scholarly journals Inclusion of flame stretch and heat loss in LES combustion model

2019 ◽  
Author(s):  
Pier Carlo Nassini ◽  
Daniele Pampaloni ◽  
Antonio Andreini
Keyword(s):  
Heat Loss ◽  
Combustion Model ◽  
Flame Stretch

Impact of Flame Stretch and Heat Loss on Heat Release Distributions in Gas Turbine Combustors: Model Comparison and Validation

2016 ◽  
Author(s):  
Noah Klarmann ◽  
Thomas Sattelmayer ◽  
Weiqun Geng ◽  
Benjamin Timo Zoller ◽  
Fulvio Magni
Keyword(s):  
Experimental Data ◽  
Heat Loss ◽  
Model Comparison ◽  
Turbulent Flame ◽  
Combustion Process ◽  
Combustion Model ◽  
Qualitative Comparison ◽  
Combustion Models ◽  
Flamelet Generated Manifold ◽  
Flame Stretch

The work presented in this paper comprises the application of an extension for the Flamelet Generated Manifold model which allows to consider elevated flame stretch rates and heat loss. This approach does not require further table dimensions. Hence, the numerical overhead is negligible, preserving the industrial applicability. A validation is performed in which stretch and heat loss dependent distributions are obtained from the combustion model to compare them to experimental data from an atmospheric single burner test rig operating at lean conditions. The reaction mechanism is extended by OH*-kinetics which allows the comparison of numerical OH*-concentrations with experimentally obtained OH*-chemiluminescence. Improvement compared to the Flamelet Generated Manifold model without extension regarding the shape and position of the turbulent flame brush can be shown and are substantiated by the validation of species distributions which better fit the experimental in situ measurements when the extension is used. These improvements are mandatory to enable subsequent modeling of emissions or thermoacoustics where high accuracy is required. In addition to the validation, a qualitative comparison of further combustion models is performed in which the experimental data serve as a benchmark to evaluate the accuracy. Most combustion models typically simplify the combustion process as flame stretch or non-adiabatic effects are not captured. It turns out that the tested combustion models show improvement when stretch or heat loss is considered by model corrections. However, satisfactory results could only be achieved by considering both effects employing the extension for the Flamelet Generated Manifold model.

Modelling of Turbulent Premixed CH4/H2/Air Flames Including the Influence of Stretch and Heat Losses

2021 ◽  
Author(s):  
Halit Kutkan ◽  
Alberto Amato ◽  
Giovanni Campa ◽  
Giulio Ghirardo ◽  
Luis Tay Wo Chong Hilares ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heat Loss ◽  
Turbulent Combustion ◽  
Turbulent Flame ◽  
Heat Losses ◽  
Flame Stabilization ◽  
Combustion Model ◽  
Flame Stretch ◽  
Turbulent Combustion Model ◽  
Turbulent Premixed

Abstract This paper presents a RANS turbulent combustion model for CH4/H2/air mixtures which includes the effect of heat losses and flame stretch. This approach extends a previous model concept designed for methane/air mixtures and improves the prediction of flame stabilization when hydrogen is added to the fuel. Heat loss and stretch effects are modelled by tabulating the consumption speed of laminar counter flow flames in a fresh-to burnt configuration with detailed chemistry at various heat loss and flame stretch values. These computed values are then introduced in the turbulent combustion model by means of a turbulent flame speed expression which is derived as a function of flame stretch, heat loss and H2 addition. The model proposed in this paper is compared to existing models on experimental data of spherical expanding turbulent flame speeds. The performance of the model is further validated by comparing CFD predictions to experimental data of an atmospheric turbulent premixed bluff-body stabilized flame fed with CH4/H2/air mixtures ranging from pure methane to pure hydrogen.

Modelling of Turbulent Premixed CH4/H2/Air Flames Including the Influence of Stretch and Heat Losses

2021 ◽  
Author(s):  
Halit Kutkan ◽  
Alberto Amato ◽  
Giovanni Campa ◽  
Giulio Ghirardo ◽  
Luis Tay Wo Chong ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heat Loss ◽  
Turbulent Combustion ◽  
Turbulent Flame ◽  
Heat Losses ◽  
Flame Stabilization ◽  
Combustion Model ◽  
Flame Stretch ◽  
Turbulent Combustion Model ◽  
Turbulent Premixed

Abstract This paper presents a RANS turbulent combustion model for CH4/H2/air mixtures which includes the effect of heat losses and flame stretch. This approach extends a previous model concept designed for methane/air mixtures and improves the prediction of flame stabilization when hydrogen is added to the fuel. Heat loss and stretch effects are modelled by tabulating the consumption speed of laminar counter flow flames in a fresh-to-burnt configuration with detailed chemistry at various heat loss and flame stretch values. These computed values are then introduced in the turbulent combustion model by means of a turbulent flame speed expression which is derived as a function of flame stretch, heat loss and H2 addition. The model proposed in this paper is compared to existing models on experimental data of spherical expanding turbulent flame speeds. The performance of the model is further validated by comparing CFD predictions to experimental data of an atmospheric turbulent premixed bluff-body stabilized flame fed with CH4/H2/air mixtures ranging from pure methane to pure hydrogen.

scholarly journals Computational Modeling of Boundary Layer Flashback in a Swirling Stratified Flame Using a LES-Based Non-Adiabatic Tabulated Chemistry Approach

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 567
Author(s):  
Xudong Jiang ◽  
Yihao Tang ◽  
Zhaohui Liu ◽  
Venkat Raman
Keyword(s):  
Boundary Layer ◽  
Heat Loss ◽  
Boundary Layers ◽  
Gas Turbines ◽  
Predictive Accuracy ◽  
Safety Issue ◽  
Combustion Model ◽  
Tabulated Chemistry ◽  
Lean Fuel ◽  
Flame Flashback

When operating under lean fuel–air conditions, flame flashback is an operational safety issue in stationary gas turbines. In particular, with the increased use of hydrogen, the propagation of the flame through the boundary layers into the mixing section becomes feasible. Typically, these mixing regions are not designed to hold a high-temperature flame and can lead to catastrophic failure of the gas turbine. Flame flashback along the boundary layers is a competition between chemical reactions in a turbulent flow, where fuel and air are incompletely mixed, and heat loss to the wall that promotes flame quenching. The focus of this work is to develop a comprehensive simulation approach to model boundary layer flashback, accounting for fuel–air stratification and wall heat loss. A large eddy simulation (LES) based framework is used, along with a tabulation-based combustion model. Different approaches to tabulation and the effect of wall heat loss are studied. An experimental flashback configuration is used to understand the predictive accuracy of the models. It is shown that diffusion-flame-based tabulation methods are better suited due to the flashback occurring in relatively low-strain and lean fuel–air mixtures. Further, the flashback is promoted by the formation of features such as flame tongues, which induce negative velocity separated boundary layer flow that promotes upstream flame motion. The wall heat loss alters the strength of these separated flows, which in turn affects the flashback propensity. Comparisons with experimental data for both non-reacting cases that quantify fuel–air mixing and reacting flashback cases are used to demonstrate predictive accuracy.

scholarly journals Numerical Simulations of a Turbulent High-Pressure Premixed Cooled Jet Flame With the Flamelet Generated Manifolds Technique

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Andrea Donini ◽  
Robert J. M. Bastiaans ◽  
Jeroen A. van Oijen ◽  
L. Philip H. de Goey
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Heat Loss ◽  
Computational Effort ◽  
Navier Stokes ◽  
Combustion Model ◽  
Jet Flame ◽  
Progress Variable ◽  
Air Jet ◽  
Flamelet Generated Manifold

In the present paper, a computational analysis of a high pressure confined premixed turbulent methane/air jet flames with heat loss to the walls is presented. In this scope, chemistry is reduced by the use of the flamelet generated manifold (FGM) method and the fluid flow is modeled in an large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) context. The reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. A generic lab scale burner for methane high-pressure (5 bar) high-velocity (40 m/s at the inlet) preheated jet is adopted for the simulations, because of its gas-turbine relevant conditions. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort. Furthermore, the present analysis indicates that the physical and chemical processes controlling carbon monoxide (CO) emissions can be captured only by means of unsteady simulations.

Ultra Rich Combustion of Natural Gas to Syngas

2011 ◽  
Author(s):  
M. H. F. Woolderink ◽  
J. B. W. Kok
Keyword(s):  
Natural Gas ◽  
Heat Loss ◽  
Soot Formation ◽  
Thermal Engineering ◽  
Combustion Model ◽  
Gaseous Species ◽  
Radiative Heat Loss ◽  
Validation Data ◽  
Soot Particles ◽  
Oxidation Reactor

In this paper the turbulent rich combustion process of perfectly premixed natural gas and oxidizer to syngas is investigated. Also an overview is given of an ultra rich combustion setup that is present at the Laboratory of Thermal Engineering of the University of Twente. The numerical investigation of the process is carried out as follows. The gaseous chemistry is described by a reaction progress variable based combustion model with detailed chemistry. The soot formation is described by the processes of nucleation, surface growth, agglomeration and oxidation. Also radiative heat loss of the gases and the soot particles is taken into account. The numerical model predicts the flow field, gaseous species, temperature, heat loss and soot mass fraction and number of soot particles. The combination of radiation and soot formation models with the combustion model will give a complete picture of the processes in the partial oxidation reactor. The numerical results will be validated with measurements on a reactor operating at pressures from 1 to 6 bar and at equivalence ratios 2 to 4. The measurements are to be done by taking samples from the reactor which are subsequently analyzed with a gas chromatograph and a Scanning Mobility Particle Sizer. The planned experiments will give valuable validation data for the performance of combustion and soot formation models at ultra rich conditions that are not yet available in literature.

A Computational Study of H2/N2 Jet Diffusion Flame With Radiation Heat Loss

2004 ◽  
Author(s):  
M. A. Alim ◽  
W. Malalasekera
Keyword(s):  
Heat Loss ◽  
Diffusion Flame ◽  
Computational Study ◽  
Mixture Fraction ◽  
Beta Function ◽  
Flame Temperature ◽  
Chemical Species ◽  
Combustion Model ◽  
Radiation Heat ◽  
Radiation Heat Loss

In this work simulation of a turbulent H2/N2 jet diffusion flame with flamelet modeling has been presented. The favre averaged mixture fraction has been employed to model the combustion. Favre-averaged scalar quantities have been calculated from flamelet libraries by making use of a presumed Probability Density Function (PDF) method. To incorporate the effect of radiation heat transfer the combustion model has been extended using the concept of enthalpy defect. The predicted flame temperature profiles and chemical species concentrations with and without radiation heat loss are compared with experimental data. Predictions considering the radiation heat loss found to be in good agreement with temperature and chemical species measurements whereas the adiabatic model significantly overestimates temperatures in the downstream regions of flames where the significant heat loss occurs. This study shows that the combustion simulation using flamelet models considering radiation heat loss are effective for predicting the flow, temperature and chemical kinetics of H2/N2 jet diffusion flame. To account for fluctuations of mixture fraction, its distribution is presumed to have the shape of a beta-function.

Including Heat Loss and Quench Effects in Algebraic Models for Large Eddy Simulation of Premixed Combustion

2012 ◽  
Author(s):  
Roman Keppeler ◽  
Michael Pfitzner ◽  
Luis Tay Wo Chong ◽  
Thomas Komarek ◽  
Wolfgang Polifke
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Heat Loss ◽  
Combustion Model ◽  
Algebraic Models ◽  
Combustion Models ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Interaction ◽  
Swirl Flame

In technically relevant combustion devices, combustion can take place in the vicinity of walls which can significantly affect the reaction and the heat transfer. However, only few studies focus on modelling of flame-wall interaction (FWI) for algebraic combustion models and virtually none consider FWI for algebraic Large Eddy Simulation combustion models. In the present work heat loss models, as previously published in the literature, are employed to extend a LES algebraic combustion model. The performance of the FWI models is evaluated by simulations of a nonadiabatic swirl flame. The simulation results are compared with experimental data of velocity field and heat release. The extent of the quenching zone and heat loss effects are determined in the simulations and compared with data from direct numerical simulations. Comparison of simulation and experimental data shows a significant improvement when heat loss effects are incorporated. Also the characteristic Peclet numbers are correctly predicted by FWI models.

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