Download or read book Effects of Spanwise and Discrete Disturbances on Separating Boundary Layers on Low Pressure Turbine Blades written by Daniel D. Reimann and published by . This book was released on 2007 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow measurements were made on two highly loaded, low pressure turbine blade configurations in a low-speed, linear cascade facility. The L1M blade has a design Zweifel coefficient of 1.34 with a peak cp near 47% cx (mid-loaded) and the Pack B blade has a design Zweifel coefficient of 1.15 with a peak cp at 63% cx (aft-loaded). Flow velocity and surface pressure measurements were taken for Rec=20,000 and 3% inlet freestream turbulence. For these operating conditions, a large separation bubble forms on the blade suction surface, beginning at 59% cx and reattaching at 86% cx on the L1M blade and a non-reattaching bubble beginning at 68% cx on the Pack B.A spanwise row of discrete vortex-generating jets located at 59% cx on the Pack B and 50% cx on the L1M were used as a separation control device and were pulsed at a frequency of 5 Hz with a duty cycle of 25%. The Pack B with its open separation bubble proved to be a better candidate for VGJ control than the L1M with its closed separation bubble. Further studies were made on the Pack B blade comparing wake and VGJ effects. A wake generator was used to simulate the periodic passing of upstream wakes through the blade passage for the Pack B configuration. The wake passing frequency of 4.5Hz was set to match a typical engine flow coefficient for a low pressure turbine. Data were taken using PIV and a hot-film anemometer mounted on a blade following device. Velocity, turbulence, and intermittency measurements were made along the suction surface of the blade to characterize the bubble dynamics and transitional behaviors for both the presence of unsteady wakes and pulsing VGJs. The wakes caused early breakdown of the separated free shear layer resulting in a thinning of the separation region. The VGJs caused an upstream disturbance which convects downstream, temporarily pushing off the separation bubble. Overall, both wakes and VGJs suppress the size of the steady-state separation bubble, though through different mechanisms. Three-dimensional aspects of the jet disturbance are studied by investigating the effects of the VGJs at two spanwise locations.
Download or read book Experimental Investigation of Boundary Layer Behavior in a Simulated Low Pressure Turbine written by Ki-Hyeon Sohn and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Use of Dimples to Suppress Boundary Layer Separation on a Low Pressure Turbine Blade written by Kurt P. Rouser and published by . This book was released on 2002-12-01 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow separation on a low pressure turbine blade is explored at Reynolds numbers of 25k, 45k and 100k, Experimental data is collected in a low- speed, draw-down wind tunnel using a cascade of eight Pak-B blades, Flow is examined from measurements of blade surface pressures, boundary layer parameters, exit velocities, and total pressure losses across the blade, Two recessed dimple shapes are assessed for suppressing flow separation and associated losses, One dimple is spherical, and the second is asymmetric, formed from a full dimple spanwise half-filled, A single row of each dimple shape is tested at 50%, 55% and 65% axial chord, Symmetric dimples reduce separation losses by as much as 28%, while asymmetric dimples reduce losses by as much as 23%, A complementary three-dimensional computational study is conducted to visualize local flow structure, Computational analysis uses Gridgen v13,3 as a mesh generator, Fluent v6,O as a flow solver and FIELDVIEW - v8,0 for graphic display and analysis, Computational results for Pak-B blades at a Reynolds number of 25k indicate that both dimple shapes cause a span-wise vortex to rollup within the dimple and provide a localized pressure drop,
Download or read book Effect of Dimple Pattern on the Suppression of Boundary Layer Separation on a Low Pressure Turbine Blade written by John P. Casey and published by . This book was released on 2004-03-01 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: Three dimple patterns were investigated to ascertain their relative effectiveness on controlling boundary layer separation from a low-pressure turbine blade. The three cases included a single row of dimples at 65% of the axial chord with 2.22 cm spacing, a single row of dimples at 65% of the axial chord with 4.44 cm spacing, and a two-row staggered pattern with rows at 65% and 76% of the axial chord with 4.44 cm spacing. The multiple row case was such that the center of the upstream dimple set at the midpoint between two downstream dimples. The dimple spacing was measured center-on-center. Each of the dimple patterns was studied and compared to an unmodified blade at axial chord Reynolds numbers based on inlet velocity of 25k, 45k, and 100k. Experimental data was collected in a low-speed, draw down wind tunnel containing a linear turbine cascade of 8 Pak-B blades. Measurements of surface pressure, boundary layer parameters, wake velocity, and total pressure losses were made to examine the flow. No dimple pattern dramatically outperformed the others. Each of the dimple patterns studied improved the average total pressure loss coefficient by 34% for Re 25k and 1% Tu. Complementing the experimental effort was a three-dimensional computational fluid dynamics study. Four models were built and analyzed. The models included an unmodified blade, blades with dimples at 65% of the axial chord with 2 cm or 4 cm spacing, respectively, and a multiple row case consisting of dimples at 65% and 76% of the axial chord with 2 cm spacing. Again the upstream dimple set at the midpoint between two downstream dimples. The computational fluid dynamics study provided detailed flow visualization in and around the dimples as well as a comparison to experimental data for solver verification. It was shown that the computational and experimental results showed similar trends in wake loss and boundary layer traverses.
Download or read book Effect of Dimple Pattern on the Supression of Boundary Layer Separation on a Low Pressure Turbine Blade written by John P. Casey and published by . This book was released on 2004 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Propulsion and Power written by and published by . This book was released on 2008 with total page 822 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effect of Wakes on Separating Boundary Layers in Low Pressure Turbines written by Rory Douglas Stieger and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions written by and published by . This book was released on 2003 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Control of Flow Separation on a Turbine Blade by Utilizing Tail Extensions written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was conducted in a two-dimensional linear cascade, focusing on the suction surface of a low pressure turbine blade. Flow Reynolds numbers, based on exit velocity and suction surface length were varied from 50,000 to 300,000. The axial chord of the blades was varied using tail extenders from 0% to 15% beyond design. The effects of Reynolds number on a low pressure turbine cascade blade with tail extensions was investigated. This study has shown that for certain cases, changing the axial chord of a low pressure turbine blade by utilizing tail extensions provided a clear improvement in boundary layer behavior which results in better overall performance. There was no additional advantage when the tail extensions were longer than 6.1% of the axial chord. The shortest tail extension resulted in the greatest zone of performance enhancement. The longer tail extension resulted in a smaller region of performance enhancement.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1977 with total page 1006 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence and Disturbances in the Boundary Layer of a Flat Plate written by A. FAVRE and published by . This book was released on 1960 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow in a boundany layer over a flat plate, with and without adverse pressure gradient, shows turbulent fluctuations in time of the instantaneous local rates of flow, and spanwise disturbances in time of the average rates of flow. Similar disturbances also affect the boundary layer thicknesses, the form parameter, the turbulent friction tensions and time and space correlations. The spanwise mean values help to decrease the scatter observed. Turbulent friction measurements made by the hot wire method are much more precise than those obtained by the method of measuring mean velocities. In the vicinity of the leading edge, during penetration in the boundary layer and in the areas of transition or separation, the equations for mean values in time and along the span should make it possible to study the mean effects of the disturbances. (Author).
Download or read book Separating and Separated Boundary Layers written by and published by . This book was released on 1996 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: The low-pressure turbine of an aircraft engine operates with a low chord Reynolds number. As such, there are regions of strong streamwise acceleration and diffusion effects. This results in extended regions of transition from laminar to turbulent flow and large zones of flow separation. In response to a need to learn more about the mechanisms that lead to transition and separation in the engine environment, a low-Reynolds-number-flow study initiated during the Summer of 1994 at Wright Labs. In this project, a low-pressure turbine airfoil cascade was installed in a wind tunnel. To simulate the engine environment, high background turbulence was imposed on the flow and a device for imposing passing wakes upon the flow was fabricated. A program for measurement of the characteristics of the boundary layer; laminar-like or turbulent, separated or attached, was initiated. The Summer project resulted in an effective start on the problem but considerably more remained to be done. This report documents the subsequent work on this project. At the University of Minnesota, an easily accessible facility which had the essential elements of the low-pressure turbine flow was designed, built, and qualified. This facility now provides a convenient means for documenting the flow and developing measurement techniques. The Wright Lab experimental program continued with the completion of the construction, the implementation of the turbulence generating device, and the qualification of the tunnel. Both facilities are now producing data to the program. These data are summarized herein. The University of Minnesota facility has generated pressure profiles for various cases of different Reynolds number and turbulence intensity. The Wright Labs facility has given pressure profiles for various Reynolds numbers.
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2007 with total page 960 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book MARE WINT written by Wiesław Ostachowicz and published by Springer. This book was released on 2016-08-30 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a holistic, interdisciplinary overview of offshore wind energy, and is a must-read for advanced researchers. Topics, from the design and analysis of future turbines, to the decommissioning of wind farms, are covered. The scope of the work ranges from analytical, numerical and experimental advancements in structural and fluid mechanics, to novel developments in risk, safety & reliability engineering for offshore wind.The core objective of the current work is to make offshore wind energy more competitive, by improving the reliability, and operations and maintenance (O&M) strategies of wind turbines. The research was carried out under the auspices of the EU-funded project, MARE-WINT. The project provided a unique opportunity for a group of researchers to work closely together, undergo multidisciplinary doctoral training, and conduct research in the area of offshore wind energy generation. Contributions from expert, external authors are also included, and the complete work seeks to bridge the gap between research and a rapidly-evolving industry.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1997 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Three Dimensional Flow in the Root Region of Wind Turbine Rotors written by Galih Bangga and published by kassel university press GmbH. This book was released on 2018-06-20 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the state of the art in the analyses of three-dimensional flow over rotating wind turbine blades. Systematic studies for wind turbine rotors with different sizes were carried out numerically employing three different simulation approaches, namely the Euler, URANS and DDES methods. The main mechanisms of the lift augmentation in the blade inboard region are described in detail. The physical relations between the inviscid and viscous effects are presented and evaluated, emphasizing the influence of the flow curvature on the resulting pressure distributions. Detailed studies concerning the lift augmentation for large wind turbine rotors are considered as thick inboard airfoils characterized by massive separation are desired to stronger contribute to power production. Special attention is given to the analyses of wind turbine loads and flow field that can be helpful for the interpretation of the occurring physical phenomena. The book is aimed at students, researchers, engineers and physicists dealing with wind engineering problems, but also for a wider audience involved in flow computations.
Download or read book Unsteady Aerodynamics Aeroacoustics and Aeroelasticity of Turbomachines written by Kenneth C. Hall and published by Springer Science & Business Media. This book was released on 2006-05-11 with total page 605 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook is a collection of technical papers that were presented at the 10th International Symposium on Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines held September 8-11, 2003 at Duke University in Durham, North Carolina. The papers represent the latest in state of the art research in the areas of aeroacoustics, aerothermodynamics, computational methods, experimental testing related to flow instabilities, flutter, forced response, multistage, and rotor-stator effects for turbomachinery.
