Comparison of Center Nozzle Staging to Outer Nozzle Staging in a Multi-Flame Combustor

2018 ◽  
Author(s):  
Wyatt Culler ◽  
Xiaoling Chen ◽  
Stephen Peluso ◽  
Domenic Santavicca ◽  
Jacqueline O’Connor ◽  
...  
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Equivalence Ratio ◽  
Dynamic Pressure ◽  
Gas Turbine Combustor ◽  
Rate Fluctuation ◽  
Fuel Staging ◽  
Model Gas Turbine Combustor ◽  
Dynamic Pressure Measurements ◽  
Similar Phase

Combustion instability in gas turbines is often mitigated using fuel staging, a strategy where the fuel is split unevenly between different nozzles of a multiple-nozzle combustor. This work examines the efficacy of different fuel staging configurations by comparing axisymmetric and non-axisymmetric fuel staging in a four-around-one model gas turbine combustor. Fuel staging is accomplished by increasing the equivalence ratio of the center nozzle (axisymmetric staging) or an outer nozzle (non-axisymmetric staging). When the global equivalence ratio is ϕ = 0.70 and all nozzles are fueled equally, the combustor undergoes longitudinal, self-excited oscillations. These oscillations are suppressed when the center nozzle equivalence ratio is increased above ϕStaging = 0.79. This bifurcation equivalence ratio varies between ϕStaging = 0.86 and ϕStaging = 0.76 for the outer nozzles, and is attributed to minor hardware differences between each nozzle. High speed CH* chemiluminescence images in combination with dynamic pressure measurements are used to determine the instantaneous phase difference between the heat release rate fluctuation and the combustor pressure fluctuation throughout the combustor. This analysis shows that the staged flame has similar phase relationships for all staging configurations. It is found that axisymmetric staging can be as effective as non-axisymmetric staging; however, the aforementioned hardware variations can impact both the bifurcation equivalence ratio and the effectiveness of staging.

The Effect of Transient Fuel Staging on Self-Excited Instabilities in a Multi-Nozzle Model Gas Turbine Combustor

2017 ◽  
Author(s):  
Wyatt Culler ◽  
Janith Samarasinghe ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca ◽  
Jacqueline O’Connor
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Equivalence Ratio ◽  
Growth Time ◽  
Stable Operation ◽  
Time Constants ◽  
Decay Times ◽  
Fuel Staging ◽  
Passive Techniques

Combustion instability in gas turbines can be mitigated using active techniques or passive techniques, but passive techniques are almost exclusively used in industrial settings. While fuel staging, a common passive technique, is effective in reducing the amplitude of self-excited instabilities in gas turbine combustors at steady-state conditions, the effect of transients in fuel staging on self-excited instabilities is not well understood. This paper examines the effect of fuel staging transients on a laboratory-scale five-nozzle can combustor undergoing self-excited instabilities. The five nozzles are arranged in a four-around-one configuration and fuel staging is accomplished by increasing the center nozzle equivalence ratio. When the global equivalence ratio is φ = 0.70 and all nozzles are fueled equally, the combustor undergoes self-excited oscillations. These oscillations are suppressed when the center nozzle equivalence ratio is increased to φ = 0.80 or φ = 0.85. Two transient staging schedules are used, resulting in transitions from unstable to stable operation, and vice-versa. It is found that the characteristic instability decay times are dependent on the amount of fuel staging in the center nozzle. It is also found that the decay time constants differ from the growth time constants, indicating hysteresis in stability transition points. High speed CH* chemiluminescence images in combination with dynamic pressure measurements are used to determine the instantaneous phase difference between the heat release rate fluctuation and the combustor pressure fluctuation throughout the combustor. This analysis shows that the instability onset process is different from the instability decay process.

Experimental Investigation of Combustion Dynamics in a Turbulent Syngas Combustor

2017 ◽  
Author(s):  
Nikhil Ashokbhai Baraiya ◽  
Baladandayuthapani Nagarajan ◽  
Satynarayanan R. Chakravarthy
Keyword(s):  
High Speed ◽  
Equivalence Ratio ◽  
Bluff Body ◽  
Dynamic Pressure ◽  
Fuel Mixture ◽  
High Amplitude ◽  
Acoustic Oscillations ◽  
Combustion Dynamics ◽  
Dynamic Pressure Measurement ◽  
Body Location

In the present work, the proportion of carbon monoxide to hydrogen is widely varied to simulate different compositions of synthesis gas and the potential of the fuel mixture to excite combustion oscillations in a laboratory-scale turbulent bluff body combustor is investigated. The effect of parameters such as the bluff body location and equivalence ratio on the self-excited acoustic oscillations of the combustor is studied. The flame oscillations are mapped by means of simultaneous high-speed CH* and OH* chemiluminescence imaging along with dynamic pressure measurement. Mode shifts are observed as the bluff body location or the air flow Reynolds number/overall equivalence ratio are varied for different fuel compositions. It is observed that the fuel mixtures that are hydrogen-rich excite high amplitude pressure oscillations as compared to other fuel composition cases. Higher H2 content in the mixture is also capable of exciting significantly higher natural acoustic modes of the combustor so long as CO is present, but not without the latter. The interchangeability factor Wobbe Index is not entirely sufficient to understand the unsteady flame response to the chemical composition.

scholarly journals The Effect of Discrete Pilot Hydrogen Dopant Injection on the Lean Blowout Performance of a Model Gas Turbine Combustor

1999 ◽  
Author(s):  
Oanh Nguyen ◽  
Scott Samuelsen
Keyword(s):  
Gas Turbine ◽  
Atmospheric Pressure ◽  
Gas Turbines ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Lean Blowout ◽  
Lean Combustion ◽  
Attractive Option ◽  
Overall Performance ◽  
Model Gas Turbine Combustor

In view of increasingly stringent NOx emissions regulations on stationary gas turbines, lean combustion offers an attractive option to reduce reaction temperatures and thereby decrease NOx production. Under lean operation, however, the reaction is vulnerable to blowout. It is herein postulated that pilot hydrogen dopant injection, discretely located, can enhance the lean blowout performance without sacrificing overall performance. The present study addresses this hypothesis in a research combustor assembly, operated at atmospheric pressure, and fired on natural gas using rapid mixing injection, typical of commercial units. Five hydrogen injector scenarios are investigated. The results show that (1) pilot hydrogen dopant injection, discretely located, leads to improved lean blowout performance and (2) the location of discrete injection has a significant impact on the effectiveness of the doping strategy.

Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Andreas Lantz ◽  
Robert Collin ◽  
Marcus Aldén ◽  
Annika Lindholm ◽  
Jenny Larfeldt ◽  
...  
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Flame Front ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Burner Exit ◽  
Planar Laser ◽  
Industrial Gas Turbines ◽  
Dynamic Pressure Measurements

The effect of hydrogen enrichment to natural gas flames was experimentally investigated at atmospheric pressure conditions using flame chemiluminescence imaging, planar laser-induced fluorescence of hydroxyl radicals (OH PLIF), and dynamic pressure monitoring. The experiments were performed using a third generation dry low emission (DLE) burner used in both SGT-700 and SGT-800 industrial gas turbines from Siemens. The burner was mounted in an atmospheric combustion test rig at Siemens with optical access in the flame region. Four different hydrogen enriched natural gas flames were investigated; 0 vol. %, 30 vol. %, 60 vol. %, and 80 vol. % of hydrogen. The results from flame chemiluminescence imaging and OH PLIF show that the size and shape of the flame was clearly affected by hydrogen addition. The flame becomes shorter and narrower when the amount of hydrogen is increased. For the 60 vol. % and 80 vol. % hydrogen flames the flame has moved upstream and the central recirculation zone that anchors the flame has moved upstream the burner exit. Furthermore, the position of the flame front fluctuated more for the full premixed flame with only natural gas as fuel than for the hydrogen enriched flames. Measurements of pressure drop over the burner show an increase with increased hydrogen in the natural gas despite same air flow thus confirming the observation that the flame front moves upstream toward the burner exit and thereby increasing the blockage of the exit. Dynamic pressure measurements in the combustion chamber wall confirms that small amounts of hydrogen in natural gas changes the amplitude of the dynamic pressure fluctuations and initially dampens the axial mode but at higher levels of hydrogen an enhancement of a transversal mode in the combustion chamber at higher frequencies could occur.

scholarly journals Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
J. Yang ◽  
G. Pavesi ◽  
S. Yuan ◽  
G. Cavazzini ◽  
G. Ardizzon
Keyword(s):  
High Speed ◽  
Dynamic Pressure ◽  
Load Condition ◽  
Rotating Stall ◽  
Pump Mode ◽  
Pump Turbine ◽  
Part Load ◽  
Time Frequency ◽  
Speed Flow ◽  
Dynamic Pressure Measurements

The unsteady phenomena of a low specific speed pump–turbine operating in pump mode were characterized by dynamic pressure measurements and high-speed flow visualization of injected air bubbles. Analyses were carried out on the pressure signals both in frequency and time–frequency domains and by bispectral protocol. The results obtained by high-speed camera were used to reveal the flow pattern in the diffuser and return vanes channels The unsteady structure identified in the return vane channel appeared both at full and part load condition. Furthermore, a rotating stall structure was found and characterized in the diffuser when the pump operated at part load. The characteristics of these two unsteady structures are described in the paper.

scholarly journals Measurement and modeling of the generation and the transport of entropy waves in a model gas turbine combustor

2017 ◽  
Vol 9 (4) ◽  
pp. 299-309 ◽  
Author(s):  
Dominik Wassmer ◽  
Bruno Schuermans ◽  
Christian Oliver Paschereit ◽  
Jonas P Moeck
Keyword(s):  
Equivalence Ratio ◽  
Fuel Injection ◽  
Fuel Mixture ◽  
Combustion Noise ◽  
Gas Temperature ◽  
Gas Turbine Combustor ◽  
Reactor Model ◽  
Convection Diffusion ◽  
Wide Range ◽  
Model Gas Turbine Combustor

Indirect combustion noise is caused by entropy spots that are accelerated at the first turbine stage. These so-called entropy waves originate from the equivalence ratio fluctuations in the air–fuel mixture upstream of the flame. As entropy waves propagate convectively through the combustion chamber, they are subject to diffusion and dispersion. Because of the inherent difficulty of accurately measuring the burned gas temperature with sufficient temporal resolution, experimental data of entropy waves are scarce. In this work, the transfer function between equivalence ratio fluctuations and entropy fluctuations is modeled by a linearized reactor model, and the transport of entropy waves is investigated based on a convection-diffusion model. Temperature fluctuations are measured by means of a novel measurement technique at different axial positions downstream of the premixed flame, which is forced by periodic fuel injection. Experiments with various flow velocities and excitation frequencies enable model validation over a wide range of parameters.

Evaluation of Combustion and Emissions Using Biodiesel and Blends With Kerosene in a Low NOx Gas Turbine Combustor

2010 ◽  
Author(s):  
Hu Li ◽  
Mohamed Altaher ◽  
Gordon E. Andrews
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Waste Cooking Oil ◽  
Industrial Applications ◽  
Liquid Fuels ◽  
Gaseous Emissions ◽  
Gas Turbine Combustor ◽  
Industrial Gas Turbines

Biofuels offer reduced CO2 emissions for both industrial and aero gas turbines. Industrial applications are more practical due to low temperature waxing problems at altitude. Any use of biofuels in industrial gas turbines must also achieve low NOx and this paper investigates the use of biofuels in a low NOx radial swirler, as used in some industrial low NOx gas turbines. A waste cooking oil derived methyl ester biodiesel (WME) has been tested on a radial swirler industrial low NOx gas turbine combustor under atmospheric pressure and 600K. The pure WME and its blends with kerosene, B20 and B50 (WME:kerosene = 20:80 and 50:50 respectively), and pure kerosene were tested for gaseous emissions and lean extinction as a function of equivalence ratio. The co-firing with natural gas (NG) was tested for kerosene/biofuel blends B20 and B50. The central fuel injection was used for liquid fuels and wall injection was used for NG. The experiments were carried out at a reference Mach number of 0.017. The inlet air to the combustor was heated to 600K. The results show that B20 produced similar NOx at an equivalence ratio of ∼0.5 and a significant low NOx when the equivalence ratio was increased comparing with kerosene. B50 and B100 produced higher NOx compared to kerosene, which indicates deteriorated mixing due to the poor volatility of the biofuel component. The biodiesel lower hydrocarbon and CO emissions than kerosene in the lean combustion range. The lean extinction limit was lower for B50 and B100 than kerosene. It is demonstrated that B20 has the lowest overall emissions. The co-firing with NG using B20 and B50 significantly reduced NOx and CO emissions.

scholarly journals A novel diagnostic method based on filter bank theory for fast and accurate detection of thermoacoustic instability

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seongpil Joo ◽  
Jongwun Choi ◽  
Namkeun Kim ◽  
Min Chul Lee
Keyword(s):  
Gas Turbine ◽  
Filter Bank ◽  
Dynamic Pressure ◽  
Single Mode ◽  
Instability Criterion ◽  
Gas Turbine Combustor ◽  
Thermoacoustic Instability ◽  
Comparable Performance ◽  
Model Gas Turbine Combustor ◽  
Multi Mode

AbstractThis study proposes and analyzes a novel methodology that can effectively detect multi-mode combustion instability (CI) in a gas turbine combustor. The experiment is conducted in a model gas turbine combustor, and dynamic pressure (DP) and flame images are examined during the transition from stable to unstable flame, which is driven by changing fuel compositions. As a powerful technique for early detection of CI in multi-mode as well as in single mode, a new filter bank (FB) method based on spectral analysis of DP is proposed. Sequential processing using a triangular filter with Mel-scaling and a Hamming window is applied to increase the accuracy of the FB method, and the instability criterion is determined by calculating the magnitude of FB components. The performance of the FB method is compared with that of two conventional methods that are based on the root-mean-squared DP and temporal kurtosis. From the results, the FB method shows comparable performance in detection speed, sensitivity, and accuracy with other parameters. In addition, the FB components enable the analysis of various frequencies and multi-mode frequencies. Therefore, the FB method can be considered as an additional prognosis tool to determine the multi-mode CI in a monitoring system for gas turbine combustors.

scholarly journals Combustion Noise at Elevated Pressures in a Liquid-Fueled Premixed Combustor

1997 ◽  
Author(s):  
Douglas Darling ◽  
Krishnan Radhakrishnan ◽  
Ayo Oyediran
Keyword(s):  
Equivalence Ratio ◽  
Dynamic Pressure ◽  
Noise Spectrum ◽  
Sound Level ◽  
Broadband Noise ◽  
Combustion Noise ◽  
Inlet Temperature ◽  
Mean Flow ◽  
Elevated Pressures ◽  
Dynamic Pressure Measurements

Noise generated in gas turbine combustors can exist in several forms — broadband noise, sharp resonant peaks, and regular or intermittent non-linear pulsing. In the present study, dynamic pressure measurements were made in several JP-5-fueled combustor configurations, at various mean pressures and temperatures. The fluctuating pressure was measured at mean pressures from 6 to 14 atm and inlet temperatures from 550 K to 850 K. The goal of the present work was to study the effect of changes in mean flow conditions on combustor noise: both broadband noise and sharp tones were considered. In general, the shape of the broadband noise spectrum was consistent from one configuration to another. The shape of the spectrum was influenced by the acoustic filtering of the combustion zone. This filtering ensured the basic consistency of the spectra. In general, the trends in broadband noise observed at low mean pressures were also seen at high mean pressures; that is, the total sound level decreased with both increasing equivalence ratio and increasing inlet temperature. The combustor configurations without a central pilot experienced higher broadband noise levels and were more susceptible to narrow peak resonances than configurations with a central pilot. The sharp peaks were more sensitive to the mean flow than was the broadband noise, and the effects were not always the same. In some situations, increasing the equivalence ratio made the sharp peaks grow, while at other conditions, increasing the equivalence ratio made the sharp peaks shrink. Thus, it was difficult to predict when resonances would occur, however, they were reproducible. Noise was also observed near lean blow out. As with other types of noise, lean blow out noise was affected by the combustion chamber acoustics, which apparently maintains the fluctuations at a uniform frequency. However, the actual conditions when this type of noise was experienced appeared to simply follow the lean blow out limit, as it varied with mean temperature and pressure.

Sign in / Sign up

Export Citation Format

Share Document