Effect of Flame Structure on the Flame Transfer Function in a Premixed Gas Turbine Combustor

The flame transfer function in a premixed gas turbine combustor is experimentally determined. The fuel (natural gas) is premixed with air upstream of a choked inlet to the combustor. Therefore, the input to the flame transfer function is the imposed velocity fluctuations of the fuel/air mixture without equivalence ratio fluctuations. The inlet-velocity fluctuations are achieved by a variable-speed siren over the forcing frequency of 75–280 Hz and measured using a hot-wire anemometer at the inlet to the combustor. The output function (heat release) is determined using chemiluminescence measurement from the whole flame. Flame images are recorded to understand how the flame structure plays a role in the global heat release response of flame to the inlet-velocity perturbation. The results show that the gain and phase of the flame transfer function depend on flame structure as well as the frequency and magnitude of inlet-velocity modulation and can be generalized in terms of the relative length scale of flame to convection length scale of inlet-velocity perturbation, which is represented by a Strouhal number. Nonlinear flame response is characterized by a periodic vortex shedding from shear layer, and the nonlinearity occurs at lower magnitude of inlet-velocity fluctuation as the modulation frequency increases. However, for a given modulation frequency, the flame structure does not affect the magnitude of inlet-velocity fluctuation at which the nonlinear flame response starts to appear.

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Effect of Flame Structure on the Flame Transfer Function in a Premixed Gas Turbine Combustor

Volume 3: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2008-51014 ◽

2008 ◽

Cited By ~ 5

Author(s):

Daesik Kim ◽

Jong Guen Lee ◽

Bryan D. Quay ◽

Domenic Santavicca ◽

Kwanwoo Kim ◽

...

Keyword(s):

Transfer Function ◽

Gas Turbine ◽

Velocity Fluctuation ◽

Modulation Frequency ◽

Flame Structure ◽

Length Scale ◽

Gas Turbine Combustor ◽

Velocity Perturbation ◽

Velocity Fluctuations ◽

Inlet Velocity

The flame transfer function in a premixed gas turbine combustor is experimentally determined. The fuel (natural gas) is premixed with air upstream of a choked inlet to combustor. Therefore, the input to the flame transfer function is the imposed velocity fluctuations of the fuel/air mixture without equivalence ratio fluctuations. The inlet-velocity fluctuations are achieved by a variable-speed siren over the forcing frequency of 75–280 Hz and measured using a hot-wire-anemometer at the inlet to the combustor. The output function (heat release) is determined using chemiluminescence measurement from the whole flame. Flame images are recorded to understand how the flame structure plays a role in the global heat release response of flame to the inlet-velocity perturbation. The results show that the gain and phase of the flame transfer function depend on flame structure as well as the frequency and magnitude of inlet-velocity modulation and can be generalized in terms of the relative length scale of flame to convection length scale of inlet-velocity perturbation, which is represented by a Strouhal number. Non-linear flame response is characterized by a periodic vortex shedding from shear layer and the non-linearity occurs at lower magnitude of inlet-velocity fluctuation as the modulation frequency increases. However, for a given modulation frequency, the flame structure does not affect the magnitude of inlet-velocity fluctuation at which the non-linearity starts.

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Flame Response Mechanisms Due to Velocity Perturbations in a Lean Premixed Gas Turbine Combustor

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2010-22380 ◽

2010 ◽

Cited By ~ 1

Author(s):

Brian Jones ◽

Jong Guen Lee ◽

Bryan D. Quay ◽

Domenic A. Santavicca ◽

Kwanwoo Kim ◽

...

Keyword(s):

Transfer Function ◽

Heat Release ◽

Gas Turbine ◽

Velocity Fluctuation ◽

Modulation Frequency ◽

Gas Turbine Combustor ◽

Velocity Fluctuations ◽

Inlet Velocity ◽

Lean Premixed ◽

Flame Response

The response of turbulent premixed flames to inlet velocity fluctuations is studied experimentally in a lean premixed, swirl-stabilized, gas turbine combustor. Overall chemiluminescence intensity is used as a measure of the fluctuations in the flame’s global heat release rate and hot wire anemometry is used to measure the inlet velocity fluctuations. Tests are conducted over a range of mean inlet velocities, equivalence ratios and velocity fluctuation frequencies, while the normalized inlet velocity fluctuation (V′/Vmean) is fixed at 5% to ensure linear flame response over the employed modulation frequency range. The measurements are used to calculate a flame transfer function relating the velocity fluctuation to the heat release fluctuation as a function of the velocity fluctuation frequency. At low frequency, the gain of the flame transfer function increases with increasing frequency to a peak value greater than one. As the frequency is further increased, the gain decreases to a minimum value, followed by a second smaller peak. The frequencies at which the gain is minimum and achieves its 2nd peak are found to depend on the convection time scale and the flame’s characteristic length scale. Phase-synchronized CH* chemiluminescence imaging is used to characterize the flame’s response to inlet velocity fluctuations. The observed flame response can be explained in terms of the interaction of two flame perturbation mechanisms, acoustic velocity fluctuations and vorticity fluctuations. Analysis of the phase-synchronized flame images show that when both perturbations arrive at the flame at the same time (or phase) they constructively interfere, producing the 2nd peak observed in the gain curves. And when the perturbations arrive at the flame 180 degrees out-of-phase, they destructively interfere, producing the observed minimum in the gain curve.

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Flame Response Mechanisms Due to Velocity Perturbations in a Lean Premixed Gas Turbine Combustor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4001996 ◽

2010 ◽

Vol 133 (2) ◽

Cited By ~ 23

Author(s):

Brian Jones ◽

Jong Guen Lee ◽

Bryan D. Quay ◽

Domenic A. Santavicca

Keyword(s):

Transfer Function ◽

Heat Release ◽

Gas Turbine ◽

Velocity Fluctuation ◽

Gas Turbine Combustor ◽

Velocity Fluctuations ◽

Inlet Velocity ◽

Lean Premixed ◽

Flame Response ◽

Second Peak

The response of turbulent premixed flames to inlet velocity fluctuations is studied experimentally in a lean premixed, swirl-stabilized, gas turbine combustor. Overall chemiluminescence intensity is used as a measure of the fluctuations in the flame’s global heat release rate, and hot wire anemometry is used to measure the inlet velocity fluctuations. Tests are conducted over a range of mean inlet velocities, equivalence ratios, and velocity fluctuation frequencies, while the normalized inlet velocity fluctuation (V′/Vmean) is fixed at 5% to ensure linear flame response over the employed modulation frequency range. The measurements are used to calculate a flame transfer function relating the velocity fluctuation to the heat release fluctuation as a function of the velocity fluctuation frequency. At low frequency, the gain of the flame transfer function increases with increasing frequency to a peak value greater than 1. As the frequency is further increased, the gain decreases to a minimum value, followed by a second smaller peak. The frequencies at which the gain is minimum and achieves its second peak are found to depend on the convection time scale and the flame’s characteristic length scale. Phase-synchronized CH∗ chemiluminescence imaging is used to characterize the flame’s response to inlet velocity fluctuations. The observed flame response can be explained in terms of the interaction of two flame perturbation mechanisms, one originating at flame-anchoring point and propagating along the flame front and the other from vorticity field generated in the outer shear layer in the annular mixing section. An analysis of the phase-synchronized flame images show that when both perturbations arrive at the flame at the same time (or phase), they constructively interfere, producing the second peak observed in the gain curves. When the perturbations arrive at the flame 180 degrees out-of-phase, they destructively interfere, producing the observed minimum in the gain curve.

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Characterization of Forced Flame Response of Swirl-Stabilized Turbulent Lean-Premixed Flames in a Gas Turbine Combustor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3204532 ◽

2010 ◽

Vol 132 (4) ◽

Cited By ~ 49

Author(s):

Kyu Tae Kim ◽

Jong Guen Lee ◽

Hyung Ju Lee ◽

Bryan D. Quay ◽

Domenic A. Santavicca

Keyword(s):

Transfer Function ◽

Natural Gas ◽

Gas Turbine ◽

Strouhal Number ◽

Premixed Flames ◽

Flame Length ◽

Gas Turbine Combustor ◽

Flame Response ◽

Flame Shape ◽

Flame Angle

Flame transfer function measurements of turbulent premixed flames are made in a model lean-premixed, swirl-stabilized, gas turbine combustor. OH∗, CH∗, and CO2∗ chemiluminescence emissions are measured to determine heat release oscillation from a whole flame, and the two-microphone technique is used to measure inlet velocity fluctuation. 2D CH∗ chemiluminescence imaging is used to characterize the flame shape: the flame length (LCH∗ max) and flame angle (α). Using H2-natural gas composite fuels, XH2=0.00–0.60, a very short flame is obtained and hydrogen enrichment of natural gas is found to have a significant impact on the flame structure and flame attachment points. For a pure natural gas flame, the flames exhibit a “V” structure, whereas H2-enriched natural gas flames have an “M” structure. Results show that the gain of M flames is much smaller than that of V flames. Similar to results of analytic and experimental investigations on the flame transfer function of laminar premixed flames, it shows that the dynamics of a turbulent premixed flame is governed by three relevant parameters: the Strouhal number (St=LCH∗ max/Lconv), the flame length (LCH∗ max), and the flame angle (α). Two flames with the same flame shape exhibit very similar forced responses, regardless of their inlet flow conditions. This is significant because the forced flame response of a highly turbulent, practical gas turbine combustor can be quantitatively generalized using the nondimensional parameters, which collapse all relevant input conditions into the flame shape and the Strouhal number.

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Characterization of Forced Flame Response of Swirl-Stabilized Turbulent Lean-Premixed Flames in a Gas Turbine Combustor

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-60031 ◽

2009 ◽

Cited By ~ 3

Author(s):

Kyu Tae Kim ◽

Jong Guen Lee ◽

Hyung Ju Lee ◽

Bryan D. Quay ◽

Domenic Santavicca

Keyword(s):

Transfer Function ◽

Natural Gas ◽

Gas Turbine ◽

Strouhal Number ◽

Premixed Flames ◽

Flame Length ◽

Gas Turbine Combustor ◽

Flame Response ◽

Flame Shape ◽

Flame Angle

Flame transfer function measurements of turbulent premixed flames were made in a model lean premixed, swirl-stabilized, gas turbine combustor. OH*, CH*, and CO2* chemiluminescence emissions were measured to determine heat release oscillation from a whole flame, and the two-microphone technique was used to measure inlet velocity fluctuation. 2-D CH* chemiluminescence imaging was used to characterize the flame shape: the flame length (LCH* max) and flame angle (α). Using H2-natural gas composite fuels, XH2 = 0.00 ∼ 0.60, very short flame was obtained and hydrogen enrichment of natural gas had a significant impact on the flame structure and flame attachment points. For a pure natural gas flame, the flames exhibit a “V” structure, whereas H2-enriched natural gas flames have an “M” structure. Results show that the gain of “M” flames is much smaller than that of “V” flames. Similar to results of analytic and experimental investigations on the flame transfer function of laminar premixed flames, it shows that the dynamics of a turbulent premixed flame is governed by three relevant parameters: the Strouhal number (St = LCH* max / Lconv), the flame length (LCH* max), and the flame angle (α). Two flames with the same flame shape exhibit very similar forced responses, regardless of their inlet flow conditions. This is significant because the forced flame response of a highly turbulent, practical gas turbine combustor can be quantitatively generalized using the non-dimensional parameters which collapse all relevant input conditions into the flame shape and the Strouhal number.

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Towards the Multiobjective Optimisation of Gas Turbine Combustors

Volume 1: Combustion and Fuels, Education ◽

10.1115/gt2006-90950 ◽

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.

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Thermoacoustic Modeling of a Gas Turbine Combustor Equipped With Acoustic Dampers

Journal of Turbomachinery ◽

10.1115/1.1791284 ◽

2005 ◽

Vol 127 (2) ◽

pp. 372-379 ◽

Cited By ~ 39

Author(s):

Valter Bellucci ◽

Bruno Schuermans ◽

Dariusz Nowak ◽

Peter Flohr ◽

Christian Oliver Paschereit

Keyword(s):

Transfer Function ◽

Gas Turbine ◽

Mixture Fraction ◽

Time Lag ◽

Multiple Input Multiple Output ◽

Three Dimensional ◽

Analytical Models ◽

Gas Turbine Combustor ◽

Input Multiple Output ◽

The Time Domain

In this work, the TA3 thermoacoustic network is presented and used to simulate acoustic pulsations occurring in a heavy-duty ALSTOM gas turbine. In our approach, the combustion system is represented as a network of acoustic elements corresponding to hood, burners, flames and combustor. The multi-burner arrangement is modeled by describing the hood and combustor as Multiple Input Multiple Output (MIMO) acoustic elements. The MIMO transfer function (linking acoustic pressures and acoustic velocities at burner locations) is obtained by a three-dimensional modal analysis performed with a Finite Element Method. Burner and flame analytical models are fitted to transfer function measurements. In particular, the flame transfer function model is based on the time-lag concept, where the phase shift between heat release and acoustic pressure depends on the time necessary for the mixture fraction (formed at the injector location) to be convected to the flame. By using a state-space approach, the time domain solution of the acoustic field is obtained. The nonlinearity limiting the pulsation amplitude growth is provided by a fuel saturation term. Furthermore, Helmholtz dampers applied to the gas turbine combustor are acoustically modeled and included in the TA3 model. Finally, the predicted noise reduction is compared to that achieved in the engine.

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Experimental Prediction of Lean Blowout Limits for 3kW Micro Gas Turbine Combustor fuelled with LPG

INCAS BULLETIN ◽

10.13111/2066-8201.2021.13.1.9 ◽

2021 ◽

Vol 13 (1) ◽

pp. 89-95

Author(s):

V. KIRUBAKARAN ◽

David BHATT

Keyword(s):

Pressure Drop ◽

Gas Turbine ◽

Pressure Loss ◽

Total Pressure ◽

Total Pressure Loss ◽

Gas Turbine Combustor ◽

Inlet Velocity ◽

Lean Blowout ◽

Micro Gas Turbine ◽

Experimental Prediction

The Lean Blowout Limit of the combustor is one of the important performance parameters for a gas turbine combustor design. This study aims to predict the total pressure loss and Lean Blowout (LBO) limits of an in-house designed swirl stabilized 3kW can-type micro gas turbine combustor. The experimental prediction of total pressure loss and LBO limits was performed on a designed combustor fuelled with Liquefied Petroleum Gas (LPG) for the combustor inlet velocity ranging from 1.70 m/s to 11 m/s. The results show that the predicted total pressure drop increases with increasing combustor inlet velocity, whereas the LBO equivalence ratio decreases gradually with an increase in combustor inlet velocity. The combustor total pressure drop was found to be negligible; being in the range of 0.002 % to 0.065 % for the measured inlet velocity conditions. These LBO limits predictions will be used to fix the operating boundary conditions of the gas turbine combustor.

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