Analysis of Time-Signal of an Industrial Gas Turbine Combustor Under an Unstable Condition

2016 ◽  
Author(s):  
D. Lengani ◽  
P. Zunino ◽  
F. Romoli ◽  
E. Bertolotto ◽  
S. Rizzo
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Limit Cycle ◽  
Limit Cycle Oscillations ◽  
Unstable Condition ◽  
Gas Turbine Combustor ◽  
Time Space ◽  
Industrial Gas Turbine

This paper analyzes the time-signals of pressure sensors mounted in an industrial gas turbine combustor under an unstable condition. The present investigation is aimed at the discussion of the sudden increase in amplitude due to the limit-cycle oscillations and of its temporal evolution. To this purpose, different post-processing tools are described and adopted: i.e. wavelet transform, cross-correlations, time-space Fourier transform and proper orthogonal decomposition (POD). The properties of the wavelet transform are used in order to identify the time of occurrence and the frequency of the limit-cycle oscillations. They occur at the second harmonic of the natural frequency of the annular combustion chamber. The amplitude of the pressure fluctuations at this characteristic frequency increases to a critical value with very large amplitude in about 0.15s that corresponds to about 26 periods of the phenomenon. Within this period, the pressure signals from two neighboring burners have a quite large and increasing degree of correlation as it is observed from the cross-correlation of the signals. The time-space Fourier transform suggests that the instability couples with a natural mode of the combustion chamber. The azimuthal wave length of such mode is half of the combustion chamber circumference (this corresponds to an azimuthal mode 2). According to this findings, the POD is used to provide an identifier for the occurrence of the limit-cycle oscillations. In fact, POD is known to isolate the deterministic fluctuations based on an energy rank. Hence, the first POD mode isolates the effect of specific frequency forcing and its energy content is retained in the first POD eigenvalue which is used as identifier.

Thermoacoustic Limit Cycle Predictions of a Pressurised Longitudinal Industrial Gas Turbine Combustor

2018 ◽  
Author(s):  
Yu Xia ◽  
Davide Laera ◽  
Aimee S. Morgans ◽  
W. P. Jones ◽  
Jim W. Rogerson
Keyword(s):  
Stability Analysis ◽  
Gas Turbine ◽  
Limit Cycle ◽  
Absolute Pressure ◽  
Nonlinear Stability Analysis ◽  
Gas Turbine Combustor ◽  
Weakly Nonlinear ◽  
Velocity Amplitude ◽  
Industrial Gas Turbine ◽  
Low Order

This article presents numerical prediction of a thermoacoustic limit cycle in an industrial gas turbine combustor. The case corresponds to an experimental high pressure test rig equipped with the full-scale Siemens SGT-100 combustor operated at two mean pressure levels of 3 bar and 6 bar. The Flame Transfer Function (FTF) characterising the global unsteady response of the flame to velocity perturbations is obtained for both operating pressures by means of incompressible Large Eddy Simulations (LES). A linear stability analysis is then performed by coupling the FTFs with a wave-based low order thermoacoustic network solver. All the thermoacoustic modes predicted at 3 bar pressure are stable; whereas one of the modes at 6 bar is found to be unstable at a frequency of 231 Hz, which agrees with the experiments. A weakly nonlinear stability analysis is carried out by combining the Flame Describing Function (FDF) predicted by LES with the low order thermoacoustic network solver. The frequency, mode shape and velocity amplitude corresponding to the predicted limit cycle at 209 Hz are used to compute the absolute pressure fluctuation amplitude in the combustor. The numerically reconstructed amplitude is found to be reasonably close to the measured dynamics.

Self-Excited High-Frequency Transverse Limit-Cycle Oscillations and Associated Flame Dynamics in a Gas Turbine Reheat Combustor Experiment

2021 ◽  
Author(s):  
Jonathan McClure ◽  
Frederik M. Berger ◽  
Michael Bertsch ◽  
Bruno Schuermans ◽  
Thomas Sattelmayer
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Limit Cycle ◽  
High Frequency ◽  
Dynamic Pressure ◽  
High Amplitude ◽  
Limit Cycle Oscillations ◽  
Flame Dynamics ◽  
Auto Ignition

Abstract This paper presents the investigation of high-frequency thermoacoustic limit-cycle oscillations in a novel experimental gas turbine reheat combustor featuring both auto-ignition and propagation stabilised flame zones at atmospheric pressure. Dynamic pressure measurements at the faceplate of the reheat combustion chamber reveal high-amplitude periodic pressure pulsations at 3 kHz in the transverse direction of the rectangular cross-section combustion chamber. Further analysis of the acoustic signal shows that this is a thermoacoustically unstable condition undergoing limit-cycle oscillations. A sensitivity study is presented which indicates that these high-amplitude limit-cycle oscillations only occur under certain conditions: namely high power settings with propane addition to increase auto-ignition propensity. The spatially-resolved flame dynamics are then investigated using CH* chemiluminescence, phase-locked to the dynamic pressure, captured from all lateral sides of the reheat combustion chamber. This reveals strong heat release oscillations close to the chamber walls at the instability frequency, as well as axial movement of the flame tips in these regions and an overall transverse displacement of the flame. Both the heat release oscillations and the flame motion occur in phase with the acoustic mode. From these observations, likely thermoacoustic driving mechanisms which lead to the limit-cycle oscillations are inferred. In this case, the overall flame-acoustics interaction is assumed to be a superposition of several effects, with the observations suggesting strong influences from autoignition-pressure coupling as well as flame displacement and deformation due to the acoustic velocity field. These findings provide a foundation for the overall objective of developing predictive approaches to mitigate the impact of high-frequency thermoacoustic instabilities in future generations of gas turbines with sequential combustion systems.

Predicting Thermoacoustic Instability in an Industrial Gas Turbine Combustor: Combining a Low Order Network Model With Flame LES

2017 ◽  
Author(s):  
Y. Xia ◽  
A. S. Morgans ◽  
W. P. Jones ◽  
J. Rogerson ◽  
G. Bulat ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Acoustic Waves ◽  
Gas Turbine Combustor ◽  
Network Modelling ◽  
Weakly Nonlinear ◽  
Thermoacoustic Instability ◽  
Reduced Chemistry ◽  
Flame Describing Function ◽  
Industrial Gas Turbine ◽  
Low Order

The thermoacoustic modes of a full scale industrial gas turbine combustor have been predicted numerically. The predictive approach combines low order network modelling of the acoustic waves in a simplified geometry, with a weakly nonlinear flame describing function, obtained from incompressible large eddy simulations of the flame region under upstream forced velocity perturbations, incorporating reduced chemistry mechanisms. Two incompressible solvers, each employing different numbers of reduced chemistry mechanism steps, are used to simulate the turbulent reacting flowfield to predict the flame describing functions. The predictions differ slightly between reduced chemistry approximations, indicating the need for more involved chemistry. These are then incorporated into a low order thermoacoustic solver to predict thermoacoustic modes. For the combustor operating at two different pressures, most thermoacoustic modes are predicted to be stable, in agreement with the experiments. The predicted modal frequencies are in good agreement with the measurements, although some mismatches in the predicted modal growth rates and hence modal stabilities are observed. Overall, these findings lend confidence in this coupled approach for real industrial gas turbine combustors.

Towards the Multiobjective Optimisation of Gas Turbine Combustors

2006 ◽  
Author(s):  
S. G. Wyse ◽  
G. T. Parks ◽  
R. S. Cant
Keyword(s):  
Transfer Function ◽  
Tabu Search ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Design Space ◽  
Objective Functions ◽  
Multiobjective Optimisation ◽  
Gas Turbine Combustor ◽  
Linear Network ◽  
Good Design

Gas turbine combustor design entails multiple, and often contradictory, requirements for the designer to consider. Multiobjective optimisation on a low-fidelity linear-network-based code is suggested as a way of investigating the design space. The ability of the Tabu Search optimiser to minimise NOx and CO, as well as several acoustic objective functions, is investigated, and the resulting “good” design vectors presented. An analysis of the importance of the flame transfer function in the model is also given. The mass flow and the combustion chamber width and area are shown to be very important. The length of the plenum and the widths of the plenum exit and combustor exit also influence the design space.

Experimental Assessment of the Emissions Benefits of a Ceramic Gas Turbine Combustor

1996 ◽  
Author(s):  
K. O. Smith ◽  
A. Fahme
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Experimental Assessment ◽  
Industrial Gas Turbine ◽  
Combustor Liner

Three subscale, cylindrical combustors were rig tested on natural gas at typical industrial gas turbine operating conditions. The intent of the testing was to determine the effect of combustor liner cooling on NOx and CO emissions. In order of decreasing liner cooling, a metal louvre-cooled combustor, a metal effusion-cooled combustor, and a backside-cooled ceramic (CFCC) combustor were evaluated. The three combustors were tested using the same lean-premixed fuel injector. Testing showed that reduced liner cooling produced lower CO emissions as reaction quenching near the liner wall was reduced. A reduction in CO emissions allows a reoptimization of the combustor air flow distribution to yield lower NOx emissions.

Investigation on flame characteristics of industrial gas turbine combustor with different mixing uniformities

Fuel ◽  
2020 ◽  
Vol 259 ◽  
pp. 116297 ◽  
Author(s):  
Zhihao Zhang ◽  
Xiao Liu ◽  
Yaozhen Gong ◽  
Zhiming Li ◽  
Jialong Yang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbine Combustor ◽  
Industrial Gas Turbine
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