Studies on Determination of Natural Frequencies of Industrial Turbine Blades

1995 ◽  
Author(s):  
Mahesh M. Bhat ◽  
V. Ramamurti ◽  
C. Sujatha
Keyword(s):  
Steam Turbine ◽  
Dynamic Behavior ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Complex Structure ◽  
Turbine Blades ◽  
Blade Root ◽  
Steam Turbine Blade ◽  
Manufacturing Tolerances

Abstract Steam turbine blade is a very complex structure. It has geometric complexities like variation of twist, taper, width and thickness along its length. Most of the time these variations are not uniform. Apart from these geometric complexities, the blades are coupled by means of lacing wire, lacing rod or shroud. Blades are attached to a flexible disc which contributes to the dynamic behavior of the blade. Root fixity also plays an important role in this behavior. There is a considerable variation in the frequencies of blades of newly assembled turbine and frequencies after some hours of running. Again because of manufacturing tolerances there can be some variation in the blade to blade frequencies. Determination of natural frequencies of the blade is therefore a very critical job. Problems associated with typical industrial turbine bladed discs of a 235 MW steam turbine are highlighted in this paper.

Failure analysis of the 350MW steam turbine blade root

2009 ◽  
Vol 16 (4) ◽  
pp. 1270-1281 ◽  
Author(s):  
J. Kubiak Sz ◽  
J.A. Segura ◽  
G. Gonzalez R ◽  
J.C. García ◽  
F. Sierra E ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Steam Turbine ◽  
Turbine Blade ◽  
Blade Root ◽  
Steam Turbine Blade

Finite Element Modal Analysis for Steam Turbine Blade Based on ANSYS

2012 ◽  
Vol 260-261 ◽  
pp. 368-371
Author(s):  
Lu Wang ◽  
Shun Qiang Ye ◽  
Rui Meng
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Steam Turbine ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Crack Location ◽  
Finite Element Software ◽  
Vibration Fatigue ◽  
Steam Turbine Blade ◽  
Twisting Deformation

In response to the vibration fatigue fracture of the steam turbine blade,we construct the 3D model of cracked blade based on the actual crack location,then modal analysis is conducted to the blade with crack and one without crack using the finite element software ANSYS.Thus,we can get the respective natural frequencies and the figure of main vibration modes.The comprasion results show that the existence of the crack can make the natural frequencies of blades drop and the blades have the greatest sway and twisting deformation along the Y axis.These characteristics above can effectively identify the presence of blade cracked. It has crucial meaning for achieving cracked blade online monitoring.

Torsional stiffness of long steam-turbine blades

1970 ◽  
Vol 5 (4) ◽  
pp. 242-248 ◽  
Author(s):  
A Scholes ◽  
D J Slater
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Torsional Vibration ◽  
Natural Frequencies ◽  
Turbine Blades ◽  
Torsional Stiffness ◽  
Steam Turbine Blades ◽  
Shear Centre

In order to obtain accurate values of the natural frequencies of torsional vibration of long steam-turbine blades it is necessary to determine the torsional stiffnesses of the blade accurately. Various empirical formulae are at present available for the calculation of the torsion constant for sections such as those of a turbine blade; to determine which is the best, a range of sections has been tested including prismatic bars as well as an actual blade. One particular formula is suggested for use. Additionally the positions of shear-centre and centre-of-twist of some of the bars were found.

Experimental Friction Damping Characteristic of a Steam Turbine Blade Coupled by Shroud and Snubber at Standstill Set-Up

2012 ◽  
Author(s):  
Jun Wu ◽  
Yonghui Xie ◽  
Di Zhang ◽  
Minghui Zhang
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Rotational Speed ◽  
Damping Ratio ◽  
Turbine Blades ◽  
Contact Forces ◽  
Normal Contact ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Steam Turbine Blade

In order to avoid the high cycle fatigue which leads to the failure of turbine blades, friction structural damping has been widely used in turbine blade designs to reduce vibratory stresses by energy dissipation. A method is developed here to analyze the influence of friction structural damping on the vibration characteristics of turbine blades. Vibratory responses of a long steam turbine blade with shroud and snubber are studied. Finite element contact analysis of the steam turbine blades which are modeled in 3-D solid elements is conducted to obtain the normal contact force on the shroud contact surface and snubber contact surface of adjacent blades under five different rotational speeds (2100rpm, 2200rpm, 2413rpm, 2600rpm and 3000rpm). A rig for the tests of non-rotating turbine blade with friction damping structure is built. The normal contact forces of the shroud and snubber are applied to the blade according to numerical results. The response curves and modal damping ratios of the blade under different normal contact forces, which each one is related to a different rotational speed, are obtained. The experimental results show that with increases in rotational speed, modal damping ratio of the blade experiences an increasing period followed by a decreasing period while the resonance amplitude decreases first and then increases when there is only shroud contact. The effects are similar when there are both shroud and snubber contact. The modal damping ratio of the blade is basically identical with that of the uncoupled blade for the rotational speed above 2600rpm. For this range of rotational speed, the resonance frequency increases with the increase of rotational speed, and the changes of the resonance frequency are very trivial.

Numerical Aerodynamic Damping Evaluation of High-Pressure Steam Turbine Blades for Aeromechanical Characterization

2016 ◽  
Author(s):  
Lorenzo Peruzzi ◽  
Juri Bellucci ◽  
Lorenzo Pinelli ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Mechanical Coupling ◽  
High Pressure Steam ◽  
Aerodynamic Damping ◽  
Blade Row ◽  
Pressure Steam ◽  
Steam Turbine Blade

A validated non-linear uncoupled method for flutter stability analysis was employed to estimate the aerodynamic damping of an HP (High-Pressure) steam turbine blade row. Usually such blade rows are not affected to flutter instability problems, yet an estimation of the aerodynamic damping can be useful for an accurate aeromechanical characterization of these kind of blade rows. The geometry under investigation is a typical steam turbine blade row at design point. Computational aeroelastic analyses are performed on the more relevant modeshape, sampling the nodal diameters, in order to well describe the typical aeroelastic stability curve. The presence of the tip shroud implies a strong mechanical coupling between adjacent blades resulting in complex modeshapes with high frequency, significantly different from those usually analyzed in the flutter analysis. The results in term of aerodynamic damping curves are rather different from the usually sinusoidal shape. This is due to the large variation of the frequency over the analyzed nodal diameters, especially at low nodal diameters range. This results are useful to give a better insight in the aeroelastic response of this type of blades.

Research on the Manufacturing of Steam Turbine Blade by Using Investment Casting Technology

2013 ◽  
Vol 789 ◽  
pp. 330-340 ◽  
Author(s):  
Hafid
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Investment Casting ◽  
Turbine Blades ◽  
Injection Pressure ◽  
Casting Process ◽  
Machining Process ◽  
Shape Accuracy ◽  
Casting Technology ◽  
Steam Turbine Blade

This paper presents the results of research on the manufacturing of steam turbine blade by using investment casting technology. Metal forming technology with precision casting process or investment casting is the right technology for the manufacture of turbine blades, because it can produce casting products that has advantages in size and shape accuracy, surface finish and the ability to produce thin casting, which the usually foundry can not be done. The purpose of this research is to produce a good quality of the casting products as an effort to reduce import dependency of steam turbine blade and to be the alternative way of making steam turbine blades in Indonesia, in addition to the machining process. Based on the experimentation trial implemented on casting products of stainless steel 304, the result indicates that the injection temperature for the wax NF-411 and optimal nozzle in hydraulic injection machine are 64°C and 30°C, injection pressure 1.75 MPa and injection time 9 seconds. The best casting induction furnace achieved at temperature 1,620°C as for to the number of ceramic mould coat which is good to be obtained at 7 layers. The testing results show that: (1) the chemical composition is appropriate with standard, (2) the hardness is 160 HB, (3) the shrinkage is 2.83%.

Reconstruction of a Steam Turbine Blade Using Piecewise Bernstein Polynomials and Transfinite Interpolation

2021 ◽  
Author(s):  
Luis David Pérez Rubio ◽  
Sergio Ricardo Galván González ◽  
Francisco Javier Domínguez Mota ◽  
Angel Cerriteño Sánchez ◽  
Miguel Angel Tamayo Soto ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Bernstein Polynomials ◽  
Turbine Blades ◽  
Maximum Efficiency ◽  
Spanwise Direction ◽  
Virtual Model ◽  
Cross Sectional ◽  
Transfinite Interpolation ◽  
Steam Turbine Blade

Abstract Turbine blades are designed to achieve its maximum efficiency, but deformations caused by the exposition to extreme operating environments provokes reduction in the engine performance. Often, operators choose to repair a damaged blade instead of replacing it to save money, however, reconstructing its virtual model, commonly the first step in the repairing process, can be challenging due to the geometrical complexity of the blades, variability in deformations and the requirement to meet the dimensions specified by the manufacturer. This paper presents the reconstruction methodology of the clean virtual model of a steam turbine blade through numerical tools, as a previous step for regenerating a worn blade. First, few cross-sectional airfoil profiles are extracted from the damaged blade and are regenerated using Bernstein polynomials; then, using the previously obtained data, many more profiles are interpolated and stacked along the spanwise direction of the blade via Transfinite Interpolation in order to obtain a smooth and continuous representation of the reference blade. Final deviation between the reference and reconstructed model resulted in an average value of 1.5496 × 10−3 % and 9.685 × 10−5 % relative to the rotor diameter in the pressure and suction sides respectively, showing an accuracy that could be considered to be used in industrial applications or optimization.

Pretwist and Shear Flexibility in the Vibrations of Turbine Blades

1985 ◽  
Vol 52 (2) ◽  
pp. 409-415 ◽  
Author(s):  
S. Krenk ◽  
O. Gunneskov
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Wall Thickness ◽  
Cross Sections ◽  
Strain Energy ◽  
Turbine Blades ◽  
Beam Element ◽  
Shear Stresses ◽  
Warping Function ◽  
Steam Turbine Blade

A theory is developed for pretwisted beams with finite shear flexibility. The effect of pretwist is accounted for via the axial derivative of the St. Venant warping function. The shear flexibility relies on a decomposition of the shear stresses into torsion and shear contributions, and the normalized strain energy of the latter is expressed in terms of the shear flexibility tensor. An explicit approximation for the shear flexibility tensor is derived for cross sections of moderate wall thickness. A special Legendre transformation is used to obtain a consistent discretization, which is then cast in the form of a finite beam element. The accuracy of the method is illustrated by comparison with experimental results for a steam turbine blade, and the effects of pretwist and shear flexibility are discussed.

scholarly journals Failure Analysis in Lacing Wire Of Last Stage Low Pressure Steam Turbine Blade

2021 ◽  
Vol 1096 (1) ◽  
pp. 012097
Author(s):  
A M Kongkong ◽  
H Setiawan ◽  
J Miftahul ◽  
A R Laksana ◽  
I Djunaedi ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Steam Turbine ◽  
Turbine Blade ◽  
Low Pressure ◽  
Pressure Steam ◽  
Steam Turbine Blade ◽  
Last Stage
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