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Ronald Scott Bunker - One of the best experts on this subject based on the ideXlab platform.
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A Review of Turbine Blade Tip Heat Transfer
Annals of the New York Academy of Sciences, 2006Co-Authors: Ronald Scott BunkerAbstract:This paper presents a review of the publicly available knowledge base concerning turbine Blade Tip heat transfer, from the early fundamental research which laid the foundations of our knowledge, to current experimental and numerical studies utilizing engine-scaled Blade cascades and turbine rigs. Focus is placed on high-pressure, high-temperature axial-turbine Blade Tips, which are prevalent in the majority of today's aircraft engines and power generating turbines. The state of our current understanding of turbine Blade Tip heat transfer is in the transitional phase between fundamentals supported by engine-based experience, and the ability to a priori correctly predict and efficiently design Blade Tips for engine service.
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effect of squealer cavity depth and oxidation on turbine Blade Tip heat transfer
Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 2001Co-Authors: Ronald Scott Bunker, Jeremy Clyde BaileyAbstract:An experimental study has been performed to investigate the effect of squealer cavity depth on the detailed distribution of convective heat transfer coefficients of a turbine Blade Tip surface. This paper presents full surface information on heat transfer coefficients within a Blade cascade which develops an appropriate pressure distribution about an airfoil Blade Tip and shroud model. A stationary Blade cascade experiment has been run consisting of three airfoils, the center airfoil having a variable Tip gap clearance. The airfoil models the aerodynamic Tip section of a high pressure turbine Blade with inlet Mach number of 0.21, exit Mach number of 0.74, pressure ratio of 1.41, Reynolds number of 2.8•106, and total turning of about 100 degrees. The cascade inlet turbulence intensity level is 9%. Tip surface heat transfer coefficient distributions are first shown for a flat, square-edge Tip with a clearance gap of 2.03 mm. Heat transfer distributions are then shown for full-perimeter squealer Tip cavities having the same clearance gap above the squealer rim, and clearance-to-cavity depth ratios from 0.67 to 2. Regionally averaged heat transfer coefficients are analyzed to discern a relationship between Tip heat transfer and cavity depth. Further tests demonstrate the effect of partial squealer rim oxidation, or material loss, on the surface heat transfer distributions.Copyright © 2001 by ASME
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heat transfer and flow on the first stage Blade Tip of a power generation gas turbine part 1 experimental results
Journal of Turbomachinery-transactions of The Asme, 2000Co-Authors: Ronald Scott Bunker, Jeremy Clyde Bailey, Ali AmeriAbstract:A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first-stage Blade Tip surface for a geometry typical of large power generation turbines (> 100 MW). This paper is concerned with the design and execution of the experimental portion of the study, which represents the first reported investigation to obtain nearly full surface information on heat transfer coefficients within an environment that develops an appropriate pressure distribution about an airfoil Blade Tip and shroud model. A stationary Blade cascade experiment has been run consisting of three airfoils, the center airfoil having a variable Tip gap clearance. The airfoil models the aerodynamic Tip section of a high-pressure turbine Blade with inlet Mach number of 0.30, exit Mach number of 0.75, pressure ratio of 1.45, exit Reynolds number based on axial chord of 2.57 x 10{sup 6}, and total turning of about 110 degrees. A hue detection based liquid crystal method is used to obtain the detailed heat transfer coefficient distribution on the Blade Tip surface for flat, smooth Tip surfaces with both sharp and rounded edges. The cascade inlet turbulence intensity level took on values of either 5 or 9%.more » The cascade also models the casing recess in the shroud surface ahead of the Blade. Experimental results are shown for the pressure distribution measurements on the airfoil near the Tip gap, on the Blade Tip surface, and on the opposite shroud surface. Tip surface heat transfer coefficient distributions are shown for sharp edge and rounded edge Tip geometries at each of the inlet turbulence intensity levels.« less
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heat transfer and flow on the first stage Blade Tip of a power generation gas turbine part 2 simulation results
Journal of Turbomachinery-transactions of The Asme, 2000Co-Authors: Ali Ameri, Ronald Scott BunkerAbstract:A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first-stage Blade Tip surface for a geometry typical of large power generation turbines (>100 MW). This paper is concerned with the numerical prediction of the Tip surface heat transfer. Good comparison with the experimental measured distribution was achieved through accurate modeling of the most important features of the Blade passage and heating arrangement as well as the details of experimental rig likely to affect the Tip heat transfer. A sharp edge and a radiused edge Tip was considered. The results using the radiused edge Tip agreed better with the experimental data. This improved agreement was attributed to the absence of edge separation on the Tip of the radiused edge Blade.
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heat transfer and flow on the first stage Blade Tip of a power generation gas turbine part 2 simulation results
ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition, 1999Co-Authors: Ali Ameri, Ronald Scott BunkerAbstract:A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first stage Blade Tip surface for a geometry typical of large power generation turbines (>100MW). This paper is concerned with the numerical prediction of the Tip surface heat transfer. Good comparison with the experimental measured distribution was achieved through accurate modeling of the most important features of the Blade passage and heating arrangement as well as the details of experimental rig likely to affect the Tip heat transfer. A sharp edge and a radiused edge Tip was considered. The results using the radiused edge Tip agreed better with the experimental data. This improved agreement was attributed to the absence of edge separation on the Tip of the radiused edge Blade.Copyright © 1999 by ASME
Michael G. Dunn - One of the best experts on this subject based on the ideXlab platform.
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casing treatment and Blade Tip configuration effects on controlled gas turbine Blade Tip shroud rubs at engine conditions
Journal of Turbomachinery-transactions of The Asme, 2011Co-Authors: Corso Padova, Michael G. Dunn, Kevin Turner, Jeffery Barton, Alan Turner, Darin DitommasoAbstract:Experimental results obtained for an Inconel ® compressor Blade rubbing bare-steel and treated casings at engine speed are described. Since 2002 a number of experiments were conducted to generate a broad database for Tip rubs, the Rotor-Blade Rub database obtained using the unique experimental facility at the The Ohio State University Gas Turbine Laboratory. As of 2007, there are seven completed groups of measurements in the database. Among them a number of Blade-Tip geometries and casing surface treatments have been investigated. The purpose of this paper is to provide a detailed interpretation of this database. Load cell, strain, temperature, and accelerometer measurements are discussed and then applied to analyze the interactions resulting from progressive and sudden incursions of varying severity, defined by incursion depths ranging from 13 μm to 762 μm (from 0.0005 in. to 0.030 in.). The influence of Blade-Tip speed on these measurements is described. The results presented describe the dynamics of rotor and casing vibro-impact response at representative operational speeds similar to those experienced in flight. Force components at the Blade Tip in the axial and circumferential directions are presented for rub incursions ranging in depth from very light (13 μm) to severe (406 μm). Trends of variation are observed during metal-to-metal and metal-to-abradable contacts for two airfoil Tip shapes and Tip speeds 390 m/s (1280 ft/s) and 180 m/s (590 ft/s). The nonlinear nature of the rub phenomena reported in earlier work is confirmed. In progressing from light rubs to higher incursion, the maximum incurred circumferential load increases significantly while the maximum incurred axial load increases much less. The manner in which casing surface treatment affects the loads is presented. Concurrently, the stress magnification on the rubbing Blade at root midchord, at Tip leading edge, and at Tip trailing edge is discussed. Computational models to analyze the nonlinear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted.
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casing treatment and Blade Tip configuration effects on controlled gas turbine Blade Tip shroud rubs at engine conditions
ASME Turbo Expo 2008: Power for Land Sea and Air, 2008Co-Authors: Corso Padova, Michael G. Dunn, Kevin Turner, Jeffery Barton, Alan Turner, Darin DitommasoAbstract:Experimental results obtained for an Inconel compressor Blade rubbing bare-steel and treated casings at engine speed are described. Since 2002 a number of experiments were conducted to generate a broad database for Tip rubs, the Rotor-Blade Rub Database (RBR database) obtained using the unique experimental facility at the OSU Gas Turbine Laboratory. As of 2007, there are seven completed groups of measurements in the database. Among them a number of Blade-Tip geometries and casing surface treatments have been investigated. The purpose of this paper is to provide a detailed interpretation of this database. Load cell, strain, temperature and accelerometer measurements are discussed and then applied to analyze the interactions resulting from progressive and sudden incursions of varying severity, defined by incursion depths ranging from 13 μm to 762 μm (0.0005 in to 0.030 in). The influence of Blade-Tip speed on these measurements is described. The results presented describe the dynamics of rotor and casing vibro-impact response at representative operational speeds similar to those experienced in flight. Force components at the Blade Tip in the axial and circumferential directions are presented for rub incursions ranging in depth from very light (13 μm) to severe (406 μm). Trends of variation are observed during metal-to-metal and metal-to-abradable contacts for two airfoil Tip shapes and Tip speed 390 m/s (1280 ft/s) and 180 m/s (590 ft/s). The non-linear nature of the rub phenomena reported in earlier work is confirmed. In progressing from light rubs to higher incursion, the maximum incurred circumferential load increases significantly while the maximum incurred axial load increases much less. The manner in which casing surface treatment affects the loads is presented. Concurrently, the stress magnification on the rubbing Blade at root mid-chord, at Tip leading edge, and at Tip trailing edge is discussed. Computational models to analyze the non-linear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted. A companion paper on a method to determine Blade Tip forces is presented separately in this Turbo Expo conference.Copyright © 2008 by ASME
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experimental results from controlled Blade Tip shroud rubs at engine speed
Journal of Turbomachinery-transactions of The Asme, 2007Co-Authors: Corso Padova, Michael G. Dunn, Jeffery Barton, Steve ManwaringAbstract:Experimental results obtained for an Inconel® compressor Blade rubbing a steel casing at engine speed are described. Load cell, strain gauge, and accelerometer measurements are discussed and then applied to analyze the metal-on-metal interaction resulting from sudden incursions of varying severity, defined by incursion depths ranging from 13 μm to 762 jam (0.0005 in. to 0.030 in.). The results presented describe the transient dynamics of rotor and casing vibro-impact response at engine operational speed similar to those experienced in flight. Force components at the Blade Tip in axial and circumferential directions for a rub of moderate incursion depth (140 μm) are compared to those for a severe rub (406 μm). Similar general trends of variation during the metal-to-metal contact are observed. However, in the nearly threefold higher incursion the maximum incurred circumferential load increases significantly, while the maximum incurred axial load increases much less, demonstrating the non-linear nature of the rub phenomena. Concurrently, the stress magnification on the rubbing Blade at root mid-chord, at Tip leading edge, and at Tip trailing edge is discussed. The results point to the possibility of failure occurring first at the airfoil trailing edge. Such a failure was in fact observed in the most severe rub obtained to date in the laboratory, consistent with field observations. Computational models to analyze the non-linear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted.
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experimental results from controlled Blade Tip shroud rubs at engine speed
Volume 5: Marine; Microturbines and Small Turbomachinery; Oil and Gas Applications; Structures and Dynamics Parts A and B, 2006Co-Authors: Corso Padova, Michael G. Dunn, Jeffery Barton, Steve ManwaringAbstract:Experimental results obtained for an Inconel compressor Blade rubbing a steel casing at engine speed are described. Load cell, strain gauge and accelerometer measurements are discussed and then applied to analyze the metal-on-metal interaction resulting from sudden incursions of varying severity, defined by incursion depths ranging from 13 μm to 762 μm (0.0005-in to 0.030-in). The results presented describe the transient dynamics of rotor and casing vibro-impact response at engine operational speed similar to those experienced in flight. Force components at the Blade Tip in axial and circumferential directions for a rub of moderate incursion depth (140 μm) are compared to those for a severe rub (406 μm). Similar general trends of variation during the metal-to-metal contact are observed. However, in the nearly three-fold higher incursion the maximum incurred circumferential load increases significantly, while the maximum incurred axial load increases much less, demonstrating the non-linear nature of the rub phenomena. Concurrently, the stress magnification on the rubbing Blade at root mid-chord, at Tip leading edge, and at Tip trailing edge is discussed. The results point to the possibility of failure occurring first at the airfoil trailing edge. Such a failure was in fact observed in the most severe rub obtained to date in the laboratory, consistent with field observations. Computational models to analyze the non-linear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted.Copyright © 2006 by ASME
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simulation of engine Blade Tip rub induced vibration
ASME Turbo Expo 2005: Power for Land Sea and Air, 2005Co-Authors: Kevin Turner, Maurice L Adams, Michael G. DunnAbstract:An analysis has been developed to simulate the time-transient vibratory motion of a general configuration engine turbomachinery free-standing Blade when subjected to in-service Blade-on-casing Tip-rub events. The analysis imports the at-speed stress-stiffened Blade stiffness matrix and lumped mass matrix from a finite element model of the actual Blade. Formulation and computational approaches are presented. Correct characterization of the Blade Tip-surface rub mechanics tribology models necessitates using empirical information that is currently being acquired from single-Blade spin-pit tests now in progress in a parallel companion phase of this research. Output results for validation cases are presented. The analysis efficiently simulates complete transients involving mulTiple successive incursions (Blade on casing hits), tracking the Blade Tip contact force distribution and Blade motion throughout the simulated time frame including Blade motion during, between and after successive casing hits.Copyright © 2005 by ASME
Yongmin Yang - One of the best experts on this subject based on the ideXlab platform.
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Sparse Representation Based Frequency Detection and Uncertainty Reduction in Blade Tip Timing Measurement for Multi-Mode Blade Vibration Monitoring.
Sensors (Basel Switzerland), 2017Co-Authors: Minghao Pan, Yongmin Yang, Fengjiao GuanAbstract:The accurate monitoring of Blade vibration under operating conditions is essential in turbo-machinery testing. Blade Tip timing (BTT) is a promising non-contact technique for the measurement of Blade vibrations. However, the BTT sampling data are inherently under-sampled and contaminated with several measurement uncertainties. How to recover frequency spectra of Blade vibrations though processing these under-sampled biased signals is a bottleneck problem. A novel method of BTT signal processing for alleviating measurement uncertainties in recovery of multi-mode Blade vibration frequency spectrum is proposed in this paper. The method can be divided into four phases. First, a single measurement vector model is built by exploiting that the Blade vibration signals are sparse in frequency spectra. Secondly, the uniqueness of the nonnegative sparse solution is studied to achieve the vibration frequency spectrum. Thirdly, typical sources of BTT measurement uncertainties are quantitatively analyzed. Finally, an improved vibration frequency spectra recovery method is proposed to get a guaranteed level of sparse solution when measurement results are biased. Simulations and experiments are performed to prove the feasibility of the proposed method. The most outstanding advantage is that this method can prevent the recovered multi-mode vibration spectra from being affected by BTT measurement uncertainties without increasing the probe number.
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Sparse reconstruction of Blade Tip-timing signals for multi-mode Blade vibration monitoring
Mechanical Systems and Signal Processing, 2016Co-Authors: Jun Lin, Zhongsheng Chen, Yongmin YangAbstract:Abstract Severe Blade vibrations may reduce the useful life of the high-speed Blade. Nowadays, non-contact measurement using Blade Tip-timing (BTT) technology is becoming promising in Blade vibration monitoring. However, Blade Tip-timing signals are typically under-sampled. How to extract characteristic features of unknown multi-mode Blade vibrations by analyzing these under-sampled signals becomes a big challenge. In this paper, a novel BTT analysis method for reconstructing unknown multi-mode Blade vibration signals is proposed. The method consists of two key steps. First, a sparse representation (SR) mathematical model for sparse Blade Tip-timing signals is built. Second, a multi-mode Blade vibration reconstruction algorithm is proposed to solve this SR problem. Experiments are carried out to validate the feasibility of the proposed method. The main advantage of this method is its ability to reconstruct unknown multi-mode Blade vibration signals with high accuracy. The minimal requirements of probe number are also presented to provide guidelines for BTT system design.
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a non uniformly under sampled Blade Tip timing signal reconstruction method for Blade vibration monitoring
Sensors, 2015Co-Authors: Zheng Hu, Zhongsheng Chen, Yongmin Yang, Xuejun LiAbstract:High-speed Blades are often prone to fatigue due to severe Blade vibrations. In particular, synchronous vibrations can cause irreversible damages to the Blade. Blade Tip-timing methods (BTT) have become a promising way to monitor Blade vibrations. However, synchronous vibrations are unsuitably monitored by uniform BTT sampling. Therefore, non-equally mounted probes have been used, which will result in the non-uniformity of the sampling signal. Since under-sampling is an intrinsic drawback of BTT methods, how to analyze non-uniformly under-sampled BTT signals is a big challenge. In this paper, a novel reconstruction method for non-uniformly under-sampled BTT data is presented. The method is based on the periodically non-uniform sampling theorem. Firstly, a mathematical model of a non-uniform BTT sampling process is built. It can be treated as the sum of certain uniform sample streams. For each stream, an interpolating function is required to prevent aliasing in the reconstructed signal. Secondly, simultaneous equations of all interpolating functions in each sub-band are built and corresponding solutions are ultimately derived to remove unwanted replicas of the original signal caused by the sampling, which may overlay the original signal. In the end, numerical simulations and experiments are carried out to validate the feasibility of the proposed method. The results demonstrate the accuracy of the reconstructed signal depends on the sampling frequency, the Blade vibration frequency, the Blade vibration bandwidth, the probe static offset and the number of samples. In practice, both types of Blade vibration signals can be particularly reconstructed by non-uniform BTT data acquired from only two probes.
G N Barakos - One of the best experts on this subject based on the ideXlab platform.
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a review of helicopter rotor Blade Tip shapes
Progress in Aerospace Sciences, 2013Co-Authors: A Brocklehurst, G N BarakosAbstract:A review of helicopter rotor Blade Tip design technology has been carried out with a view to undertaking subsequent computations to evaluate the performance of new Tip designs. The review starts by briefly looking at (fixed) wing Tip design concepts and the underlying fluid mechanics on which they are based in order to see if there is any carry-over of ideas on which improved Tip design concepts might be based. Then, rotor Blade Tip shapes that have been used, or suggested for use, on past and present rotorcraft are examined to obtain a better understanding of the helicopter Tip design problem. In parallel, the review traces the development of analysis tools to evaluate the performance of the rotor and Blade Tip design. It is clear that in the past, the designer relied heavily on classical aerodynamic knowledge, supplemented by experience and intuition, supported by wind tunnel and model rotor testing, and relatively low-order aerodynamic calculations. New rotor designs were, and still are the subject of intensive flight test verification. However, recent development of Computational Fluid Dynamics (CFD) now offers an opportunity to accurately predict the viscous, compressible flow-field in the Tip region, and thus predict the performance of new rotor and Tip designs, provided that the solver has adequate resolution, is able to handle all aspects of the helicopter problem, and sufficient computational resources are available to complete the design in a practical time-scale.
Asif Afzal - One of the best experts on this subject based on the ideXlab platform.
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thermo mechanical analysis and estimation of turbine Blade Tip clearance of a small gas turbine engine under transient operating conditions
Applied Thermal Engineering, 2020Co-Authors: Rahul Kumar, Veera Sesha Kumar, Mursaleen M Butt, Nazir Ahmed Sheikh, Sher Afghan Khan, Asif AfzalAbstract:Abstract Turbine Blade Tip clearance is one of the significant factors that influence turbine efficiency, Specific Fuel Consumption (SFC), Exhaust Gas Temperature (EGT), and emissions. Controlling these parameters in a small gas turbine engine (SGT) is a challenging task due to small Blade height and viscous working environment. SGT are subjected to high-temperature gradients at the combustor outlet, which affects the turbine Blade Tip clearance. This paper presents the thermo-mechanical analysis of a typical SGT engine to study the Blade Tip clearance influenced by the deformation of turbine stage components (turbine rotor, nozzle guide vane (NGV) with integral Blade shroud) during transient phases. ANSYS Workbench is used to perform transient thermal and structural analyses. The structural analysis is performed taking the material properties to be temperature-dependent. The SGT engine under consideration operates at a design speed of 45,000 rpm. Initially, steady-state thermal analysis and static structural analysis were carried out to understand the structural behaviour of the system under a thermal and centrifugal loading environment. Since different components of the engine assembly operate at different temperatures, the effects of convection and conduction at the interfaces influence the radial clearances between the static and rotating parts of the engine. A one-way coupled transient thermal-structural analysis was performed on a three-dimensional model to capture the actual behaviour of the Tip clearance during transient operating conditions. Significant growth of Blade and rotor was observed relative to the casing resulting in minimal clearances during these transient operations. Hence, it is important to estimate desired cold clearance, considering transient phenomena, to avoid mechanical Blade rub with the shroud. It is observed that high-temperature gradients contribute primarily to the stresses and radial displacement of the rotor compared to centrifugal effects. The turbine rotor takes more time (t = 600 s) to reach steady-state temperatures compared to NGV (t = 120 s) due to the solid mass of the disc. The location and magnitude of maximum and minimum equivalent stress changes with time in NGV and rotor, and they experience maximum stress at the initial time steps compared to steady-state.