The Influence of Cooling Flows on the Operating Conditions of the Ultra-Supercritical Steam Turbine Components

2010 ◽  
Author(s):  
Wojciech Kosman
Keyword(s):  
Numerical Modeling ◽  
Steam Turbine ◽  
Power Plants ◽  
Measurement Data ◽  
Test Stand ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Inlet Section ◽  
Steam Turbines ◽  
Cooling Flows

This paper presents the results of the analysis on the heat transfer in the inlet section of an ultra-supercritical steam turbine. Such power generating units become the foundation of new coal-fired power plants. The monitoring of their operation is in many aspects similar to the traditional, sub-critical steam turbines. However, higher live and reheat steam parameters result in several key differences, which must be taken into the consideration when assessing the thermal and strength states of the turbines main components for the diagnostic supervision. One of the main differences is the presence of the cooling and designs specific for ultra-supercritical steam turbines, which aim to protect their components against overheating. The research described in this paper investigates the inlet section of the turbines, which is the area exposed to the highest thermal loads. The scope of the research includes both, numerical modeling and laboratory testing. A test stand has been built for the analysis of the flows in the inlet section. Cooling flows are under special attention here as their temperature field is coupled to the temperature fields of the turbine components (the rotor and the inner casing) due to the relatively small amount of the coolant. The paper provides detailed description of the test stand and some early measurement results, which involve the operation with cooling. Also the numerical modeling results are shown and compared to the measurement data.

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%.

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.

Efficient Multi-Objective Optimization of Labyrinth Seal Leakage in Steam Turbines Based on Hybrid Surrogate Models

2016 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Simon Hecker ◽  
Peter Dumstorff ◽  
Henning Almstedt ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Surrogate Model ◽  
Power Plants ◽  
Polynomial Regression ◽  
Renewable Energy Sources ◽  
Surrogate Models ◽  
Future Market ◽  
Steam Turbines ◽  
Model Calculations ◽  
Highly Efficient

The demand for energy is increasingly covered through renewable energy sources. As a consequence, conventional power plants need to respond to power fluctuations in the grid much more frequently than in the past. Additionally, steam turbine components are expected to deal with high loads due to this new kind of energy management. Changes in steam temperature caused by rapid load changes or fast starts lead to high levels of thermal stress in the turbine components. Therefore, todays energy market requires highly efficient power plants which can be operated under flexible conditions. In order to meet the current and future market requirements, turbine components are optimized with respect to multi-dimensional target functions. The development of steam turbine components is a complex process involving different engineering disciplines and time-consuming calculations. Currently, optimization is used most frequently for subtasks within the individual discipline. For a holistic approach, highly efficient calculation methods, which are able to deal with high dimensional and multidisciplinary systems, are needed. One approach to solve this problem is the usage of surrogate models using mathematical methods e.g. polynomial regression or the more sophisticated Kriging. With proper training, these methods can deliver results which are nearly as accurate as the full model calculations themselves in a fraction of time. Surrogate models have to face different requirements: the underlying outputs can be, for example, highly non-linear, noisy or discontinuous. In addition, the surrogate models need to be constructed out of a large number of variables, where often only a few parameters are important. In order to achieve good prognosis quality only the most important parameters should be used to create the surrogate models. Unimportant parameters do not improve the prognosis quality but generate additional noise to the approximation result. Another challenge is to achieve good results with as little design information as possible. This is important because in practice the necessary information is usually only obtained by very time-consuming simulations. This paper presents an efficient optimization procedure using a self-developed hybrid surrogate model consisting of moving least squares and anisotropic Kriging. With its maximized prognosis quality, it is capable of handling the challenges mentioned above. This enables time-efficient optimization. Additionally, a preceding sensitivity analysis identifies the most important parameters regarding the objectives. This leads to a fast convergence of the optimization and a more accurate surrogate model. An example of this method is shown for the optimization of a labyrinth shaft seal used in steam turbines. Within the optimization the opposed objectives of minimizing leakage mass flow and decreasing total enthalpy increase due to friction are considered.

Unsteady Aerodynamics of Low-Pressure Steam Turbines Operating Under Low Volume Flow

2013 ◽  
Author(s):  
Benjamin Megerle ◽  
Timothy Stephen Rice ◽  
Ivan McBean ◽  
Peter Ott
Keyword(s):  
Unsteady Flow ◽  
Steam Turbine ◽  
Measurement Data ◽  
Unsteady Aerodynamics ◽  
Low Pressure ◽  
Rotating Stall ◽  
Stage Model ◽  
Steam Turbines ◽  
Multi Stage ◽  
Low Volume

Non-synchronous excitation under low volume operation is a major risk to the mechanical integrity of last stage moving blades (LSMBs) in low-pressure (LP) steam turbines. These vibrations are often induced by a rotating aerodynamic instability similar to rotating stall in compressors. Currently extensive validation of new blade designs is required to clarify whether they are subjected to the risk of not admissible blade vibration. Such tests are usually performed at the end of a blade development project. If resonance occurs a costly redesign is required, which may also lead to a reduction of performance. It is therefore of great interest to be able to predict correctly the unsteady flow phenomena and their effects. Detailed unsteady pressure measurements have been performed in a single stage model steam turbine operated with air under ventilation conditions. 3D CFD has been applied to simulate the unsteady flow in the air model turbine. It has been shown that the simulation reproduces well the characteristics of the phenomena observed in the tests. This methodology has been transferred to more realistic steam turbine multi stage environment. The numerical results have been validated with measurement data from a multi stage model LP steam turbine operated with steam. Measurement and numerical simulation show agreement with respect to the global flow field, the number of stall cells and the intensity of the rotating excitation mechanism. Furthermore, the air model turbine and model steam turbine numerical and measurement results are compared. It is demonstrated that the air model turbine is a suitable vehicle to investigate the unsteady effects found in a steam turbine.

Lifetime Assessments of an Old Westinghouse-Design Steam Chest

2012 ◽  
Author(s):  
Sazzadur Rahman ◽  
Waheed Abbasi ◽  
Thomas W. Joyce
Keyword(s):  
Steam Turbine ◽  
Material Properties ◽  
Power Plants ◽  
Real Life ◽  
Cyclic Stress ◽  
Steam Turbines ◽  
Reliable Operation ◽  
Steady State Operation ◽  
Different Temperatures ◽  
Transient Events

Fossil steam turbines were designed for approximately thirty years of reliable operation based on a normal duty cycle. During operation, highly stressed components of steam turbine power plants undergo a change in material properties due to cyclic stress and exposure to different temperatures. Among all the components of a steam turbine, the steam chest is affected the most as it experiences a wide variation of stresses and loads during transient events and steady-state operation. These factors can strongly influence the metallurgical condition and overall reliable life of steam chests. In this paper, Siemens’ overall approach for lifetime assessments will be discussed with a real life example on a 40 year old Westinghouse-design steam chest. The methodology and the findings from the assessment are also discussed.

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.

Numerical Investigation of Exhaust Diffuser Performances in Low Pressure Turbine Casings

2011 ◽  
Author(s):  
Tadashi Tanuma ◽  
Yasuhiro Sasao ◽  
Satoru Yamamoto ◽  
Shinji Takada ◽  
Yoshiki Niizeki ◽  
...  
Keyword(s):  
Steam Turbine ◽  
High Performance ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Measurement Data ◽  
Boundary Layer Separation ◽  
Low Pressure ◽  
Tvd Scheme ◽  
Steam Turbines ◽  
Exhaust Hood

Low pressure (LP) exhaust hoods are an important component of steam turbines. The aerodynamic loss of LP exhaust hoods is almost the same as those of the stator and rotor blading in LP steam turbines. Designing high performance LP exhaust hoods should lead further enhancement of steam turbine efficiency. This paper presents the results of exhaust hood computational fluid dynamics (CFD) analyses using last stage exit velocity distributions measured in a full-scale development steam turbine as the inlet boundary condition to improve the accuracy of the CFD analysis. One of the main difficulties in predicting the aerodynamic performance of the exhaust hoods is the unsteady boundary layer separation of exhaust hood diffusers. A highly accurate unsteady numerical analysis is introduced in order to simulate the diffuser flows in LP exhaust hoods. Compressible Navier-Stokes equations and mathematical models for nonequilibrium condensation are solved using the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe’s approximate Riemann solver, and the LU-SGS scheme. The SST turbulence model is also solved for evaluating the eddy viscosity. The computational results were validated using the measurement data, and the present CFD method was proven to be suitable as a useful tool for determining optimum three-dimensional designs of LP turbine exhaust diffusers.

Validation of Advanced Steam Turbine Technology: A Case Study of an Ultra Super Critical Steam Turbine Power Plant

2011 ◽  
Author(s):  
Rainer Quinkertz ◽  
Thomas Thiemann ◽  
Kai Gierse
Keyword(s):  
High Pressure ◽  
Power Plant ◽  
Steam Turbine ◽  
Power Plants ◽  
High Efficiency ◽  
State Of The Art ◽  
Cooling System ◽  
Operational Experience ◽  
Internal Cooling ◽  
Steam Turbines

High efficiency and flexible operation continue to be the major requirements for power generation because of the benefits of reduced emissions and reduced fuel consumption, i.e. reduced operating costs. Ultra super critical (USC) steam parameters are the basis for state of the art technology of coal fired power plants with highest efficiency. An important part of the development process for advanced steam turbines is product validation. This step involves more than just providing evidence of customer guaranteed values (e.g. heat rate or electric output). It also involves proving that the design targets have been achieved and that the operational experience is fed back to designers to further develop the design criteria and enable the next step in the development of highly sophisticated products. What makes product validation for large size power plant steam turbines especially challenging is the fact that, due to the high costs of the required infrastructure, steam turbine manufacturers usually do not have a full scope / full scale testing facility. Therefore, good customer relations are the key to successful validation. This paper describes an extensive validation program for a modern state of the art ultra supercritical steam turbine performed at an operating 1000 MW steam power plant in China. Several measuring points in addition to the standard operating measurements were installed at one of the high pressure turbines to record the temperature distribution, e.g. to verify the functionality of the internal cooling system, which is an advanced design feature of the installed modern high pressure steam turbines. Predicted 3D temperature distributions are compared to the actual measurements in order to verify and evaluate the design rules and the design philosophy applied. Conclusions are drawn regarding the performance of modern 3D design tools applied in the current design process and an outlook is given on the future potential of modern USC turbines.

Repowering Considerations for Converting Existing Power Plants to Combined Cycle Power Plants

2002 ◽  
Author(s):  
Anup Singh ◽  
Don Kopecky
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Current Status ◽  
Entire System ◽  
Steam Turbines ◽  
Good Shape ◽  
The Usa ◽  
Overall Performance ◽  
Cost Studies

Most of the recent combined cycle plants have been designed and constructed as Greenfield Plants. These new plants have been designed mostly as Merchant Plants, owned and operated by Independent Power Producers. There is about 260,000 MW of conventional coal-fired and gas-fired capacity in the USA that is more than 30 years old. About 30,000 MW of conventional gas-fired capacity exists in the area of The Electric Reliability Council of Texas (ERCOT) with relatively poor heat rates in comparison to modern combined cycle plants. These plants are good candidates for HRSG repowering. In addition, there are several coal-fired units in the 200 MW range with steam turbines in relatively good shape or in a condition that can be refurbished and used in repowering. The installed cost of repowered (also called Brownfield) capacity is about 20%–40% less than for comparable Greenfield capacity. There are also other advantages to repowering. Since the site is already existing, it is easier to get the various environmental and construction permits. The efficiency of the repowered units will be significantly higher than the existing units in their current status thus increasing the overall performance of the entire system. The paper will discuss various considerations required for repowering, including steam turbine refurbishment, demolition/relocation of existing equipment, recent cost studies, and various considerations for equipment such as HRSGs.

Development of LP Blade Module for High Back Pressure-Aerodynamic Design

2017 ◽  
Author(s):  
Ambrish ◽  
Nand Kumar Singh
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Volume Flow Rate ◽  
Back Pressure ◽  
Operating Conditions ◽  
Total Efficiency ◽  
Aerodynamic Design ◽  
Streamline Curvature ◽  
Pressure Application ◽  
Wide Range

In steam turbine power plants, the appropriate design of the last stage blades is critical in determining the plant efficiency and reliability. The development of LP module for desert applications is finding applications for a number of industrial steam turbine operating with air cooled condensers. The conventional LP Module for water cooled condenser operates at low back pressure (Pexit = 0.09 bar) and are generally not suitable for high back pressure application. This paper focuses on the aerodynamic design & optimization of last stages of LP blade module for high back pressure application and validation through 3D CFD. The guide and moving blade are designed with seven equally-spaced profiles section from hub to shroud through Axstream S/w. The profile and incidence losses are minimized for the design and off-design conditions. Aeromechanical design of LP blade module consisting of 2 stages for 0.2 bar back pressure, 1.1 bar inlet static pressure and a mass flow of 61.2 kg/s is carried out. An optimization process through a streamline curvature code and design optimization software using Optimus is established and flow path contours is optimized thoroughly, a total to total efficiency of 81.4% is achieved for the rated condition. The off-design performance is investigated for a wide range of operating conditions, especially at low volume flow rate of steam condition.

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