Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"Fan noise"”.
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Fan noise reduction from a supersonic inlet
… was conducted to investigate the radiation of fan noise through a supersonic inlet. A scaled-down model of an axisymmetric, mixed-compression, supersonic inlet (P-inlet) was used in conjunction with a 10.4 cm (4.1 in) diameter turbofan engine simulator as the noise source. The tests were …
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Predicting fan noise propagation in aeroengine bypass ducts
This thesis explores the prediction of rearwards fan noise propagation within the bypass duct and its radiation into the far feld. Two recently developed models: B-induct and GXMunt, are exploited in application to real engine bypass ducts and their performance is evaluated. These methods are an …
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Reduced fan noise radiation from a supersonic inlet
… used in conjunction with a 10.4cm (4.1 in.) turbofan engine simulator to test a new inlet door geometry designed to reduce flow distortion and noise radiation. The new door geometry uses door passages with increased circumferential span to improve the distribution of the flow entering through the …
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Flow Control Optimization for Improvement of Fan Noise Reduction
The study of the flow of a fan blade was conducted to improve tonal fan noise reduction by optimizing an existing flow control configuration. The current configuration consisted of a trailing edge Slot with a flow control area of 0.045 in² per inch span with an exit angle of -3.3° with respect to …
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Compact Integrated Active-Passive Approach for Axial Fan Noise Control
A new active-passive approach for the control of noise radiated from a small axial fan was investigated. The approach involved the installation of an axial fan into a short duct with both passive and active noise control functions. First, a systematic methodology for the analytical modeling of …
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Advanced Trailing Edge Blowing Concepts for Fan Noise Control: Experimental Validation
… performed to reduce rotor / stator interaction noise in turbofan engines. The existing technique of filling every velocity deficit requires a large amount of air and is therefore impractical. The purpose of this research is to investigate new blowing configurations in order to achieve noise …
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Application of microperforated elements in axial fan noise control and silencer design
… this study, microperforated panels were used in fan noise control and in acoustic silencers, where both of the devices are easily accessible by humans.
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Analysis and Synthesis of Aicraft Engine Fan Noise for Use in Psychoacoustic Studies
Community noise impact is an important factor in design of current generation aircraft, especially when considering projected trends in flight volume and urbanization. Simulation is a useful tool to evaluate the human annoyance response due to both current and proposed aircraft, and it has some …
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Advanced modeling of active control of fan noise for ultra high bypass turbofan engines
An advanced model of active control of fan noise for ultra high bypass turbofan engines has been developed. This model is based on a boundary integral equation method and simulates the propagation, radiation and control of the noise generated by an engine fan surrounded by a duct of finite length …
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Investigation of a compact acoustic source array for the active control of aircraft engine fan noise
… interact with a duct similar to that of a turbofan engine inlet. The sources were cylindrically curved aluminum panels excited in vibration by the application of a sinusoidally varying voltage to a piezoceramic actuator bonded to them. The finite element method was used as a design tool to size …
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Feedback Applications in Active Noise Control for Small Axial Cooling Fans
Feedback active noise control (ANC) has been applied as a means of attenuating broadband noise from a small axial cooling fan. Such fans are used to maintain thermal stability inside of computers, projectors, and other office equipment and home appliances. The type of low-level noise radiated from …
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In-duct measurement techniques for the characterisation of broadband aeroengine noise
… of this thesis is the measurement of broadband fan noise, which due to reductions in tonal and jet noise, is now the dominant source at approach, and a major contributor at takeoff. This thesis proposes three new in-duct measurement techniques for the characterisation and measurement of …
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Error Sensor Placement for Active Control of an Axial Cooling Fan
Recent experimental achievements in active noise control (ANC) for cooling fans have used near-field error sensors whose locations are determined according to a theoretical condition of minimized sound power. A theoretical point source model, based on the condition previously stated, reveals the …
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Optimum Design of Compact, Quiet, and Efficient Ventilation Fans
Axial ventilation fans are used to improve the air quality, remove contaminants, and to control the temperature and humidity in occupied areas. Ventilation fans are one of the most harmful sources of noise due to their close proximity to occupied areas and widespread use. The prolonged exposure to …
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Optimization of Active Noise Control for Small Axial Cooling Fans
Previous work has shown that active noise control is a feasible solution to attenuate tonal noise radiated by small axial cooling fans, such as those found in desktop computers. One such control system reduced noise levels of a baffled 80-mm fan in the free field with four small loudspeakers …
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Random-vortex-particle methods applied to broadband fan interaction noise
… linearised Euler equations to predict broadband fan interaction noise. In modern turbofan designs broadband fan noise is a dominant source of aircraft noise, the most efficient source being the interaction between upstream turbulence and the stator vanes. The stochastic method developed to …
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A multidomain spectral method for computational aeroacoustics
… sound propagation in, and radiation from, turbofan inlets. The physics of sound propagation is modeled by the system of partial differential equations that describe conservation of mass, momentum and energy in inviscid flows. The equations are solved numerically in the time domain as an initial …
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Noise Reduction in an Axisymmetric Supersonic Aircraft Inlet using Trailing Edge Blowing
… Trailing Edge Blowing (TEB) to reduce the engine fan noise from a turbofan propulsion simulator (TPS). The TPS is 4.1 in. (10.4 cm) in diameter and is powered by compressed air. The supersonic inlet is connected to the TPS and is geometrically and acoustically scaled from a working design. The …
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Prediction and control of sound propagation in turbofan engine bypass ducts
… liners in the bypass duct of modern turbofan aeroengines. The liners provide the most<br/>effective means with which to suppress the rear fan noise. It is therefore important to make<br/>the best possible use of the available lined area by optimising the liner configuration. A set<br/>of …
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Aeroacoustics of the bifurcated 2D supersonic inlet
… civil transport aircraft. To provide the typical noise signature of a high bypass turbofan engine, a 10.4 cm (4.1 in.) turbofan engine simulator was used in conjunction with the supersonic inlets. The experiment was tested under static conditions. Steady state measurements of the inlet’s flow …
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