Simulation of the Ignition Process in an Annular Multiple-Injector Combustor and Comparison With Experiments

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Maxime Philip ◽  
Matthieu Boileau ◽  
Ronan Vicquelin ◽  
Thomas Schmitt ◽  
Daniel Durox ◽  
...  
Keyword(s):  
High Speed ◽  
Burning Velocity ◽  
Flame Structure ◽  
Combustion Model ◽  
Ignition Process ◽  
High Speed Imaging ◽  
Flamelet Model ◽  
Swirl Injectors ◽  
Eddy Simulation ◽  
Annular Combustor

Ignition is a problem of fundamental interest with critical practical implications. While there are many studies of ignition of single injector configurations, the transient ignition of a full annular combustor has not been extensively investigated, mainly because of the added geometrical complexity. The present investigation combines simulations and experiments on a complete annular combustor. The setup, developed at EMC2 (Energétique Moléculaire et Macroscopique Combustion) Laboratory (Mesa, AZ), features sixteen swirl injectors and quartz walls allowing direct visualization of the flame. High speed imaging is used to record the space time flame structure and study the dynamics of the light-round process. On the numerical side, massively parallel computations are carried out in the large eddy simulation (LES) framework using the filtered tabulated (F-TACLES) flamelet model. Comparisons are carried out at different instants during the light-round process between experimental data and results of calculations. It is found that the simulation results are in remarkable agreement with experiments provided that the thermal effects at the walls are considered. Further analysis indicate that the flame burning velocity and flame front geometry are close to those found in the experiment. This investigation confirms that the LES framework used for these calculations and the selected combustion model are adequate for such calculations but that further work is needed to show that ignition prediction can be used reliably over a range of operating parameters.

Simulation of the Ignition Process in an Annular Multiple-Injector Combustor and Comparison With Experiments

2014 ◽  
Author(s):  
Maxime Philip ◽  
Matthieu Boileau ◽  
Ronan Vicquelin ◽  
Thomas Schmitt ◽  
Daniel Durox ◽  
...  
Keyword(s):  
High Speed ◽  
Burning Velocity ◽  
Flame Structure ◽  
Combustion Model ◽  
Ignition Process ◽  
High Speed Imaging ◽  
Flamelet Model ◽  
Swirl Injectors ◽  
Geometrical Complexity ◽  
Annular Combustor

Ignition is a problem of fundamental interest with critical practical implications. While there are many studies of ignition of single injector configurations, the transient ignition of a full annular combustor has not been extensively investigated, mainly because of the added geometrical complexity. The present investigation combines simulations and experiments on a complete annular combustor. The setup, developed at EM2C laboratory, features sixteen swirl injectors and quartz walls allowing direct visualization of the flame. High speed imaging is used to record the space time flame structure and study the dynamics of the light-round process. On the numerical side, massively parallel computations are carried out in the LES framework using the Filtered Tabulated (F-TACLES) flamelet model. Comparisons are carried out at different instants during the light-round process between experimental data and results of calculations. It is found that the simulation results are in remarkable agreement with experiments provided that the thermal effects at the walls are considered. Further post-processings indicate that the flame burning velocity and flame front geometry are close to those found in the experiment. This analysis confirms that the LES framework used for these calculations and the selected combustion model are adequate for such calculations but that further work is needed to confirm that ignition prediction can be used reliably over a range of operating parameters.

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

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Théa Lancien ◽  
Kevin Prieur ◽  
Daniel Durox ◽  
Sébastien Candel ◽  
Ronan Vicquelin
Keyword(s):  
Large Eddy Simulation ◽  
High Speed ◽  
Flame Structure ◽  
Ignition Process ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Annular Combustor ◽  
Intensified Charge Coupled Device ◽  
Aero Engines

The light-round is defined as the process by which the flame initiated by an ignition spark propagates from burner to burner in an annular combustor, eventually leading to a stable combustion. Combining experiments and numerical simulation, it was recently demonstrated that under perfectly premixed conditions, this process could be suitably described by large eddy simulation (LES) using massively parallel computations. The present investigation aims at developing light-round simulations in a configuration that is closer to that found in aero-engines by considering liquid n-heptane injection. The LES of the ignition sequence of a laboratory scale annular combustion chamber comprising sixteen swirled spray injectors is carried out with a monodisperse Eulerian approach for the description of the liquid phase. The objective is to assess this modeling approach of 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 charge-coupled device camera and to the corresponding experimental delays. The dynamics of the flow is also analyzed to identify and characterize mechanisms controlling flame propagation during the light-round process.

Different Flame Patterns Linked With Swirling Injector Interactions in an Annular Combustor

2015 ◽  
Author(s):  
Daniel Durox ◽  
Kevin Prieur ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
High Speed ◽  
Light Emission ◽  
Burning Velocity ◽  
High Speed Imaging ◽  
Direct Observations ◽  
Annular Combustor ◽  
Expansion Angle ◽  
Combustion Region ◽  
Flame Region ◽  
Side Walls

It is known from cold flow experiments that linear arrays of injectors may feature different types of aerodynamic patterns (see for example ASME-GT2013-94280, ASME-GT2014-25094). There are however no indications on what can happen under hot fire conditions since most experiments have been carried out in the absence of reaction or in single injector configurations. It is now possible to investigate this issue by making use of a recently developed annular combustion chamber. This device designated as MICCA is equipped with multiple swirling injectors and its side walls are made of quartz providing full optical access to the flame region thus allowing detailed studies of the combustion region structure and dynamics. Experiments reported in this article rely on direct observations of the flame region through light emission imaging using two standard cameras and an intensified high speed CMOS camera. The data gathered indicate that interactions between successive injectors give rise to patterns of flames which exhibit an alternate geometry where one flame has a relatively low expansion angle while the next spreads sideways. This pattern is then repeated with a period which corresponds to twice the injector spacing. Such arrangements arise when the angle of the cup used as the end-piece of each injector exceeds a critical value. Effects of mass flow rate, equivalence ratio, and injector offset are also investigated. It is shown that the angle which defines the cup opening is the main control parameter. It is also found that when this angle exceeds a certain value and when the laminar burning velocity is fast enough, the flame pattern switches in an unsteady manner between two possible configurations. This unsteady behavior is characterized using high-speed imaging. It is finally shown that these alternating flame patterns lead to alternating heat release rate distributions and inhomogeneous heat transfer to the chamber walls featuring a helicoidal pattern.

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.

scholarly journals Ignition Probability and Lean Ignition Behaviour of a Swirled Premixed Bluff Body Stabilised Annular Combustor

2020 ◽  
Author(s):  
Roberto Ciardiello ◽  
Rohit S. Pathania ◽  
Patton M. Allison ◽  
Pedro M. de Oliveira ◽  
Epaminondas Mastorakos
Keyword(s):  
High Speed ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Ignition Process ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Flame Kernel ◽  
Annular Combustor ◽  
Initial Flame ◽  
Limiting Condition

Abstract An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess the ignition probability and to provide insights into the mechanisms of failure and of successful propagation. The experiments are done at conditions that are close to the lean blow-off limit (LBO) and hence the ignition is difficult and close to the limiting condition when ignition is not possible. Two configurations were employed, with 12 and 18 burners, the mixture velocity was varied between 10 and 30 m/s, and the equivalence ratio (ϕ) between 0.58 and 0.68. Ignition was initiated by a sequence of sparks (2 mm gap, 10 sparks of 10 ms each) and “ignition” is defined as successful ignition of the whole annular combustor. The mechanism of success and failure of the ignition process and the flame propagation patterns were investigated via high-speed imaging (10 kHz) of OH* chemiluminescence. The lean ignition limits were evaluated and compared to the lean blow-off limits, finding the 12-burner configuration is more stable than the 18-burner. It was found that failure is linked to the trapping of the initial flame kernel inside the inner recirculation zone (IRZ) of a single burner adjacent to the spark, followed by localised quenching on the bluff body probably due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner or for a flame pocket to be convected downstream in the chamber to grow and start propagating upwards. Finally, the ignition probability (Pign) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in Pign ∼ 0 for most conditions, while Pign increased moving the spark away from the bluff-body or placing it between two burners and peaked to Pign ∼ 1 when the spark was located downstream in the combustion chamber, where the velocities are lower and the turbulence less intense. The results provide information on the most favourable conditions for achieving ignition in a complex multi-burner geometry and could help the design and optimisation of realistic gas turbine combustors.

scholarly journals Flame and Spray Dynamics During the Light-Round Process in an Annular System Equipped With Multiple Swirl Spray Injectors

2018 ◽  
Author(s):  
Kevin Prieur ◽  
Daniel Durox ◽  
Guillaume Vignat ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
Flame Front ◽  
High Speed ◽  
Laser Sheet ◽  
Pressure Fluctuations ◽  
Flame Structure ◽  
Frame Rate ◽  
Ignition Process ◽  
Liquid Droplets ◽  
Spray Flames ◽  
Annular Combustor

The ignition process of an annular combustor can be divided in several steps that end with the light-round. This corresponds to the sequence from the ignition of the first injector to the merging of the two flame fronts spreading in the annular system. The present article focuses on this important step, where two arch-like flame branches propagate in the chamber. These two turbulent travelling flames, nearly perpendicular to the combustor backplane, successively ignite the injection units and finally collide head-on and merge. In the present study, light-round of spray flames fed by liquid n-heptane is investigated. A high-speed camera operating at a frame rate of 6000 Hz and equipped with a filter centered on CH* emission is positioned on the side of the annular combustor, at the chamber backplane level and records images of one half of the chamber annulus. Acoustic pressure fluctuations are recorded through waveguide microphones plugged on the chamber backplane and microphones flush mounted in the annular plenum. The behavior of one injector ignited by the passing flame front is examined. One finds that the swirling flame structure formed by each injection unit evolves in time and that the anchoring location changes just after the passage of the travelling flame and during a period of a few milliseconds. This behavior can eventually lead to a flashback of the flame in the injector with possible severe damages. This dynamical phenomenon is described in detail. The propagation of the arch-like flame branch is then investigated. Flame images are used to determine the direction and velocity of the flame front by making use of a PIV like processing. One may distinguish two regions for the flame propagation. One is near the backplane, moving in a purely azimuthal direction, while the other corresponds to the remaining flame motion in the azimuthal and axial directions due to the volumetric expansion of the burnt gases. Filtered light images give some indications on the complex flame structures and on the typical length scales characterizing the moving front. Information is also obtained on the dynamics of the spray by shining a continuous laser sheet passing through one injector central axis and recording the light scattered by the n-heptane spray of droplets. These images are used to determine the influence of the incoming flame front on the evaporating n-heptane liquid droplets. A major result is that the flame modifies the spray much before its leading point reaches the injector unit and that its passage through the spray drastically changes the local droplet concentration and thus the local mixture composition.

scholarly journals Ignition Probability and Lean Ignition Behaviour of a Swirled Premixed Bluff-Body Stabilised Annular Combustor

2020 ◽  
Author(s):  
Roberto Ciardiello ◽  
Rohit Pathania ◽  
Patton Allison ◽  
Pedro M. de Oliveira ◽  
Epaminondas Mastorakos
Keyword(s):  
High Speed ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Ignition Process ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Flame Kernel ◽  
Design And Optimization ◽  
Annular Combustor ◽  
Favorable Conditions

Abstract An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess ignition probability and provide insights into the mechanisms of failure and of successful flame propagation. Two configurations were employed, with 12 and 18 burners, mixture velocity was varied between 10 and 30 m/s, and equivalence ratio between 0.58 and 0.68. Ignition was initiated by a sequence of sparks and "ignition" is defined as successful ignition of the whole annular combustor. Mechanism of success and failure of the ignition process was investigated via high-speed imaging of OH*chemiluminescence. Lean ignition limits were evaluated and compared to the lean blow-off limits. It was found that failure is linked to the trapping of the flame kernel inside the inner recirculation zone (IRZ) of a single burner, followed by localised quenching on the bluff body due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner. Finally, the ignition probability(Pign) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in Pign~0 for most conditions, while Pign increased moving the spark away from the bluff body or placing it between two burners and peaked to Pign~1 when the spark was located downstream in the combustion chamber. The results provide information on the most favorable conditions for achieving ignition and could help design and optimization of realistic gas turbine combustors.

scholarly journals Flow Inhomogeneities in a Realistic Aeronautical Gas-Turbine Combustor: Formation, Evolution and Indirect Noise

2018 ◽  
Author(s):  
Andrea Giusti ◽  
Luca Magri ◽  
Marco Zedda
Keyword(s):  
Gas Turbines ◽  
Transfer Functions ◽  
Guide Vane ◽  
Flame Structure ◽  
Combustion Noise ◽  
Moment Closure ◽  
Combustion Model ◽  
Conditional Moment ◽  
Eddy Simulation ◽  
Nozzle Guide

Indirect noise generated by the acceleration of combustion inhomogeneities is an important aspect in the design of aeroengines because of its impact on the overall noise emitted by an aircraft and the possible contribution to combustion instabilities. In this study, a realistic rich-quench-lean combustor is numerically investigated, with the objective of quantitatively analyzing the formation and evolution of flow inhomogeneities and determine the level of indirect combustion noise in the nozzle guide vane (NGV). Both entropy and compositional noise are calculated in this work. A high-fidelity numerical simulation of the combustion chamber, based on the Large-Eddy Simulation (LES) approach with the Conditional Moment Closure (CMC) combustion model, is performed. The contributions of the different air streams to the formation of flow inhomogeneities are pinned down and separated with seven dedicated passive scalars. LES-CMC results are then used to determine the acoustic sources to feed an NGV aeroacoustic model, which outputs the noise generated by entropy and compositional inhomogeneities. Results show that non-negligible fluctuations of temperature and composition reach the combustor’s exit. Combustion inhomogeneities originate both from finite-rate chemistry effects and incomplete mixing. In particular, the role of mixing with dilution and liner air flows on the level of combustion inhomogeneities at the combustor’s exit is highlighted. The species that most contribute to indirect noise are identified and the transfer functions of a realistic NGV are computed. The noise level indicates that indirect noise generated by temperature fluctuations is larger that the indirect noise generated by compositional inhomogeneities, although the latter is not negligible and is expected to become louder in supersonic nozzles. It is also shown that relatively small fluctuations of the local flame structure can lead to significant variations of the nozzle transfer function, whose gain increases with the Mach number. This highlights the necessity of an on-line solution of the local flame structure, which is performed in this paper by CMC, for an accurate prediction of the level of compositional noise. This study opens new possibilities for the identification, separation and calculation of the sources of indirect combustion noise in realistic aeronautical gas turbines.

Observation on Solid Propellant Ignition Using High Speed Camera: The Effect of Hot Wire Position on the Combustion Flame Contour

2014 ◽  
Vol 71 (2) ◽  
Author(s):  
Wan Khairuddin Wan Ali ◽  
Ang Kiang Long ◽  
Mohammad Nazri Mohd. Jaafar
Keyword(s):  
Solid Propellant ◽  
High Speed ◽  
Flame Structure ◽  
Combustion Process ◽  
Ignition Process ◽  
High Speed Camera ◽  
Hot Wire ◽  
Composite Propellant ◽  
Burning Behavior ◽  
Insight Into

This paper reports on the discovery of unique flame structure of a composite propellant sample under hot wire ignition. The entire combustion process at atmospheric pressure condition was recorded using a high speed camera. Three hot wire orientations were chosen in this experiment for examining their effects on the propellant burning behavior. The results show that the wire orientations are crucial in propellant combustion process, as different flame patterns were observed when the hot wire orientation was altered. This paper provides an important insight into this specific ignition process that can be useful for researchers in the aerospace industry for better design and more realistic simulation results in ignition control.

scholarly journals Flow Inhomogeneities in a Realistic Aeronautical Gas-Turbine Combustor: Formation, Evolution, and Indirect Noise

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Andrea Giusti ◽  
Luca Magri ◽  
Marco Zedda
Keyword(s):  
Gas Turbines ◽  
Transfer Functions ◽  
Guide Vane ◽  
Flame Structure ◽  
Combustion Noise ◽  
Moment Closure ◽  
Combustion Model ◽  
Conditional Moment ◽  
Eddy Simulation ◽  
Aero Engines

Indirect noise generated by the acceleration of combustion inhomogeneities is an important aspect in the design of aero-engines because of its impact on the overall noise emitted by an aircraft and the possible contribution to combustion instabilities. In this study, a realistic rich-quench-lean (RQL) combustor is numerically investigated, with the objective of quantitatively analyzing the formation and evolution of flow inhomogeneities and determining the level of indirect combustion noise in the nozzle guide vane (NGV). Both entropy and compositional noise are calculated in this work. A high-fidelity numerical simulation of the combustion chamber, based on the large-eddy simulation (LES) approach with the conditional moment closure (CMC) combustion model, is performed. The contributions of the different air streams to the formation of flow inhomogeneities are pinned down and separated with seven dedicated passive scalars. LES-CMC results are then used to determine the acoustic sources to feed an NGV aeroacoustic model, which outputs the noise generated by entropy and compositional inhomogeneities. Results show that non-negligible fluctuations of temperature and composition reach the combustor's exit. Combustion inhomogeneities originate both from finite-rate chemistry effects and incomplete mixing. In particular, the role of mixing with dilution and liner air flows on the level of combustion inhomogeneities at the combustor's exit is highlighted. The species that most contribute to indirect noise are identified and the transfer functions of a realistic NGV are computed. The noise level indicates that indirect noise generated by temperature fluctuations is larger than the indirect noise generated by compositional inhomogeneities, although the latter is not negligible and is expected to become louder in supersonic nozzles. It is also shown that relatively small fluctuations of the local flame structure can lead to significant variations of the nozzle transfer function, whose gain increases with the Mach number. This highlights the necessity of an on-line solution of the local flame structure, which is performed in this paper by CMC, for an accurate prediction of the level of compositional noise. This study opens new possibilities for the identification, separation, and calculation of the sources of indirect combustion noise in realistic aeronautical gas turbines.

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