scholarly journals On the Flow Structure and Dynamics of Methane and Syngas Lean Flames in a Model Gas-Turbine Combustor

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8267
Author(s):  
Vladimir Dulin ◽  
Leonid Chikishev ◽  
Dmitriy Sharaborin ◽  
Aleksei Lobasov ◽  
Roman Tolstoguzov ◽  
...  
Keyword(s):  
Flame Front ◽  
Gas Turbine ◽  
Flow Structure ◽  
High Speed ◽  
Longitudinal Mode ◽  
Elevated Pressure ◽  
Transverse Instability ◽  
Flame Dynamics ◽  
Instability Modes ◽  
Lift Off

The present paper compares the flow structure and flame dynamics during combustion of methane and syngas in a model gas-turbine swirl burner. The burner is based on a design by Turbomeca. The fuel is supplied through injection holes between the swirler blades to provide well-premixed combustion, or fed as a central jet from the swirler’s centerbody to increase flame stability via a pilot flame. The measurements of flow structure and flame front are performed by using the stereo particle image velocimetry and OH planar laser-induced fluorescence methods. The measurements are performed for the atmospheric pressure without preheating and for 2 atm with the air preheated up to 500 K. The flow Reynolds numbers for the non-reacting flows at these two conditions are 1.5 × 103 and 1.0 × 103, respectively. The flame dynamics are analyzed based on a high-speed OH* chemiluminescence imaging. It is found that the flame dynamics at elevated conditions are related with frequent events of flame lift-off and global extinction, followed by re-ignition. The analysis of flow structure via the proper orthogonal decomposition reveals the presence of two different types of coherent flow fluctuations, namely, longitudinal and transverse instability modes. The same procedure is applied to the chemiluminescence images for visualization of bulk movement of the flame front and similar spatial structures are observed. Thus, the longitudinal and transverse instability modes are found in all cases, but for the syngas at the elevated pressure and temperature the longitudinal mode is related to strong thermoacoustic fluctuations. Therefore, the present study demonstrates that a lean syngas flame can become unstable at elevated pressure and temperature conditions due to a greater flame propagation speed, which results in periodic events of flame flash-back, extinction and re-ignition. The reported data is also useful for the validation of numerical simulation codes for syngas flames.

Synchronization During Multi-Mode Thermoacoustic Oscillations in a Liquid-Fueled Gas Turbine Combustor at Elevated Pressure

2019 ◽  
Author(s):  
Mitchell L. Passarelli ◽  
J. D. Maxim Cirtwill ◽  
Timothy Wabel ◽  
Adam M. Steinberg ◽  
A. J. Wickersham
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Heat Release Rate ◽  
Release Rate ◽  
High Speed ◽  
Elevated Pressure ◽  
Fuel Injector ◽  
Frequency Pulling ◽  
Industrial Gas Turbine ◽  
Thermoacoustic Oscillations

Abstract This paper analyzes intermittent self-excited thermoacoustic oscillations in which the pressure (P′) and heat release rate (q̇′) fluctuations are harmonically coupled. That is to say, P′ and q̇′ do not oscillate at the same frequencies, but rather at frequencies in integer ratios. Thus, this system represents a case dominated by nonlinear cross-mode coupling. The measurements were obtained in an optically-accessible combustor equipped with an industrial gas turbine fuel injector operating with liquid fuel under partially-premixed conditions at elevated pressure. High-speed chemiluminescence (CL) imaging of OH* was used as an indicator of the heat release rate. The data was processed using spectral proper orthogonal decomposition (SPOD) to isolate the dominant heat release and pressure modes. Synchronization theory was used to determine when the modes are coupled and how their interaction manifests in the measurements, particularly how it relates to the observed intermittency. The results show three distinct intervals of synchronized oscillation shared by all the mode pairs analyzed. The first interval exhibits the same characteristics as a pair of noisy, phase-locked self-oscillators, with phase-slipping and frequency-pulling. While the behaviour of the second interval differs among mode pairs, strong frequency-pulling is observed during the third interval for all pairs.

scholarly journals High-speed laser diagnostics for the study of flame dynamics in a lean premixed gas turbine model combustor

2010 ◽  
Vol 52 (3) ◽  
pp. 555-567 ◽  
Author(s):  
Isaac Boxx ◽  
Christoph M. Arndt ◽  
Campbell D. Carter ◽  
Wolfgang Meier
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Laser Diagnostics ◽  
Flame Dynamics ◽  
Lean Premixed ◽  
Turbine Model

scholarly journals Numerical Modeling of Gaseous Partially Premixed Low-Swirl Lifted Flame at Elevated Pressure

2020 ◽  
Author(s):  
Leonardo Langone ◽  
Julia Sedlmaier ◽  
Pier Carlo Nassini ◽  
Lorenzo Mazzei ◽  
Stefan Harth ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flame Front ◽  
Gas Turbine ◽  
Nozzle Exit ◽  
Numerical Results ◽  
Pollutant Emissions ◽  
Lifted Flame ◽  
Lifted Flames ◽  
Partially Premixed ◽  
Lift Off

Abstract Lifted flames have been investigated in the past years for their benefits in terms of NOx emissions reduction for gas turbine applications. In a lifted flame, the flame front stabilized on a position that is significantly detached from the nozzle exit, improving the premixing process before the reaction zone. The distance between the flame front and the nozzle exit is called lift-off height and it represents the main parameter that characterize this type of flame. In the present work, a partially premixed lifted flame employing air-methane mixture is investigated through numerical simulation. Indeed, even if lifted jet flames have been widely studied in the literature, there are only a few examples of lifted partially premixed flames. Nevertheless, this kind of flames assumes an important role considering the current gas turbine applications, since their benefits in terms of stability and low pollutant emissions. This study has been performed with LES calculations using a commercial software suite and the numerical results are compared with experimental data coming from a dedicated campaign held at Karlsruher Institute für Technologie (KIT) on a novel low-swirl injector nozzle. Quenching effects due to strain, curvature and heat loss have been introduced into the combustion model thanks to a correction of the source term in the progress variable equation within the FGM model. The comparison between numerical results and experimental data have been performed in terms of lift-off height and OH* chemiluminescence maps, showing the capability to properly predict the overall flow and to catch flame lift-off even if with an underpredicted height. This points out promising capability of the numerical model in the representation of lifted flames, allowing further investigations of the flame structure otherwise not available from experimental techniques.

Flame and Flow Dynamics of a Self-Excited, Standing Wave Circumferential Instability in a Model Annular Gas Turbine Combustor

2013 ◽  
Author(s):  
Jacqueline O’Connor ◽  
Nicholas A. Worth ◽  
James R. Dawson
Keyword(s):  
Gas Turbine ◽  
Standing Wave ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Ring Vortex ◽  
Oh Radicals ◽  
Similar Frequency ◽  
Flame Dynamics ◽  
Annular Combustor

Azimuthal instabilities are prevalent in annular gas turbine combustors; these instabilities have been observed in industrial systems and research combustors, and have been predicted in simulations. Recent experiments in a model annular combustor have resulted in self-excited, circumferential instability modes at a variety of operating conditions. The instability mode “drifts” between standing and spinning waves, both clockwise and counter-clockwise rotating, during the course of operation. In this study, we analyze the flame response to standing wave modes by comparing the flame dynamics in a self-excited annular combustor with the flame dynamics in a single nozzle, transverse forcing rig. In the model annular combustor, differences in flame fluctuation have been observed at the node and anti-node of the standing pressure wave. Flames at the pressure anti-node display symmetric fluctuations, while flames at the pressure node execute asymmetric, flapping motions. This flame motion has been measured using both OH* chemiluminescence and planar laser induced fluorescence of OH radicals. To better understand these flame dynamics, the time-resolved velocity fields from a transverse forcing experiment are presented, and show that such a configuration can capture the symmetric and asymmetric disturbance fields at similar frequency ranges. Using high-speed PIV in multiple planes of the flow, it has been found that symmetric ring vortex shedding is driven by pressure fluctuations at the pressure anti-node whereas helical vortex disturbances drive the asymmetric flame disturbances at pressure nodes. By comparing the results of these two experiments, we are able to more fully understand flame dynamics during self-excited combustion instability in annular combustion chambers.

Flow-Field and Flame Dynamics of a Gas Turbine Model Combustor During Transition Between Thermo-Acoustically Stable and Unstable States

2010 ◽  
Author(s):  
Christoph M. Arndt ◽  
Adam M. Steinberg ◽  
Isaac G. Boxx ◽  
Wolfgang Meier ◽  
Manfred Aigner ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Ambient Pressure ◽  
Optical Measurements ◽  
Unstable State ◽  
Quiet State ◽  
Flame Dynamics ◽  
Planar Laser ◽  
Component Velocity ◽  
Lift Off ◽  
Burner Nozzle

Laser-based and optical measurements of a gas turbine (GT) model combustor undergoing transitions between a thermo-acoustically stable and unstable state are presented. Planar laser-induced fluorescence of the OH radical, OH chemiluminescence and the planar three-component velocity field were simultaneously measured at a sustained repetition rate of 5 kHz. The combustor was operated with a lean, technically premixed CH4/air flame at ambient pressure that transitioned unpredictably between a thermo-acoustically unstable (‘noisy’) state and a state without pulsations (‘quiet’ state). The transition from the noisy to the quiet state was correlated with the lift-off of the flame from the burner nozzle and a subsequent stabilization of the flame above the nozzle. During the transition from the quiet to the noisy state, the flame reattached to the nozzle. It was observed that the transitions occurred consistently at a particular phase of the thermo-acoustic cycle. The axial velocity fields indicated that the reattachment of the flame was assisted by an increase of the backflow velocity in the inner recirculation zone.

Validation of a New Turbulent Flame Speed Facility for the Study of Gas Turbine Fuel Blends at Elevated Pressure

2019 ◽  
Author(s):  
Anibal Morones ◽  
Mattias A. Turner ◽  
Victor León ◽  
Kyle Ruehle ◽  
Eric L. Petersen
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Turbulent Flame ◽  
Elevated Pressure ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Turbulent Flame Speed ◽  
Fuel Blends ◽  
New Apparatus ◽  
Fundamental Insight

Abstract Turbulent combustion is a very active and challenging research topic of direct interest to the design and operation of gas turbine engines. A spherically expanding flame immersed in a turbulent field is one way to gain fundamental insight on the effect of turbulence on combustion. This kind of experiment is often conducted inside a fan-stirred flame bomb, preferably at conditions of high pressure, high temperature, and intense turbulence. A new fan-stirred flame bomb was designed and built to provide a device for conducting fundamental turbulent flame measurements at conditions of interest to gas turbine engines. A literature review on existing systems was used as guidance in the design of the turbulence-generation elements in the present rig. A few options of impellers were explored. The flow field produced by the chosen impeller was measured with Laser Doppler Velocimetry (LDV). A detailed exposition of the vessel engineering and construction are presented, including current activities that will extend the use of the facility for heated experiments up to at least 400 K. Before turbulent experiments were attempted, a validation of the rig accuracy and pressure worthiness was made. Finally, a demonstration of the new apparatus was made by testing a lean mixture of syngas. The experiment matrix using hydrogen and H2/CO mixtures included three levels of pressure (1, 5, and, 10 bar) and three levels of turbulence fluctuation rms (1.4, 2.8, and 5.5 m/s). Data based on the high-speed schlieren diagnostic are presented.

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