Nonlinear Behavior of Acoustic Waves in Combustion Chambers PDF Download
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Author: Fred Culick
Publisher:
ISBN:
Category : Combustion chambers
Languages : en
Pages : 138
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Author: Fred Culick
Publisher:
ISBN:
Category : Combustion chambers
Languages : en
Pages : 138
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Author: N. Ananthkrishnan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Vigor Yang
Publisher:
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Category :
Languages : en
Pages :
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Author: G. A. Flandro
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
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Book Description
In order to carry out useful predictive analyses of solid propellant rocket or ramjet combustion oscillation problems, it is necessary that all loss and gain mechanisms be accounted for. Recent motor experience has demonstrated that flow of oscillatory energy from vortex shedding to the acoustic field of the chamber is one of these mechanisms; in the ramjet problem it is probably the major source of oscillatory behavior. The coupling between the vortex instability which arises in regions of highly sheared flow and the chamber acoustic field represents a problem of great complexity. In this paper, a detailed analysis is described which addresses several basic features of this coupling. Some of the goals of the analysis are: (1) Determine growth rate corrections for use in standard stability assessment codes, (2) Determine the limit cycle processes of the vortical region of flow, and (3) Assess the global limiting behavior of the coupled nonlinear acoustical/vortical flow.
Author:
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Category :
Languages : en
Pages : 106
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The Rijke tube device has been employed since its invention in 1859 in the experimental study of many examples of thermo-acoustic phenomena. The device exhibits generation of acoustic oscillations by heat energy supplied to the flow field in the fashion of a selfexcited oscillator. In recent times, the Rijke tube has proved to be a valuable tool in simulation of combustion instability phenomena in rockets and industrial burners. Despite the simplicity of the device, the Rijke tube simulates most important geometrical and physical features that lead to the growth of nonlinear pressure oscillations in combustion chambers. For example it provides a through-flow as in a rocket chamber and is fixed with an energy source that can cause unsteady combustion. The open ends and geometrical simplicity leads to easy accessibility for instrumentation to make measurements that would not be possible in actual combustion chambers. During operation, wave motions are generated by transfer of energy from a heated grid placed at a point within the chamber that can be related to theoretical models for the phenomenon by Rayleigh and other investigators. However, initially, there is exponential growth of these oscillations to high amplitude and transition to a nonlinear limit cycle at a nearly fixed amplitude (usually lasting several seconds) due to natural nonlinearities in the system. The hypothesis advanced in this thesis to explain this nonlinear limiting effect that is the wave steepening occurs in a manner analogous to similar generation of steep wave fronts in rocket motor chambers. The latter proposal is based on: 1) direct observation (using Schlieren techniques) of traveling shock-like waves in axial mode instability, 2) correlation of the observed waves with spectral components similar to that of sawtooth structure, and 3) theoretical calculations showing that the limit amplitude phenomenon is directly related to the cascade of energy from lower frequency standing acoustic modes to higher harmonics leading to characteristic spectrum similar to that of a traveling steep-fronted wave. In prior research, the 'mechanism' of initiation of instability in the system has been the main focus. The goal of the research described in this thesis is to measure and to characterize the signal produced during the highiv amplitude amplitude (nearly steady state) oscillations at the limit cycle. The intent was to demonstrate in a very simple way that the gas motions produced during the limit cycle in the Rijke tube have the same characteristics observed in many years of rocket testing. The observations again verify the great utility of the Rijke tube in seeking better understanding of the analogous rocket instability.
Author: Tim C. Lieuwen
Publisher: Cambridge University Press
ISBN: 1108841317
Category : Science
Languages : en
Pages : 533
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Book Description
Explore a unified treatment of the dynamics of combustor systems, including acoustics, fluid mechanics, and combustion in a single rigorous text. This updated new edition features an expansion of data and experimental material, updates the coverage of flow stability, and enhanced treatment of flame dynamics. Addresses system dynamics of clean energy and propulsion systems used in low emissions systems. Synthesizing the fields of fluid mechanics and combustion into a coherent understanding of the intrinsically unsteady processes in combustors. This is a perfect reference for engineers and researchers in fluid mechanics, combustion, and clean energy.
Author:
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ISBN:
Category :
Languages : en
Pages : 146
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A linear and nonlinear acoustic wave analysis has been developed for baffled combustion chambers. Results suggest three important effects of baffles on transverse modes of combustion instability. First, transverse waves can be longitudinalized inside baffle compartments. This may decouple combustion response from oscillatory motions if the processes near the injector face are sensitive to transverse variations in pressure. Second, severe restriction of the transverse component of acoustic velocity fluctuations is observed in baffle compartments. This may be key in stabilizing systems with velocity-sensitive combustion. Third, the frequency of oscillation is decreased with the addition of baffles, in agreement with experiments. One potentially destabilizing effect of baffles is the observed pressure concentration at the injector face. Pressure sensitive processes in this region may enhance instability. Limit cycles were observed for both two- and three-dimensional baffled chambers. Their most remarkable characteristic is high frequency modulation of the limit cycle amplitude ... Combustion instability; Liquid rocket propulsion; Acoustic waves.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 836
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Author: Elias Atieh Awad
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 286
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Author: Eric James Jacob
Publisher:
ISBN:
Category :
Languages : en
Pages : 162
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Combustion instability (CI) has been persistent in all forms of propulsion since their inception. CI is characterized by pressure oscillations within the propulsion system. If even a small fraction of the dense energy within the system is converted to acoustic oscillations the system vibrations can be devastating. The coupling of combustion and uid dynamic phenomena in a nonlinear system poses CI as a signicant engineering challenge. Drawing from previous analysis, second order acoustic energy models are taken to third order. Second order analysis predicts exponential growth. The addition of the third order terms capture the nonlinear acoustic phenomena (such as wave steepening) observed in experiments. The analytical framework is derived such that the energy sources and sinks are properly accounted for. The resulting third order solution is compared against a newly performed simplied acoustic closed tube experiment. This experiment provides the interesting result that in a forced system, as the 2nd harmonic is driven, no energy is transferred back into the 1st mode. The subsequent steepened waveform is a summation of 2nd mode harmonics (2, 4, 6, 8 ...) where all odd modes are nonexistent. The current third order acoustic model recreates the physics as seen in the experiment. Numerical experiments show the sensitivity of the pressure wave limit cycle amplitude to the second order growth rate, highlighting the importance of correctly calculating the growth rates. The sensitivity of the solution to the third order parameter is shown as well. Exponential growth is found if the third order parameter is removed, and increased nonlinear behavior is found if it retained and as it is increased. The solutions sensitivity to this term highlights its importance and shows the need for continued analysis via increasing the models generality by including neglected eects. In addition, the aect of a time varying second order growth rate is shown. This eect shows the importance of modeling the system in time because of the time lag between changes in the growth rate to a change in the limit cycle amplitude.
