scholarly journals Ageing Effect on Creep-fatigue Properties of Super-clean 9% CrMoV Steel for Steam Turbine Rotors of Combined Cycle Power Plants

2003 ◽  
Vol 89 (7) ◽  
pp. 796-802 ◽  
Author(s):  
Li-Bin NIU ◽  
Masato OKADO ◽  
Tsukasa AZUMA ◽  
Yoshihiro SAKAI ◽  
Mitsuyuki KOBAYASHI ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Fatigue Properties ◽  
Ageing Effect ◽  
Creep Fatigue ◽  
Turbine Rotors

Mechanical Design of Highly Loaded Large Steam Turbines

2011 ◽  
Author(s):  
N. Lu¨ckemeyer ◽  
H. Almstedt ◽  
T.-U. Kern ◽  
H. Kirchner
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Power Plants ◽  
Mechanical Design ◽  
Ductile Failure ◽  
Combined Cycle ◽  
Material Behavior ◽  
Integral Approach ◽  
Steam Turbines ◽  
Creep Fatigue

There are no internationally recognized standards, such as the ASME Boiler and Pressure Vessel Code or European boiler and pipe codes, for the mechanical design of large steam turbine components in combined cycle power plants, steam power plants and nuclear power plants. One reason for this is that the mechanical design of steam turbines is very complex as the steam pressure is only one of many aspects which need to be taken into account. In more than one hundred years of steam turbine history the manufacturers have developed internal mechanical design philosophies based on both experience and research. As the design of steam turbines is pushed to its limits with greater lifetimes, efficiency improvements and higher operating flexibility requested by customers, the validity and accuracy of these design philosophies become more and more important. This paper describes an integral approach for the structural analysis of large steam turbines which combines external design codes, material tests, research on the material behavior in co-operation with universities and experience gained from the existing fleet to derive a substantiated design philosophy. The paper covers the main parameters that need to be taken into account such as pressure, rotational forces and thermal loads and displacements, and identifies the relevant failure mechanisms such as creep fatigue, ductile failure and creep fatigue crack growth. It describes the efforts taken to improve the accuracy for materials already used in power plants today and materials with possible future use such as advanced steels or nickel based alloys.

Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Adrian Willuweit ◽  
Steffen Bergholz ◽  
Christian Philippek ◽  
Jevgenij Kobzarev
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hybrid Approach ◽  
Combined Cycle ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Constitutive Material Model ◽  
Standard Design ◽  
Creep Fatigue

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.

Repowering and Retrofitting

2002 ◽  
Author(s):  
Andreas Pickard
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Free Market ◽  
Leading Edge ◽  
Project Planning ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Planning Stage ◽  
Reheat Steam ◽  
Plant Optimization

At the start of this new century, environmental regulations and free-market economics are becoming the key drivers for the electricity generating industry. Advances in Gas Turbine (GT) technology, allied with integration and refinement of Heat Recovery Steam Generators (HRSG) and Steam Turbine (ST) plant, have made Combined Cycle installations the most efficient of the new power station types. This potential can also be realized, to equal effect, by adding GT’s and HRSG’s to existing conventional steam power plants in a so-called ‘repowering’ process. This paper presents the economical and environmental considerations of retrofitting the steam turbine within repowering schemes. Changing the thermal cycle parameters of the plant, for example by deletion of the feed heating steambleeds or by modified live and reheat steam conditions to suit the combined cycle process, can result in off-design operation of the existing steam turbine. Retrofitting the steam turbine to match the combined cycle unit can significantly increase the overall cycle efficiency compared to repowering without the ST upgrade. The paper illustrates that repowering, including ST retrofitting, when considered as a whole at the project planning stage, has the potential for greater gain by allowing proper plant optimization. Much of the repowering in the past has been carried out without due regard to the benefits of re-matching the steam turbine. Retrospective ST upgrade of such cases can still give benefit to the plant owner, especially when it is realized that most repowering to date has retained an unmodified steam turbine (that first went into operation some decades before). The old equipment will have suffered deterioration due to aging and the steam path will be to an archaic design of poor efficiency. Retrofitting older generation plant with modern leading-edge steam-path technology has the potential for realizing those substantial advances made over the last 20 to 30 years. Some examples, given in the paper, of successfully retrofitted steam turbines applied in repowered plants will show, by specific solution, the optimization of the economics and benefit to the environment of the converted plant as a whole.

Steam Injected Gas Turbine (STIG) for Load Flexible CHP: Aspects of Dynamic Behaviour, Control and Water Recovery

2019 ◽  
Author(s):  
Thorsten Lutsch ◽  
Uwe Gampe ◽  
Guntram Buchheim
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Operating Cost ◽  
Combined Cycle ◽  
System Response ◽  
Water Recovery ◽  
Operating Range ◽  
Demand Fluctuations ◽  
Wide Operating

Abstract Industrial combined heat and power (CHP) plants are often faced with highly variable demand of heat and power. Demand fluctuations up to 50% of nominal load are not uncommonly. The cost and revenue situation in the energy market represents a challenge, also for cogeneration of heat and power (CHP). More frequent and rapid load changes and a wide operating range are required for economic operation of industrial power plants. Maintaining pressure in steam network is commonly done directly by a condensation steam turbine in a combined cycle or indirectly by load changes of the gas turbine in a gas turbine and heat recovery steam generator arrangement. Both result in a change of the electric output of the plant. However, operating cost of a steam turbine are higher than a single gas turbine. The steam injected gas turbine (STIG) cycle with water recovery is a beneficial alternative. It provides an equivalent degree of freedom of power and heat generation. High process efficiency is achieved over a wide operating range. Although STIG is a proven technology, it is not yet widespread. The emphasis of this paper is placed on modeling the system behavior, process control and experiences in water recovery. A dynamic simulation model, based on OpenModelica, has been developed. It provides relevant information on system response for fluctuating steam injection and helps to optimize instrumentation and control. Considerable experience has been gained on water recovery with respect to condensate quality, optimum water treatment architecture and water recovery rate, which is also presented.

Design of Fast and Reliable Steam Surface Condensers

2020 ◽  
Author(s):  
Ranga Nadig
Keyword(s):  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Design Features ◽  
Surface Condenser ◽  
Combined Cycle Plant ◽  
Startup Time ◽  
On Line ◽  
To Come

Abstract Power plants operating in cyclic mode, standby mode or as back up to solar and wind generating assets are required to come on line on short notice. Simple cycle power plants employing gas turbines are being designed to come on line within 10–15 minutes. Combined cycle plants with heat recovery steam generators and steam turbines take longer to come on line. The components of a combined cycle plant, such as the HRSG, steam turbine, steam surface condenser, cooling tower, circulating water pumps and condensate pumps, are being designed to operate in unison and come on line expeditiously. Major components, such as the HRSG, steam turbine and associated steam piping, dictate how fast the combined cycle plant can come on line. The temperature ramp rates are the prime drivers that govern the startup time. Steam surface condenser and associated auxiliaries impact the startup time to a lesser extent. This paper discusses the design features that could be included in the steam surface condenser and associated auxiliaries to permit quick startup and reliable operation. Additional design features that could be implemented to withstand the demanding needs of cyclic operation are highlighted.

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.

Effects of Steam Reheat in Advanced Steam Injected Gas Turbine Cycles

1998 ◽  
Author(s):  
A. Hofstädter ◽  
H. U. Frutschi ◽  
H. Haselbacher
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Steam Injection ◽  
Combined Cycle ◽  
Back Pressure ◽  
Turbine Efficiency ◽  
Pressure Steam ◽  
Additional Improvement ◽  
Gas Turbine Exhaust

Steam injection is a well-known principle for increasing gas turbine efficiency by taking advantage of the relatively high gas turbine exhaust temperatures. Unfortunately, performance is not sufficiently improved compared with alternative bottoming cycles. However, previously investigated supplements to the STIG-principle — such as sequential combustion and consideration of a back pressure steam turbine — led to a remarkable increase in efficiency. The cycle presented in this paper includes a further improvement: The steam, which exits from the back pressure steam turbine at a rather low temperature, is no longer led directly into the combustion chamber. Instead, it reenters the boiler to be further superheated. This modification yields additional improvement of the thermal efficiency due to a significant reduction of fuel consumption. Taking into account the simpler design compared with combined-cycle power plants, the described type of an advanced STIG-cycle (A-STIG) could represent an interesting alternative regarding peak and medium load power plants.

Exergy Evaluation of Two Current Advanced Power Plants: Supercritical Steam Turbine and Combined Cycle

1997 ◽  
Vol 119 (4) ◽  
pp. 250-256 ◽  
Author(s):  
H. Jin ◽  
M. Ishida ◽  
M. Kobayashi ◽  
M. Nunokawa
Keyword(s):  
Steam Turbine ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Power Plants ◽  
Exergy Analysis ◽  
Combined Cycle ◽  
Exergy Loss ◽  
Heat Recovery Steam Generator ◽  
Combined Cycle Plant ◽  
Steam Plant

Two operating advanced power plants, a supercritical steam plant and a gas-steam turbine combined cycle, have been analyzed using a methodology of graphical exergy analysis (EUDs). The comparison of two plants, which may provide the detailed information on internal phenomena, points out several inefficient segments in the combined cycle plant: higher exergy loss caused by mixing in the combustor, higher exergy waste from the heat recovery steam generator, and higher exergy loss by inefficiency in the power section, especially in the steam turbine. On the basis of these fundamental features of each plant, we recommend several schemes for improving the thermal efficiency of current advanced power plants.

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