Development and Verification of 3000 rpm 48 Inch Integral Shroud Blade for Steam Turbine

2005 â—½  
Author(s):  
Yasutomo Kaneko â—½  
Kazushi Mori â—½  
Hiroharu Ohyama
Keyword(s):  
Steam Turbine â—½  
Field Test â—½  
High Speed â—½  
Vibration Characteristics â—½  
Operating Conditions â—½  
Blade Design â—½  
Vibration Stress â—½  
Rotational Vibration â—½  
Verification Test â—½  
Vibration Tests

The 3000 rpm 48 inch blade for steam turbine was developed as one of the new standard series of LP end blades. The new LP end blades are characterized by the ISB (Integral Shroud Blade) structure. In the ISB structure, blades are continuously coupled by blade untwist due to centrifugal force when the blades rotate at high speed. Therefore, the number of the resonant vibration modes can be reduced by virtue of the vibration characteristics of the circumferentially continuous blades, and the resonant stress can be decreased due to the additional friction damping generated at shrouds and stubs. In order to develop the 3000 rpm 48 inch blade, the latest analysis methods to predict the vibration characteristics of the ISB structure were applied, after confirming their validity to the blade design. Moreover, the verification tests such as rotational vibration tests and model turbine tests were carried out in the shop to confirm the reliability of the developed blade. As the final verification test, the field test of the actual steam turbine was carried out in the site during the trial operation, and the vibration stress of the 3000 rpm 48 inch blade was measured by use of telemetry system. In the field test, the vibratory stress of the blade was measured under various operating conditions for more than one month. This paper first presents the up-to-date design technology applied to the design of the 3000 rpm 48 inch blade. In the second place, the results of the various verification tests carried out in the shop are presented as well as their procedure. Lastly, the results of the final verification tests of 3000 rpm 48 inch blade carried out in the site are presented.

Static and Dynamic Analysis of 48″ Steel Last Stage Blade for Steam Turbine

2009 â—½  
Author(s):  
Tomas Misek â—½  
Zdenek Kubin â—½  
Karel Duchek
Keyword(s):  
Steam Turbine â—½  
Centrifugal Force â—½  
High Speed â—½  
Structural Damping â—½  
Static And Dynamic Analysis â—½  
Speed Test â—½  
Rotational Vibration â—½  
Eigen Frequencies â—½  
Last Stage â—½  
Vibration Tests

The 3000 rpm 48 inch blade for steam turbine has been developed with the application of new design features. The last stage moving blade was designed with integral cover, mid-span tie-boss connection, and fir-tree dovetail. Blades are continuously coupled by the blade untwist due to the centrifugal force, so vibration control and increased structural damping are provided. The last stage airfoil was optimized from view of minimization of its centrifugal force which helped to reach higher safety factors. The blade was well tuned in order to have eigen-frequencies safely away from possible excitation. Because of connection members, the number of the resonant vibration modes can be reduced by virtue of the vibration characteristics of the circumferentially continuous blades. In order to develop the 3000 rpm 48 inch blade, the latest analysis methods were applied to predict dynamic behavior of the bladed structure. Coupled rotor-blade analysis was also aim of the attention. To validate calculated results the verification measurement such as rotational vibration tests was carried out in the high-speed test rig. The test rotor was fitted with the actual full scale 48″ blades. Relation of the friction damping of the bladed structure on amount of excitation level was also monitored and evaluated.

scholarly journals Vibration Characteristics of Underground Structure and Surrounding Soil Underneath High Speed Railway Based on Field Vibration Tests

Shock and Vibration â—½  
2018 â—½  
Vol 2018 â—½  
pp. 1-16 â—½  
Author(s):  
Biao Zhou â—½  
Fengshou Zhang â—½  
Xiongyao Xie
Keyword(s):  
Frequency Response â—½  
Wave Velocity â—½  
High Speed â—½  
Underground Structure â—½  
Vibration Characteristics â—½  
High Speed Railway â—½  
Metro Station â—½  
Attenuation Index â—½  
Vibration Tests â—½  
Surrounding Soil

A series of field vibration tests were carried out at an underground metro station underneath the high speed railway by installing accelerometers both on the side wall of the metro station and in the surrounding soil. Within the frequency domain of 0–200 Hz, the attenuation, transmission, and frequency response properties of vibration for both the underground structure and the surrounding soil were analyzed and compared. The attenuation index is found to be decreased with the increase of underground structure stiffness. The existence of damping and coupling effect of the surrounding soil, as well as the interference of axle spectrum from excitation sources, makes it very challenging to separate the frequency response characteristics of structures from soil at FFT (Fast Fourier Transform) spectrum. The combined NExT (Natural Excitation Technique) and HHT (Hilbert–Huang Transform) method are thus used to study the waveforms and propagation velocities of vibration waves in underground structure and surrounding soil. The wave types and their speeds are determined and used for evaluating the structural elastic modulus. Compared with the attenuation index or natural frequency, wave velocity is easier to be recognized, is sensitive to the change of the structural stiffness, and requires limited number of sensors in the field. Based on the properties of the vibration characteristics studied in this work, the wave velocity based method is recommended for the health monitoring of underground structures.

scholarly journals Fatigue Failure Results for Multi-Axial versus Uniaxial Stress Screen Vibration Testing

Shock and Vibration â—½  
10.1155/2002/109715 â—½  
2002 â—½  
Vol 9 (6) â—½  
pp. 319-328 â—½  
Author(s):  
Wayne E. Whiteman â—½  
Morris S. Berman
Keyword(s):  
Fatigue Failure â—½  
Research Effort â—½  
Uniaxial Stress â—½  
Operating Conditions â—½  
Damage Mechanisms â—½  
Military Equipment â—½  
Great Debate â—½  
Uniaxial Testing â—½  
Vibration Stress â—½  
Vibration Tests

To date, the failure potential and prediction between simultaneous multi-axial versus sequentially applied uniaxial vibration stress screen testing has been the subject of great debate. In most applications, current vibration tests are done by sequentially applying uniaxial excitation to the test specimen along three orthogonal axes. The most common standards for testing military equipment are published in MIL-STD-810F and NAVMAT P-9492. Previous research had shown that uniaxial testing may be unrealistic and inadequate. This current research effort is a continuing effort to systematically investigate the differences between fatigue damage mechanisms and the effects of uniaxial versus tri-axial testing. This includes assessing the ability of the tri-axial method in predicting the formation of damage mechanisms, specifically looking at the effects of stress or fatigue failure. Multi-axial testing achieves the synergistic effect of exciting all modes simultaneously and induces a more realistic vibration stress loading condition. As such, it better approximates real-world operating conditions. This paper provides the latest results on the differences between multi-axial and uniaxial testing of a simple notched cantilever beam.

Gas Path Blade Tip Seals: Abradable Seal Material Testing at Utility Gas and Steam Turbine Operating Conditions

2001 â—½  
Author(s):  
Douglas E. Chappel â—½  
Ly Vo â—½  
Harold W. Howe
Keyword(s):  
Steam Turbine â—½  
Gas Turbine â—½  
High Speed â—½  
Material Testing â—½  
Operating Conditions â—½  
Steam Turbines â—½  
Low Speed â—½  
Tip Leakage â—½  
Blade Tip â—½  
Testing And Evaluation

Abradable seals have long been used to enhance turbomachinery performance by limiting blade tip leakage losses. Most of the literature regarding this subject has focused on aerospace gas turbine materials and conditions. Furthermore, testing and evaluation described in this literature has been conducted on disparate rigs, making direct comparison among the abradable materials investigated difficult. This study broadens the scope of available data by evaluating fibermetal, thermal-sprayed and honeycomb abradable materials at conditions found in utility gas turbine compressors and steam turbines. High speed rub interaction, low speed rub interaction and erosion data were collected and are discussed in detail.

Numerical and Experimental Investigation on the Controlling for Rotor-to-Stationary Part Rubbing in Rotating Machinery

2011 â—½  
Author(s):  
Weimin Wang â—½  
Jinji Gao â—½  
Ya Zhang â—½  
Jianfei Yao
Keyword(s):  
Field Test â—½  
High Speed â—½  
Rotating Machinery â—½  
Numerical Results â—½  
Operating Conditions â—½  
Experimental Investigations â—½  
Low Speed â—½  
Secondary Phenomenon â—½  
Main Component â—½  
External Forces

Rotor may physically contacts with stationary elements of a rotating machine, and the subsequent rubbing at the contact area is a serious malfunction in rotating machinery that may lead to the machine’s catastrophic failure. Usually, it is deemed as a secondary phenomenon resulting from a primary cause which perturbs the machine during normal operating conditions. Generally, there are two types of rubs, i.e., radial rub and axial rub. In this paper, the dynamic response of a rotor system with two types of rubs and unbalances is investigated numerically. Then, characteristics of dynamic behavior for both types of rubs could be achieved. It indicates that symptoms of axial rub are similar with that of unbalance, where 1X vibration is the main component in FFT results. While, radial rub will result 0.5X and 1X vibration in FFT result. Combing a troubleshooting process of a steam turbine in an ammonia plant and field test data, the numerical results are confirmed furthermore although there are some differences in vibration characteristics between numerical results and field test results. Under axial rub impact, the fault force emerges even at low speed. Its spectrum characteristics are more like those of radial rub impact at low speed and more like those of unbalance at high speed. On these bases, methods of preventing rub-impact faults as the machine operating are presented and investigated theoretically focusing on how to exert external forces to counteract those forces resulting from rubbing. Experimental investigations are conducted and their results indicate that the method presented in this paper is useful and feasible.

Vibration Characteristics of a 75kW Turbo Machine With Air Foil Bearings

10.1115/1.2718220 â—½  
2006 â—½  
Vol 129 (3) â—½  
pp. 843-849 â—½  
Author(s):  
Kyeong-Su Kim â—½  
In Lee
Keyword(s):  
High Speed â—½  
Performance Test â—½  
Pressure Ratio â—½  
Vibration Characteristics â—½  
Operating Conditions â—½  
Maximum Pressure â—½  
Stable Operation â—½  
Foil Bearings â—½  
Wide Range â—½  
Free Environment

Air foil bearings are very attractive bearing systems for turbomachinery because they have several advantages over conventional bearings in terms of oil-free environment, low power loss, long life, and no maintenance. However, most of the developed machines using air foil bearings are limited to small and high-speed rotors of 60,000–120,000 rpm, since the increase in power of turbomachinery requires lower rotor speed and greater loading in bearings, which makes it difficult to use air foil bearings for large machines. In this paper, a 75 kW turboblower using air foil bearings is introduced, and the vibration characteristics of the machine have been investigated experimentally under a wide range of operating conditions, including compressor surge in the performance test. The machine is designed to be fully air lubricated and air cooled, and its operating speed is 20,000–26,000 rpm with maximum pressure ratio of 1.8. The results show that the air foil bearings offer adequate damping to ensure dynamically stable operation in the whole range.

A Correlation Between Vibration Stresses and Flow Features of Steam Turbine Long Blades in Low Load Conditions

2011 â—½  
Author(s):  
Naoki Shibukawa â—½  
Tomohiro Tejima â—½  
Yoshifumi Iwasaki â—½  
Itaru Murakami â—½  
Ikuo Saito
Keyword(s):  
Steam Turbine â—½  
Pressure Fluctuation â—½  
Cfd Simulation â—½  
Aerodynamic Force â—½  
Turbine Blades â—½  
Operating Conditions â—½  
Unsteady Pressure â—½  
Low Load â—½  
Vibration Stress â—½  
Blade Tip

The vibration stress of long steam turbine blades during low load operating conditions is examined in this paper. A series of experiments has been carried out to investigate the vibration stress behavior, and the steady and unsteady pressure fluctuation. It is found that a steady pressure distribution over the blade tip is much to do with the unsteady pressure and fluctuation of the vibration stress. A precise investigation of unsteady wall pressure near blade tip explains the relationship between pressure fluctuation and the vibration stress, and reveals the existence of particular frequency which affects blade axial modes. Blade to blade flow mechanisms and aerodynamic force and properties during low load operating condition were investigated by a steady CFD simulation. FFT of aerodynamic force by another steady full arc CFD simulation provides various pattern of harmonic excitation which account for the behavior of vibration stresses well. The mechanism of the rapid stress increase and a step drop were examined by considering CFD results and measured unsteady pressure data together.

scholarly journals Turbine Cascades of Last Stage Blades for Wide Range of Operating Conditions

2019 â—½  
Vol 4 (4) â—½  
pp. 33 â—½  
Author(s):  
Ondrej Novak â—½  
Marek Bobcik â—½  
Martin Luxa â—½  
Jaroslav Fort â—½  
Bartolomej Rudas â—½  
...  
Keyword(s):  
Steam Turbine â—½  
High Speed â—½  
Power Plants â—½  
Electric Energy â—½  
Combined Cycle â—½  
Operating Conditions â—½  
Biomass Waste â—½  
Wide Range â—½  
Last Stage â—½  
Turbine Cascades

Recent trends in the electric energy market such as biomass, waste incineration or combined cycle power plants require innovative solutions in steam turbine design. Variable operating conditions cause significant changes in flow field surrounding the steam turbine last stage blades. Therefore, the enlargement of operating range for last stage blades presents new challenges in design of turbine cascades. Several turbine cascades were designed and analyzed by commercial and in-house software of CTU Prague. Selected profiles were experimentally validated in the high-speed wind tunnel for 2D cascade measurements of the Institute of Thermomechanics of the Czech Academy of Sciences which is equipped by an adjustable supersonic inlet nozzle, perforated inserts at side walls and adjustable perforated tailboard. Comparisons are presented of numerical results with optical and pneumatic measurements for a wide range of inlet and outlet Mach numbers for optimized hub and tip profile cascades.

scholarly journals Finite Element Modeling and Vibration Analysis of Sprag Clutch-Flexible Rotor System

2020 â—½  
Author(s):  
chuang huang â—½  
yongqiang zhao â—½  
guanghu jin
Keyword(s):  
Finite Element â—½  
Finite Element Model â—½  
High Speed â—½  
Element Model â—½  
Vibration Characteristics â—½  
Rotor System â—½  
Operating Conditions â—½  
Resonant Peak â—½  
Flexible Rotor â—½  
Calculation Results

Abstract To study the overall vibration characteristics of the sprag clutch-flexible rotor system (SC-FRS) under high-speed operating conditions, a finite element model of SC-FRS considering rotor flexibility and bearing support stiffness is established based on the proposed calculation method of the stiffness matrix. According to this model, the natural frequency and mode shape of the system are calculated, and the correctness of the model is verified by comparing it with the calculation results of ANSYS software. Under the action of unbalance, the bending-torsion coupled vibration and the dynamic load of the inter-shaft bearings are analyzed, and it is found that the resonant peak in the torsional direction has the same resonance frequency as that in the bending direction. A test rig for the sprag clutch-rotor system is built, and the axis trajectory and critical speed are tested. The test results show that the finite element model of SC-FRS can accurately describe the vibration characteristics of the system.

Development of a Robust LP Blade Family for Variable Speed Applications

2018 â—½  
Author(s):  
Martin Schubert â—½  
Johannes Tusche
Keyword(s):  
Steam Turbine â—½  
High Speed â—½  
Design Method â—½  
Suction Side â—½  
Operating Conditions â—½  
Subsequent Paper â—½  
Variable Speed â—½  
Design Changes â—½  
Last Stage â—½  
High Flexibility

Industrial steam turbine applications require a high flexibility in terms of aerodynamically as well as mechanically operating conditions. Mechanical drives run at variable rotor speeds and often face high backpressure levels, which is a particularly challenging aspect for the last-stage moving blade (LSMB) row of a low-pressure (LP) steam turbine. As speed synchronous blade resonances cannot be excluded over the entire operating speed range, the LSMB needs to be designed resonance proof from viewpoint of dynamics and mechanical strength. The subsequent paper describes a new developed LP stage group for variable speed applications, which is available as fully scaled blade family with distinct exhaust area and rotational speed limit reaching from conventional 3000rpm up to high speed utilities for special purposes. It consists of two standard stages, which can be operated at off resonance as well as resonance conditions. For that reason frictional elements were implemented in both moving blade rows. They are loosely assembled into pockets, which are placed on the pressure as well as suction side of each airfoil. Basically, this feature was already introduced for certain Siemens LP blades, see [1], [2], [3] and [4]. However, the recent development on this field utilizes several design changes for the benefit of robustness and reliability. The present paper focuses on the non-linear dynamic behavior of the friction damped, coupled blade rows and outlines the underlying design method as well as calculation process.

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