Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Acoustic Characterization Of Combustors With Azimuthally Resolved Acoustic Forcing
Download Acoustic Characterization Of Combustors With Azimuthally Resolved Acoustic Forcing full books in PDF, epub, and Kindle. Read online Acoustic Characterization Of Combustors With Azimuthally Resolved Acoustic Forcing ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Acoustic Characterization of Combustors with Azimuthally Resolved Acoustic Forcing by : Shayna Levenson
Download or read book Acoustic Characterization of Combustors with Azimuthally Resolved Acoustic Forcing written by Shayna Levenson and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermoacoustic instabilities are a significant operational issue for low-emissions gas turbines in both the power and propulsion industries. Specifically, gas turbines that use lean-burn technology in an effort to reduce NOx emissions are highly susceptible to instabilities. Within the combustor, thermoacoustic instabilities can couple with a number of acoustic modes. Focusing on annular combustors, common in aircraft and power generation engines, the azimuthal mode that dominates the thermoacoustic feedback process excites the flame asymmetrically, which can lead to unique flame response. Therefore, the goal of this research is to create asymmetric acoustic fields to understand the acoustic field and how it's affecting the flow and the flame. In order to better understand these acoustic fields, Comsol models were generated to mimic both a laboratory combustor and a simplified system in which only the combustion chamber is considered. From this analysis, it is clear that the exit boundary condition of the combustion chamber has a large impact on the acoustic field. It is also evident that if the system is forced at a frequency close to one of its natural frequencies, it will experience a stronger response. However, it has also been shown that higher modes of forcing will produce a weaker acoustic response. Finally, the same acoustic modes were visible in both the combustion chamber and full lab experiment at the same eigenfrequencies when acoustic forcing was applied at lower modes. Experimental validation of the Comsol models mimicked the results from both the simplified geometry and laboratory experimental simulations. Additional resonant frequencies were identified through the use of white-noise excitation in the experiment. The implications of these results are discussed and future work proposed.
Book Synopsis Acoustic Characterization of Flame Blowout Phenomenon by : Suraj Nair
Download or read book Acoustic Characterization of Flame Blowout Phenomenon written by Suraj Nair and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustor blowout is a very serious concern in modern land-based and aircraft engine combustors. The ability to sense blowout precursors can provide significant payoffs in engine reliability and life. The objective of this work is to characterize the blowout phenomenon and develop a sensing methodology which can detect and assess the proximity of a combustor to blowout by monitoring its acoustic signature, thus providing early warning before the actual blowout of the combustor. The first part of the work examines the blowout phenomenon in a piloted jet burner. As blowout was approached, the flame detached from one side of the burner and showed increased flame tip fluctuations, resulting in an increase in low frequency acoustics. Work was then focused on swirling combustion systems. Close to blowout, localized extinction/re-ignition events were observed, which manifested as bursts in the acoustic signal. These events increased in number and duration as the combustor approached blowout, resulting an increase in low frequency acoustics. A variety of spectral, wavelet and thresholding based approaches were developed to detect precursors to blowout. The third part of the study focused on a bluff body burner. It characterized the underlying flame dynamics near blowout in greater detail and related it to the observed acoustic emissions. Vorticity was found to play a significant role in the flame dynamics. The flame passed through two distinct stages prior to blowout. The first was associated with momentary strain levels that exceed the flames extinction strain rate, leading to flame holes. The second was due to large scale alteration of the fluid dynamics in the bluff body wake, leading to violent flapping of the flame front and even larger straining of the flame. This led to low frequency acoustic oscillations, of the order of von Karman vortex shedding. This manifested as an abrupt increase in combustion noise spectra at 40-100 Hz very close to blowout. Finally, work was also done to improve the robustness of lean blowout detection by developing integration techniques that combined data from acoustic and optical sensors.
Book Synopsis Congrès des société savantes de la province de Savoie by :
Download or read book Congrès des société savantes de la province de Savoie written by and published by . This book was released on 1972 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Thermoacoustic Combustion Instability Control by : Dan Zhao
Download or read book Thermoacoustic Combustion Instability Control written by Dan Zhao and published by Academic Press. This book was released on 2023-02-13 with total page 1145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermoacoustic Combustion Instability Control: Engineering Applications and Computer Codes provides a unique opportunity for researchers, students and engineers to access recent developments from technical, theoretical and engineering perspectives. The book is a compendium of the most recent advances in theoretical and computational modeling and the thermoacoustic instability phenomena associated with multi-dimensional computing methods and recent developments in signal-processing techniques. These include, but are not restricted to a real-time observer, proper orthogonal decomposition (POD), dynamic mode decomposition, Galerkin expansion, empirical mode decomposition, the Lattice Boltzmann method, and associated numerical and analytical approaches. The fundamental physics of thermoacoustic instability occurs in both macro- and micro-scale combustors. Practical methods for alleviating common problems are presented in the book with an analytical approach to arm readers with the tools they need to apply in their own industrial or research setting. Readers will benefit from practicing the worked examples and the training provided on computer coding for combustion technology to achieve useful results and simulations that advance their knowledge and research. Focuses on applications of theoretical and numerical modes with computer codes relevant to combustion technology Includes the most recent modeling and analytical developments motivated by empirical experimental observations in a highly visual way Provides self-contained chapters that include a comprehensive, introductory section that ensures any readers new to this topic are equipped with required technical terms
Author :Timothy C. Lieuwen Publisher :AIAA (American Institute of Aeronautics & Astronautics) ISBN 13 : Total Pages :688 pages Book Rating :4.3/5 (91 download)
Book Synopsis Combustion Instabilities in Gas Turbine Engines by : Timothy C. Lieuwen
Download or read book Combustion Instabilities in Gas Turbine Engines written by Timothy C. Lieuwen and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 2005 with total page 688 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers gas turbine users and manufacturers a valuable resource to help them sort through issues associated with combustion instabilities. In the last ten years, substantial efforts have been made in the industrial, governmental, and academic communities to understand the unique issues associated with combustion instabilities in low-emission gas turbines. The objective of this book is to compile these results into a series of chapters that address the various facets of the problem. The Case Studies section speaks to specific manufacturer and user experiences with combustion instabilities in the development stage and in fielded turbine engines. The book then goes on to examine The Fundamental Mechanisms, The Combustor Modeling, and Control Approaches.
Book Synopsis Acoustic Characteristics of a Research Step Combustor by : S. P. Heneghan
Download or read book Acoustic Characteristics of a Research Step Combustor written by S. P. Heneghan and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Natural Dynamics of a Precessing Vortex Core in Swirling Flows by : Mark Frederick
Download or read book Natural Dynamics of a Precessing Vortex Core in Swirling Flows written by Mark Frederick and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion instability, or the coupling between flame heat release rate oscillations and combustor acoustics, is a significant issue in the operation of gas turbine combustors. This coupling is often driven by oscillations in the flow field. Shear layer roll-up, in particular, has been shown to drive longitudinal combustion instability in multiple systems, including both laboratory and industrial combustors. One method for suppressing combustion instability in these engines would be to suppress the receptivity of the shear layer to acoustic oscillations, severing the coupling mechanism between the acoustics and the flame. Previous work suggested that the existence of a precessing vortex core (PVC) may suppress the receptivity of the shear layer. The goal of this study is to first, understand the basic behavior of a PVC within a flow field, second, confirm that shear layer receptivity suppression is occurring, and lastly, understand the mechanism by which the PVC suppresses the shear layer receptivity. In this work, we couple experiment with linear stability analysis to determine whether a PVC can suppress shear layer receptivity to longitudinal acoustic forcing in a non-reacting swirling flow at a variety of swirl numbers. The shear layer response to the longitudinal acoustic forcing manifests as an m=0 mode since the acoustic field is axisymmetric. The PVC has been shown both in experiment and linear stability analysis to have m=1 and m=-1 modal content. By comparing the relative magnitude of the m=0 and m=-1, 1 modes, we quantify the impact that the PVC has on the shear layer response. The mechanism for shear layer response is determined using companion forced response analysis, where the shear layer disturbance growth rates mirror the experimental results. Differences in shear layer thickness and azimuthal velocity profiles drive the suppression of the shear layer receptivity to acoustic forcing.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721636020 Total Pages :32 pages Book Rating :4.6/5 (36 download)
Book Synopsis Systems Characterization of Combustor Instabilities with Controls Design Emphasis by : National Aeronautics and Space Administration (NASA)
Download or read book Systems Characterization of Combustor Instabilities with Controls Design Emphasis written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-21 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: This effort performed test data analysis in order to characterize the general behavior of combustor instabilities with emphasis on controls design. The analysis is performed on data obtained from two configurations of a laboratory combustor rig and from a developmental aero-engine combustor. The study has characterized several dynamic behaviors associated with combustor instabilities. These are: frequency and phase randomness, amplitude modulations, net random phase walks, random noise, exponential growth and intra-harmonic couplings. Finally, the very cause of combustor instabilities was explored and it could be attributed to a more general source-load type impedance interaction that includes the thermo-acoustic coupling. Performing these characterizations on different combustors allows for more accurate identification of the cause of these phenomena and their effect on instability. Kopasakis, George Glenn Research Center NASA/TM-2004-212912, AIAA Paper 2004-0638, E-14345
Book Synopsis Combustion Acoustic Instability Analysis of LPP Combustor by : Z. Yang
Download or read book Combustion Acoustic Instability Analysis of LPP Combustor written by Z. Yang and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Restricted Acoustic Modal Analysis Applied to Internal Combustor Spectra and Cross-Spectra Measurements by : Jeffrey Hilton Miles
Download or read book Restricted Acoustic Modal Analysis Applied to Internal Combustor Spectra and Cross-Spectra Measurements written by Jeffrey Hilton Miles and published by BiblioGov. This book was released on 2013-07 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A treatment of the modal decomposition of the pressure field in a combustor as determined by two Kulite pressure measurements is developed herein. It is applied to a Pratt & Whitney PW4098 engine combustor over a range of operating conditions. For modes other than the plane wave the new part of the treatment is the assumption that there are distinct frequency bands in which the individual modes, including the plane wave mode, overlap such that if circumferential mode m and circumferential mode m-1 are present than circumferential mode m 2 is not. Consequently, in the analysis used herein at frequencies above the first cut-off mode frequency, only pairs of circumferential modes are individually present at each frequency. Consequently, this is a restricted modal analysis. A new result is that the successful use of the same modal span frequencies over a range of operating conditions for this particular engine suggests that the temperature, T, and the velocity, v, of the flow at each operating condition are related by c(sup 2)-v(sup 2) = a constant where c is the speed of sound.
Book Synopsis Acoustic Characterization of a Piloted, Pre-mixed Flame Under Near Blowout Conditions by : Suraj Nair
Download or read book Acoustic Characterization of a Piloted, Pre-mixed Flame Under Near Blowout Conditions written by Suraj Nair and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Coupled acoustic-structure analysis of an annular DLE combustor, ASME 98-GT-502 by : Peter J. M. Cronemyr
Download or read book Coupled acoustic-structure analysis of an annular DLE combustor, ASME 98-GT-502 written by Peter J. M. Cronemyr and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Stockholm, Sweden, Jun 2-5, 1998.
Book Synopsis Multi-phase Combustion and Transport Processes Under the Influence of Acoustic Excitation by : Jeffrey L. Wegener
Download or read book Multi-phase Combustion and Transport Processes Under the Influence of Acoustic Excitation written by Jeffrey L. Wegener and published by . This book was released on 2014 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: This experimental study examined the coupling of acoustics with reactive multiphase transport processes and shear flows. The first portion of this dissertation deals with combustion of various liquid fuels when under the influence of externally applied acoustic excitation. For this study, an apparatus at the Energy and Propulsion Research Laboratory, UCLA, used a horizontal waveguide to create a standing acoustic wave, wherein burning fuel droplets were positioned near pressure nodes within the waveguide. Alcohol fuels (ethanol and methonal) as well as aviation fuel replacements (Fischer-Tropsch (FT) synfuel and an FT blend with JP-8) were studied here. During acoustic excitation, the flame surrounding the droplet was observed to be deflected in a manner consistent with the direction of a theoretical acoustic radiation force, analogous to a buoyancy force, acting on the burning system. Based on this degree of deflection, a method was developed for experimentally quantifying the acoustic acceleration and relating it to the theoretical acoustic acceleration. This technique employed phase-locked optical imaging of the flame in the ultraviolet band in order to capture hydroxyl radical (OH*) chemiluminescence as an indication of the flame structure and shape. The flame was observed to be deflected in a bulk manner, but also with micro-scale oscillations in time. The bulk or mean flame alteration was used to determine an experimental value of the acoustic acceleration for a range of different fuels and excitation conditions. This investigation showed experimentally determined acoustic accelerations which were quite consistent qualitatively with theory, but which were quantitatively inconsistent with theoretical predictions. Observed flame deformations were greatest for a droplet situated immediately next to a pressure node, in contrast to the theory, while milder flame deflections were observed for droplets positioned closer to a pressure antinode. These observations were consistent among all fuels studied, qualitatively and with the same mean qualitative trends. Phase-locked OH* chemiluminescence imaging revealed significant differences in the amplitude of flame oscillation based on the applied frequency and droplet location. Low frequency acoustic excitation and proximity to the pressure node produced higher amplitude flame oscillations, suggesting an enhanced degree of acoustically-coupled combustion that could be responsible for qualitative differences between theory and experimental measurements of acoustic acceleration. The second portion of this dissertation utilized a similar, but more advanced facility which was recently constructed at the Air Force Research Laboratory, Propulsion Directorate (RQR). These experiments explored the interaction between acoustics and nonreactive shear-coaxial jets under high chamber pressure, acoustically resonant conditions, using liquid nitrogen as the inner jet and gaseous helium as the outer jet. The shear-coaxial jet was placed within the chamber, for which piezoelectric sirens could create a standing wave. The coaxial jet could thus be situated at either a pressure node or a pressure antinode location, and backlit high-speed imaging was used to resolve the naturally unstable mixing layer between the inner and outer jets. For jets with and without exposure to acoustic forcing, two different reduced basis methods were applied to the gray-scale pixel intensity data in order to extract instability frequencies and mode shapes from image sets; these included proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). A new POD-based method was used to quantify the susceptibility of coaxial jets to external acoustic forcing by comparing the pixel intensity variance induced by the acoustic mode to the total variance of pixel intensity caused by fluctuations in jet mixing. A novel forcing susceptibility diagram was then created for coaxial jet momentum flux ratios of 2 and 6 for both pressure node and pressure antinode locations. Measurements of the critical forcing amplitude were made to quantify the acoustic perturbation amplitudes required in order for the forced mode to overtake the natural mode as the most dominant instability in the jet, which is generally classified as "lock-in" to the applied mode. It was found that, for forcing frequencies greater than the natural frequency of the jet, an increase in the forcing frequency caused the jet to be less susceptible to applied acoustic disturbances, thus requiring higher acoustic forcing to achieve "lock-in". This relationship held true for both pressure node and pressure antinode conditions. The shear layer instability characteristics of unforced jets were also investigated, and a theoretical convection velocity which depends on inner and outer jet velocities and densities was validated for the range of experimental flow conditions used in this study. An extensive description of the design of the experimental reactive facility is also offered, including preliminary results for oxygen-hydrogen coaxial jet flames acquired using high-speed OH* chemiluminescence imaging.
Author :National Aeronautics and Space Adm Nasa Publisher :Independently Published ISBN 13 :9781793905758 Total Pages :28 pages Book Rating :4.9/5 (57 download)
Book Synopsis Characterization and Simulation of the Thermoacoustic Instability Behavior of an Advanced, Low Emissions Combustor Prototype by : National Aeronautics and Space Adm Nasa
Download or read book Characterization and Simulation of the Thermoacoustic Instability Behavior of an Advanced, Low Emissions Combustor Prototype written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019-01-13 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extensive research is being done toward the development of ultra-low-emissions combustors for aircraft gas turbine engines. However, these combustors have an increased susceptibility to thermoacoustic instabilities. This type of instability was recently observed in an advanced, low emissions combustor prototype installed in a NASA Glenn Research Center test stand. The instability produces pressure oscillations that grow with increasing fuel/air ratio, preventing full power operation. The instability behavior makes the combustor a potentially useful test bed for research into active control methods for combustion instability suppression. The instability behavior was characterized by operating the combustor at various pressures, temperatures, and fuel and air flows representative of operation within an aircraft gas turbine engine. Trends in instability behavior versus operating condition have been identified and documented, and possible explanations for the trends provided. A simulation developed at NASA Glenn captures the observed instability behavior. The physics-based simulation includes the relevant physical features of the combustor and test rig, employs a Sectored 1-D approach, includes simplified reaction equations, and provides time-accurate results. A computationally efficient method is used for area transitions, which decreases run times and allows the simulation to be used for parametric studies, including control method investigations. Simulation results show that the simulation exhibits a self-starting, self-sustained combustion instability and also replicates the experimentally observed instability trends versus operating condition. Future plans are to use the simulation to investigate active control strategies to suppress combustion instabilities and then to experimentally demonstrate active instability suppression with the low emissions combustor prototype, enabling full power, stable operation. DeLaat, John C. and Paxson, Daniel E. Glenn Research Cent
Book Synopsis Thermoacoustic Instability by : R. I. Sujith
Download or read book Thermoacoustic Instability written by R. I. Sujith and published by Springer Nature. This book was released on 2021-12-14 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book systematically presents the consolidated findings of the phenomenon of self-organization observed during the onset of thermoacoustic instability using approaches from dynamical systems and complex systems theory. Over the last decade, several complex dynamical states beyond limit cycle oscillations such as quasiperiodicity, frequency-locking, period-n, chaos, strange non-chaos, and intermittency have been discovered in thermoacoustic systems operated in laminar and turbulent flow regimes. During the onset of thermoacoustic instability in turbulent systems, an ordered acoustic field and large coherent vortices emerge from the background of turbulent combustion. This emergence of order from disorder in both temporal and spatiotemporal dynamics is explored in the contexts of synchronization, pattern formation, collective interaction, multifractality, and complex networks. For the past six decades, the spontaneous emergence of large amplitude, self-sustained, tonal oscillations in confined combustion systems, characterized as thermoacoustic instability, has remained one of the most challenging areas of research. The presence of such instabilities continues to hinder the development and deployment of high-performance combustion systems used in power generation and propulsion applications. Even with the advent of sophisticated measurement techniques to aid experimental investigations and vast improvements in computational power necessary to capture flow physics in high fidelity simulations, conventional reductionist approaches have not succeeded in explaining the plethora of dynamical behaviors and the associated complexities that arise in practical combustion systems. As a result, models and theories based on such approaches are limited in their application to mitigate or evade thermoacoustic instabilities, which continue to be among the biggest concerns for engine manufacturers today. This book helps to overcome these limitations by providing appropriate methodologies to deal with nonlinear thermoacoustic oscillations, and by developing control strategies that can mitigate and forewarn thermoacoustic instabilities. The book is also beneficial to scientists and engineers studying the occurrence of several other instabilities, such as flow-induced vibrations, compressor surge, aeroacoustics and aeroelastic instabilities in diverse fluid-mechanical environments, to graduate students who intend to apply dynamical systems and complex systems approach to their areas of research, and to physicists who look for experimental applications of their theoretical findings on nonlinear and complex systems.
Book Synopsis Characterization of Acoustic Modes in Aeroengines by : Michelle Otero
Download or read book Characterization of Acoustic Modes in Aeroengines written by Michelle Otero and published by . This book was released on 2018 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic instabilities remain a key design concern faced in the development of liquid rocket engines. The interaction between the acoustic modes and the occurring combustion reactions can be detrimental to the engine. The fluctuating pressure waves resulting from the flame oscillations in the system can potentially lead to engine failure. For this reason, research in acoustic instabilities and methods to minimize the influences on the engine, has maintain interest in the aerospace community. The scope of this study was to design, optimize and characterize acoustic behaviors of a scaled rocket combustion chamber simulating acoustic pressure waves. Tangential and longitudinal acoustic waves of the system were extracted and validated through analytical and computational fluids dynamics models. The results of this study will assist with the process of extracting dominant oscillation frequencies of a system essential in the design of acoustic suppression devices for attenuation of critical frequencies.
Book Synopsis Computational Analysis of Acoustic Instabilities in Dump Combustor Configuration by : K. Molavi
Download or read book Computational Analysis of Acoustic Instabilities in Dump Combustor Configuration written by K. Molavi and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
