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 29 for “"engine noise"”.
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Theoretical Modeling with Validation of a Combined HQ-Liner System for Turbofan Engine Noise Control
… proposed in this work as a device for Turbofan Engine Noise Control. The approach consists of installing circumferential arrays of HQ tubes on the lined sector of the inlet of a turbofan engine. A theoretical model is developed to predict the performance of this system assuming that the engine …
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Scaling finite difference methods in large eddy simulation of jet engine noise to the petascale: numerical methods and their efficient and automated implementation
<p>Reduction of jet engine noise has recently become a new arena of competition between aircraft manufacturers. As a relatively new field of research in computational fluid dynamics (CFD), computational aeroacoustics (CAA) prediction of jet engine noise based on large eddy simulation (LES) is a …
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An Intermittent-Combustion General Aviation Aircraft Engine Exhaust Noise Prediction Algorithm
… point of view, the reduction of aircraft noise has become an important factor recently. There are two factors that make airplane noise: propeller noise and engine noise. This report puts emphasis on only the engine noise in order to begin understanding what airplane engine exhaust noise …
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Design trade studies and assessment for advanced quiet aircraft concepts
… for a baseline silent aircraft planform and engine was determined. A silent aircraft was designed for a range of 4,000nm and 250 passengers. A noise assessment was conducted on the engine and airframe noise sources of the resulting design. The noise impacts of five engine (jet, fan forward, …
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Use of fan rig data for the understanding and prediction of fan broadband noise and noise changes due to a variable area nozzle
… understanding and prediction of fan broadband noise and noise<br/>changes due to a variable area nozzle<br/>As suggested by the title, fan rig noise measurements form an integral part of this thesis. The<br/>analysis of a database of rig noise measurements forms the first section of this …
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Broadband Acoustic Liner Optimization Study Using Novel Poro-elastic Materials
… challenges associated with reducing aircraft engine noise, there is need for acoustic liner configurations that target broadband performance. This thesis experimentally and analytically investigates passive noise control methods to improve broadband frequency attenuation through various …
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Intricate dynamics and hydrodynamic frictional losses of the piston-ring assembly in internal combustion engines
<p>Frictional losses in internal combustion engines approximately account for 10% of the expended fuel energy. Moreover, forty percent of these losses are attributed to the reciprocating motion of the piston-assembly. Besides the adverse effect of friction on fuel economy, the intricate dynamics of …
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An Investigation on Acoustic Metamaterial Physics to Inspire the Design of Novel Aircraft Engine Liners
Attenuation of low frequency turbofan engine noise has been a challenging task in an industry that requires low weight and tightly-packed solutions. Without innovative advancements, the technology currently used will not be able to keep up with the increasingly stringent requirements on aircraft …
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Design and acoustic shielding prediction of hybrid wing-body aircraft
… are investigated with the goal to meet the N+2 noise, fuel burn, and emissions requirements. As part of the N+2 program, this thesis is focused on the design and assessment of an HWB aircraft and the development of a prediction method for turbomachinery noise shielding. Based on MIT's previous …
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Extension of the high load limit in the Homogeneous Charge Compression Ignition engine
… Homogeneous Charge Compression Ignition (HCCI) engine offers diesel-like efficiency with very low soot and NOx emissions. In a HCCI engine, a premixed charge of air, fuel and burned gas is compressed to achieve autoigntion. Combustion occurs throughout the chamber volume resulting in short …
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Characterization of Structure-Borne Tire Noise Using Virtual Sensing
… which have been made to the vehicle (reduced engine noise, reducedaerodynamic related NVH), have resulted in tire road noise as the dominant source of thevehicle interior noise. Generally, vehicle interior noise has two main sources, 1) travellinglow frequency excitation below 800 Hz from road …
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Improvement In Acoustic Liner Attenuation In Turbofan Engines By Means Of Plasma Synthetic Jet Actuator
Despite many advances in aviation noise control over the past 50 years, the industry is continually striving to reduce noise emissions. Turbofan engine acoustic liners are efficient attenuators of engine noise. Plasma actuators have been used as flow control devices in other settings and will now …
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A Conceptual Design Methodology for Predicting the Aerodynamics of Upper Surface Blowing on Airfoils and Wings
… is Upper Surface Blowing (USB), where the engines are placed above the wing and the engine exhaust jet becomes attached to the upper surface. The jet thrust can then be vectored by use of the trailing edge curvature since the jet flow tends to remain attached by the "Coanda Effect". Wind …
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Predicting fan noise propagation in aeroengine bypass ducts
… 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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Aeroacoustic computation of sound radiation from ducts
Modern high-bypass turbofan engines produce high levels of nuisance noise that has a significant impact on the environment near airports as well as the crew and passengers inside the aircraft. Significant research is being undertaken to understand the aeroacoustic noise source mechanisms and to …
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Development of a numerical model of piston secondary motion for internal combustion engines
… motion of the piston of an internal combustion engine in the vertical plane is referred to as its primary motion, and it is this primary motion that produces power in the engine. Due to the fact that there is a clearance between the piston and the liner, and that certain forces on the piston …
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Active Minimization of Acoustic Energy Density in a Mock Tractor Cab
<p>An active noise control (ANC) system has been applied to the problem of attenuating low-frequency tonal noise inside small enclosures. The intended target application of the system was the reduction of the engine firing frequency inside heavy equipment cabins. The ANC system was based on a …
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Acoustic Scattering in Sheared Flow
Airframe noise, the noise of an aircraft in flight not due to the engine or other mechanical devices, is often a major contribution to the sound heard from an aircraft during landing approach. Over the past few decades certification requirements have gradually tightened, reaching the point where …
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