A higher fidelity approach for incorporating tip shroud geometry into aerodynamic flutter computations of rotating turbomachinery

2019 ◽  
Author(s):  
Alexander V. Rozendaal ◽  
Alex Torkaman ◽  
Gregory Vogel ◽  
Alfio Lo Balbo
Keyword(s):  
Tip Shroud

The Application of Ceramic Matrix Composite to Low Pressure Turbine Blade

2016 ◽  
Author(s):  
Fumiaki Watanabe ◽  
Takeshi Nakamura ◽  
Ken-ichi Shinohara
Keyword(s):  
Centrifugal Force ◽  
Failure Modes ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix ◽  
Low Pressure ◽  
Screening Tests ◽  
Low Pressure Turbine ◽  
Load Tests ◽  
Tip Shroud ◽  
Block Approach

The structural reliability of composite parts for aircraft is established through the “building block” approach, which is a series of tests that are conducted using specimens of various levels of complexity. In this approach, the failure modes and criteria are validated step by step with tests and analysis at coupon, element, sub-component, and component levels. IHI is developing ceramic matrix composite (CMC) components for aircraft engines to realize performance improvement and weight reduction. We conducted the concept design of CMC low pressure turbine (LPT) blade with the building block approach. In this paper, we present the processes and results of the design, which was supported by a series of tests. Typical low pressure turbine blade has dovetail, airfoil and tip shroud. Each element has different function and characteristic shape. In order to select the configuration of CMC LPT blade, we conducted screening tests for each element. The function of dovetail is to sustain the connection with blade and disk against centrifugal force. The failure modes and strength of dovetail elements were examined by static load tests and cyclic load tests. The configuration of airfoil was selected by modal tests. The function of tip shroud is forming gas passage and reducing the leakage flow, therefore this portion needs to sustain the shape against the centrifugal force and the rubbing force. The feasibility of tip shroud was verified by spin tests and rubbing tests. The initial CMC LPT blades were designed as combination of the selected elements by these screening tests. Prototype parts were made and tested to check the manufacturability and the structural feasibility. The static strength to the centrifugal force was examined by spin test. The durability to vibration was examined by HCF test.

scholarly journals The Effect of Shell Thickness, Insulation and Casting Temperature on Defects Formation During Investment Casting of Ni-base Turbine Blades

2015 ◽  
Vol 15 (4) ◽  
pp. 115-123 ◽  
Author(s):  
M. Raza ◽  
M. Irwin ◽  
B. Fagerström
Keyword(s):  
Grain Size ◽  
Investment Casting ◽  
Shell Thickness ◽  
Turbine Blades ◽  
Shrinkage Porosity ◽  
Grain Structure ◽  
Casting Temperature ◽  
Free Form ◽  
Thin Sections ◽  
Tip Shroud

Abstract Turbine blades have complex geometries with free form surface. Blades have different thickness at the trailing and leading edges as well as sharp bends at the chord-tip shroud junction and sharp fins at the tip shroud. In investment casting of blades, shrinkage at the tip-shroud and cord junction is a common casting problem. Because of high temperature applications, grain structure is also critical in these castings in order to avoid creep. The aim of this work is to evaluate the effect of different process parameters, such as, shell thickness, insulation and casting temperature on shrinkage porosity and grain size. The test geometry used in this study was a thin-walled air-foil structure which is representative of a typical hot-gas-path rotating turbine component. It was observed that, in thin sections, increased shell thickness helps to increase the feeding distance and thus avoid interdendritic shrinkage. It was also observed that grain size is not significantly affected by shell thickness in thin sections. Slower cooling rate due to the added insulation and steeper thermal gradient at metal mold interface induced by the thicker shell not only helps to avoid shrinkage porosity but also increases fill-ability in thinner sections.

Multi-Wave Flutter Vibrations in Mistuned Cascades with Tip-Shroud Friction

2020 ◽  
Author(s):  
Johann Gross ◽  
Malte Krack
Keyword(s):  
Single Mode ◽  
Wave Form ◽  
Modal Interaction ◽  
Modal Interactions ◽  
Multiple Wave ◽  
Aero Engine ◽  
Wave Forms ◽  
Nonlinear Modal Interaction ◽  
The Rich ◽  
Tip Shroud

Abstract Measurements taken during aero engine tests and in the field showed that flutter vibrations of shrouded blades can feature rich wave content (multi-wave flutter vibrations). In a previous work, we demonstrated that this behavior can be explained by the nonlinear interaction of aeroelastically unstable traveling wave modes. The resulting vibrations are quasi-periodic. In the present work, we show that the nonlinear modal interaction is not strictly needed, but actually mistuning alone can explain the multi-wave form of flutter vibrations. The resulting vibrations are periodic and dominated by only a single mode shape of the mistuned system. However, unrealistically high mistuning intensities are needed to obtain significant contributions of multiple wave forms under the considered strong inter-blade coupling. Thus, we conclude that mistuning cannot explain the rich wave content observed in the measurements. Moreover, mistuning tends to hamper the nonlinear modal interactions and, thus, the occurrence of quasi-periodic multi-wave flutter vibrations. This implies that intentional mistuning is not only useful to stabilize flutter, but might also play an important role in developing flutter-tolerant blade designs.

Experimental Results From Controlled Blade Tip/Shroud Rubs at Engine Speed

2006 ◽  
Author(s):  
Corso Padova ◽  
Jeffery Barton ◽  
Michael G. Dunn ◽  
Steve Manwaring
Keyword(s):  
Computational Models ◽  
Engine Speed ◽  
Leading Edge ◽  
Experimental Results ◽  
Trailing Edge ◽  
Metal On Metal ◽  
Non Linear ◽  
Blade Tip ◽  
Force Components ◽  
Tip Shroud

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.

Tip-Shroud Labyrinth Seal Effect on the Flutter Stability of Turbine Rotor Blades

2019 ◽  
Author(s):  
Roque Corral ◽  
Michele Greco ◽  
Almudena Vega
Keyword(s):  
Rotor Blade ◽  
Labyrinth Seal ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Stability Prediction ◽  
Labyrinth Seals ◽  
Turbine Rotor Blade ◽  
The Stability ◽  
Shrouded Rotor ◽  
Tip Shroud

Abstract The effect of the tip-shroud seal on the flutter onset of a shrouded turbine rotor blade, representative of a modern gas turbine, is numerically tested and the contribution to the work-per-cycle of the aerofoil and the tip-shroud are clearly identified. The numerical simulations are conducted using a linearised frequency domain solver. The flutter stability of the shrouded rotor blade is evaluated for an edgewise mode and compared with the standard industrial approach of not including the tip-shroud cavity. It turns out that including the tip shroud significantly changes the stability prediction of the rotor blade. This is due to the fact that the amplitude of the unsteady pressure created in the inter-fin cavity, due to the motion of the airfoil, is much greater than that of the airfoil. It is concluded that the combined effect of the seal and its platform tends to stabilise the rotor blade for all the examined nodal diameters and reduced frequencies. Finally, the numerical results are shown to be consistent with those obtained using an analytical simplified model to account for the effect of the labyrinth seals.

Requirements and Limitations of Controlling Turbine Tip Shroud Cavity Flow Mixing With Bladelets on Rotating Shroud

2015 ◽  
Author(s):  
Timothy R. Palmer ◽  
Choon S. Tan ◽  
Matthew Montgomery ◽  
Anthony Malandra ◽  
David Little ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Cavity Flow ◽  
Efficiency Gain ◽  
Turbine Stage ◽  
Loss Mechanism ◽  
Inlet Flow ◽  
Flow Asymmetry ◽  
Low Reynolds ◽  
Tip Shroud

A potential means of significantly reducing the cavity exit mixing loss, a dominant primary loss mechanism in turbine tip shroud cavity flow, is assessed. The operational constraints on the turbine stage dictate that losses may only be mitigated through configuration changes within the cavity. A configuration, known herein as the Hybrid Blade, features a shrouded main blade with a row of high aspect ratio bladelets affixed to the rotating shroud is formulated and shown to nearly eliminate the cavity exit mixing loss. However the Hybrid Blade configuration incurs a penalty associated with bladelet low Reynolds number effects, cavity inlet flow asymmetry introduced by the scalloped shroud, and a resulting mismatch with the upstream vane as well as downstream diffuser. This penalty offsets the efficiency gain from mitigating cavity exit mixing loss. For the Hybrid Blade system, it can thus be inferred that the turbine stage and the diffuser need to be reconfigured to accommodate the modified tip shroud, and the bladelets redesigned for low Reynolds number operation and cavity inlet flow asymmetry to achieve an overall benefit.

Experimental Results From Controlled Blade Tip/Shroud Rubs at Engine Speed

2006 ◽  
Vol 129 (4) ◽  
pp. 713-723 ◽  
Author(s):  
Corso Padova ◽  
Jeffery Barton ◽  
Michael G. Dunn ◽  
Steve Manwaring
Keyword(s):  
Computational Models ◽  
Engine Speed ◽  
Leading Edge ◽  
Experimental Results ◽  
Trailing Edge ◽  
Metal On Metal ◽  
Non Linear ◽  
Blade Tip ◽  
Force Components ◽  
Tip Shroud

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 13μm to 762μm (0.0005in. to 0.030in.). 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 (140μm) are compared to those for a severe rub (406μm). 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.

A Fiber-Optic Tip-Shroud Deflection Measurement System

2000 ◽  
Vol 123 (2) ◽  
pp. 359-362 ◽  
Author(s):  
R. A. Rooth ◽  
W. Hiemstra
Keyword(s):  
Gas Turbine ◽  
Fiber Optic ◽  
Turbine Blades ◽  
Stable Operation ◽  
Distance Information ◽  
Optical Signals ◽  
Good Spatial Resolution ◽  
Characteristic Features ◽  
The Individual ◽  
Tip Shroud

A Dutch utility faced the fact that a second stage set of turbine blades of a gas turbine had to be replaced long before the estimated lifetime as a result of tip shroud deflection. This deflection caused the risk of loss of support between the individual tip shroud segments. The goal of this paper is to find the cause of the problem, to see how it increases with time, and to take appropriate action to prevent the problem from occurring again. A fiber-optic tip-shroud deflection monitor has been developed and tested on a gas turbine to study this phenomenon in real time. The optical system is based on astigmatism to derive distance information from the measured optical signals. Characteristic features from the system are the good spatial resolution of about 1 mm, the distance resolution of about 0.1 mm and the distance from the probe tip to the target of about 20 mm. These specifications are difficult to achieve with, for example, capacitive sensors. The probe tip can with stand temperatures of about 500°C. The system can be calibrated in situ, given a stable operation of the gas turbine. This is accomplished by stepping the probe tip over some distance and recording the signals corresponding to a certain point on the tip shroud. The instrument has been used to monitor the tip-shroud deflection in a gas turbine at various loads and over a time span of several months. The results indicate that the deflection can be divided in a part depending on the load and a part that is a permanent deflection. Based on the results, it can be judged whether blades need to be rejected because of a too large deflection.

Performance Evaluation of Pumps in Air and Water

1968 ◽  
Vol 90 (2) ◽  
pp. 145-148
Author(s):  
Glenn M. Wood
Keyword(s):  
Reynolds Number ◽  
Performance Evaluation ◽  
Shaft Speed ◽  
Pump Performance ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Significant Difference ◽  
Reynolds Number Effects ◽  
Tip Leakage Flows ◽  
Tip Shroud

To explore the feasibility of establishing pump performance in air, two different designs were tested over the same range of shaft speed and flow rate in both water and air. The larger unit of 3000-gpm capacity was of unshrouded design, whereas the smaller, 195-gpm capacity pump was fabricated with a full tip shroud on the impeller. Although similar trends in performance were observed for each pump tested in air and water, some dissimilarities were observed. In particular, the head rise characteristic curves for both pumps were noticeably higher in air than in water. This is contrary to trends predicted by Reynolds number effects and is apparently due to significant difference in the impeller tip leakage flows when pumping liquid or gas.

Experimental and Computational Investigation of Heat Transfer Effectiveness and Pressure Distribution of a Shrouded Blade Tip Section

2004 ◽  
Author(s):  
Nirm V. Nirmalan ◽  
Jeremy C. Bailey ◽  
Mark E. Braaten
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Distribution ◽  
Coolant Flow ◽  
Tip Clearance ◽  
Computational Investigation ◽  
Blade Tip ◽  
Flow Through ◽  
Tip Shroud ◽  
Unique Study

An experimental and computational investigation was conducted to study the detailed distribution of heat transfer effectiveness and pressure on an attached tip-shroud of a turbine blade. Temperatures and pressures were measured on the airfoil-side and gap-side surfaces of the shrouded tip in a three-airfoil stationary cascade. The instrumented center airfoil and the two slave airfoils modeled the aerodynamic tip section of a blade and have the capability to vary tip clearance. The experiments were run at gaps varying of 0.25% to 1.67% of blade span and at an airfoil exit Reynolds number of 1.26×106 and Mach number of 0.95. The effect of coolant flow through the radial-cooled airfoil was also studied. The experimental results are compared with a computational model using the commercially available code, CFX. This unique study presents the influence of gap and coolant flow on the pressure distribution and heat transfer effectiveness of an attached tip-shroud surface.

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