Download or read book The Effects of Blade Count on Boundary Layer Development in a Low Pressure Turbine written by Daniel J. Dorney and published by . This book was released on 2000 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of Boundary Layer Development in a Two Stage Low Pressure Turbine written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the transition models available for low Reynolds number flows in turbomachinery. The results of the simulations have been compared with experimental data, including airfoil loadings and integral boundary layer quantities. The predicted unsteady results display similar trends to the experimental data, but significantly overestimate the amplitude of the unsteadiness. The time-averaged results show close agreement with the experimental data.Dorney, Daniel J. and Ashpis, David E. and Halstead, David E. and Wisler, David C.Glenn Research CenterJET ENGINES; TWO STAGE TURBINES; COMPUTERIZED SIMULATION; BALDWIN-LOMAX TURBULENCE MODEL; BOUNDARY LAYER TRANSITION; TRANSITION FLOW; FLOW VISUALIZATION; BOUNDARY LAYER SEPARATION; SEPARATED FLOW; ROTOR BLADES (TURBOMACHINERY); TAKEOFF; CRUISING FLIGHT; COMPUTATIONAL GRIDS; NOZZLE FLOW; SKIN FRICTION; TURBINE BLADES; REYNOLDS NUMBER; FLOW CHARACTERISTICS; FLOW DISTRIBUTION
Download or read book Study of Boundary Layer Development in a Two Stage Low Pressure Turbine written by Daniel J. Dorney and published by . This book was released on 1999 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Combined Effects of Reynolds Number Turbulence Intensity and Periodic Unsteady Wake Flow Conditions on Boundary Layer Development and Heat Transfer of a Low Pressure Turbine Blade written by Burak Ozturk and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Detailed experimental investigation has been conducted to provide a detailed insight into the heat transfer and aerodynamic behavior of a separation zone that is generated as a result of boundary layer development along the suction surface of a highly loaded low pressure turbine (LPT) blade. The research experimentally investigates the individual and combined effects of periodic unsteady wake flows and freestream turbulence intensity (Tu) on heat transfer and aerodynamic behavior of the separation zone. Heat transfer experiments were carried out at Reynolds number of 110,000, 150,000, and 250,00 based on the suction surface length and the cascade exit velocity. Aerodynamic experiments were performed at Re = 110,000 and 150,000. For the above Re-numbers, the experimental matrix includes Tus of 1.9%, 3.0%, 8.0%,13.0% and three different unsteady wake frequencies with the steady inlet flow as the reference configuration. Detailed heat transfer and boundary layer measurements are performed with particular attention paid to the heat transfer and aerodynamic behavior of the separation zone at different Tus at steady and periodic unsteady flow conditions. The objectives of the research are (a) to quantify the effect of Tu on the aero-thermal behavior of the separation bubble at steady inlet flow condition, (b) to investigate the combined effects of Tu and the unsteady wake flow on the aero-thermal behavior of the separation bubble, and (c) to provide a complete set of heat transfer and aerodynamic data for numerical simulation that incorporates Navier-Stokes and energy equations. The analysis of the experimental data reveals details of boundary layer separation dynamics which is essential for understanding the physics of the separation phenomenon under periodic unsteady wake flow and different Reynolds number and Tu. To provide a complete picture of the transition process and separation dynamics, extensive intermittency analysis was conducted. Ensemble averaged maximum and minimum intermittency functions were determined leading to the relative intermittency function. In addition, the detailed intermittency analysis reveals that the relative intermittency factor follows a Gaussian distribution confirming the universal character of the relative intermittency function.
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 Comparison of Results of Experimental and Theoretical Studies of Blade outlet Boundary layer Characteristics of Stator Blade for a High Subsonic Mach Number Turbine written by Cavour H. Hauser and published by . This book was released on 1957 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of Low Reynolds Number Effects on the Losses in Low Pressure Turbine Blade Rows written by and published by . This book was released on 1998 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 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 Axial Turbine Aerodynamics for Aero engines written by Zhengping Zou and published by Springer. This book was released on 2018-01-11 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a monograph on aerodynamics of aero-engine gas turbines focusing on the new progresses on flow mechanism and design methods in the recent 20 years. Starting with basic principles in aerodynamics and thermodynamics, this book systematically expounds the recent research on mechanisms of flows in axial gas turbines, including high pressure and low pressure turbines, inter-turbine ducts and turbine rear frame ducts, and introduces the classical and innovative numerical evaluation methods in different dimensions. This book also summarizes the latest research achievements in the field of gas turbine aerodynamic design and flow control, and the multidisciplinary conjugate problems involved with gas turbines. This book should be helpful for scientific and technical staffs, college teachers, graduate students, and senior college students, who are involved in research and design of gas turbines.
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 Experimental Study of Boundary Layer Behavior in a Simulated Low Pressure Turbine written by Rickey J. Shyne and published by . This book was released on 1998 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Detached Eddy Simulation Analysis of Pak B Low Pressure Turbine Blade written by Kyle P. Malone and published by . This book was released on 2004-06-01 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two cases were computationally investigated using the detached eddy simulation (DES) turbulence model: an unmodified Pak-B blade and a Pak-B blade with a dimple located at 65% of axial chord. Both cases were created so that they simulated an infinite span with an infinite number of dimples. The cases were run for an inlet Reynolds number of 25,000. The computed results were used to resolve the location of separation and reattachment, visualize the streamlines for the dimpled case, build velocity magnitude contour and vector plots, and map the thickness of the boundary layer. The results were then compared to previous computational and experimental studies in order to validate the detached eddy simulation model for future research into the effect of dimples on low pressure turbine flow fields. For the unmodified blade, the performance of the DES model compared favorably to other available viscous and turbulence models. For the dimpled blade, preliminary results also compare favorably to other models although further development of the flow field is needed to verify this. Based on these results, future researchers studying dimples on turbine blades should strongly consider using the DES turbulence model.
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 1995 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
