Download or read book Impact of Free stream Turbulence Intensity on the Endwall Region of Low Pressure Turbine Blades written by Molly Hope Donovan and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbomachinery components, such as the low pressure turbine, are highly complex rotating machines, therefore, conducting fundamental fluid mechanics studies in them is exceedingly difficult. For this reason, testing is generally completed in facilities such as linear cascades, like the one present in the Low Speed Wind Tunnel Facility at AFRL, which typically utilize a low freestream turbulence intensity, when in reality, the freestream turbulence intensity in a full, rotating low pressure turbine is likely much higher. Slightly elevating the freestream turbulence intensity (e.g., 3%) typically improves the Reynolds-lapse characteristics of a blade profile by affecting the transition process, reducing the detrimental effects of laminar boundary layer separation, and shifting the knee in the loss curve. Front loaded blades are more resistant to separation, however, they can experience high losses in the endwall region due to the complex vortical structures present. Therefore, a better understanding whether high levels of freestream turbulence intensity will increase the overall losses generated in the passage is important. An intial study with a jet based active grid was completed on the L2F blade. Based of the insight gained from that study, a new mechanical agitator based active grid was implemented into a linear cascade of L3FHW-LS blades in order to more effectively study how elevated FSTI impacts the endwall flow behavior and loss production. Coefficient of pressure measurements, three planes of SPIV, two additional planes of flow visualization, and three planes of total pressure loss measurements were collected. Impacts of incoming turbulence on the endwall losses as well as the endwall flow structures were assessed.

Download or read book Study of Low Reynolds Number Effects on the Losses in Low pressure Turbine Blade Rows written by Daniel J. Dorney 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 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 Effects of High Turbulence and Wakes on Mass Transfer from Gas Turbine Blades written by Steven John Olson and published by . This book was released on 1999 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Two equation Low Reynolds number Turbulence Modeling of Transitional Boundary Layer Flows Characteristic of Gas Turbine Blades written by Rodney C. Schmidt and published by . This book was released on 1988 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A FUNDAMENTAL INVESTIGATION OF THE EFFECT OF FREESTREAM TURBULENCE PARAMETERS ON THE TIME MEAN AND DYNAMIC BEHAVIOR OF JUNCTION FLOW written by Eric Lange and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Junction flow is a phenomenon that is common to both natural and industrial processes, occurring where an incoming flow above a wall meets an obstacle protruding from the wall, such as occurs at wing-body junctions on aircraft or turbine blade/vane endwalls in a gas turbine. This obstacle produces a region of adverse pressure which causes the incoming boundary layer to lift off of the wall, curl down upon itself, and form a region of backflow along the endwall in front of the obstacle. This backflow sustains the presence of a horseshoe vortex system a coherent vortex feature centered near the endwall in front of the obstacle leading edge, with legs that wrap around the obstacle following the mainstream flow. In turbulent flows, the horseshoe vortex system is known to be complex in structure and highly unsteady in regards to the position of its primary vortex core. Due in part to its unsteadiness, the presence of the horseshoe vortex system within the junction significantly increases endwall heat transfer in front of the obstacle. It can also produce significant dynamic pressure loads on obstacle surfaces near the junction. Understanding and potentially controlling the dynamic behavior of the horseshoe vortex in an applied setting is currently difficult due to the need for a fundamental understanding of how freestream parameters such as Reynolds number and freestream turbulence levels affect flow in the junction. To address this need, a study was constructed to determine the effect of freestream Reynolds number, turbulence intensity, and integral length scale conditions on the dynamic and time-mean unsteadiness of the horseshoe vortex system and the surrounding junction flow field in front of a symmetric wing. Time-resolved measurements of the junction flow field were made using stereo particle image velocimetry (SPIV). These were analyzed to quantify the unsteadiness of the junction region and the horseshoe vortex system under a wide range of freestream turbulence levels (2%, 10%, and 17%) and body-thickness Reynolds number (7000, 25000, 80000) conditions relevant to industrial applications. This unsteadiness is dominated by oscillatory motions of the horseshoe vortex between backflow and zero-flow modes. Dynamic analysis of these motions and the temporal unsteadiness of the horseshoe vortex under varying Reynolds number and turbulence intensity conditions are highly unique contributions of this work.Freestream Reynolds number significantly influences the structure of the horseshoe vortex system and other vorticity features along the junction endwall. At low Reynolds number, the horseshoe vortex has a coherent dynamic structure and moves along the endwall in a coherent manner driven by large hairpin structures in the incoming boundary layer. This motion produces an elliptical distribution of time-mean turbulent kinetic energy along the junction endwall. At high Reynolds numbers, however, the incoming boundary layer is significantly more turbulent, causing the dynamic structure of the vortex and its motions along the endwall to be more chaotic. This is due to disruptive interactions with locally generated hairpin vortices and other small scale vorticity features in the incoming lower boundary layer, which occur frequently at high Reynolds number. These features destabilizing the vortex in backflow mode and increase local flow field unsteadiness. The result is a greater degree of randomness in vortex core position and a modest increase in time-mean turbulent kinetic energy in the core region at high Reynolds number, particularly beneath the time-mean core location. The presence of moderate to high freestream turbulence intensity significantly increases turbulent kinetic energy in the junction under low turbulent Reynolds number conditions, but is less effective as Reynolds number increases. Much of this augmentation occurs in the horseshoe vortex region and along the wing leading edge. This effect is caused by the impingement of freestream and upper boundary layer turbulence features along the wing leading edge and the subsequent transport of this fluctuating momentum along the wing leading edge to the junction corner region. At low Reynolds number, features are frequently entrained within the horseshoe vortex or endwall backflow, causing high fluctuating momentum in the region along the endwall. The presence of turbulence features in the junction can also initiate and energize sweeping vortex oscillatory motions at low Reynolds number. These mechanisms are less effective at high Reynolds numbers due to smaller scale of freestream turbulent eddy penetration which occurs at high Reynolds number in the junction, and the lack of large hairpin structures in the incoming boundary layer. At high freestream turbulence intensities, large integral length scales also played a role in augmenting the effect of turbulence intensity. Appreciable augmentation of the unsteadiness in the vortex core region and leading edge regions of the junction is observed for large integral length scales at high turbulence intensity under low and moderate turbulent Reynolds number conditions in comparison to the unsteadiness observed at similar turbulence intensity but smaller length scales. This is due to the increased rate of impingement of large turbulence features along the wing leading edge that occurs at length scale magnitudes above a certain threshold. Altogether, this work provides a detailed fundamental understanding of the effects of Reynolds number and freestream turbulence on the unsteadiness of flow in the junction, and a detailed explanation of the mechanisms that drive these effects to occur. The dynamic motion patterns of the horseshoe vortex are highly sensitive to turbulence in the incoming boundary layer, which varies in nature at varying Reynolds number. High levels of freestream turbulence can lead to a significant increase in unsteadiness of flow near the junction surfaces at low Reynolds number due in part to energized motions of the horseshoe vortex system. This understanding directly supports efforts to predict or control junction heat transfer and pressure loading effects in applications that include high freestream turbulence conditions. It is clear that any attempt to model the unsteady behavior of the junction flow field under moderate to high freestream turbulence conditions must account for Reynolds number, turbulence intensity, and at high turbulence levels, integral length scale, as influential driving parameters of unsteadiness in the junction.

Download or read book Endwall Losses and Flow Unsteadiness in a Turbine Blade Cascade written by L. Adjlout and published by . This book was released on 1990 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this paper is to describe an investigation of the flow within and downstream of a turbine blade cascade of high aspect ratio. A detailed experimental investigation into the changes in the endwall boundary layer in the cascade (100 deg camber angle) and total pressure loss downstream of the cascade was carried out. Flow visualization was used in order to obtain detailed photographs of the flow patterns on the endwall and for exhibiting the trailing edge vortices. Pressure measurements were carried out using a miniature cranked Kiel probe for three planes downstream of the cascade, with two levels of turbulence intensity of the free stream. Pressure distributions on the blade were measured at three spanwise locations, namely 4, 12, and 50 percent of the full span from the wall. Hot-wire anenometry combined with a spectrum analyzer program was used to determine the frequencies of the flow oscillations. The change in turbulence level of the free stream has a significant influence on all three pressure distributions. The striking difference between two of the pressure distributions is in the aft half of the suction side where the distribution with the lower turbulence intensity has the larger lift. The oil flow visualization reveals what appear to be two separation lines within the passage and are believed to originate from the horseshoe vortex. The pitchwise-averaged total pressure loss coefficient increases with the distance of the measurement plane downstream of the cascade blades. A substantial part of this loss increase close to the wall is caused by the high rate of shear of the new boundary layer on the endwall.5.

Download or read book Effects of High Intensity Large Scale Freestream Combustor Turbulence on Heat Transfer in Transonic Turbine Blades written by and published by . This book was released on 2003 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of freestream turbulence representative of the flow downstream of a modem gas turbine combustor and the first stage vane on turbine blade heat transfer has been measured and analytically modeled in a linear, transonic turbine cascade. Measurements were performed on a high turning, transonic turbine blade. The facility is capable of heated flow with inlet total temperature of 120 degrees C and inlet total pressure of 10 psig. The Reynolds number based on blade chord and exit conditions (5x10(exp 6)) and the inlet and exit Mach numbers (0.4 and 1.2, respectively) are representative of conditions in a modem gas turbine engine. High intensity, large length-scale freestream turbulence was generated using a passive turbulence-generating grid to simulate the turbulence generated in modem combustors after it has passed through the first stage vane row. The grid produced freestream turbulence with intensity of approximately 10-12% and an integral length scale of 2 cm near the entrance of the cascade passages, which is believed to be representative of the core flow entering a first stage gas turbine rotor blade row. Mean heat transfer results showed an increase in heat transfer coefficient of approximately 8% on the suction surface of the blade, with increases on the pressure surface on the order of two times higher than on the suction surface (approximately 17%). This corresponds to increases in blade surface temperature of 5- 10%, which can significantly reduce the life of a turbine blade. The heat transfer data were compared with correlations from published literature with good agreement.

Download or read book The Effects of Inlet Turbulence and Rotor stator Interactions on the Aerodynamics and Heat Transfer of a Large scale Rotating Turbine Model Volume 1 written by Robert P. Dring and published by . This book was released on 1987 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gas Turbine Heat Transfer and Cooling Technology Second Edition written by Je-Chin Han and published by CRC Press. This book was released on 2012-11-27 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive reference for engineers and researchers, Gas Turbine Heat Transfer and Cooling Technology, Second Edition has been completely revised and updated to reflect advances in the field made during the past ten years. The second edition retains the format that made the first edition so popular and adds new information mainly based on selected published papers in the open literature. See What’s New in the Second Edition: State-of-the-art cooling technologies such as advanced turbine blade film cooling and internal cooling Modern experimental methods for gas turbine heat transfer and cooling research Advanced computational models for gas turbine heat transfer and cooling performance predictions Suggestions for future research in this critical technology The book discusses the need for turbine cooling, gas turbine heat-transfer problems, and cooling methodology and covers turbine rotor and stator heat-transfer issues, including endwall and blade tip regions under engine conditions, as well as under simulated engine conditions. It then examines turbine rotor and stator blade film cooling and discusses the unsteady high free-stream turbulence effect on simulated cascade airfoils. From here, the book explores impingement cooling, rib-turbulent cooling, pin-fin cooling, and compound and new cooling techniques. It also highlights the effect of rotation on rotor coolant passage heat transfer. Coverage of experimental methods includes heat-transfer and mass-transfer techniques, liquid crystal thermography, optical techniques, as well as flow and thermal measurement techniques. The book concludes with discussions of governing equations and turbulence models and their applications for predicting turbine blade heat transfer and film cooling, and turbine blade internal cooling.

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 Handbook of Turbomachinery written by Earl Logan, Jr. and published by CRC Press. This book was released on 2003-05-01 with total page 829 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building on the success of its predecessor, Handbook of Turbomachinery, Second Edition presents new material on advances in fluid mechanics of turbomachinery, high-speed, rotating, and transient experiments, cooling challenges for constantly increasing gas temperatures, advanced experimental heat transfer and cooling effectiveness techniques, and propagation of wake and pressure disturbances. Completely revised and updated, it offers updated chapters on compressor design, rotor dynamics, and hydraulic turbines and features six new chapters on topics such as aerodynamic instability, flutter prediction, blade modeling in steam turbines, multidisciplinary design optimization.

Download or read book The Effects of Free steam Turbulence Quantities on Heat Transfer to Turbine Blading written by W. J. Priddy and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Modeling of Laminar to Turbulent Transition on Turbine Vanes and Blades written by and published by . This book was released on 1996 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Endwall Heat Transfer Measurements in a Transonic Turbine Cascade written by and published by . This book was released on 1996 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbine blade endwall heat transfer measurements are given for a range of Reynolds and Mach numbers. Data were obtained for Reynolds numbers based on inlet conditions of 0.5 and 1.0 x 10(exp 6), for isentropic exit Mach numbers of 1.0 and 1.3, and for freestream turbulence intensities of 0.25% and 7.0%. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The test article was a turbine rotor with 136 deg of turning and an axial chord of 12.7 cm. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for CFD code and model verification. The flow field in the cascade is highly three-dimensional as a result of thick boundary layers at the test section inlet. Endwall heat transfer data were obtained using a steady-state liquid crystal technique.

Download or read book The Boundary Layer Over Turbine Blade Models with Realistic Rough Surfaces written by and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface roughness is known to have a significant impact on turbine heat loads and performance. Over time, as the turbine blades are exposed to these loads, the external surfaces become rougher, which results in increased heat loads and friction losses. The objective of the present investigation is to conduct measurements that will reveal the influence of realistic surface roughness on the near-wall behavior of the boundary layer. LDV measurements have been conducted in a Matched-Index-Of-Refraction (MIR) oil tunnel. The tunnel has been modified to operate with an accelerating freestream and an elevated freestream turbulence level in order to simulate conditions on the suction side of a high pressure turbine blade. We have made extensive boundary layer measurements over a smooth plate model and over a model with a strip of realistic rough surface. The realistic rough surface was developed by scaling actual turbine blade surface data that was provided by AFRL. The results include velocity profiles, streamwise and vertical turbulence intensity profiles, and Reynolds stress profiles. The oil tunnel arrangement has permitted velocity measurements very close to the wall (down to