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The Influence Of Comubstion Noise On Acoustic Instabilities
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Book Synopsis The Influence of Comubstion Noise on Acoustic Instabilities by :
Download or read book The Influence of Comubstion Noise on Acoustic Instabilities written by and published by . This book was released on 1997 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although flows in combustors contain considerable noise, arising from several kinds of sources, there is a sound basis for treating organized oscillations as distinct motions. That has been an essential assumption incorporated in virtually all treatments of combustion instabilities. However, certain characteristics of the organized or deterministic motions seem to have the nature of stochastic processes. For example, the amplitudes in limit cycles always exhibit a random character and even the occurrence of instabilities seems occasionally to possess some statistical features. Analysis of nonlinear coherent motions in the presence of stochastic sources is therefore an important part of the theory. We report here a few results for organized oscillations in the presence of noise. The most significant deficiency of this work is that, owing to the low level of current understanding, the stochastic sources of noise are modeled in ad hoc fashion and are not founded on a solid physical basis appropriate to combustion chambers.
Download or read book Combustion Noise written by Anna Schwarz and published by Springer Science & Business Media. This book was released on 2009-06-17 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: November, 2008 Anna Schwarz, Johannes Janicka In the last thirty years noise emission has developed into a topic of increasing importance to society and economy. In ?elds such as air, road and rail traf?c, the control of noise emissions and development of associated noise-reduction techno- gies is a central requirement for social acceptance and economical competitiveness. The noise emission of combustion systems is a major part of the task of noise - duction. The following aspects motivate research: • Modern combustion chambers in technical combustion systems with low pol- tion exhausts are 5 - 8 dB louder compared to their predecessors. In the ope- tional state the noise pressure levels achieved can even be 10-15 dB louder. • High capacity torches in the chemical industry are usually placed at ground level because of the reasons of noise emissions instead of being placed at a height suitable for safety and security. • For airplanes the combustion emissions become a more and more important topic. The combustion instability and noise issues are one major obstacle for the introduction of green technologies as lean fuel combustion and premixed burners in aero-engines. The direct and indirect contribution of combustion noise to the overall core noise is still under discussion. However, it is clear that the core noise besides the fan tone will become an important noise source in future aero-engine designs. To further reduce the jet noise, geared ultra high bypass ratio fans are driven by only a few highly loaded turbine stages.
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 Passive Mitigation of Combustion Noise and Thermo-acoustic Instability Using Porous Inert Media at Elevated Pressure by : Larry Justin Williams
Download or read book Passive Mitigation of Combustion Noise and Thermo-acoustic Instability Using Porous Inert Media at Elevated Pressure written by Larry Justin Williams and published by . This book was released on 2012 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion instabilities have presented major problems in high-pressure, turbulent combustion systems for nearly a century, beginning with rocket propulsion systems. To enhance combustion efficiencies, other engines, such as gas turbines for power generation, operate at high pressures and reactant flow rates that are only small relative to those of rocket engine operation. The majority of power generation systems today extract energy from such efficient combustion processes. Recently, gas turbine engines, both power generation and propulsion platforms, are operated under very lean conditions to reduce flame temperatures and thus, emissions of the primary smog forming constituent, NOx. Extinction, flashback, blowoff, and autoignition pose challenges when operating at lean-premixed conditions. Flame stability at such lean conditions is problematic; thus, a swirled flow method is used to anchor and stabilize these flames. Intense turbulence, resulting from the pressure drop across flow swirlers, drives fluctuations in pressure and heat release rate. The feedback between pressure oscillations and heat release fluctuations in the reaction zone often drives resonant instabilities that propagate through the flow and surrounding structures. Such self-excited instabilities influence high rates of heat release in the reaction zone, which is located near the point of injection. Vibrations and high temperatures lead to the fatigue of injection components, instrumentation, and downstream turbine blades. A novel passive combustion noise control technique is experimentally investigated in the present study. The approach involves the mating of a porous inert material (PIM) with the inlet of a swirl-stabilized, lean-premixed combustor. The foam insert reduces turbulent intensities within the inner and outer recirculation zones of a common swirl-stabilized burner, thus reducing the amplitude of combustion driven instabilities. Experiments are conducted at high pressures, with high reactant flow rates and equivalence ratios. Results show that the ceramic foam insert is effective at mitigating combustion instabilities, suppressing combustion noise, and potentially, acoustic damping. The total sound pressure level for many of the cases investigated is reduced by 10 dB and greater. Furthermore, the approach can easily be retrofitted to commercial, industrial, and propulsion gas turbine combustion systems.
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
Book Synopsis Solid Rocket Propulsion Technology by : A. Davenas
Download or read book Solid Rocket Propulsion Technology written by A. Davenas and published by Newnes. This book was released on 2012-12-02 with total page 623 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, a translation of the French title Technologie des Propergols Solides, offers otherwise unavailable information on the subject of solid propellants and their use in rocket propulsion. The fundamentals of rocket propulsion are developed in chapter one and detailed descriptions of concepts are covered in the following chapters. Specific design methods and the theoretical physics underlying them are presented, and finally the industrial production of the propellant itself is explained. The material used in the book has been collected from different countries, as the development of this field has occurred separately due to the classified nature of the subject. Thus the reader not only has an overall picture of solid rocket propulsion technology but a comprehensive view of its different developmental permutations worldwide.
Book Synopsis Passive Control of Combustion Noise and Thermo-acoustic Instability with Porous Inert Media by : Zachary A. Smith
Download or read book Passive Control of Combustion Noise and Thermo-acoustic Instability with Porous Inert Media written by Zachary A. Smith and published by . This book was released on 2011 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion noise and thermo-acoustic instability present a major area of concern for many industrial combustion applications, especially those operating under lean-premixed (LPM) conditions. While LPM combustion reduces thermal NOx by allowing operation at reduced flame temperatures, LPM flames are particularly susceptible to combustion noise and instability. While combustion noise and thermo-acoustic instability are distinctly different phenomena; both originate from the same source -- unsteady heat release in a turbulent flow field. Instabilities are self-excited and arise when energy from combustion is added to the system faster than energy is dissipated by heat transfer. In a typical swirl-stabilized combustor, flame is stabilized downstream of the dump plane and is sustained by central and corner recirculation zones. The present study combines porous inert media (PIM) assisted combustion with swirl-stabilized combustion to alter the combustor flow field in an advantageous manner. A ring-shaped PIM insert is placed directly at the dump plane to eliminate zones of intense turbulent fluctuations, thereby mitigating combustion noise at the source. With PIM, a central flame is confined within the annular void of the insert while a small portion of reactants flow through the PIM and stabilize on the downstream surface. Additionally, the porous insert provides acoustic damping and passive attenuation of pressure waves. This study is a preliminary step towards implementing the technique at elevated operating pressures, and eventually, liquid fuel combustors. Atmospheric combustion tests are conducted for a variety operating conditions to determine effectiveness of PIM to reduce combustion noise and instability. Parameters varied include air preheat temperature, air flow rate, equivalence ratio, and swirler axial location. Experiments are conducted with a high swirl angle, as opposed to previous experiments which used a lower swirl angle. For most conditions, PIM is shown to reduce total sound pressure level (SPL) in cases where instability is not intense. For all cases where instability is the dominant component of total SPL, PIM is extremely effective in eliminating instability. In these cases, total SPL is reduced by as much as 30 dB with PIM combustion. Furthermore, experiments show that no significant pressure drop penalty is incurred with porous media.
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 Effect of Noise on a Model Thermoacoustic System at its Stability Boundary by : Richard Steinert
Download or read book Effect of Noise on a Model Thermoacoustic System at its Stability Boundary written by Richard Steinert and published by Springer. This book was released on 2016-04-20 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: In experiments on a prototypical combustor, Richard Steinert identifies new insights on the impact of noise on the phenomenon known as thermoacoustic instability. The phenomenon is a concerning issue which creates a technical limit on the efficiency and environmental impact of fossil fuels combustion in industrial combustors. It poses a threat to the structural integrity of practical systems such as gas turbine combustors and rocket engines. The experiments demonstrate that thermoacoustic systems feature an interesting noise-induced behaviour known as coherence resonance – a coherent response of dynamical systems close to their stability boundary that is induced by stochastic excitation. The work contained in this publication is an example illustrating the importance of fundamental considerations in solving perplexing engineering issues.
Book Synopsis Combustion Instabilities Driven by Thermo-chemical Acoustic Sources by : American Society of Mechanical Engineers. Winter Annual Meeting
Download or read book Combustion Instabilities Driven by Thermo-chemical Acoustic Sources written by American Society of Mechanical Engineers. Winter Annual Meeting and published by . This book was released on 1989 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Review of Combustion-acoustic Instabilities by : Ayo Oyediran
Download or read book Review of Combustion-acoustic Instabilities written by Ayo Oyediran and published by . This book was released on 1995 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Flow Diagnostic of Swirl Stabilized Combustion Without and with Porous Inert Media for Mitigation of Combustion Noise and Thermo-acoustic Instabilities by : Joseph Warren Meadows
Download or read book Flow Diagnostic of Swirl Stabilized Combustion Without and with Porous Inert Media for Mitigation of Combustion Noise and Thermo-acoustic Instabilities written by Joseph Warren Meadows and published by . This book was released on 2014 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Study of combustion dynamics has gained significant research attention since low-emission systems are increasingly employed in the industry. In particular, combustion noise and thermo-acoustic instabilities are of great importance in highly critical applications such as power generation, jet propulsion engines, and rocket propulsion systems. Recently, porous inert media (PIM), also referred to as foam insert, has shown promise in mitigating combustion noise and thermo-acoustic instabilities in lean premixed (LPM), swirl-stabilized combustion at atmospheric pressure and elevated pressures. In this study, the flow field without and with PIM is investigated to understand the underlying mechanisms responsible for mitigating thermo-acoustic instabilities. Experiments are conducted for LPM combustion and lean direct injection (LDI) combustion. First, time-resolved PIV technique is utilized to measure the non-reacting flow field without and with PIM. Although the flow field inside the annulus of the foam insert was optically inaccessible, measurements immediately downstream provide insight into the instantaneous flow field and turbulence characteristics. The study highlights the role of the foam insert on vorticity, velocity, shear layer spreading angle, recirculation zone dynamics, and turbulent kinetic energy; which ultimately affects the acoustics behavior of the combustor in a favorable manner. The effect of PIM on the dominant turbulent structures in the flow field is quantified using proper orthogonal decomposition (POD) technique. Next, flow field measurements are acquired for LPM swirl-stabilized combustion without and with PIM. The turbulent structures similar to the non-reacting flow field are also present in the reacting flow field, with notable difference in size and shape. The instantaneous and average flow fields provide insight into the effects of PIM on the velocity and turbulence fields. POD analysis is used to quantify the effect of PIM on the dominant turbulent structures, and PIM is shown to distribute the turbulent energy from the large scale structures to smaller scale structures. By harmonically reconstructing the flow field at the frequency of thermo-acoustic instability, the feedback mechanism is found to be the vortical structures in the corner recirculation zones, and PIM is shown to eliminate the feedback mechanism. The efficacy of PIM in mitigating combustion noise and thermo-acoustic instabilities is demonstrated for liquid fuel combustion utilizing the LDI concept. In this system, the flame stabilizes downstream of the dump plane due to a balance of flow velocity and flame speed of the fuel-air mixture created upstream. The ring shaped PIM is placed at the dump plane of the combustor to alter the flow field in an advantageous manner. Sound pressure levels (SPL) and CO and NOx emissions are measured for combustion without and with PIM inserts. Effect of atomizing air to liquid mass ratio on SPL suggests equivalence ratio oscillations are the driving force for thermo-acoustic instabilities. Results show that the PIM insert reduces broad band combustion noise, mitigates peak instabilities occurring at the first longitudinal mode of the natural frequency of the combustor, and facilitates thermal feedback from the flame to the fuel atomization process. Different insert geometries were examined and they all reduced SPLs, but the converging foam geometry provided the best performance. Finally, flow fields of LDI combustion are experimentally measured using time-resolved PIV technique without and with PIM. The instantaneous flow field highlights the role of PIM on the fluctuating velocity field. The driving mechanism for thermo-acoustic instability is identified by analyzing the fluctuating flow field, and PIM is found to decrease the driving force for thermo-acoustic instability. The average flow field is used to show the effect of PIM on the turbulence and POD analysis is used to quantify the effect of PIM on the turbulent structures. The study identifies spatial and temporal non-homogeneities in equivalence ratio as the feedback mechanisms for exciting thermo-acoustic instabilities in LDI swirl-stabilized combustion. In general, PIM decreases the driving force while increasing the dampening force in both LPM and LDI combustion systems.
Book Synopsis Fundamentals of Aeroacoustics with Applications to Aeropropulsion Systems by : Xiaofeng Sun
Download or read book Fundamentals of Aeroacoustics with Applications to Aeropropulsion Systems written by Xiaofeng Sun and published by Elsevier. This book was released on 2020-10-14 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Aeroacoustics with Applications to Aeropropulsion Systems from the Shanghai Jiao Tong University Press Aerospace series, is the go-to reference on the topic, providing a modern take on the fundamental theory and applications relating to prediction and control of all major noise sources in aeropropulsion systems. This important reference compiles the latest knowledge and research advances, considering both the physics of aerodynamic noise generation in aero-engines and related numerical prediction techniques. Additionally, it introduces new vortex sound interaction models, a transfer element method, and a combustion instability model developed by the authors. Focusing on propulsion systems from inlet to exit, including combustion noise, this new resource will aid graduate students, researchers, and R&D engineers in solving the aircraft noise problems that currently challenge the industry. Updates the knowledge-base on the sound source generated by aeropropulsion systems, from inlet to exit, including combustion noise Covers new aerodynamic noise control technology aimed at the low-noise design of next generation aero-engines, including topics such as aerodynamic noise and aero-engine noise control Includes new, cutting-edge models and methods developed by an author team led by the editor-in-chief of the Chinese Journal of Aeronautics and Astronautics Considers both the physics of aerodynamic noise generation in aero-engines and related numerical prediction techniques
Book Synopsis The Influence of Accelerating Entropy Inhomogeneities on Combustor Thermoacoustics by : Chee Su Goh
Download or read book The Influence of Accelerating Entropy Inhomogeneities on Combustor Thermoacoustics written by Chee Su Goh and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The growing global concern over environmental emissions such as nitrogen oxides and noise sets challenging problems for aero-propulsion engineers. Acoustic waves generated by unsteady combustion not only contribute towards the overall noise transmission, but may also cause thermoacoustic instability in combustors, particularly those designed for low NOx emissions. Combustion noise is generated by unsteady combustion - either by the direct generation of acoustic waves or indirectly by the creation of entropy waves. Entropy waves by themselves are silent, but when accelerated, such as through the combustor exit, they create further acoustic waves known as entropy noise. This thesis aims to study transmitted and reflected combustion noise. Current predictions for noise transmission often assume that the wavelengths of the flow perturbations are large compared to the combustor length, known as the compact assumption. We will develop predictions for finite-length combustors accurate to first-order in frequency. The effect of the interaction between an oscillating shock wave with combustion noise is also studied analytically. The predictions agree with data from numerical simulations. Combustion acoustics reflected at the combustor exit may go on to interfere with the combustion process, setting up a feedback mechanism that may lead to thermoacoustic instability. A modified combustor model is presented to study the effect of dissipation and dispersion of entropy waves on the instability, and it was found that the extent of dissipation or dispersion not only plays a significant role on whether instability occurs, but also determines the dominant frequency of oscillations. Furthermore, analytical and numerical investigations suggest that entropy waves are convected with the flow undissipated, and that modelling improvements may be made to take entropy dispersion into account. The findings in this work provide better tools to understand indirect combustion acoustics and to analyse their importance in both transmitted combustion noise and the thermoacoustic instability experienced by low NOx combustors.
Book Synopsis Liquid Rocket Engine Combustion Instability by : Vigor Young
Download or read book Liquid Rocket Engine Combustion Instability written by Vigor Young and published by AIAA. This book was released on 1995 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Since the invention of the V-2 rocket during World War II, combustion instabilities have been recognized as one of the most difficult problems in the development of liquid propellant rocket engines. This book is the first published in the United States on the subject since NASA's Liquid Rocket Combustion Instability (NASA SP-194) in 1972. In this book, experts cover four major subject areas: engine phenomenology and case studies, fundamental mechanisms of combustion instability, combustion instability analysis, and engine and component testing. Especially noteworthy is the inclusion of technical information from Russia and China--a first.
Book Synopsis Chemical-Acoustic Interactions in Combustion Systems by : E. S. Oran
Download or read book Chemical-Acoustic Interactions in Combustion Systems written by E. S. Oran and published by . This book was released on 1985 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review is presented of chemical-acoustic coupling in terms of its role as a basic interaction which can alter the behavior of combustion systems. Effects resulting from this interaction include sound amplification, changes in sound speed and frequency, sound-induced changes in reaction rates, and acoustic stimulation of chemical oscillation and instabilities. Such effects are important in a variety of problems including combustion instability in jet and rocket engines, the structure of propagating detonations, and turbulence in chemically reacting flows. Background material is presented starting with the early work Lord Raleigh and continuing into a discussion of the relevant properties of sound waves. This leads to a discussion of the influence of energy release on sound waves and the influence of sound waves on chemical reactions. The conclusion is a discussion of chemical-acoustic coupling in combustion environments.
Book Synopsis Effects of Turbulence-induced Colored Noise on Thermoacoustic Instabilities in Combustion Chambers by : Giacomo Biociolini
Download or read book Effects of Turbulence-induced Colored Noise on Thermoacoustic Instabilities in Combustion Chambers written by Giacomo Biociolini and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
