Prediction of Combustion Noise of a Swirl-Stabilized Flame Using Laser Interferometric Vibrometry Validated by Acoustic Measurements

2017 ◽  
Author(s):  
Felix Greiffenhagen ◽  
Johannes Peterleithner ◽  
Jakob Woisetschläger
Keyword(s):  
Gas Turbines ◽  
Local Density ◽  
Signal To Noise Ratio ◽  
Laser Interferometry ◽  
Density Fluctuations ◽  
Combustion Noise ◽  
Sound Power ◽  
Operation Conditions ◽  
Methane Flame ◽  
Laser Interferometric

Modern gas turbines rely more and more on premixed combustion systems. While they produce less emission, they are more prone to combustion instabilities. The combustion noise emitted by turbulent swirl-stabilized flames can be calculated directly if density fluctuations in the flame are known as a function of time and space. Recently it was shown that laser interferometry records density fluctuations in the flame quantitatively. In this work a swirl-stabilized, rotationally-symmetric unconfined methane flame at lean operation conditions and low air mass flow rate was scanned by laser interferometric vibrometry (LIV) in order to calculate the overall sound power emitted by the flame. To validate the outcome calculated from the LIV data, sound power was also measured in a half-hemisphere by microphones, using pressure-pressure-probes. These probes record the total sound power of the combustion noise emitted by the flame. To improve signal to noise ratio for this measurement, a siren was used to generate a reproducible excitation of the flame at 212Hz. Both measurement methods were in good agreement. With the LIV data detailed information about the local density fluctuations in the flame causing the sound emission was obtained. Also a preferred acoustic propagation direction between 40° and 80° to the burner axis in downstream direction was observed. This deviation from a uniform distribution is likely to be caused by temperature gradients in the flame. A discussion of systematic errors inherent to the LIV technique and data reduction concludes this publication.

Analysis of Combustion Noise Using Locally Resolved Density Fluctuations and a Microphone Array

2016 ◽  
Author(s):  
Johannes Peterleithner ◽  
Stefan Zerobin ◽  
Jakob Woisetschläger
Keyword(s):  
Microphone Array ◽  
Measurement Techniques ◽  
Time Derivative ◽  
Sound Intensity ◽  
Density Fluctuations ◽  
Combustion Noise ◽  
Sound Power ◽  
Direct Combustion ◽  
Laser Interferometric ◽  
Good Agreement

For turbulent swirl-stabilized flames combustion noise can be directly calculated, if density fluctuations as a function of time and space are known. It is however not easily possible to assess the density fluctuations directly. Therefore, in the past, combustion noise has been expressed as a function of chemiluminescence, an approach bringing in more assumptions. Now, by using interferometry, density fluctuations in the flame can be measured quantitatively. The advantage of this technique is that it measures the time derivative of density fluctuations directly. In this work laser interferometric vibrometry (LIV) was used to scan a two dimensional field in the flame in order to calculate the sound power emitted by the flame. Sound intensity was measured in a half-hemisphere by pressure-pressure-probes in order to record the total sound power of the direct combustion noise emitted by the unconfined flame. The goal of this study was to compare the measured sound power exhibited by the flame with the sound power predicted due to fluctuations of density within the flame. By using a siren to generate linear excitation, it was possible to qualitatively predict combustion noise with good agreement in trend. A quantitative comparison between both measurement techniques showed a deviation of a factor of six.

scholarly journals Aero-Thermal Design and Testing of Advanced Turbine Blades

1997 ◽  
Author(s):  
M. Haendler ◽  
D. Raake ◽  
M. Scheurlen
Keyword(s):  
Gas Turbines ◽  
Full Range ◽  
Turbine Blades ◽  
Design Procedure ◽  
Thermal Design ◽  
Test Facility ◽  
Optical Pyrometer ◽  
Electrical Systems ◽  
Operation Conditions ◽  
Improved Performance

Based on the experience gained with more than 80 machines operating worldwide in 50 and 60 Hz electrical systems respectively, Siemens has developed a new generation of advanced gas turbines which yield substantially improved performance at a higher output level. This “3A-Series” comprises three gas turbine models ranging from 70 MW to 240 MW for 50 Hz and 60 Hz power generation applications. The first of the new advanced gas turbines with 170 MW and 3600 rpm was tested in the Berlin factory test facility under the full range of operation conditions. It was equipped with various measurement systems to monitor pressures, gas and metal temperatures, clearances, strains, vibrations and exhaust emissions. This paper presents the aero-thermal design procedure of the highly thermal loaded film cooled first stage blading. The predictions are compared with the extensive optical pyrometer measurements taken at the Siemens test facility on the V84.3A machine under full load conditions. The pyrometer was inserted at several locations in the turbine and radially moved giving a complete surface temperature information of the first stage vanes and blades.

scholarly journals Flow Inhomogeneities in a Realistic Aeronautical Gas-Turbine Combustor: Formation, Evolution and Indirect Noise

2018 ◽  
Author(s):  
Andrea Giusti ◽  
Luca Magri ◽  
Marco Zedda
Keyword(s):  
Gas Turbines ◽  
Transfer Functions ◽  
Guide Vane ◽  
Flame Structure ◽  
Combustion Noise ◽  
Moment Closure ◽  
Combustion Model ◽  
Conditional Moment ◽  
Eddy Simulation ◽  
Nozzle Guide

Indirect noise generated by the acceleration of combustion inhomogeneities is an important aspect in the design of aeroengines because of its impact on the overall noise emitted by an aircraft and the possible contribution to combustion instabilities. In this study, a realistic rich-quench-lean combustor is numerically investigated, with the objective of quantitatively analyzing the formation and evolution of flow inhomogeneities and determine the level of indirect combustion noise in the nozzle guide vane (NGV). Both entropy and compositional noise are calculated in this work. A high-fidelity numerical simulation of the combustion chamber, based on the Large-Eddy Simulation (LES) approach with the Conditional Moment Closure (CMC) combustion model, is performed. The contributions of the different air streams to the formation of flow inhomogeneities are pinned down and separated with seven dedicated passive scalars. LES-CMC results are then used to determine the acoustic sources to feed an NGV aeroacoustic model, which outputs the noise generated by entropy and compositional inhomogeneities. Results show that non-negligible fluctuations of temperature and composition reach the combustor’s exit. Combustion inhomogeneities originate both from finite-rate chemistry effects and incomplete mixing. In particular, the role of mixing with dilution and liner air flows on the level of combustion inhomogeneities at the combustor’s exit is highlighted. The species that most contribute to indirect noise are identified and the transfer functions of a realistic NGV are computed. The noise level indicates that indirect noise generated by temperature fluctuations is larger that the indirect noise generated by compositional inhomogeneities, although the latter is not negligible and is expected to become louder in supersonic nozzles. It is also shown that relatively small fluctuations of the local flame structure can lead to significant variations of the nozzle transfer function, whose gain increases with the Mach number. This highlights the necessity of an on-line solution of the local flame structure, which is performed in this paper by CMC, for an accurate prediction of the level of compositional noise. This study opens new possibilities for the identification, separation and calculation of the sources of indirect combustion noise in realistic aeronautical gas turbines.

Error Considerations for Turbine-Generator Torsional Vibration Monitoring

2020 ◽  
Author(s):  
Jindrich Liska ◽  
Jan Jakl ◽  
Sven Kunkel
Keyword(s):  
Power Systems ◽  
Torsional Vibration ◽  
Gas Turbines ◽  
Measurement Errors ◽  
Power Plants ◽  
Signal To Noise Ratio ◽  
Vibration Monitoring ◽  
Turbine Generator ◽  
Turbine Generators ◽  
Incremental Encoder

Abstract Turbine-generator torsional vibration is linked to electrical events in the power grid by the generator air-gap torque. Modern power systems are subject to gradual transformation by increasing flexibility demands and incorporation of renewable resources. As a result, electrical transient events are getting more frequent and thus torsional vibration is getting more and more attention. Especially in the case of large steam and gas turbines torsional vibration can cause material fatigue and present a hazard for safe machine operation. This paper freely builds on previous work, where a method for torsional vibration evaluation using an incremental encoder measurement was presented, in that it supplements error considerations to this methodology. Measurement errors such as precision of the rotor encoder manufacturing, choice of the proper sensor, its signal to noise ratio and the error of instantaneous velocity computation algorithm are analyzed. The knowledge of these errors is essential for torsional vibration as there is an indirect and relatively complicated path from the measurement to the final torsional vibration results compared to other kinds of vibration. The characteristics of particular errors of the processing chain are validated both on experimental data from a test rig as well as field data measured on turbine-generators in power plants.

scholarly journals Testing general relativity with the Doppler magnification effect

2019 ◽  
Vol 488 (3) ◽  
pp. 3759-3771 ◽  
Author(s):  
Sambatra Andrianomena ◽  
Camille Bonvin ◽  
David Bacon ◽  
Philip Bull ◽  
Chris Clarkson ◽  
...  
Keyword(s):  
General Relativity ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
Density Fluctuations ◽  
Signal To Noise ◽  
Tests Of General Relativity ◽  
Velocity Statistics ◽  
The Cross ◽  
Noise Ratio ◽  
Magnification Effect

ABSTRACT The apparent sizes and brightnesses of galaxies are correlated in a dipolar pattern around matter overdensities in redshift space, appearing larger on their near side and smaller on their far side. The opposite effect occurs for galaxies around an underdense region. These patterns of apparent magnification induce dipole and higher multipole terms in the cross-correlation of galaxy number density fluctuations with galaxy size/brightness (which is sensitive to the convergence field). This provides a means of directly measuring peculiar velocity statistics at low and intermediate redshift, with several advantages for performing cosmological tests of general relativity (GR). In particular, it does not depend on empirically calibrated scaling relations like the Tully–Fisher and Fundamental Plane methods. We show that the next generation of spectroscopic galaxy redshift surveys will be able to measure the Doppler magnification effect with sufficient signal-to-noise ratio to test GR on large scales. We illustrate this with forecasts for the constraints that can be achieved on parametrized deviations from GR for forthcoming low-redshift galaxy surveys with DESI and SKA2. Although the cross-correlation statistic considered has a lower signal-to-noise ratio than RSD, it will be a useful probe of GR since it is sensitive to different systematics.

Density fluctuations as door-opener for diffusion on crowded surfaces

Science ◽  
2019 ◽  
Vol 363 (6428) ◽  
pp. 715-718 ◽  
Author(s):  
Ann-Kathrin Henß ◽  
Sung Sakong ◽  
Philipp K. Messer ◽  
Joachim Wiechers ◽  
Rolf Schuster ◽  
...  
Keyword(s):  
High Speed ◽  
Density Functional ◽  
Local Density ◽  
Variable Temperature ◽  
Industrial Process ◽  
Density Fluctuations ◽  
Scanning Tunneling ◽  
Fast Diffusion ◽  
Tunneling Microscopy ◽  
Adsorption Sites

How particles can move on a catalyst surface that, under the conditions of an industrial process, is highly covered by adsorbates and where most adsorption sites are occupied has remained an open question. We have studied the diffusion of O atoms on a fully CO-covered Ru(0001) surface by means of high-speed/variable-temperature scanning tunneling microscopy combined with density functional theory calculations. Atomically resolved trajectories show a surprisingly fast diffusion of the O atoms, almost as fast as on the clean surface. This finding can be explained by a “door-opening” mechanism in which local density fluctuations in the CO layer intermittently create diffusion pathways on which the O atoms can move with low activation energy.

Operation Experiences of Siemens IGCC Gas Turbines Using Gasification Products From Coal and Refinery Residues

2000 ◽  
Author(s):  
M. Huth ◽  
A. Heilos ◽  
G. Gaio ◽  
J. Karg
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Strong Impact ◽  
Coal Gas ◽  
Operation Conditions ◽  
Wide Range ◽  
Commercial Operation ◽  
Burner Design

The Integrated Gasification Combined Cycle concept is an emerging technology that enables an efficient and clean use of coal as well as residuals in power generation. After several years of development and demonstration operation, now the technology has reached the status for commercial operation. SIEMENS is engaged in 3 IGCC plants in Europe which are currently in operation. Each of these plants has specific characteristics leading to a wide range of experiences in development and operation of IGCC gas turbines fired with low to medium LHV syngases. The worlds first IGCC plant of commercial size at Buggenum/Netherlands (Demkolec) has already demonstrated that IGCC is a very efficient power generation technology for a great variety of coals and with a great potential for future commercial market penetration. The end of the demonstration period of the Buggenum IGCC plant and the start of its commercial operation has been dated on January 1, 1998. After optimisations during the demonstration period the gas turbine is running with good performance and high availability and has exceeded 18000 hours of operation on coal gas. The air-side fully integrated Buggenum plant, equipped with a Siemens V94.2 gas turbine, has been the first field test for the Siemens syngas combustion concept, which enables operation with very low NOx emission levels between 120–600 g/MWh NOx corresponding to 6–30 ppm(v) (15%O2) and less than 5 ppm(v) CO at baseload. During early commissioning the syngas nozzle has been recognised as the most important part with strong impact on combustion behaviour. Consequently the burner design has been adjusted to enable quick and easy changes of the important syngas nozzle. This design feature enables fast and efficient optimisations of the combustion performance and the possibility for easy adjustments to different syngases with a large variation in composition and LHV. During several test runs the gas turbine proved the required degree of flexibility and the capability to handle transient operation conditions during emergency cases. The fully air-side integrated IGCC plant at Puertollano/Spain (Elcogas), using the advanced Siemens V94.3 gas turbine (enhanced efficiency), is now running successfully on coal gas. The coal gas composition at this plant is similar to the Buggenum example. The emission performance is comparable to Buggenum with its very low emission levels. Currently the gas turbine is running for the requirements of final optimization runs of the gasifier unit. The third IGCC plant (ISAB) equipped with Siemens gas turbine technology is located at Priolo near Siracusa at Sicilly/Italy. Two Siemens V94.2K (modified compressor) gas turbines are part of this “air side non-integrated” IGCC plant. The feedstock of the gasification process is a refinery residue (asphalt). The LHV is almost twice compared to the Buggenum or Puertollano case. For operation with this gas, the coal gas burner design was adjusted and extensively tested. IGCC operation without air extraction has been made possible by modifying the compressor, giving enhanced surge margins. Commissioning on syngas for the first of the two gas turbines started in mid of August 1999 and was almost finished at the end of August 1999. The second machine followed at the end of October 1999. Since this both machines are released for operation on syngas up to baseload.

scholarly journals Flow Inhomogeneities in a Realistic Aeronautical Gas-Turbine Combustor: Formation, Evolution, and Indirect Noise

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Andrea Giusti ◽  
Luca Magri ◽  
Marco Zedda
Keyword(s):  
Gas Turbines ◽  
Transfer Functions ◽  
Guide Vane ◽  
Flame Structure ◽  
Combustion Noise ◽  
Moment Closure ◽  
Combustion Model ◽  
Conditional Moment ◽  
Eddy Simulation ◽  
Aero Engines

Indirect noise generated by the acceleration of combustion inhomogeneities is an important aspect in the design of aero-engines because of its impact on the overall noise emitted by an aircraft and the possible contribution to combustion instabilities. In this study, a realistic rich-quench-lean (RQL) combustor is numerically investigated, with the objective of quantitatively analyzing the formation and evolution of flow inhomogeneities and determining the level of indirect combustion noise in the nozzle guide vane (NGV). Both entropy and compositional noise are calculated in this work. A high-fidelity numerical simulation of the combustion chamber, based on the large-eddy simulation (LES) approach with the conditional moment closure (CMC) combustion model, is performed. The contributions of the different air streams to the formation of flow inhomogeneities are pinned down and separated with seven dedicated passive scalars. LES-CMC results are then used to determine the acoustic sources to feed an NGV aeroacoustic model, which outputs the noise generated by entropy and compositional inhomogeneities. Results show that non-negligible fluctuations of temperature and composition reach the combustor's exit. Combustion inhomogeneities originate both from finite-rate chemistry effects and incomplete mixing. In particular, the role of mixing with dilution and liner air flows on the level of combustion inhomogeneities at the combustor's exit is highlighted. The species that most contribute to indirect noise are identified and the transfer functions of a realistic NGV are computed. The noise level indicates that indirect noise generated by temperature fluctuations is larger than the indirect noise generated by compositional inhomogeneities, although the latter is not negligible and is expected to become louder in supersonic nozzles. It is also shown that relatively small fluctuations of the local flame structure can lead to significant variations of the nozzle transfer function, whose gain increases with the Mach number. This highlights the necessity of an on-line solution of the local flame structure, which is performed in this paper by CMC, for an accurate prediction of the level of compositional noise. This study opens new possibilities for the identification, separation, and calculation of the sources of indirect combustion noise in realistic aeronautical gas turbines.

Numerical Assessment of SCAP: A Passive System for Preventing Thermoacoustic Oscillations in Gas Turbine Annular Combustors

2007 ◽  
Author(s):  
Stefano Tiribuzi
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Research Unit ◽  
Combined Cycle ◽  
Computational Time ◽  
Computational Domain ◽  
Ambient Conditions ◽  
Pressure Oscillations ◽  
Operation Conditions ◽  
Thermoacoustic Oscillations

ENEL operates a dozen combined cycle units whose V94.3A gas turbines are equipped with annular combustors. In such lean premixed gas turbines, particular operation conditions could trigger large pressure oscillations due to thermoacoustic instabilities. The ENEL Research unit is studying this phenomenon in order to find out methods which could avoid or mitigate such events. The use of effective numerical analysis techniques allowed us to investigate the realistic time evolution and behaviour of the acoustic fields associated with this phenomenon. KIEN, an in-house low diffusive URANS code capable of simulating 3D reactive flows, has been used in the Very Rough Grid approach. This approach permits the simulation, with a reasonable computational time, of quite long real transients with a computational domain extended over all the resonant volumes involved in the acoustic phenomenon. The V94.3A gas turbine model was set up with a full combustor 3D grid, going from the compressor outlet up to the turbine inlet, including both the annular plenum and the annular combustion chamber. The grid extends over the entire circular angle, including all the 24 premixed burners. Numerical runs were performed with the normal V94.3A combustor configuration, with input parameters set so as no oscillations develop in the standard ambient conditions. Wide pressure oscillations on the contrary are associated with the circumferential acoustic modes of the combustor, which have their onset and grow when winter ambient conditions are assumed. These results also confirmed that the sustaining mechanism is based on the equivalence ratio fluctuation of premix mixture and that plenum plays an important role in such mechanism. Based on these findings, a system for controlling the thermoacoustic oscillation has been conceived (Patent Pending), which acts on the plenum side of the combustor. This system, called SCAP (Segmentation of Combustor Annular Plenum), is based on the subdivision of the plenum annular volume by means of a few meridionally oriented walls. Repetition of KIEN runs with a SCAP configuration, in which a suitable number of segmentation walls were properly arranged in the annular plenum, demonstrated the effectiveness of this solution in preventing the development of wide thermoacoustic oscillations in the combustor.

Assessment of the Indirect Combustion Noise Generated in a Transonic High-Pressure Turbine Stage

2015 ◽  
Author(s):  
Dimitrios Papadogiannis ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Gaofeng Wang ◽  
Stéphane Moreau ◽  
...  
Keyword(s):  
High Pressure ◽  
Acoustic Waves ◽  
Gas Turbines ◽  
Guide Vane ◽  
Combustion Noise ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Noise Generation ◽  
Turbine Stage ◽  
High Pressure Turbine

Indirect combustion noise, generated by the acceleration and distortion of entropy waves through the turbine stages, has been shown to be the dominant noise source of gas turbines at low-frequencies and to impact the thermoacoustic behavior of the combustor. In the present work, indirect combustion noise generation is evaluated in the realistic, fully 3D transonic high-pressure turbine stage MT1 using Large-Eddy Simulations (LES). An analysis of the basic flow and the different turbine noise generation mechanisms is performed for two configurations: one with a steady inflow and a second with a pulsed inlet, where a plane entropy wave train at a given frequency is injected before propagating across the stage generating indirect noise. The noise is evaluated through the Dynamic Mode Decomposition of the flow field. It is compared with previous 2D simulations of a similar stator/rotor configuration, as well as with the compact theory of Cumpsty and Marble. Results show that the upstream propagating entropy noise is reduced due to the choked turbine nozzle guide vane. Downstream acoustic waves are found to be of similar strength to the 2D case, highlighting the potential impact of indirect combustion noise on the overall noise signature of the engine.

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