- About
-
The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
Search results
Showing 1 to 8 of 8 (0.131 seconds)Spelling suggestions: "subject:"airplanes -- tet propulsion."" "subject:"airplanes -- feet propulsion.""
| 1 |
Experimental investigations of on-axis discrete frequency fan noise.Leggat, Lennox John January 1973 (has links)
The thesis describes experimental techniques used and results obtained in the investigation of the pure tone components of sound radiation from a commercial 19 inch axial flow fan. The causes and extent of the discrete tone sources were investigated by several methods: cross-correlation of fan surface pressure fluctuations with far field sound, spectral analysis of surface pressure, and examination of surface pressure waveforms. A unique feature involved the design of an apparatus for detecting and transmitting fan-borne pressure fluctuations off the rotating blades.
"Causality Correlations" with the on-axis far field sound rendered dipole source strength distribution functions over a span wise line at 15 per cent chord from the leading edge of the fan blade and around a circumferential ring on the motor support strut at a fan radius of 89 per cent.
Results indicate that the on-axis discrete tones are a result of source mechanisms causing force fluctuations on the blades and struts which in turn lead to sound radiation which is dipole in nature and is most intense on the axis of the fan. These mechanisms include ingestion of a concentrated vortex, modulation of the clearance between the blade tips and the fan shroud, flow separation around the inlet bell mouth, and fluctuations in the inflow velocity due to the proximity of the fan to the wedged wall of the Anechoic chamber. Crude integral approximations of source strength distributions over the surfaces of the blades and the struts indicated that sound radiation at the blade passage frequency from these two contributors to the overall sound would be about equal, although more sound radiation is expected to originate at the rotor. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate
|
| 2 |
Performance and stalling behavior of an axial-flow compressor subjected to three circumferential inlet distortion levelsGauden, William H. 28 July 2010 (has links)
The performance and stalling behavior of an axial-flow compressor subjected to several different inlet distortion patterns was investigated. The effect of inlet distortion on overall compressor performance was determined through the measurement of compressor characteristics for each inlet flow condition. Dynamic pressure transducers were employed to investigate rotating stall cell behavior during the inception of stall. Rotor blade response to distorted inflow was measured in the form of average blade pressure profiles by using a scanning valve. Results indicated a substantial reduction in total pressure rise capability for distorted operation. A 25 per cent loss in stall pressure rise was observed for the most severe distortion level. The stall cell was found to rotate in the direction of rotor motion, but at one-half the rotor speed. The cell encompassed the rotor blade tip region down to approximately midspan. During the onset of stall, the circumferential extent of the cell was observed to vary from 60 to 80 degrees. At the rotor blade tip the stall cell relative pressure fluctuations indicated zero flow through the cell. The amplitude of the stall cell was attenuated in the distorted flow region due to the lower air velocity behind the distortion screens. Rotor blade suction side pressure measurements indicated that increasing the circumferential extent of distortion above some "critical" value induced blade stall at higher flow rates. For the low speed compressor used, it appears that the critical angle phenomena is a function of compressor design and is independent of distortion level. / Master of Science
|
| 3 |
Dynamic surface temperature measurement on the first stage turbine blades in a turbofan jet engine test rigBecker, William J. 15 July 2010 (has links)
Turbine blade surface temperatures were studied during transient operation in a turbofan engine test rig. A single fiber radiation pyrometer was used to view the suction side of the blades from approximately 60 percent axial chord to the trailing edge at an average radial location of 70 percent blade height. A single ceramic-coated blade produced a once-per-revolution signal that allowed for the tracking of individual blades during the transients. The investigation concentrated on the light-off starting transient and the transients obtained during accelerating and decelerating between power settings. During starting and acceleration transients, the blade surface temperature gradient was observed to reverse. This phenomenon was most apparent during starting when the trailing edge was initially much hotter than the 60 percent chord location, resulting in large temperature gradients. In steady operation the trailing edge temperature was lower than the 60 percent chord location, and the gradients were less severe. During deceleration transients, the trailing edge cooled more rapidly than the 60 percent chord location. This resulted in larger temperature gradients than were seen in steady operation, but no profile inversion was observed. These temperature gradients and profile inversions represent a cycling of thermally-induced stresses which may contribute to low cycle fatigue damage. A simple one-dimensional heat transfer model is presented as a means of explaining the different heating rates observed during the transients. / Master of Science
|
| 4 |
Hypersonic internal flow over blunt leading edges.D'Souza, Norbert. January 1971 (has links)
No description available.
|
| 5 |
Missed opportunities: NACA and jet propulsionNegrel, Christian Claude January 1989 (has links)
This study examines NACA's organization in the light of Alfred D. Chandler's <i>Strategy and Structure</i>. It analyzes the agency's administration. NACA's strategy of maximizing existing technology and its committee's structure were the key elements in its failure to develop jet propulsion in the early 1940s. We will focus first on NACA and its organization. The second chapter will describe jet propulsion, particularly the acquisition of a Whittle engine from England and General Arnold 's role in keeping NACA out of the development of the Whittle engine in the United States. The third chapter will concentrate on the reasons that combined and led to the difficulties of NACA in the mid-forties and the 1950s. That chapter will look at the rise of the aviation industry, the criticism it expressed against NACA, and finally NACA's strategy as one of the causes of failure. / Master of Arts
|
| 6 |
Hypersonic internal flow over blunt leading edges.D'Souza, Norbert. January 1971 (has links)
No description available.
|
| 7 |
Basic Comparison of Three Aircraft Concepts: Classic Jet Propulsion, Turbo-Electric Propulsion and Turbo-Hydraulic PropulsionRodrigo, Clinton January 2019 (has links) (PDF)
Purpose - This thesis presents a comparison of aircraft design concepts to identify the superior propulsion system model among turbo-hydraulic, turbo-electric and classic jet propulsion with respect to Direct Operating Costs (DOC), environmental impact and fuel burn. --- Approach - A simple aircraft model was designed based on the Top-Level Aircraft Requirements of the Airbus A320 passenger aircraft, and novel engine concepts were integrated to establish new models. Numerous types of propulsion system configurations were created by varying the type of gas turbine engine and number of propulsors. --- Findings - After an elaborate comparison of the aforementioned concepts, the all turbo-hydraulic propulsion system is found to be superior to the all turbo-electric propulsion system. A new propulsion system concept was developed by combining the thrust of a turbofan engine and utilizing the power produced by the turbo-hydraulic propulsion system that is delivered via propellers. The new partial turbo-hydraulic propulsion concept in which 20% of the total cruise power is coming from the (hydraulic driven) propellers is even more efficient than an all turbo-hydraulic concept in terms of DOC, environmental impact and fuel burn. --- Research Limitations - The aircraft were modelled with a spreadsheet based on handbook methods and relevant statistics. The investigation was done only for one type of reference aircraft and one route. A detailed analysis with a greater number of reference aircraft and types of routes could lead to other results. --- Practical Implications - With the provided spreadsheet, the DOC and environmental impact can be approximated for any commercial reference aircraft combined with the aforementioned propulsion system concepts. --- Social Implications - Based on the results of this thesis, the public will be able to discuss the demerits of otherwise highly lauded electric propulsion concepts. --- Value - To evaluate the viability of the hydraulic propulsion systems for passenger aircraft using simple mass models and aircraft design concept.
|
| 8 |
Evaluation of the Hybrid-Electric Aircraft Project Airbus E-Fan XBenegas Jayme, Diego January 2019 (has links) (PDF)
Purpose - This master thesis evaluates the hybrid-electric aircraft project E-Fan X with respect to its economical and environmental performance in comparison to its reference aircraft, the BAe 146-100. The E-Fan X is replacing one of the four jet engines of the reference aircraft by an electric motor and a fan. A turboshaft engine in the cargo compartment drives a generator to power the electric motor. --- Methodology - The evaluation of this project is based on standard aircraft design equations. Economics are based on Direct Operating Costs (DOC), which are calculated with the method of the Association of European Airlines (AEA) from 1989, inflated to 2019 values. Environmental impact is assessed based on local air quality (NOx, Ozone and Particulate Matter), climate impact (CO2, NOx, Aircraft-Induced Cloudiness known as AIC) and noise pollution estimated with fundamental acoustic equations. --- Findings - The battery on board the E-Fan X it is not necessary. In order to improve the proposed design, the battery was eliminated. Nevertheless, due to additional parts required in the new configuration, the aircraft is 902 kg heavier. The turboshaft engine saves only 59 kg of fuel. The additional mass has to be compensated by a payload reduced by 9 passengers. The DOC per seat-mile are up by more than 10% and equivalent CO2 per seat-mile are more than 16% up in the new aircraft. --- Research limitations - Results are limited in accuracy by the underlying standard aircraft design calculations. The results are also limited in accuracy by the lack of knowledge of some data of the project. --- Practical implications - The report contributes arguments to the discussion about electric flight. --- Social implications - Results show that unconditional praise given to the environmental characteristics of this industry project are not justified.
|
Page generated in 0.1364 seconds