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Author: Avandelino Santana Jr.
Publisher: LAP Lambert Academic Publishing
ISBN: 9783838369921
Category :
Languages : en
Pages : 172
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Book Description
Combustion instability problems have been experienced during nearly every rocket engine development program, characterized by pressure oscillations and release of energy. Several distinct types of instability have been observed, including the high frequency instability or acoustic instability, which is usually suppressed by means of passive control devices. The main purpose of this work was the experimental investigation of Helmholtz resonators and baffles to control acoustic instabilities in combustion chambers. Firstly, cold tests were carried out on full-scale model to analyze the efficiency of resonators. Experimental frequency spectrum data, in excellent agreement with theory, demonstrated the resonator is capable to reduce significantly the SPL amplitude. Afterwards, results of hot tests were compared with cold tests and with theory. The experimental data validated the methodology to design resonators useable to control combustion instabilities. This book provides a step-by-step procedure, which can be helpful to engineers and designers of liquid rocket engines, rocket motors and industrial burners, or anyone else who has already faced acoustic instability problems.
Author: Avandelino Santana Jr.
Publisher: LAP Lambert Academic Publishing
ISBN: 9783838369921
Category :
Languages : en
Pages : 172
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Book Description
Combustion instability problems have been experienced during nearly every rocket engine development program, characterized by pressure oscillations and release of energy. Several distinct types of instability have been observed, including the high frequency instability or acoustic instability, which is usually suppressed by means of passive control devices. The main purpose of this work was the experimental investigation of Helmholtz resonators and baffles to control acoustic instabilities in combustion chambers. Firstly, cold tests were carried out on full-scale model to analyze the efficiency of resonators. Experimental frequency spectrum data, in excellent agreement with theory, demonstrated the resonator is capable to reduce significantly the SPL amplitude. Afterwards, results of hot tests were compared with cold tests and with theory. The experimental data validated the methodology to design resonators useable to control combustion instabilities. This book provides a step-by-step procedure, which can be helpful to engineers and designers of liquid rocket engines, rocket motors and industrial burners, or anyone else who has already faced acoustic instability problems.
Author: Chuan-Han Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Dan Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Robert C. Steele
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Indianapolis, Indiana, June 7-June 10, 1999.
Author: Timothy C. Lieuwen
Publisher: AIAA (American Institute of Aeronautics & Astronautics)
ISBN:
Category : Science
Languages : en
Pages : 688
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Book Description
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.
Author: Dan Zhao
Publisher: Academic Press
ISBN: 0323899188
Category : Technology & Engineering
Languages : en
Pages : 1145
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Book Description
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: Michael D. Cornwell
Publisher:
ISBN:
Category :
Languages : en
Pages : 415
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Book Description
Combustion at high pressure in applications such as rocket engines and gas turbine engines commonly experience destructive combustion instabilities. These instabilities results from interactions between combustion heat release, fluid mechanics and acoustics. This research explores the significant affect of unstable fluid mechanics processes in augmenting unstable periodic combustion heat release. The frequency of the unstable heat release may shift to match one of the combustors natural acoustic frequencies which then can result in significant energy exchange from chemical to acoustic energy resulting in thermoacoustic instability. The mechanisms of the fluid mechanics in coupling combustion to acoustics are very broad with many varying mechanisms explained in detail in the first chapter. Significant effort is made in understanding these mechanisms in this research in order to find commonalities, useful for mitigating multiple instability mechanisms. The complexity of combustion instabilities makes mitigation of combustion instabilities very difficult as few mitigation methods have historically proven to be very effective for broad ranges of combustion instabilities. This research identifies turbulence intensity near the forward stagnation point and movement of the forward stagnation point as a common link in what would otherwise appear to be very different instabilities. The most common method of stabilization of both premixed and diffusion flame combustion is through the introduction of swirl. Reverse flow along the centerline is introduced to transport heat and chemically active combustion products back upstream to sustain combustion. This research develops methods to suppress the movement of the forward stagnation point without suppressing the development of the vortex breakdown process which is critical to the transport of heat and reactive species necessary for flame stabilization. These methods are useful in suppressing the local turbulence at the forward stagnation point, limiting dissipation of heat and reactive species significantly improving stability. Combustion hardware is developed and tested to demonstrate the stability principles developed as part of this research. In order to more completely understand combustion instability a very unique method of combustion was researched where there are no discrete points of combustion initiation such as the forward stagnation point typical in many combustion systems including swirl and jet wake stabilized combustion. This class of combustion which has empirical evidence of great stability and efficient combustion with low CO, NOx and UHC emissions is described as high oxidization temperature distributed combustion. This mechanism of combustion is shown to be stable largely because there are no stagnations points susceptible to fluid mechanic perturbations. The final topic of research is active combustion control by fuel modulation. This may be the only practical method of controlling most instabilities with a single technique. As there are many papers reporting active combustion control algorithms this research focused on the complexities of the physics of fuel modulation at frequencies up to 1000 Hz with proportionally controlled flow amplitude. This research into the physics of high speed fluid movement, oscillation mechanical mechanisms and electromagnetics are demonstrated by development and testing of a High Speed Latching Oscillator Valve.
Author: J. Hermann
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Book Description
Reducing the output of NOx pollutants and enhancing efficiency are the two major aims pursued by developers of modern gas turbines. In order to achieve them. lean premix combustion is preferred turbine inlet temperatures and thus power densities within the combustion chamber system being continuously increased to augment efficiency. Due to this fact. the tendency of modern combustion systems to develop so-called self- excited combustion oscillations keeps increasing. After briefly discussing the oscillation problems encountered with the annular combustion chamber of a Siemens type V94.3A stationary gas turbine. particular attention will be paid to suppressing these oscillations by passive and active means. The passive measures presented. i.e. extending the burner nozzle were intended to detune the combustion system by prolonging the time lag required by the combustible mixture exiting the burner outlet to reach the combustion zone Moreover. to suppress periodic vortex shedding. another possible cause for combustion instabilities. those extensions were inclined in a certain angle with respect to the main flow direction. To prevent the in-phase lock of all 24 burners promoting the excitation of any azimuthal mode the burners were selected to have different time lags and were arranged asymmetrically within the annular combustion chamber. In addition to these passive measures, a multi-channel Active Instability Control (AIC) system was implemented to achieve further damping. With the AIC system presented. any homer oscillations occurring are measured by p-ressure sensors their signals are processed by means of a multi-channel controller and then transmitted to actuators designed to damp down combustion oscillations. The points of intervention selected to do so were the gas supplies of the pilot flames.
Author: R. I. Sujith
Publisher: Springer Nature
ISBN: 3030811352
Category : Science
Languages : en
Pages : 484
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Book Description
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.
Author: Zachary A. Smith
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 244
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Book Description
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.
