Torsional Vibrations of the Steam Turbine Shaft Line and Estimation of the Residual Life of Its Elements

2020 ◽  
Vol 63 (6) ◽  
pp. 91-98
Author(s):  
Vladimir Grabovskii ◽  
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Residual Life ◽  
Operating Time ◽  
Electromagnetic Transients ◽  
Torsional Vibrations ◽  
Steam Turbines ◽  
Shaft Line ◽  
Operating Modes ◽  
Design Life

A comparative quantitative assessment of the damage and residual life of the shaft line elements for differ-ent types of high-power steam turbines at the end of their design life is made by mathematical modeling. The analysis covers all elements of the shaft line: from the steam turbine Central pump to the turbine generator ex-citer. The simulated circuit includes turbo generators, transformers, gate converters, AC and DC power lines. When modeling, an approach is used from the position of proper coordinates, which provides maximum meth-odological consistency of the models of the listed devices and allows you to directly reproduce electromagnetic and mechanical transients with the determination of instantaneous values of currents, voltages, electromagnet-ic and torsional moments. To estimate damage, we used the deformation criterion for soft and hard loads in the zone of low-cycle and force criterion in the zone of multi-cycle fatigue. The influence of the number of starts and running time of a steam turbine on the damage and residual life of its shaft elements is studied. When de-termining the remaining life, in addition to starts, other abnormal operating modes of the turbo generator were taken into account during the turbine operating time: short circuits and their disconnections, unsuccessful high-speed automatic re-activation, subsynchronous resonance due to both the operation of the control system of the PPT and the automatic generator excitation regulator. The influence of attenuation of electromagnetic transients in the generator and damping of torsional vibrations on the degree of reduction of the residual life of the shaft elements is analyzed. The results obtained can be used for a comprehensive solution of the issue of further operation of steam turbines that have spent their design life.

An Optimization Design Platform for Fir-Tree Root and Groove for Steam Turbine

2018 ◽  
Author(s):  
Deqi Yu ◽  
Xiaojun Zhang ◽  
Jiandao Yang ◽  
Kai Cheng ◽  
Weilin Shu ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Steam Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Optimization Design ◽  
Turbine Blades ◽  
Local Stress ◽  
Optimization Method ◽  
Steam Turbines ◽  
Geometry Configuration

Fir-tree root and groove profiles are widely used in gas turbine and steam turbine. Normally, the fir-tree root and groove are characterized with straight line, arc or even elliptic fillet and splines, then the parameters of these features were defined as design variables to perform root profile optimization. In ultra-long blades of CCPP and nuclear steam turbines and high-speed blades of industrial steam turbine blades, both the root and groove strength are the key challenges during the design process. Especially, in industrial steam turbines, the geometry of blade is very small but the operation velocity is very high and the blade suffers stress concentration severely. In this paper, two methods for geometry configuration and relevant optimization programs are described. The first one is feature-based using straight lines and arcs to configure the fir-tree root and groove geometry and genetic algorithm for optimization. This method is quite fit for wholly new root and groove design. And the second local optimization method is based on B-splines to configure the geometry where the local stress concentration occurs and the relevant optimization algorithm is used for optimization. Also, several cases are studied as comparison by using the optimization design platform. It can be used not only in steam turbines but also in gas turbines.

Investigation on Flow Induced Vibrations of a Steam Turbine Inlet Valve Considering Fluid Structure Interaction Effects

2016 ◽  
Author(s):  
Clemens Bernhard Domnick ◽  
Friedrich-Karl Benra ◽  
Dieter Brillert ◽  
Hans Josef Dohmen ◽  
Christian Musch
Keyword(s):  
Steam Turbine ◽  
Structural Dynamics ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Element Model ◽  
Feedback Mechanism ◽  
Steam Turbines ◽  
Turbine Inlet ◽  
Flow Induced Vibrations ◽  
The One

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate a huge amount of energy in throttled operation. The dissipation process generates strong pressure fluctuations resulting in high dynamic forces causing valve vibrations. A brief survey of the literature dealing with valve vibrations reveals that vibrational problems and damages mostly occur in throttled operation when high speed jets, shocks, and shear layers are present. As previous investigations reveal that a feedback mechanism between the dynamic flow field and the vibrating valve plug exists, the vibrations are investigated with two-way coupled simulations. The fluid dynamics are solved with a scale-adaptive approach to resolve the pressure fluctuations generated by the turbulent flow. The finite element model solving the structural dynamics considers both frictional effects at the valve packing and contact effects caused by the plug impacting on the valve bushing. As different flow topologies causing diverse dynamic loads exist, the fluid flow and the structural dynamics are simulated at different operating points. The simulations show that differences to the one-way coupled approach exist leading to a change of the vibrational behavior. The physics behind the feedback mechanisms causing this change are analyzed and conclusions regarding the accuracy of the one-way coupled approach are drawn.

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

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

Investigation on Flow-Induced Vibrations of a Steam Turbine Inlet Valve Considering Fluid–Structure Interaction Effects

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Clemens Bernhard Domnick ◽  
Friedrich-Karl Benra ◽  
Dieter Brillert ◽  
Hans Josef Dohmen ◽  
Christian Musch
Keyword(s):  
Steam Turbine ◽  
Structural Dynamics ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Element Model ◽  
Feedback Mechanism ◽  
Steam Turbines ◽  
Turbine Inlet ◽  
Flow Induced Vibrations ◽  
The One

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate a huge amount of energy in throttled operation. The dissipation process generates strong pressure fluctuations resulting in high dynamic forces causing valve vibrations. A brief survey of the literature dealing with valve vibrations reveals that the vibrational problems and damages mostly occur in throttled operation when high speed jets, shocks, and shear layers are present. As previous investigations reveal that a feedback mechanism between the dynamic flow field and the vibrating valve plug exists, the vibrations are investigated with two-way coupled simulations. The fluid dynamics are solved with a scale-adaptive approach to resolve the pressure fluctuations generated by the turbulent flow. The finite element model (FEM) solving the structural dynamics considers both frictional effects at the valve packing and contact effects caused by the plug impacting on the valve bushing. As different flow topologies causing diverse dynamic loads exist, the fluid flow and the structural dynamics are simulated at different operating points. The simulations show that differences to the one-way-coupled approach exist leading to a change of the vibrational behavior. The physics behind the feedback mechanisms causing this change are analyzed and conclusions regarding the accuracy of the one-way-coupled approach are drawn.

Performance Improvements of Nuclear Power Plants by the Application of Longer LP Last Stage Blades and Advanced Design Techniques

2014 ◽  
Author(s):  
Mike Jones ◽  
Robert Crossland
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Power Plants ◽  
Steam Turbines ◽  
Diverse Range ◽  
Performance Improvements ◽  
Shaft Line ◽  
Last Stage ◽  
Water Reactors ◽  
As Stress

Over the last decade, the Author’s company (Alstom Power) has retrofitted the steam turbines in 34 nuclear units on a diverse range of half and full-speed machines, powered by Pressurised and Boiling Water Reactors. Some of those projects have been described in other papers, with an explanation of the novel laser measurement and fast-track installation techniques that have been developed to meet the onerous demands of nuclear plants and authorities. The ageing global nuclear fleet has suffered reduced levels of reliability and performance due to effects such as Stress Corrosion Cracking (SCC), moisture erosion and shaft line torsional faults. Alstom has developed a range of steam turbine retrofit solutions that are resistant to SCC and erosion, have extended maintenance intervals and deliver high levels of efficiency. A portfolio of rear stage blades is available, from which an optimum design can be selected to suit each project. This paper focuses on the improvements in thermal performance and reliability of a number of recent nuclear steam turbine retrofits. It outlines the existing designs and some of the challenges faced by the plants concerning reliability, operation and efficiency and then describes the approach to addressing those issues by retrofitting with modern designs. The paper describes the blading design and the techniques which are used to evaluate exhaust performance. It will also show the methods which have been used to integrate longer Last Stage Blades into existing LP frames. The paper concludes by presenting the experience, in terms of performance and installation, of some of the projects.

Thermo-Structural Analysis of Steam Turbine Start-Up With and Without Integrated Pre-Warming System Using Hot Air

2020 ◽  
Author(s):  
Piotr Łuczyński ◽  
Lukas Pehle ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
Jan Vogt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Power Plants ◽  
Thermal Contact ◽  
Steam Turbines ◽  
Operating Modes ◽  
Hot Air ◽  
Start Up ◽  
Simulation Strategy ◽  
Transient Thermal

Abstract Motivated by the urgent need for flexibility and start-up capability improvements of conventional power plants in addition to extending their life cycle, General Electric provides its customers with a product to pre-warm steam turbines using hot air. In this paper, the transient thermal and structural analyses of a 19-stage IP steam turbine in various start-up operating modes are discussed in detail. The presented research is based on previous investigations and utilises a hybrid (HFEM - numerical FEM and analytical) approach to efficiently determine the time-dependent temperature distribution in the components of the steam turbine. The simulation strategy of the HFEM model applies various analytical correlations to describe heat transfer in the turbine channel. These are developed by means of extensive unsteady multistage conjugate heat transfer simulations for both start-up turbine operation with steam and pre-warming operation with hot air. Moreover, the complex numerical setup of the HFEM model also considers the thermal contact resistance (TCR) on the surfaces between vane and casing as well as blades and rotor. Prior to the analysis of other turbine start-up operating modes, the typical start-up turbine process is calculated and validated against an experimental data as a benchmark for subsequent analysis. In addition to heat transfer correlations, the simulation of a turbine start-up from cold state uses an innovative analytic pressure model to allow for a consideration of condensation effects during first phase of start-up procedure.

scholarly journals Demonstration of a Dynamic Clearance Seal in a Rotating Test Facility

2017 ◽  
Author(s):  
Andrew Messenger ◽  
Richard Williams ◽  
Grant Ingram ◽  
Simon Hogg ◽  
Stacie Tibos ◽  
...  
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Labyrinth Seal ◽  
Test Facility ◽  
Steam Turbines ◽  
Rotor Position ◽  
Seal Design ◽  
Start Up ◽  
Steam Turbine Plant ◽  
Transient Events

The successful demonstration of the “Aerostatic Seal” in a half scale rotating facility is described in this paper. The Aerostatic seal is a novel dynamic clearance seal specifically designed for steam turbine secondary gas path applications. The seal responds to radial rotor excursions, so a reduced clearance can be maintained compared to conventional labyrinth seal without damage to the seal. This enables increased turbine performance through reduced leakage and increased tolerance of turbine transient events typically found during start up. The seal is an extension of the existing retractable seal design already deployed in commercial steam turbines. The seal was tested in the Durham Rotating Seals Rig, which was developed specifically to test this device. The rig featured a rotor designed to run with large eccentricities to model high speed radial rotor excursions, and the seal was instrumented to measure the real time seal response to the rotor. The experimental campaign has conclusively demonstrated the ability of the seal to dynamically respond to the rotor position. The key result is that the seal is able to track the rotor position at high speed, and hence maintain a mean seal clearance that is lower than the rotor eccentricity. Overall this work marks a key milestone in the development of the Aerostatic Seal, and leads the way to testing in a steam environment and application in steam turbine plant.

High-Speed Steam Turbine Systems for Small-Scale Power Generation Applications

2012 ◽  
Author(s):  
Miroslav P. Petrov ◽  
Jens Fridh ◽  
Ake Göransson ◽  
Torsten H. Fransson
Keyword(s):  
Power Generation ◽  
Steam Turbine ◽  
High Speed ◽  
Waste Heat ◽  
Electrical Power ◽  
Energy Utilization ◽  
Electricity Production ◽  
Small Scale ◽  
Low Grade ◽  
Steam Turbines

Energy utilization from low-grade fuels of either fossil or renewable origin, or from medium-temperature heat sources such as solar, industrial waste heat, or small nuclear reactors, for small-scale power generation via steam cycles, can be reasonably enhanced by a simple technology shift. This study evaluates the technical feasibility of a compact power generation package comprising a steam turbine directly coupled to a high-speed alternator delivering around 8–12 MW of electrical power. Commercial or research-phase high-speed electrical generators at MW-scale are reviewed, and a basic thermodynamic design and flow-path analysis of a steam turbine able to drive such a generator is attempted. High-speed direct drives are winning new grounds due to their abilities to be speed-controlled and to avoid the gearbox otherwise typical for small system drivetrains. These two features may offer a reasonable advantage to conventional drives in terms of higher reliability and better economy. High-speed alternators with related power electronics are nowadays becoming increasingly available for the MW-size market. A generic 8 to 12 MW synchronous alternator running respectively at 15,000 to 10,000 rpm, have been used as a reference for evaluating the fundamental design of a directly coupled steam turbine prime mover. The moderate steam parameter concept suits well for converting mid-temperature thermal energy into electrical power with the help of low-tech steam cycles, allowing for distributed electricity production at reasonable costs and efficiency. Steam superheat temperatures below 350°C (660°F) at pressures of maximum 20 bar would keep the steam volumetric flow sufficiently high in order to restrain the turbine losses typical for small-scale turbines, while helping also with simpler certification and safety procedures and using primarily established technology and standard components. The proposed steam turbines designs and their characteristics thereof have been evaluated by computer simulations using the in-house code ProSteam and its sub-procedures AXIAL and VaxCalc, by courtesy of Siemens Industrial Turbomachinery and its steam turbine division located in Finspong, Sweden. The first results from this study show that high-speed steam turbines of the proposed size and type are possible to design and manufacture based on conventional components, and can be expected to deliver a very satisfactory performance at variable power output.

Fault diagnosis method of peak-load-regulation steam turbine based on improved PCA-HKNN artificial neural network

2021 ◽  
pp. 1748006X2110105
Author(s):  
Yifan Wu ◽  
Wei Li ◽  
Deren Sheng ◽  
Jianhong Chen ◽  
Zitao Yu
Keyword(s):  
Neural Network ◽  
Fault Diagnosis ◽  
Steam Turbine ◽  
Power Plants ◽  
Peak Load ◽  
Clean Energy ◽  
Steam Turbines ◽  
Peak Shaving ◽  
Diagnosis Method ◽  
Load Regulation

Clean energy is now developing rapidly, especially in the United States, China, the Britain and the European Union. To ensure the stability of power production and consumption, and to give higher priority to clean energy, it is essential for large power plants to implement peak shaving operation, which means that even the 1000 MW steam turbines in large plants will undertake peak shaving tasks for a long period of time. However, with the peak load regulation, the steam turbines operating in low capacity may be much more likely to cause faults. In this paper, aiming at peak load shaving, a fault diagnosis method of steam turbine vibration has been presented. The major models, namely hierarchy-KNN model on the basis of improved principal component analysis (Improved PCA-HKNN) has been discussed in detail. Additionally, a new fault diagnosis method has been proposed. By applying the PCA improved by information entropy, the vibration and thermal original data are decomposed and classified into a finite number of characteristic parameters and factor matrices. For the peak shaving power plants, the peak load shaving state involving their methods of operation and results of vibration would be elaborated further. Combined with the data and the operation state, the HKNN model is established to carry out the fault diagnosis. Finally, the efficiency and reliability of the improved PCA-HKNN model is discussed. It’s indicated that compared with the traditional method, especially handling the large data, this model enhances the convergence speed and the anti-interference ability of the neural network, reduces the training time and diagnosis time by more than 50%, improving the reliability of the diagnosis from 76% to 97%.

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