scholarly journals Multiphase Flow Large-Eddy Simulation Study of the Fuel Split Effects on Combustion Instabilities in an Ultra-Low-NOx Annular Combustor

2015 ◽  
Vol 138 (6) ◽  
Author(s):  
M. Bauerheim ◽  
T. Jaravel ◽  
L. Esclapez ◽  
E. Riber ◽  
L. Y. M. Gicquel ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Multiphase Flow ◽  
Analytical Model ◽  
Vortex Shedding ◽  
Gaseous Fuel ◽  
Combustion Instabilities ◽  
Eddy Simulation ◽  
Flame Dynamics ◽  
Large Eddy ◽  
Annular Combustor

This paper describes the application of a coupled acoustic model/large-eddy simulation approach to assess the effect of fuel split on combustion instabilities in an industrial ultra-low-NOx annular combustor. Multiphase flow LES and an analytical model (analytical tool to analyze and control azimuthal modes in annular chambers (ATACAMAC)) to predict thermoacoustic modes are combined to reveal and compare two mechanisms leading to thermoacoustic instabilities: (1) a gaseous type in the multipoint zone (MPZ) where acoustics generates vortex shedding, which then wrinkle the flame front, and (2) a multiphase flow type in the pilot zone (PZ) where acoustics can modify the liquid fuel transport and the evaporation process leading to gaseous fuel oscillations. The aim of this paper is to investigate these mechanisms by changing the fuel split (from 5% to 20%, mainly affecting the PZ and mechanism 2) to assess which mechanism controls the flame dynamics. First, the eigenmodes of the annular chamber are investigated using an analytical model validated by 3D Helmholtz simulations. Then, multiphase flow LES are forced at the eigenfrequencies of the chamber for three different fuel split values. Key features of the flow and flame dynamics are investigated. Results show that acoustic forcing generates gaseous fuel oscillations in the PZ, which strongly depend on the fuel split parameter. However, the correlation between acoustics and the global (pilot + multipoint) heat release fluctuations highlights no dependency on the fuel split staging. It suggests that vortex shedding in the MPZ, almost not depending on the fuel split, is the main feature controlling the flame dynamics for this engine.

scholarly journals Multiphase Flow LES Study of the Fuel Split Effects on Combustion Instabilities in an Ultra Low-NOx Annular Combustor

2015 ◽  
Author(s):  
M. Bauerheim ◽  
T. Jaravel ◽  
L. Esclapez ◽  
E. Riber ◽  
L. Y. M. Gicquel ◽  
...  
Keyword(s):  
Multiphase Flow ◽  
Analytical Model ◽  
Vortex Shedding ◽  
Liquid Fuel ◽  
Gaseous Fuel ◽  
Combustion Instabilities ◽  
Thermoacoustic Instabilities ◽  
Flame Dynamics ◽  
Global Correlation ◽  
Annular Combustor

This paper describes the application of a coupled Acoustic model/LES approach to assess the effect of fuel split on combustion instabilities in an industrial ultra low-NOx annular combustor. Multiphase flow LES and an analytical model (ATACAMAC) to predict thermoacoustic modes are combined to reveal and compare two mechanisms leading to thermoacoustic instabilities: 1) a gaseous type in the multi-point zone where acoustics generates vortex shedding, wrinkling the flame front and 2) a multiphase flow type in the pilot zone where acoustics can modify the liquid fuel transport and the evaporation process leading to gaseous fuel oscillations. The aim of this paper is to investigate these mechanisms by changing the fuel split (from 5% to 20%, mainly affecting the pilot zone and mechanism 2) and therefore assess which mechanism controls the flame dynamics. First, the eigenmodes of the annular chamber are investigated using the analytical model and validated by 3D Helmholtz simulations. Then, multiphase flow LES are forced at the eigenfrequencies of the chamber for three different fuel split values. Key features of the flow and flame dynamics are investigated. Results show that acoustic forcing generates gaseous fuel oscillations which strongly depend on the fuel split parameter. However, the global correlation between heat release fluctuations and acoustics highlights no dependency on the fuel split staging. It suggests that vortex shedding in the multi-point zone, almost not depending on the fuel split here, is the main feature controlling the flame dynamics for this LEMCOTEC engine.

Mixed Acoustic-Entropy Combustion Instabilities in a Model Aeronautical Combustor: Large Eddy Simulation and Reduced Order Modeling

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Florent Lacombe ◽  
Yoann Méry
Keyword(s):  
Large Eddy Simulation ◽  
Diffusion Flame ◽  
Combustion Process ◽  
Premixed Flame ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Combustion Instabilities ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Large Eddy

This article focuses on combustion instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, and outlet nozzle), while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, and circular nozzle at the outlet). A large eddy simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, dynamic mode decomposition (DMD) is used to visualize, analyze, and model the complex phasing between different processes affecting the reacting zones. Using these data, a zero-dimensional (0D) modeling of the premixed flame and of the diffusion flame is proposed. These models provide an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.

Characterization of Confined Swirl Flows Using Large Eddy Simulations

2001 ◽  
Author(s):  
Jörg Schlüter ◽  
Thilo Schönfeld ◽  
Thierry Poinsot ◽  
Werner Krebs ◽  
Stefan Hoffmann
Keyword(s):  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Vortex Shedding ◽  
Swirling Flow ◽  
Vortical Structure ◽  
Swirl Flow ◽  
Eddy Simulation ◽  
Swirl Flows ◽  
Large Eddy ◽  
Combustion Systems

Since the flame of high intense low NOx gas turbine combustion systems is stabilized by swirl, the analysis of the swirl flow is very crucial to the design and optimization of such combustion systems. Although a huge amount of publications have been provided on this field just a few have used Large Eddy Simulation due to limits in computer resources. Using Large Eddy Simulation the large vortical structure of the flow is resolved leading to a much better insight of the flow features. Hence, in this paper the Large Eddy Simulation has been applied to investigate the non reacting confined swirling flow downstream of a gas turbine burner. A high accuracy of the prediction of the full three dimensional simulation could be pointed out by comparison of the computational results to measurements. Further the large vortical structure and the dynamic behavior of the flow has been analyzed. The formation of a precessing vortex core is visualized. Due to the precessing motion of the central recirculation zone an alternate vortex shedding at the edges of the burner nozzle is induced. From LES Strouhal numbers for the vortex shedding process are calculated which are confirmed by hot wire measurements.

Large eddy simulation of turbulent vertical wall fires supplied with gaseous fuel through porous burners

2016 ◽  
Vol 169 ◽  
pp. 194-208 ◽  
Author(s):  
Ning Ren ◽  
Yi Wang ◽  
Sébastien Vilfayeau ◽  
Arnaud Trouvé
Keyword(s):  
Large Eddy Simulation ◽  
Vertical Wall ◽  
Gaseous Fuel ◽  
Eddy Simulation ◽  
Large Eddy

Prediction of Premixed Flame Dynamics Using Large Eddy Simulation With Tabulated Chemistry and Eulerian Stochastic Fields

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Alexander Avdonin ◽  
Alireza Javareshkian ◽  
Wolfgang Polifke
Keyword(s):  
Large Eddy Simulation ◽  
Time Series Data ◽  
Series Data ◽  
Combustion Model ◽  
Stochastic Fields ◽  
Progress Variable ◽  
Eddy Simulation ◽  
Flame Dynamics ◽  
Tabulated Chemistry ◽  
Large Eddy

Abstract This paper demonstrates that a large Eddy simulation (LES) combustion model based on tabulated chemistry and Eulerian stochastic fields can successfully describe the flame dynamics of a premixed turbulent swirl flame. The combustion chemistry is tabulated from one-dimensional burner-stabilized flamelet computations in dependence on progress variable and enthalpy. The progress variable allows to efficiently include a detailed reaction scheme, while the dependence on enthalpy describes the effect of heat losses on the reaction rate. The turbulence-chemistry interaction is modeled by eight Eulerian stochastic fields. An LES of a premixed swirl burner with a broadband velocity excitation is performed to investigate the flame dynamics, i.e., the response of heat release rate to upstream velocity perturbations. In particular, the flame impulse response and the flame transfer function (FTF) are identified from LES time series data. Simulation results for a range of power ratings are in good agreement with the experimental data.

scholarly journals Large-Eddy Simulation of Light-Round in an Annular Combustor With Liquid Spray Injection and Comparison With Experiments

2017 ◽  
Author(s):  
Théa Lancien ◽  
Kevin Prieur ◽  
Daniel Durox ◽  
Sébastien Candel ◽  
Ronan Vicquelin
Keyword(s):  
Large Eddy Simulation ◽  
Flame Propagation ◽  
High Speed ◽  
Complex Geometry ◽  
Numerical Study ◽  
Ignition Process ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Annular Combustor

A combined experimental and numerical study of light-round, defined as the flame propagation from burner to burner in an annular combustor, under perfectly premixed conditions has previously demonstrated the ability of large-eddy simulation (LES) to predict such ignition processes in a complex geometry using massively parallel computations. The present investigation aims at developing light-round simulations in a configuration closer to real applications by considering liquid n-heptane injection. The large-eddy simulation of the ignition sequence of a laboratory scale annular combustion chamber comprising sixteen swirled two-phase injectors is carried out with a mono-disperse Eulerian approach for the description of the liquid phase. The objective is to assess this modeling approach to describe the two-phase reactive flow during the ignition process. The simulation results are compared in terms of flame structure and light-round duration to the corresponding experimental images of the flame front recorded by a high-speed intensified CCD camera. The dynamics of the flow is also analyzed to identify and characterize mechanisms controlling flame propagation during the light-round process.

Mixed Acoustic-Entropy Combustion Instabilities in a Model Aeronautical Combustor: Large Eddy Simulation and Reduced Order Modeling

2017 ◽  
Author(s):  
Florent Lacombe ◽  
Yoann Mery
Keyword(s):  
Large Eddy Simulation ◽  
Diffusion Flame ◽  
Combustion Process ◽  
Premixed Flame ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Combustion Instabilities ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Large Eddy

This article focuses on Combustion Instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, outlet nozzle) while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, circular nozzle at the outlet). A Large Eddy Simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, Dynamic Mode Decomposition (DMD) is used to visualize, analyze and model the complex phasing between the different processes affecting the reacting zones. Using these data, a 0D modeling of the premixed flame and of the diffusion flame is proposed. These models provides an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.

Sign in / Sign up

Export Citation Format

Share Document