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Articles 1 - 13 of 13
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Investigation On Interactions Of Unsteady Wakes And Film Cooling On An Annular Endwall, Matthew J. Golsen
Investigation On Interactions Of Unsteady Wakes And Film Cooling On An Annular Endwall, Matthew J. Golsen
HIM 1990-2015
In recent decades, greater interest in the effect of rotational wakes on gas turbine film cooling applications has produced increasing numbers of studies on these unsteady phenomena. Wakes are primarily shed from upstream components such as transition duct walls, stator vanes, and rotors. Studies have shown that in areas of unsteady flow, the best performing parameters in conventional steady investigations may not be the best for unsteady applications. One common method of modeling the unsteady wake interaction in subsonic flows is the use of spoke wheel type wake generators using cylindrical rods to produce the velocity detriment and local increase …
An Experimental And Numerical Study Of Secondary Flows And Film Cooling Effectiveness In A Transonic Cascade, James C. Kullberg
An Experimental And Numerical Study Of Secondary Flows And Film Cooling Effectiveness In A Transonic Cascade, James C. Kullberg
HIM 1990-2015
Experimental tests on a transonic annular rig are time-consuming and expensive, so it is desirable to use experimental results to validate a computational model which can then be used to extract much more information. The purpose of this work is to create a numerical model that can be used to simulate many different scenarios and then to apply these results to experimental data.; In the modern world, gas turbines are widely used in aircraft propulsion and electricity generation. These applications represent a massive use of energy worldwide, so even a very small increase in efficiency would have a significant beneficial …
Heat Transfer And Friction Augmentation In A Narrow Rectangular Duct With Symmetrical And Non-Symmetrical Wedge-Shaped Turbulators, Michelle Valentino
Heat Transfer And Friction Augmentation In A Narrow Rectangular Duct With Symmetrical And Non-Symmetrical Wedge-Shaped Turbulators, Michelle Valentino
Electronic Theses and Dissertations
The need for cleaner and more fuel efficient means to produce electricity is growing steadily. Advancements in cooling technologies contribute to the improvements in turbine efficiency and are used for gas turbines and for power generation in automotive, aviation, as well as in naval applications, and many more. Studies introducing turbulators on walls of internal cooling channels, which can be applied to hot gas components and in recuperative heat exchangers, have been reviewed for their ability to promote heat transfer in the channel while observing pressure loss caused by adding the features. Several types of turbulators have been studied; ribs, …
Measurements In Air-Water Bubbly Flow Through A Vertical Narrow High-Aspect Ratio Channel, Benjamin R. Patrick
Measurements In Air-Water Bubbly Flow Through A Vertical Narrow High-Aspect Ratio Channel, Benjamin R. Patrick
Electronic Theses and Dissertations
Two-Phase bubbly flows are encountered in a wide range of industrial applications, particularly where phase changes occur as seen in high performance heat exchangers and boiling reactors for power generation. These flows have been extensively studied in channels with circular geometries using air-water flows, though little data exists for flows through narrow rectangular channels. Measurements in thin geometries are particularly challenging since large bubbles bridge the gap, and it is difficult to compare point measurements with photographic techniques. The objective of this study is to explore the abilities of hot-film anemometry and high speed photography for taking measurements in a …
Effect Of Rib Aspect Ratio On Heat Transfer And Friction In Rectangular Channels, Lucky Vo Tran
Effect Of Rib Aspect Ratio On Heat Transfer And Friction In Rectangular Channels, Lucky Vo Tran
HIM 1990-2015
The heat transfer and friction augmentation in the fully developed portion of a 2:1 aspect ratio rectangular channel with orthogonal ribs at channel Reynolds numbers of 20,000, 30,000, and 40,000 is studied both experimentally and computationally. Ribs are applied to the two opposite wide walls. The rib aspect ratio is varied systematically at 1, 3, and 5, with a constant rib height and constant rib pitch (rib-pitch-to-rib-height ratio of 10). The purpose of the study is to extend the knowledge of the performance of rectangular channels with ribs to include high aspect ratio ribs. The experimental investigation is performed using …
Toward Increasing Performance And Efficiency In Gas Turbines For Power Generation And Aero-Propulsion Unsteady Simulation Of Angled Discrete-Injection Coolant In A Hot Gas Path Crossflow, Perry L. Johnson
HIM 1990-2015
This thesis describes the numerical predictions of turbine film cooling interactions using Large Eddy Simulations. In most engineering industrial applications, the Reynolds-Averaged Navier-Stokes equations, usually paired with two-equation models such as k-Greek lowercase letter epsilon] or k-Greek lowercase letter omega], are utilized as an inexpensive method for modeling complex turbulent flows. By resolving the larger, more influential scale of turbulent eddies, the Large Eddy Simulation has been shown to yield a significant increase in accuracy over traditional two-equation RANS models for many engineering flows. In addition, Large Eddy Simulations provide insight into the unsteady characteristics and coherent vortex structures of …
Heat Transfer Study Of A Triple Row Impingement Channel At Large Impingement Heights, Roberto Claretti
Heat Transfer Study Of A Triple Row Impingement Channel At Large Impingement Heights, Roberto Claretti
HIM 1990-2015
Advanced cooling techniques are required to increase the Brayton cycle temperature ratio necessary for the increase of the overall cycle's efficiency. Current turbine components are cooled with an array of internal cooling channels in the midchord section of the blade, pin fin arrays at the trailing edge and impingement channels in the leading edge. Impingement channels provide the designer with high convective coefficients on the target surface. Increasing the heat transfer coefficient of these channels has been a subject of research for the past 20 years. In the current study, a triple row impingement channel is studied with a jet …
Study Of High Efficiency Micro Thermoelectric Energy Harvesters, Steven Michael Pedrosa
Study Of High Efficiency Micro Thermoelectric Energy Harvesters, Steven Michael Pedrosa
Electronic Theses and Dissertations
Thermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat sources, and convert the captured heat into usable electricity. The operating principle of a thermoelectric device requires that a temperature gradient be present across the device, which induces the flow of electrons from …
Modeling Of Thermal Properties Of Fiber Glass Polyester Resin Composite Under Thermal Degradation Condition, Marvin S. Tsoi
Modeling Of Thermal Properties Of Fiber Glass Polyester Resin Composite Under Thermal Degradation Condition, Marvin S. Tsoi
Electronic Theses and Dissertations
Composites, though used in a variety of applications from chairs and office supplies to structures of U.S. Navy ships and aircrafts, are not all designed to hold up to extreme heat flux and high temperature. Fiber-reinforced polymeric composites (FRPC) have been proven to provide the much needed physical and mechanical properties under fire exposure. FRPC notable features are its combination of high specific tensile strength, low weight, along with good corrosion and fatigue resistance. However FRPC are susceptible to thermal degradation and decomposition, which yields flammable gas, and are thus highly combustible. This property restricts polymeric material usage. This study …
Purge And Secondary Flow Interaction Control By Means Of Platform Circumferential Contouring, Melissa Harris
Purge And Secondary Flow Interaction Control By Means Of Platform Circumferential Contouring, Melissa Harris
Electronic Theses and Dissertations
This study presents an attempt to reduce the losses produced by the purge flow in a turbine stage by incorporating circumferential platform contouring. Two contours are proposed and compared against a baseline at different levels of swirl. The computational simulations were performed using a RANS three-dimensional Computational Fluid Dynamics code with the Shear Stress Transport turbulence model. The results of steady simulations demonstrate that for the first contour, when the flow is swirled to 50% of the rim speed, the purge flow exits the cavity with less cross flow. This in turn reduces the strength of the passage vortex. However, …
Design And Optimization Of A Wave Energy Harvester Utilizing A Flywheel Energy Storage System, Steven Alexander Helkin
Design And Optimization Of A Wave Energy Harvester Utilizing A Flywheel Energy Storage System, Steven Alexander Helkin
Electronic Theses and Dissertations
This thesis details the design and optimization of a buoy used to collect renewable energy from ocean waves. The proposed buoy is a point absorber—a device that transforms the kinetic energy of the vertical motion of surface waves into electrical energy. The focus of the research is on the mechanical system used to collect the energy, and methods to improve it for eventual use in an actual wave energy harvester. A flywheel energy storage system was utilized in order to provide an improved power output from the system, even with the intermittent input of force exerted by ocean waves. A …
Heat Transfer In A Coupled Impingement-Effusion Cooling System, Mark W. Miller
Heat Transfer In A Coupled Impingement-Effusion Cooling System, Mark W. Miller
Electronic Theses and Dissertations
Gas turbine engines are prevalent in the today’s aviation and power generation industries. The majority of commercial aircraft use a turbofan gas turbine engines. Gas turbines used for power generation can achieve thermodynamic efficiencies as high as 60% when coupled with a steam turbine as part of a combined cycle. The success of gas turbines is a direct result of a half century’s development of the technology necessary to create such efficient, powerful, and reliable machines. One key area of technical advancement is the turbine cooling system. In short, increasing the turbine inlet temperature leads to a rise in cycle …
Multi-Sensor Optimization Of The Simultaneous Turning And Boring Operation, Erick Johan Deane
Multi-Sensor Optimization Of The Simultaneous Turning And Boring Operation, Erick Johan Deane
Electronic Theses and Dissertations
To remain competitive in today’s demanding economy, there is an increasing demand for improved productivity and scrap reduction in manufacturing. Traditional manufacturing metal removal processes such as turning and boring are still one of the most used techniques for fabricating metal products. Although the essential metal removal process is the same, new advances in technology have led to improvements in the monitoring of the process allowing for reduction of power consumption, tool wear, and total cost of production. Replacing used CNC lathes from the 1980’s in a manufacturing facility may prove costly, thus finding a method to modernize the lathes …