No description available.

No description available.

No description available.

An experimental investigation has been carried out to determine the aerodynamic performance of an annular S-shaped duct representative of that used to connect the compressor spools of aircraft gas turbine engines. Measurements of both the mean flow and turbulent structure have been obtained using both 5 hole pressure probes and a3 component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. For inlet conditions in which boundary layers are developed along an upstream entry length the static pressure, shear stress and velocity distributions are presented. The data shows that as a result of flow curvature significant streamwise pressure gradients exist within the duct, with this curvature also affecting the generation and suppression of turbulence. The stagnation pressure loss within the duct is also assessed and is consistent with the measured distributions of shear stress. More engine representative conditions are provided by locating a single stage compressor at inlet to the duct. Relative to the naturally developed inlet conditions the flow within the duct is less likely to separate, but mixing out of the compressor blade wakes increases the measured duct loss. With both types of inlet conditions the effect of a radial strut, such as that used for carrying loads and engine services, is also described both in terms of the static pressure distribution along the strut and its contribution to overall loss. The effects of inlet swirl on the flow field that develops within an annular S-shaped duct have also been investigated. By removing the outlet guide vanes from an upstream single stage compressor swirl angles in excess of 30° were generated. Results show that within the S-shaped duct tangential momentum is conserved, leading to increasing swirl velocities through the duct as its radius decreases. Furthermore, this component influences the streamwise velocity as pressure gradients are established to ensure the mean flow follows the duct curvature. Consequently in the critical region adjacent to the inner casing, where separation is most likely to occur, higher streamwise velocities are observed. Within the duct substantial changes also occur to the turbulence field which results in an increased stagnation pressure loss between duct inlet and exit. Data is also presented showing the increasing swirl angles through the duct which has consequences both for the design of the downstream compressor spool and of any radial struts which may be located within the duct.

Graduation date: 1981

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1966. / Bibliography: leaves [91]-97. / ix, 97 l graphs, tables

Energy is an essential and critical commodity and our reliance on it has fuelled much of the debate and interest in society and academia alike. Environmental concerns, depleted energy resources and higher energy prices are the main factors that drive this interest. Energy efficiency is one of the main avenues to preserve and better utilize this valuable commodity. The energy exchange by employment of heat exchangers is extensive and tube-fin heat exchangers are widely used in industrial and commercial applications. Smarter designs could not only improve energy efficiency but may also save on material costs. Although mass production and improved manufacturing techniques have reduced manufacturing costs, tube fin heat exchangers have not evolved greatly to take advantage of these improvements. There has been a large range of fin surface enhancements proposed, such as waffled fins or louvres and while limited improvements in capacity have been achieved, this is generally accomplished at a much larger pressure drop penalty. Numerous studies have been performed in order to examine the potential of various surface enhancement geometries on an ad hoc basis. These presumably operate on the basis of enhanced convection due to increased turbulence levels. However very few of these studies examine the actual nature of turbulence that is responsible for convection enhancement. A series of experiments and numerical studies have been conducted to quantify the effect of the turbulence vortex characteristics on the air side heat convection of a tube-fin heat exchanger. Homogeneous, transverse and streamwise vortical structures were investigated. The thermal transfer performance resulting from these flows was compared to that of standard louver fin geometries by considering sensible heat transfer only, applicable to radiator applications. Several novel coils designed to achieve these vortex structures, were developed and their heat transfer characteristics were quantified. These coil designs can be described as the Tube Mesh, Tube Strut and a Delta-Winglet fin surface.The Tube Mesh heat exchanger consisted entirely of horizontal and vertical tubes arranged in an approximate homogeneous turbulence generating grid. While they had a lower heat transfer of between 53% to 63% of that of the louvre fin surface, they had an extremely low pressure drop of 25% to 33%. This has the potential to make them suitable for certain low pressure drop applications, especially if energy saving is a prerequisite. The range of Tube Strut coils consisted of a tube bundle with interconnecting heat conducting struts to form a parallel plate array were also investigated. Three different strut thicknesses and strut spacing were trialled. In general these had similar performance to the tube mesh at 45% to 65% the heat transfer capacity of the louver fin surface. The resulting pressure drop was 38% to 42% of that of the louver fin surface. A delta-winglet design which positioned the deltas in a flow up configuration just in front of the tubes was examined. It was found that this configuration had an almost comparable capacity of 87% to a louver surface having the same fin pitch. On the other hand it had approximately half the pressure drop of 54% of the similar louver fin surface. This particularly low pressure drop makes this design preferable from an energy utilisation perspective. While a slight increase in coil area is required, this is offset by an almost 50% reduction in operating costs by reducing the parasitic energy requirements of the convection fans. The experimental data gathered for this Delta-Winglet design served to validate a succession of numerical simulations which were performed to estimate the performance of other configurations of multiple vortex generators. In addition the performance of combining a delta-wing with a louvred surface was investigated. It was found that increasing the number of delta-winglets or combining deltas with a louvred surface provided little improvement in heat transfer but increased pressure drop substantially. The louvre design itself was examined, and simulations were undertaken to estimate the effect of louvre angle, as well as louvre pitch. A hitherto unexamined concept was to investigate the effect of having louvres with serrated edges. It was found that an increase in louver angle by 5 degrees had negligible effect on heat transfer but increased the pressure drop by 17%. A variation in louver pitch showed a minimal variation in both heat transfer and pressure drop. Surprisingly a serrated louver showed a slight reduction in both heat transfer and pressure drop but this was miniscule. It was established throughout the course of the investigations that the bulk of the coil heat transfer is performed by the first tube row. Therefore the potential for increasing heat transfer by shifting some heat exchange to the down stream rows was examined. This was attempted by having progressively increasing louvre angles from the front of the coil to the rear. While a slight increase in heat transfer performance was achieved, this accomplished at the expense of a 13%-14% increase in pressure drop. The outcomes have shown that substantial net improvement of heat exchanger energy efficiency can be achieved through optimization of the turbulence generation along the fins of a tube fin heat exchanger. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1253254 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2006

No description available.

Thesis (Ph. D.)--University of Washington, 1989. / Vita. Bibliography: (leaves [181]-186).

Thesis (Ph. D.)--University of Adelaide, Dept. of Mechanical Engineering, 1984. / A supplement to this thesis containing tabulations of all acoustic data is available from the Department of Mechanical Engineering, University of Adelaide. Includes bibliographical references (leaves 109-113).