Laser-Based Investigations of Periodic Combustion Instabilities in a Gas Turbine Model Combustor

2005 ◽  
Vol 127 (3) ◽  
pp. 492-496 ◽  
Author(s):  
R. Giezendanner ◽  
P. Weigand ◽  
X. R. Duan ◽  
W. Meier ◽  
U. Meier ◽  
...  
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
Gas Turbine ◽  
Axial Velocity ◽  
Mixture Fraction ◽  
Oh Radicals ◽  
Driving Mechanism ◽  
Pulsation Period ◽  
Combustion Instabilities ◽  
Validation Data

The driving mechanism of pulsations in gas turbine combustors depends on a complex interaction between flow field, chemistry, heat release, and acoustics. Experimental data on all these factors are therefore required to obtain insight into the coupling mechanisms during a pulsation period. In order to develop a comprehensive experimental database to support a phenomenological understanding and to provide validation data for numerical simulation, a standard burner for optical investigations was established that exhibits strong self-excited oscillations. The burner was a swirl-stabilized nonpremixed model combustor designed for gas turbine applications and operated using methane as fuel at atmospheric pressure. It was mounted in a combustion chamber, which provides almost unobstructed optical access. The periodic combustion instabilities were studied by a variety of phase-resolved laser-based diagnostic techniques, locked to the frequency of the dominant pressure oscillation. Measurement techniques used were LDV for velocity measurements, planar laser-induced fluorescence for imaging of CH and OH radicals, and laser Raman scattering for the determination of the major species concentrations, temperature, and mixture fraction. The phase-resolved measurements revealed significant variations of all measured quantities in the vicinity of the nozzle exit, which trailed off quickly with increasing distance. A strong correlation of the heat release rate and axial velocity at the nozzle was observed, while the mean mixture fraction as well as the temperature in the periphery of the flame is phase shifted with respect to axial velocity oscillations. A qualitative interpretation of the experimental observations is given, which will help to form a better understanding of the interaction between flow field, mixing, heat release, and temperature in pulsating reacting flows, particularly when accompanied by corresponding CFD simulations that are currently underway.

Laser Based Investigations of Periodic Combustion Instabilities in a Gas Turbine Model Combustor

2004 ◽  
Author(s):  
R. Giezendanner ◽  
P. Weigand ◽  
X. R. Duan ◽  
W. Meier ◽  
U. Meier ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Heat Release ◽  
Gas Turbine ◽  
Axial Velocity ◽  
Mixture Fraction ◽  
Oh Radicals ◽  
Driving Mechanism ◽  
Pulsation Period ◽  
Combustion Instabilities

The driving mechanism of pulsations in gas turbine combustors depends on a complex interaction between flow field, chemistry, heat release, and acoustics. Experimental data on all these factors are therefore required to obtain insight into the coupling mechanisms during a pulsation period. In order to develop a comprehensive experimental data base to support a phenomenological understanding and to provide validation data for numerical simulation, a standard burner for optical investigations was established that exhibits strong self-excited oscillations. The burner was a swirl-stabilized non-premixed model combustor designed for gas turbine applications and operated using methane as fuel at atmospheric pressure. It was mounted in a combustion chamber which provides almost unobstructed optical access. The periodic combustion instabilities were studied by a variety of phase-resolved laser based diagnostic techniques, locked to the frequency of the dominant pressure oscillation. Measurement techniques used were LDV for velocity measurements, planar laser-induced fluorescence for imaging of CH and OH radicals, and laser Raman scattering for the determination of the major species concentrations, temperature, and mixture fraction. The phase-resolved measurements revealed significant variations of all measured quantities in the vicinity of the nozzle exit, which trailed off quickly with increasing distance. A strong correlation of heat release rate and axial velocity at the nozzle was observed, while the mean mixture fraction as well as the temperature in the periphery of the flame is phase-shifted with respect to axial velocity oscillations. A qualitative interpretation of the experimental observations is given, which will help to form a better understanding of the interaction between flow field, mixing, heat release, and temperature in pulsating reacting flows, particularly when accompanied by corresponding CFD simulations which are currently under way.

Numerical Characterisation of a Gas Turbine Model Combustor Applying Scale-Adaptive Simulation

2009 ◽  
Author(s):  
Axel Widenhorn ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Mixture Fraction ◽  
Thermal Power ◽  
Three Dimensional ◽  
Combustion Model ◽  
Reacting Flow ◽  
Adaptive Simulation ◽  
Power Load ◽  
Turbine Model

In this contribution the three-dimensional reacting turbulent flow field of a swirl-stabilized gas turbine model combustor is analyzed numerically. The investigated partially premixed and lifted CH4/air flame has a thermal power load of Pth = 35kW and a global equivalence ratio of φ = 0.65. To study the reacting flow field the Scale Adaptive Simulation (SAS) turbulence model in combination with the Eddy Dissipation/Finite Rate Chemistry combustion model was applied. The simulations were performed using the commercial CFD software package ANSYS CFX-11.0. The numerically achieved time-averaged values of the velocity components and their appropriate turbulent fluctuations (RMS) are in very good agreement with the experimental values (LDA). The same excellent results were found for other flow quantities like temperature and mixture fraction. Here, the corresponding time-averaged and the appropriate RMS profiles are compared to Raman measurements. Furthermore the instantaneous flow features are discussed. In accordance with the experiment the numerical simulation evidences the existence of a precessing vortex core (PVC). The PVC rotates with a frequency of 1596Hz. Moreover it is shown that in the upper part of the combustion chamber a tornado-like vortical structure is established.

Comparison of Equivalence Ratio Transients on Combustion Instability in Single-Nozzle and Multi-Nozzle Combustors

2018 ◽  
Author(s):  
Xiaoling Chen ◽  
Wyatt Culler ◽  
Stephen Peluso ◽  
Domenic Santavicca ◽  
Jacqueline O’Connor
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Heat Release Rate ◽  
Release Rate ◽  
Equivalence Ratio ◽  
Combustion Instability ◽  
Driving Mechanism ◽  
Gas Turbine Combustor ◽  
Rate Distribution ◽  
Ratio Change

Low-emissions gas turbine combustion, achieved through the use of lean, premixed fueling strategies, is susceptible to combustion instability. The driving mechanism for this instability arises from fluctuations of pressure, fuel/air flow rate, and heat release rate. If these fluctuations are relatively in-phase, the combustion system will evolve to a self-excited state. The self-excited instability frequency and amplitude depend mainly on the operating condition and the geometry of the combustor. In this study, we consider the onset and decay of self-excited instabilities, resulting from transients in fuel/air ratio, in both single-nozzle and multi-nozzle combustors. In particular, we examine the differences in the instability onset and decay processes between these two flame configurations, as most gas turbine combustors have multiple nozzles, but most gas turbine combustor experiments utilize a single-nozzle. A nonlinear logistic regression analysis is applied to study the timescales of the decay and onset transients. Variations in the equivalence ratio change the heat release rate distribution inside the combustor, which is captured using chemiluminescence imaging. The normalized Rayleigh index, which shows the spatial distribution of the instability driving, is calculated to analyze the driving strength in different regions of the flame. Comparisons between the single- and multi-nozzle flame transients, including both center and outer flames for the multi-nozzle combustor, suggest that both confinement from the wall and flame-flame interaction are crucial to determining flame dynamics as the equivalence ratio transient changes the heat release rate distribution near corner recirculation zone and flame shear layers.

Computational and Experimental Study of Enhanced Mixing in a Gas Turbine Combustor Using Guide Vanes

2013 ◽  
Author(s):  
Alka Gupta ◽  
Mohammed Saeed Ibrahim ◽  
Benjamin Wiegand ◽  
Ryoichi Amano
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Film Cooling ◽  
Mixture Fraction ◽  
Effective Means ◽  
Turbine Blades ◽  
Primary Flow ◽  
Guide Vanes ◽  
Exit Nozzle ◽  
Blade Failure

A number of studies have shown that the flow field exiting a combustor of a gas turbine cycle is highly non-uniform in pressure, velocity and, most importantly, temperature. Much research has been dedicated to the cooling of gas turbine blades using internal, film cooling, impingement jets, and pin/fin cooling technologies. Such designs allow for heated blades to be cooled from the inside out. While advancements in this type of blade cooling technology provide effective means to reduce the occurrence of blade failure due to material overheat conditions, the effect of externally reducing or eliminating the temperature non-uniformities in the exit flow from the combustor would assist in the solution. The goal of this study is to optimize the mixing of primary and dilution air in the dilution zone of the combustor using guide vanes. This improvement in mixing would lead to increase in the degree of temperature uniformity with respect to the radial position at the exit nozzle. To achieve this objective, both experimental and computational studies were performed to investigate the heat and flow behaviors with 45° spherically swept guide vanes attached to the dilution holes. These guide vanes were intended to direct the dilution jets into the primary flow and enhance mixing. A parameter was defined in terms of the temperatures of the dilution and primary flow streams at the inlet and the exit plane, called the mixture fraction. Based on the mixture fraction value, it was found that the guide vanes produce a more uniform exit temperature flow field as compared to the case when there were no guide vanes used. Also, the design was modified for different alignment orientations of the guide vanes — 0°, 30°, 60° and 90° with respect to the primary flow — with the 60° orientation fostering the best results.

Experimental and Numerical Analysis of FLOX®-Based Combustor for a 3kW Micro Gas Turbine Under Atmospheric Conditions

2017 ◽  
Author(s):  
Hannah Seliger ◽  
Michael Stöhr ◽  
Zhiyao Yin ◽  
Andreas Huber ◽  
Manfred Aigner
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
Gas Turbine ◽  
Stokes Equations ◽  
Numerical Study ◽  
Electrical Power ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Atmospheric Conditions ◽  
Micro Gas Turbine

This paper presents an experimental and numerical study of the flow field and heat release (HRL) zone of a six-nozzle FLOX®-based combustor at atmospheric pressure. The combustor is suitable for the use in a micro gas turbine (MGT) based combined heat and power (CHP) system with an electrical power output of 3 kW. The velocity field was measured using stereoscopic particle image velocimetry (PIV). The heat release zone was visualized by OH*-chemiluminescence (OH* CL) and the flame front by OH planar laser-induced fluorescence (OH PLIF). The results are compared with CFD simulations to evaluate the quality of the applied numerical turbulence and combustion models. The simulations were performed using Reynolds-averaged Navier-Stokes equations in combination with the k-ω-SST-turbulence model. Since the FLOX®-based combustion is dominated by chemical kinetics, a reaction mechanism with detailed chemistry, including 22 species and 104 reactions (DRM22), has been chosen. To cover the turbulence-chemistry interaction, an assumed probability density function (PDF) approach for species and temperature was used. Except for minor discrapancies in the flow field, the results show that the applied models are suitable for the design process of the combustor. In terms of the location of the heat release zone, it is necessary to consider possible heat losses, especially at lean operating conditions with a distributed heat release zone.

A Mutual Nearest Neighbours Based Chaotic Synchronization Index to Detect Thermo-Acoustic Coupling in Gas Turbine Combustion Instabilities

2016 ◽  
Author(s):  
S. Chiocchini ◽  
T. Pagliaroli ◽  
R. Camussi ◽  
E. Giacomazzi
Keyword(s):  
Heat Release ◽  
Frequency Domain ◽  
Gas Turbine ◽  
Coherence Function ◽  
Radiant Energy ◽  
Chaotic Synchronization ◽  
Nonlinear Behaviour ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Combustion Regimes

The characterization of unstable combustion regimes is often performed in the light of the Rayleigh Criterion, in the frequency domain, employing the Power Spectral Analysis of pressure (p′) and heat-release (q′) fluctuations. Equally often, it is assumed a priori that the thermo-acoustic oscillations are periodic, with a dominant frequency and a fixed amplitude (Period-1Llimit Cycle Oscillations). However one has to consider that: 1) p′ and q′, involved in the Rayleigh instability index, are governed by the Linearized Acoustic Energy Perturbation Balance Equations; 2) in the frequency domain any interdependence is measured by the coherence function, based on cross spectral densities, or Fourier spectra of cross-correlations, that in turn suppose a linear interdependence between sampled quantities. Conversely, recent experiments reveal that even simple thermo-acoustic systems exhibit nonlinear behaviour, far more elaborate than period-1 limit cycle oscillations. Therefore, in addition to the conventional linear analysis, a new approach based on Nonlinear Dynamics will be required to characterize the unstable regimes in lean gas-turbine combustors. With such approach, one may avoid the risk of misunderstanding the Deterministic Chaos, underlying in the measured signals also during stable combustion regimes, as stochastic noise. The preserved information will be thus available to analytically formulate an index acting as the earliest warning signal of an impending oscillatory combustion instability. In the light of this, we have applied the Interdependence Index E, based on chaotic synchronization theory, to pressure and radiant energy signals sampled from an industrial combustor. The index was found: 1) low computationally demanding, since based on quantities already calculated for the phase space reconstruction; 2) really effective in the early detection of self sustained (chaotic or not) thermo-acoustic oscillations; 3) valid for a range of coupling strength, and thus smoothly increasing at the instability onset, as requested by the control system time response; 4) unaffected by the non linear relationship between heat release an chemiluminescence, that may make invalid the pseudo-Rayleigh index, computed from pressure and radiant energy fluctuations; 5) asymmetric and thus able to identify the driven and driver (sub)systems, as in combustion instabilities with no thermo-acoustic feed-back.

Study of Combustion Instabilities Imposed by Inlet Velocity Disturbance in Combustor Using LES

2009 ◽  
Author(s):  
Kenji Sato ◽  
Ed Knudsen ◽  
Heinz Pitsch
Keyword(s):  
Transfer Function ◽  
Flow Field ◽  
Heat Release ◽  
Combustion Chamber ◽  
Combustion Process ◽  
Variable Density ◽  
Combustion Model ◽  
Combustion Instabilities ◽  
Inlet Velocity ◽  
Good Agreement

Stable combustion is one of the most important requirements for the development of heavy duty gas turbine engines that comply with stringent environmental regulations at high firing temperatures. In this research, one of the typical combustion instabilities which is caused by an acoustically forced velocity disturbance is investigated using variable density LES simulations. The G-equation approach for LES is used as the combustion model [1], and an experiment by Balachandran et al. [2, 3] is selected for case study. The velocity profiles in the experimental combustion chamber are compared with experimentally measured data at non-reacting conditions and it is confirmed that these are in good agreement. At the reacting conditions, predicted flame shapes are compared with OH PLIF measurements. The transfer function of the heat release due to inlet velocity forcing at 40 Hz and 160 Hz frequencies is also compared with the experimental data. These are in good agreement, including the nonlinear response of heat release. The transfer function is highly related to the flow field. The non-linearity of the transfer function can be traced to the interaction of the flow field in the combustion chamber with the combustion process itself.

Effect of Hydrogen Content on the Gas Turbine Combustion Performance of Synthetic Natural Gas

2013 ◽  
Author(s):  
Min Chul Lee ◽  
Seik Park ◽  
Uisik Kim ◽  
Sungchul Kim ◽  
Jisu Yoon ◽  
...  
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Gas Turbine ◽  
Hydrogen Content ◽  
Gas Turbines ◽  
Combustion Instabilities ◽  
Synthetic Natural Gas ◽  
Natural Gases ◽  
Combustion Performance ◽  
Gas Turbine Combustion

This paper investigates the effect of hydrogen content on the gas turbine combustion performance of synthetic natural gases to determine whether they are adaptable to industrial gas turbines. Synthetic natural gases which are composed of methane, propane and varying amounts of hydrogen (0%, 1%, 3% and 5%), are tested in ambient pressure and high temperature conditions at the combustion test facility of a 60kWth industrial gas turbine. Combustion instabilities, flame structures, temperatures at nozzle, dump plane and turbine inlet, and emissions of NOx and CO are investigated for the power outputs from 35 to 60kWth. With increasing hydrogen content, combustion instabilities are slightly alleviated and the frequency of pressure fluctuation and heat release oscillation is increased. NOx and CO emissions are almost similar in trends and amounts for all tested fuels, and the undesirable phenomena from addition of hydrogen such as flashback, auto-ignition and overheating of fuel nozzle were not observed. Synthetic natural gas with less than 1% hydrogen showed no difference in gas turbine combustion characteristics, while synthetic natural gases containing hydrogen of over 3% showed a slight difference in combustion instability such as amplitude and frequency of pressure fluctuations and heat release oscillations. From these results, we conclude that the synthetic natural gas containing less than 1% hydrogen is adaptable without retrofitting any part of the combustor, and Korea coal-SNG Quality Standard Bureau is planning to establish the SNG quality standards, guaranteeing hydrogen content of up to 1%.

Experimental Investigations of Flame Stabilization of a Gas Turbine Combustor

2011 ◽  
Author(s):  
Rainer Lu¨ckerath ◽  
Oliver Lammel ◽  
Michael Sto¨hr ◽  
Isaac Boxx ◽  
Ulrich Stopper ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flow Field ◽  
Gas Turbine ◽  
Mixture Fraction ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Diagnostic Methods ◽  
Laser Raman Spectroscopy ◽  
Experimental Investigations ◽  
Combustion System

While today’s gas turbine (GT) combustion systems are designed for specific fuels there is an urgent demand for fuel-flexible stationary GT combustors capable of burning natural gas as well as hydrogen-rich fuels in future. For the development of a fuel flexible, low-emission, and reliable combustion system a better understanding of the flow field – flame interaction and the flame stabilization mechanism is necessary. For this purpose, a down-scaled staged can combustion system provided with an optical combustion chamber was investigated in a high pressure test rig. Different optical diagnostic methods were used to analyze the combustion behavior with a focus on flame stabilization and to generate a comprehensive set of data for validation of numerical simulation methods (CFD) employed in the industrial design process. For different operating conditions the size and position of the flame zone were visualized by OH* chemiluminescence measurements. Additionally, the exhaust gas emissions (NOx and CO) and the acoustic flame oscillations were monitored. Besides many different operating conditions with natural gas different fuel mixtures of natural gas and hydrogen were investigated in order to characterize the flashback behavior monitored with OH* chemiluminescence. For selected operating conditions detailed laser diagnostic experiments were performed. The main flow field with the inner recirculation zone was measured with two-dimensional particle image velocimetry (PIV) in different measuring planes. One-dimensional laser Raman spectroscopy was successfully applied for the measurement of the major species concentration and the temperature. These results show the variation of the local mixture fraction allowing conclusions to be drawn about the good premix quality. Furthermore, mixing effects of unburnt fuel/air and fully reacted combustion products are studied giving insights into the process of the turbulence-chemistry interaction and reaction progress.

Numerical simulations and analysis of the turbulent flow field in a practical gas turbine engine combustor

2021 ◽  
pp. 095765092110632
Author(s):  
Veeraraghava R Hasti ◽  
Prithwish Kundu ◽  
Sibendu Som ◽  
Jay P Gore
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Gas Turbine ◽  
Adaptive Mesh Refinement ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Turbulent Structures ◽  
Cut Cell ◽  
Turbulent Flow Field

The turbulent flow field in a practical gas turbine combustor is very complex because of the interactions between various flows resulting from components like multiple types of swirlers, dilution holes, and liner effusion cooling holes. Numerical simulations of flows in such complex combustor configurations are challenging. The challenges result from (a) the complexities of the interfaces between multiple three-dimensional shear layers, (b) the need for proper treatment of a large number of tiny effusion holes with multiple angles, and (c) the requirements for fast turnaround times in support of engineering design optimization. Both the Reynolds averaged Navier–Stokes simulation (RANS) and the large eddy simulation (LES) for the practical combustor geometry are considered. An autonomous meshing using the cut-cell Cartesian method and adaptive mesh refinement (AMR) is demonstrated for the first time to simulate the flow in a practical combustor geometry. The numerical studies include a set of computations of flows under a prescribed pressure drop across the passage of interest and another set of computations with all passages open with a specified total flow rate at the plenum inlet and the pressure at the exit. For both sets, the results of the RANS and the LES flow computations agree with each other and with the corresponding measurements. The results from the high-resolution LES simulations are utilized to gain fundamental insights into the complex turbulent flow field by examining the profiles of the velocity, the vorticity, and the turbulent kinetic energy. The dynamics of the turbulent structures are well captured in the results of the LES simulations.

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