Integrated Approach for Steam Turbine Thermostructural Analysis and Lifetime Prediction at Transient Operations

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Leonid Moroz ◽  
Glenn Doerksen ◽  
Fernando Romero ◽  
Roman Kochurov ◽  
Boris Frolov
Keyword(s):  
Power Plant ◽  
Steam Turbine ◽  
Thermal Stresses ◽  
Low Cycle Fatigue ◽  
Integrated Approach ◽  
Combined Cycle ◽  
Secondary Flows ◽  
Lifetime Prediction ◽  
Start Up ◽  
Differential Expansion

In order to achieve the highest power plant efficiency, original equipment manufacturers continuously increase turbine working parameters (steam temperatures and pressures), improve components design, and modify start-up cycles to reduce time while providing more frequent start-up events. All these actions result in much higher levels of thermostresses, a lifetime consumption of primary components and an increased demand for accurate thermostructural and low cycle fatigue (LCF) simulations. In this study, some aspects of methodological improvement are analyzed and proposed in the frame of an integrated approach for steam turbine components thermostructural analysis, reliability, and lifetime prediction. The full scope of the engineering tasks includes aero/thermodynamic flow path and secondary flows analysis to determine thermal boundary conditions (BCs), detailed thermal/structural two-dimensional and three-dimensional (3D) finite element (FE) models preparation, components thermal and stress–strain simulation, rotor–casing differential expansion and clearances analysis, and finally, turbine unit lifetime estimation. Special attention is paid to some of the key factors influencing the accuracy of thermal stresses prediction, specifically, the effect of “steam condensation” on thermal BC, the level of detailing for thermal zones definition, thermal contacts, and mesh quality in mechanical models. These aspects have been studied and validated against test data, obtained via a 30 MW steam turbine for combined cycle application based on actual start-up data measured from the power plant. The casing temperatures and rotor–stator differential expansion, measured during the commissioning phase of the turbine, were used for methodology validation. Finally, the evaluation of the steam turbine HPIP rotor lifetime by means of a LCF approach is performed.

Integrated Approach for Steam Turbine Thermo-Structural Analysis and Lifetime Prediction at Transient Operations

2017 ◽  
Author(s):  
Leonid Moroz ◽  
Glenn Doerksen ◽  
Fernando Romero ◽  
Roman Kochurov ◽  
Boris Frolov
Keyword(s):  
Structural Analysis ◽  
Power Plant ◽  
Steam Turbine ◽  
Thermal Stresses ◽  
Integrated Approach ◽  
Combined Cycle ◽  
Secondary Flows ◽  
Lifetime Prediction ◽  
Start Up ◽  
Differential Expansion

In order to achieve the highest power plant efficiency, original equipment manufacturers (OEMs) continuously increase turbine working parameters (steam temperatures and pressures), improve components design and modify start-up cycles to reduce time while providing more frequent start-up events. All these actions result in much higher levels of thermo-stresses, a lifetime consumption of primary components and an increased demand for accurate thermo-structural and LCF simulations. In this study, some aspects of methodological improvement are analyzed and proposed in the frame of an integrated approach for steam turbine components thermo-structural analysis, reliability and lifetime prediction. The full scope of the engineering tasks includes aero/thermodynamic flow path and secondary flows analysis to determine thermal boundary conditions, detailed thermal/structural 2D and 3D FE models preparation, components thermal and stress-strain simulation, rotor-casing differential expansion and clearances analysis, and finally, turbine unit lifetime estimation. Special attention is paid to some of the key factors influencing the accuracy of thermal stresses prediction, specifically, the effect of ‘steam condensation’ on thermal BC, the level of detailing for thermal zones definition, thermal contacts and mesh quality in mechanical models. These aspects have been studied and validated against test data, obtained via a 30 MW steam turbine for combined cycle application based on actual start-up data measured from the power plant. The casing temperatures and rotor-stator differential expansion, measured during the commissioning phase of the turbine, were used for methodology validation. Finally, the evaluation of the steam turbine HPIP rotor lifetime by means of a low cycle fatigue approach is performed.

Combined-Cycle Start-Up Procedures: Dynamic Simulation and Measurement

2016 ◽  
Author(s):  
Nicolas J. Mertens ◽  
Falah Alobaid ◽  
Bernd Epple ◽  
Hyun-Gee Kim
Keyword(s):  
Power Plant ◽  
Dynamic Simulation ◽  
Steam Generator ◽  
Heat Recovery ◽  
Thermal Stresses ◽  
Measurement Data ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Start Up ◽  
Fast Start

The daily operation of combined-cycle power plants is increasingly characterized by frequent start-up and shutdown procedures. In addition to the basic requirement of high efficiency at design load, plant operators therefore acknowledge the relevance of enhanced flexibility in operation — in particular, fast start-ups — for plant competitiveness under changing market conditions. The load ramps during start-up procedure are typically limited by thermal stresses in the heat recovery steam generator (HRSG) due to thick-walled components in the high pressure circuit. Whereas conventional HRSG design is largely based on simple steady-state models, detailed modelling and dynamic simulation of the relevant systems are necessary in order to optimize HRSG design with respect to fast start-up capability. This study investigates the capability of a comprehensive process simulation model to accurately predict the dynamic response of a triple-pressure heat recovery steam generator with reheater from warm and hot initial conditions to the start-up procedure of a heavy-duty gas turbine. The commercial combined-cycle power plant (350 MWel) was modelled with the thermal-hydraulic code Apros. Development of the plant model is based on geometry data, system descriptions and heat transfer calculations established in the original HRSG design. The numerical model is validated with two independent sets of measurement data recorded at the real power plant, showing good agreement.

Coordinated Control of Gas and Steam Turbines for Efficient Fast Start-Up of Combined Cycle Power Plants

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Kazunori Yamanaka ◽  
Atsushi Yamashita ◽  
Norihiro Iyanaga ◽  
Takuya Yoshida
Keyword(s):  
Thermal Stress ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Stresses ◽  
Control Method ◽  
Coordinated Control ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Start Up

In the fast start-up for combined cycle power plants (CCPP), the thermal stresses of the steam turbine rotor are generally controlled by the steam temperatures or flow rates by using gas turbines (GTs), steam turbines, and desuperheaters to avoid exceeding the thermal stress limits. However, this thermal stress sensitivity to steam temperatures and flow rates depends on the start-up sequence due to the relatively large time constants of the heat transfer response in the plant components. In this paper, a coordinated control method of gas turbines and steam turbine is proposed for thermal stress control, which takes into account the large time constants of the heat transfer response. The start-up processes are simulated in order to assess the effect of the coordinated control method. The simulation results of the plant start-ups after several different cool-down times show that the thermal stresses are stably controlled without exceeding the limits. In addition, the steam turbine start-up times are reduced by 22–28% compared with those of the cases where only steam turbine control is applied.

Steam Turbine Rotor Transient Thermo-Structural Analysis and Lifetime Prediction

2016 ◽  
Author(s):  
Leonid Moroz ◽  
Boris Frolov ◽  
Roman Kochurov
Keyword(s):  
Heat Exchange ◽  
Structural Analysis ◽  
Steam Turbine ◽  
Thermal Stresses ◽  
Cold Start ◽  
Turbine Rotor ◽  
Measured Data ◽  
Lifetime Prediction ◽  
Start Up ◽  
Transient Thermal

Market requirements for faster and more frequent power unit start-up events result in a much faster deterioration of equipment, and a shorter equipment lifespan. Significant heat exchange occurs between steam and turbine rotors during the start-up process and even more intensive heat exchange takes place during the condensation phase in cold start-up mode, which leads to further thermal stresses and lifetime reduction. Therefore, the accuracy of lifetime prediction is strongly affected and dependent on the accuracy of transient thermal state prediction. In this study, transient thermal and structural analyses of a 30 MW steam turbine for a combined High and Intermediate pressures (HPIP) rotor during a full cold start cycle is performed and special attention is paid to initial start-up phase with ‘condensation’ thermal BC. All steps for rotor design and the thermal model preparation were done using the AxSTREAM™* software platform. It included the development of a two dimensional model of the rotor, thermal zones and corresponding thermal boundary conditions (heat transfer coefficients and steam temperatures) calculation during turbine start-up and shut down operation. Rotor thermal and structural simulations were done using commercial FE analysis software to evaluate the thermo-stress-strain state of the turbine rotor. Calculation and validation of thermal and structural state of the rotor was done using actual start-up cycle and measured data from a power plant, and it showed good agreement of the calculated and the measured data. Based on the results of thermo-structural analysis, the evaluation of rotor lifetime by means of a low cycle fatigue approach was performed and presented in this paper.

Steam Turbine Driving Compressor for Gas-Steam Combined Cycle Power Plant

2009 ◽  
Author(s):  
Wancai Liu ◽  
Hui Zhang
Keyword(s):  
Power Generation ◽  
Power Plant ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Combined Cycle ◽  
Thermodynamic Process ◽  
Combined Cycle Power Plant ◽  
Steam Cycle

Gas turbine is widely applied in power-generation field, especially combined gas-steam cycle. In this paper, the new scheme of steam turbine driving compressor is investigated aiming at the gas-steam combined cycle power plant. Under calculating the thermodynamic process, the new scheme is compared with the scheme of conventional gas-steam combined cycle, pointing its main merits and shortcomings. At the same time, two improved schemes of steam turbine driving compressor are discussed.

Investigation Into the Thermal Limitations of Steam Turbines During Start-Up Operation

2017 ◽  
Author(s):  
Monika Topel ◽  
Björn Laumert ◽  
Åsa Nilsson ◽  
Markus Jöcker
Keyword(s):  
Electricity Market ◽  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Limiting Factor ◽  
Steam Turbines ◽  
Expansion Behavior ◽  
Start Up ◽  
Schedule Design ◽  
Turbine Component ◽  
Differential Expansion

Liberalized electricity market conditions and concentrating solar power technologies call for increased power plant operational flexibility. Concerning the steam turbine component, one key aspect of its flexibility is the capability for fast starts. In current practice, turbine start-up limitations are set by consideration of thermal stress and low cycle fatigue. However, the pursuit of faster starts raises the question whether other thermal phenomena can become a limiting factor to the start-up process. Differential expansion is one of such thermal properties, especially since the design of axial clearances is not included as part of start-up schedule design and because its measurement during operation is often limited or not a possibility at all. The aim of this work is to understand differential expansion behavior with respect to transient operation and to quantify the effect that such operation would have in the design and operation of axial clearances. This was accomplished through the use of a validated thermo-mechanical model that was used to compare differential expansion behavior for different operating conditions of the machine. These comparisons showed that faster starts do not necessarily imply that wider axial clearances are needed, which means that the thermal flexibility of the studied turbine is not limited by differential expansion. However, for particular locations it was also obtained that axial rubbing can indeed become a limiting factor in direct relation to start-up operation. The resulting approach presented in this work serves to avoid over-conservative limitations in both design and operation concerning axial clearances.

A Combined Cycle Power Plant With Absorption Cooling for Houses Air Conditioning

2012 ◽  
Author(s):  
Hamad H. Almutairi ◽  
Jonathan Dewsbury ◽  
Gregory F. Lane-Serff
Keyword(s):  
Power Plant ◽  
Steam Turbine ◽  
Air Conditioning ◽  
Computer Models ◽  
Simulation Software ◽  
Combined Cycle ◽  
Cooling Load ◽  
Direct Expansion ◽  
Absorption Chiller ◽  
Combined Cycle Power Plant

This study examined the viability of a single-effect water/lithium bromide absorption chiller driven by steam extracted from the steam turbine in the configuration of a combined cycle power plant (CCPP). System performance was verified based on the annual cooling load profile of 1,000 typical houses in Kuwait obtained from DesignBuilder building simulation software. Computer models that represented a CCPP with an absorption chiller and a CCPP with a Direct-Expansion (DX) air conditioning system were developed using Engineering Equation Solver software. The computer models interacted with the cooling load profiles obtained from DesignBuilder. Analysis shows that the CCPP with the absorption chiller yielded less net electrical power to the utility grid compared to similar CCPPs giving electricity both to the grid and to the Direct-Expansion air conditioning systems given the same cooling requirements. The reason for this finding is the reduction in steam turbine power output resulting from steam extraction.

Medway: A High-Efficiency Combined Cycle Power Plant Design

1995 ◽  
Vol 117 (4) ◽  
pp. 713-723 ◽  
Author(s):  
D. M. Leis ◽  
M. J. Boss ◽  
M. P. Melsert
Keyword(s):  
Power Plant ◽  
Steam Turbine ◽  
High Reliability ◽  
System Optimization ◽  
Combined Cycle ◽  
Advanced Technology ◽  
Plant Design ◽  
Turbine Generator ◽  
Combined Cycle Power Plant ◽  
Plant System

The Medway Project is a 660 MW combined cycle power plant, which employs two of the world’s largest advanced technology MS9001FA combustion turbine generators and an advanced design reheat steam turbine generator in a power plant system designed for high reliability and efficiency. This paper discusses the power plant system optimization and design, including thermodynamic cycle selection, equipment arrangement, and system operation. The design of the MS9001FA combustion turbine generator and the steam turbine generator, including tailoring for the specific application conditions, is discussed.

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