Finding the Stiffnesses of Interface Contact Elements for the Computational Model of Steam Turbine Blading

2017 ◽  
Author(s):  
Josef Voldřich ◽  
Jan Lazar ◽  
Pavel Polach ◽  
Štefan Morávka
Keyword(s):  
Computational Model ◽  
Steam Turbine ◽  
Nonlinear Dynamic ◽  
Natural Frequencies ◽  
Resonant Response ◽  
Nonlinear Dynamic Model ◽  
Interface Elements ◽  
Bladed Disk ◽  
Interface Contact ◽  
Turbine Blading

A method is proposed for fitting the so-called contact stiffnesses (CSs) of interface elements for a nonlinear dynamic model (NDM) of a bladed disk with integral contact couplings. The method is based on comparison between frequencies of the resonant response of NDM and known natural frequencies in limiting linear cases. For this purpose, an effective approach for calculation of the resonant response NDM is presented allowing CSs to be picked individually. The method is demonstrated for the case of steam turbine bladed disk equipped with 48 inch blades.

Optimal Stiffness Parameters of the Turbine Bladed Disk Computational Model

2013 ◽  
Author(s):  
Pavel Polach
Keyword(s):  
Computational Model ◽  
Steam Turbine ◽  
Topical Application ◽  
Natural Vibration ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Centrifugal Forces ◽  
Bladed Disk ◽  
Real Contact ◽  
Optimal Stiffness

Motivation for introducing this paper is the topical application of the method using the rotational periodicity of the structure at calculating natural vibration characteristics of the steam turbine bladed disk with continuous binding, in this case in the form of integral shrouding and in the middle of the blade with the tie-boss connection. Part of the shroud and the part of the tie-boss are the integral parts of the blade. Blades are free at non-rotating bladed disk. Blades of the advanced design are continuously coupled in the zone of the shroud and in the tie-boss zone by the blades untwist caused by the centrifugal forces acting at turbine rotation. The method used for the calculation of natural frequencies and mode shapes of the bladed disk with the continuous binding does not enable to model the real contact properties. The contact must be modeled by the flexible connection. The stiffness of the connection in the zones of adjoining blades contact is “tuned” at turbine operational speed (i.e. at 3000 rpm) in such a way that the values of calculated natural frequencies may come as near as possible to the values of the measured natural frequencies.

Establishment of Nonlinear Dynamic Model for Prediction of Rotordynamic Instability of Steam Turbine Rotor-Bearing System Caused by Partial Admission

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Ying Cui ◽  
Zhansheng Liu ◽  
Daren Yu ◽  
Yanfeng Duan
Keyword(s):  
Steam Turbine ◽  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Turbine Rotor ◽  
Nonlinear Dynamic Model ◽  
Steam Turbine Rotor ◽  
Rotor Bearing ◽  
Partial Admission ◽  
Bearing System

A nonlinear dynamic model is developed for a rotor-bearing system with radial steam force due to partial admission, taking into account the prediction of subsynchronous instability of a steam turbine. The optimum schemes are obtained by comparing the rotor responses subjected to maximal radial steam forces in different partial admission schemes. It is found through comparison that the instability of a rotor-bearing system is directly related to the direction of the radial steam force in the partial admission scheme.

Free Vibration in a Mistuned Steam Turbine Last Stage Bladed Disk

2015 ◽  
Author(s):  
Marcin Drewczynski ◽  
Romuald Rzadkowski ◽  
Artur Maurin ◽  
Piotr Marszalek
Keyword(s):  
Steam Turbine ◽  
Natural Frequencies ◽  
Numerical Study ◽  
Mode Shapes ◽  
Fem Model ◽  
Bladed Disk ◽  
Turbine Efficiency ◽  
Pressure Steam ◽  
Fourth Series ◽  
Last Stage

The design of blades in the last stage of a steam turbine is one of the most demanding engineering tasks in the turbomachinery field. Increasing turbine efficiency has led to the designing of higher tip-to-hub ratios. Slender blading conforms to reliability requirements, such as high blade stiffness and a high first mode natural frequency. Several high vibration amplitude problems were reported regarding a slender last stage blading of a commercial low-pressure steam turbine. During maintenance it was decided that the blades would be geometrically mistuned to prevent self-excitation. This paper presents a numerical study of LP steam turbine last stage bladed disk mistuning. Two different approaches to mistuning were applied and numerically compared: geometrical and material. The mode shapes and natural frequencies of the steam turbine bladed disk were calculated on the basis of an FEM model. The smallest range of mistuning (0,5Hz) in a bladed disk contaminates nodal diameters up to the fourth series. This should be taken into account when tip-timing method is adapted for steam turbine operation monitoring.

Analysis of Tourism Ecology Capacity Based on the Nonlinear Dynamic Model

2009 ◽  
Vol 11 (2) ◽  
pp. 163-168
Author(s):  
Long LV ◽  
Zhenfang HUANG ◽  
Jiang WU
Keyword(s):  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Model

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.

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