was especially more sensitive to the kinetics mechanism. Both versions of the GRI-mech fell short in predicting emissions. Overall, the MFL mechanism was found to yield the closest match with the data for flame structure, CO, and NO.

Simulation of Pollutant Emissions in a Small-Sized Combustion Chamber With a Gas Fuel for Various Regime Modes

2019 ◽  
Author(s):  
Nikita I. Gurakov ◽  
Ivan A. Zubrilin ◽  
Ivan V. Chechet ◽  
Vladislav M. Anisimov ◽  
Sergey S. Matveev ◽  
...  
Keyword(s):  
Experimental Data ◽  
Combustion Chamber ◽  
Equivalence Ratio ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Combustion Products ◽  
Pollutant Emissions ◽  
Eddy Simulation ◽  
Flamelet Generated Manifold ◽  
Combustion Processes

Abstract The study shows the results of the emission simulation in a small-sized combustion chamber. The influence of temperature and equivalence ratio on CO and CxHy in the combustion chamber was investigated. Experiments and calculations were carried out for the following modes: temperature at the inlet of the combustion chamber Tinlet = 323 ... 523 K; equivalence ratio φ = 0.2 ... 0.33; normalized flow rate at the inlet of the combustion chamber λ = 0.1 ... 0.3. The simulation of combustion of natural gas was carried out. The studies were conducted using CFD software and experimental methods. Measurements of the combustion products composition were carried out by the method of sampling collection and subsequent chromatographic analysis. The flow and combustion processes were simulated in a three-dimensional steady formulation using the Reynolds-averaged Novier-Stokes equations (RANS) and in a transient formulation using the Large Eddy Simulation (LES) method. The combustion processes were simulated by Flamelet Generated Manifold model in conjunction with the probability density function method (PDF). In addition to the above methods, the method of the reactor network model (RNM) was used to simulate the emission. As a result, a comparison of the calculated and experimental data of concentrations values of combustion products and emissions indices averaged over the combustion chamber outlet was conducted. According to the results of the calculated-experimental study obtained: - the simulated concentrations values of the main combustion products such as CO2 and H2O qualitatively and quantitatively coincide with the experimental data (the discrepancy is less than 5%) for all three approaches — RANS, LES, RNM; - when modeling CO emissions, the discrepancy between the calculated emission indices obtained by the RANS and LES methods is greatly underestimated relative to the experimental data, whereas the values calculated by the RNM method deviate from the experiment by less than 10%; - mass concentration values of unburned hydrocarbons obtained by the RANS method are overestimated relative to the experimental values, while using the LES with RNM methods, the discrepancy does not exceed 10%.

Investigation of Flamelet Generated Manifold Reaction Source Term Closure Models Applied to an Industrial Gas Turbine

2019 ◽  
Author(s):  
George Mallouppas ◽  
Graham Goldin ◽  
Yongzhe Zhang ◽  
Piyush Thakre ◽  
Jim Rogerson
Keyword(s):  
Gas Turbine ◽  
Source Term ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed ◽  
Progress Variable ◽  
Flamelet Generated Manifold ◽  
Reactor Types ◽  
Industrial Gas Turbine

Abstract Three Flamelet Generated Manifold reaction source term closure options and two different reactor types are examined with Large Eddy Simulation of an industrial gas turbine combustor operating at 3 bar. This work presents the results for the SGT-100 Dry Low Emission (DLE) gas turbine provided by Siemens Industrial Turbomachinery Ltd. The related experimental study was performed at the German Aerospace Centre, DLR, Stuttgart, Germany. The FGM model approximates the thermo-chemistry in a turbulent flame as that in a simple 0D constant pressure ignition reactors and 1D strained opposed-flow premixed reactors, parametrized by mixture fraction, progress variable, enthalpy and pressure. The first objective of this work is to compare the flame shape and position predicted by these two FGM reactor types. The Kinetic Rate (KR) model, studied in this work, uses the chemical rate from the FGM with assumed shapes, which are a Beta function for mixture fraction and delta functions for reaction progress variable and enthalpy. Another model investigated is the Turbulent Flame-Speed Closure (TFC) model with Zimont turbulent flame speed, which propagates premixed flame fronts at specified turbulent flame speeds. The Thickened Flame Model (TFM), which artificially thickens the flame to sufficiently resolve the internal flame structure on the computational grid, is also explored. Therefore, a second objective of this paper is to compare KR, TFC and TFM with the available experimental data.

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