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  • 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.
1

One-dimensional transient numerical modeling of a micro-power generation system

Tatli, Emre. January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains x, 107 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 61-63).
2

Combustor simulators for scaled turbine experiments

Hall, Benjamin F. January 2015 (has links)
Gas turbine combustors employing a single lean combustion stage represent the next generation of design for reduced NO<sub>X</sub>emissions. These lean-burn combustors rely on swirl-stabilised flames resulting in highly non-uniform outflows. Non-uniform conditions adversely affect high-pressure turbine performance. 3D numerical simulations provide a means to understand and optimise engine design, however, the modelling of turbulence means experimental validation is crucial. Turbine test facilities operating at scaled, non-reacting conditions, with simulated combustor flows are an important source of validation data. This thesis presents advances in combustor simulator design, testing and instrumentation relevant to the challenges of modern, highly-integrated turbine testing. The design of a lean-burn combustor simulator, characterised by swirl and non-uniform temperature, is presented. The design was based on measurements and predictions of engine conditions. Unsteady numerical simulations were employed as a predictive design tool. An engine-scale combustor simulator was manufactured and characterised experimentally in a bespoke facility. Surveys of flow structure are presented, focusing on experimental turbine inlet data. These data confirmed that the combustor simulator reproduces the important features of a lean-burn combustor; e.g. swirling mainstream flow and high turbulence intensity. The lean-burn combustor simulator will be the first of its kind to be implemented in a rotating turbine test facility, and will provide important validation data. Measurement techniques were developed alongside the core work. Miniaturised five-hole probe rakes for turbine inlet measurements were developed using additive manufacturing (AM). Building on this work, an open source AM five-hole probe design is presented with experimental validation. The problem of estimating pressure probe bandwidth was also addressed, and a simplified model is presented. These tools have direct applications in turbomachinery research.
3

Theoretical analysis of unsteady supersonic flow around harmonically oscillating turbofan cascades

Caruthers, John Everett 12 1900 (has links)
No description available.
4

Simulation of 3-dimensional aeroelastic effects in turbomachinery cascades

McBean, Ivan William, 1974- January 2002 (has links)
Abstract not available
5

Power Harvesting from Shock Waves: the Axial Bladeless Turbine

James Braun (7042724) 16 December 2020 (has links)
<div>A new class of bladeless turbines was developed which allows for power extraction from harsh environments with minimal maintenance cost. This is achieved through a wavy hub surface that promotes shocks and expansion fans and hence generates torque besides trust if used as bottoming or topping cycle. </div><div>A numerical procedure to design, mesh, and model this new expansion device through steady and unsteady Reynolds Averaged Navier Stokes simulations is outlined. Then, the full three-dimensional flow field is replicated using a two-dimensional geometry to enable a simpler test section with full optical access at the Purdue Experimental Turbine Aerothermal Lab. Pressure, heat flux, and skin friction are computed via several measurement techniques to provide an accurate estimation of the uncertainties on the power, efficiency, and heat flux of the bladeless turbine. High-frequency pressure sensors (160 kHz) along with a high-frequency heat flux sensor (atomic layer thermopile) are used to characterize the unsteady phenomena on the hub and the shroud. Unsteadiness in the flow field is assessed through 10 kHz shadowgraph, density gradients are quantitatively assessed via 3 kHz Background Oriented Schlieren, and unsteady velocity components and flow angles are characterized with 1 kHz Femtosecond Laser Electronic Excitation Tagging. A reduced order model is constructed with Spectral Proper Orthogonal Decomposition to retrieve the dominant frequencies in the flow field, which could be associated with a multitude of shock-boundary layer, shock-shock, and shock-shear layer interactions.</div><div>A parametric study and multi-objective optimization to maximize power extraction while minimizing pressure loss and heat flux are performed. The operational envelope and scaling of the bladeless turbine are described for several reduced mass flows, reduced speeds, and swirl angles. Based on all the gathered simulations, a guideline for the design of bladeless turbines is provided.</div><div><br></div><div>Finally, the operation of the bladeless turbine is analyzed considering the unsteady propagation of a rotating oblique shock throughout the passage. Non-dimensional parameters to generically describe rotating shocks are discussed, and their influence on the operation of the turbine is assessed. Correction terms for the power and pressure loss during the unsteady operation of the bladeless turbine are developed with results of this section.</div><div><br></div>
6

A study of tip-leakage flow through orifice investigations

Henry, Gregory S. 17 November 2012 (has links)
"Compressible fluid dynamics of flow through plain-faced long orifices was investigated with the hope of gaining insight into the fluid dynamics of tip leakage flow. The Reynolds number range investigated was greater than 10*. Measurements were made of the discharge coefficient as a function of back pressure ratio for a sharp-edged orifice and long orifices with an l/d from 1/2 to 8. The discharge coefficient measurements indicate the mass flow rate in an orifice with an l/d of approximately 2 is the largest and the flow rate in a sharp-edged orifice is the smallest for pressure ratios greater than 0.27. The mass flow rate in a sharp-edged orifice is largest for pressure ratios below 0.27. To visualize the flow in a long orifice and model centerline pressure variation, a water table study was performed. The results demonstrate that the flow separates from the sharp corner at the orifice entrance, it accelerates to a maximum Mach number, and then the pressure increases. For back pressures above 0.50, a pressure decrease follows the initial pressure increase. If the maximum Mach number is supersonic, oblique shocks will exist. At the higher back pressures that produce supersonic maximum Mach numbers (0.50 P<sub>B</sub>/P₀ < 0.70), the oblique shocks reflect from the centerline as ""Mach reflections"" and the flow is subsonic after the pressure increase. The maximum Mach number for a back pressure ratio of 0.50 is approximately 1.5. At lower back pressure ratios (P<sub>B</sub>/P₀ <0.70), the oblique shocks reflect from the centerline in a ""regular"" manner and the flow remains supersonic on the centerline once supersonic speeds are reached. The flow in a long orifice is relatively constant for all back pressure ratios below approximately 0.30. The maximum Mach number for pressure ratios below 0.30 is approximately 1.8. One-dimensional analyses were used to model the flow in long orifices with maximum Mach numbers less than 1.3. Higher discharge coefficients of long orifices compared to sharp-edged orifices are due to pressure rises in the orifices caused by mixing and shock waves. These increases in the discharge coefficients are partly offset by friction and boundary layer blockage. For maximum Mach numbers greater than 1.3, the flow in long orifices is believed to become significantly two-dimensional because of supersonic effects." / Master of Science
7

Numerical Assessment of Eddy-Viscosity Turbulence Models of an Axial-Flow Turbine at a Low Reynolds Number

Unknown Date (has links)
The flow field behavior of axial flow turbines is of great importance, especially in modern designs that may operate at a low Reynolds number. At these low Reynolds numbers, the efficiency loss is significantly augmented compared to higher Reynolds number flows. A detailed incompressible numerical study of a single stage axial-flow turbine at a low Reynolds number is investigated with the use of multiple eddy-viscosity turbulence models. The study includes epistemic uncertainty quantification as a form of numerical error estimation. The numerical results show good qualitative and quantitative agreement with experimental data. It was found that the shear stress transport (SST) k - ω turbulence model with rotation/curvature correction and inclusion of transition modeling is most capable at predicting the mean velocity distribution, which is further enhanced when the URANS formulation is employed. However, all the cases indicate a large variation in the prediction of the root-mean-squared of the turbulent velocity fluctuations. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
8

Computational analysis of stall and separation control in centrifugal compressors

Stein, Alexander 05 1900 (has links)
No description available.
9

Response Of A Laminar Separation Bubble To External Excitation

Suhas, Diwan Sourabh 02 1900 (has links) (PDF)
No description available.
10

Predicting the flow & noise of a rotor in a turbulent boundary layer using an actuator disk – Rans approach

Unknown Date (has links)
The numerical method presented in this study attempts to predict the mean, non-uniform flow field upstream of a propeller partially immersed in a thick turbulent boundary layer with an actuator disk using CFD based on RANS in ANSYS FLUENT. Three different configurations, involving an infinitely thin actuator disk in the freestream (Configuration 1), an actuator disk near a wall with a turbulent boundary layer (Configuration 2), and an actuator disk with a hub near a wall with a turbulent boundary layer (Configuration 3), were analyzed for a variety of advance ratios ranging from J = 0.48 to J =1.44. CFD results are shown to be in agreement with previous works and validated with experimental data of reverse flow occurring within the boundary layer above the flat plate upstream of a rotor in the Virginia Tech’s Stability Wind Tunnel facility. Results from Configuration 3 will be used in future aero-acoustic computations. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

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