Thermally Sprayed Abradable Coatings in Steam Turbines: Design Integration and Functionality Testing

2010 ◽  
Author(s):  
Dieter Sporer ◽  
Scott Wilson ◽  
Petr Fiala ◽  
Ruediger Schuelein
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Labyrinth Seal ◽  
Test Methods ◽  
Steam Turbines ◽  
Coating Materials ◽  
Design Integration ◽  
Abradable Coatings ◽  
Thermally Sprayed

The concept of thermally sprayed abradable sealing technology has successfully been used in aero engines and industrial gas turbines for several decades now. More recently efforts were undertaken to implement the concept of seal coatings in steam turbine designs. As these typically use labyrinth type sealing, the application and test methods for sprayed seals applied to improve efficiency and reduce emissions need to be tailored to this particular seal configuration. This paper reviews how steam turbines can benefit from abradable coating technology and how it can be implemented into existing labyrinth seal designs for various seal locations in a steam turbine. A detailed review of high temperature rig abradability testing capabilities for labyrinth seal layouts using abradable coatings will be provided. Coating materials and their performance in a high temperature steam environment at 650 °C ( 1200 °F ) will be discussed. The application of coatings to various steam turbine components including large casings will be reviewed.

scholarly journals Advances in Abradable Coatings for Gas Turbines

1994 ◽  
Author(s):  
R. Schmid ◽  
A. R. Nicoll
Keyword(s):  
Gas Turbines ◽  
Environmental Changes ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
Mechanism Analysis ◽  
Coating Materials ◽  
Turbine Engine ◽  
Plasma Sprayed ◽  
Abradable Coatings ◽  
Sprayed Coatings

Gas turbine engine development continues to accelerate, creating more demanding requirements for abradable seal coatings. These coatings are necessary to provide very small clearances between the rotating and stationary parts in order to minimize gap losses and so Increase efficiency. The relatively few abradable coating materials developed over the last 20 years still perform well in many blade tip seal and labyrinth seal applications. However, rising operating temperatures, corrosion and other environmental changes, longer overhaul times and even better tip clearances are dictating the design of new coating materials which requires a strong scientific approach. For example, ways are being Investigated to replace Nickel-Graphite and other flame sprayed coatings being used between 450 and 700°C respectively because of steady state/corrosion/oxidation/erosion and wear problems respectively. New plasma and HVOF sprayed coatings have been developed using a systematic approach based on material response to operating conditions, minimizing trial and error. The major steps in the programme were: 1. Selection of constituent materials able to withstand service temperatures up to 325 (AISI-Polyester or Polyimide), 450 (AISI base), 700 (MCrAlY base) and 1100°C (ceramic base) respectively. 2. Powder particle manufacture and coating deposition to guarantee highly reproducible coatings. 3. Coating optimization based on wear tests carried out using a fully instrumented abradability test rig and wear mechanism analysis. 4. An investigation of blade tipping systems for high temperature applications. This paper discusses the results of plasma sprayed coatings developed for use at 450 and 700°C.

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.

Suppression of Subsynchronous Vibrations in a 11 MW Steam Turbine Using Integral Squeeze Film Damper Technology at the Exhaust Side Bearing

2016 ◽  
Author(s):  
Riccardo Ferraro ◽  
Michael Catanzaro ◽  
Jongsoo Kim ◽  
Michela Massini ◽  
Davide Betti ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Labyrinth Seal ◽  
Squeeze Film ◽  
Stable Operation ◽  
Steam Turbines ◽  
Squeeze Film Damper ◽  
Full Load ◽  
Steam Admission ◽  
Before And After ◽  
Full Speed

The presence of high subsynchronous vibrations and other rotordynamic instabilities in steam turbines can prevent operation at full speed and/or full load. The destabilizing forces generating subsynchronous vibrations can be derived from bearings, seals, impellers or other aerodynamic sources. The present paper describes the case of an 11 MW steam turbine, driving a syngas centrifugal compressor train, affected by subsynchronous vibrations at full load. After the occurrence of anomalous vibrations at high load and a machine trip due to the high vibrations, the analysis of data collected at the site confirmed instability of the first lateral mode. Further calculations identified that the labyrinth seal at the balance drum was the main source of destabilizing effects, due to the high pre-swirl and the relatively tight seal clearance. The particular layout of the turbine, a passing-through machine with a combined journal/double thrust bearing on the steam admission side, together with the need for a fast and reliable corrective action limited the possible solutions. Based on the analyses performed, adjusting the clearance and preload of the journal bearings could not have ensured stable operation at each operating condition. The use of swirl brakes to reduce the steam pre-swirl at the recovery seal entrance would have required a lengthy overhaul of the unit and significant labor to access and modify the parts. The final choice was a drop-in replacement of only the rear bearing (on the steam exhaust side) with a bearing featuring integral squeeze film damper (ISFD) technology. In addition to being a time efficient solution, the ISFD technology ensured an effective tuning of stiffness and damping, as proven by the field results. The analyses carried out to understand the source of the subsynchronous vibrations and to identify possible corrective actions, as well as the comparison of rotordynamic data before and after the application of the bearing with ISFD technology, are discussed.

Numerical Investigation of an Improved Gas and Steam Turbine Seal

1996 ◽  
Vol 210 (6) ◽  
pp. 477-479 ◽  
Author(s):  
M H Gordon ◽  
U M Kelkar ◽  
M C Johnson
Keyword(s):  
High Temperature ◽  
Numerical Investigation ◽  
High Speed ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Labyrinth Seal ◽  
Optimal Shape ◽  
Steam Turbines ◽  
Brush Seal ◽  
Sealing Mechanism

A numerical study has been conducted to assess the viability of a new sealing mechanism for gas and steam turbines. This new static-to-rotating sealing mechanism is mounted on flexible legs which permit radial movement and is designed to take advantage of the hydro-dynamic pressure forces, which result from fluid leaking around the seal, to maintain an ideally small and constant clearance. Relatively simple seal geometries have been numerically tested to find an optimal shape. These results indicate that a substantial sealing improvement (between two and four times less leakage) relative to a labyrinth seal is possible. Although these results show that a brush seal is more effective than the present seal, the present seal is designed to operate in high-speed and high-temperature environments in which the brush seal would degrade.

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.

Power Cycle Integration and Efficiency Increase of Molten Carbonate Fuel Cell Systems

2005 ◽  
Vol 3 (4) ◽  
pp. 375-383 ◽  
Author(s):  
Petar Varbanov ◽  
Jiří Klemeš ◽  
Ramesh K. Shah ◽  
Harmanjeet Shihn
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbines ◽  
Waste Heat ◽  
Combined Cycle ◽  
Molten Carbonate Fuel Cell ◽  
Steam Turbines ◽  
Molten Carbonate ◽  
Carbonate Fuel Cell

A new view is presented on the concept of the combined cycle for power generation. Traditionally, the term “combined cycle” is associated with using a gas turbine in combination with steam turbines to better utilize the exergy potential of the burnt fuel. This concept can be broadened, however, to the utilization of any power-generating facility in combination with steam turbines, as long as this facility also provides a high-temperature waste heat. Such facilities are high temperature fuel cells. Fuel cells are especially advantageous for combined cycle applications since they feature a remarkably high efficiency—reaching an order of 45–50% and even close to 60%, compared to 30–35% for most gas turbines. The literature sources on combining fuel cells with gas and steam turbines clearly illustrate the potential to achieve high power and co-generation efficiencies. In the presented work, the extension to the concept of combined cycle is considered on the example of a molten carbonate fuel cell (MCFC) working under stationary conditions. An overview of the process for the MCFC is given, followed by the options for heat integration utilizing the waste heat for steam generation. The complete fuel cell combined cycle (FCCC) system is then analyzed to estimate the potential power cost levels that could be achieved. The results demonstrate that a properly designed FCCC system is capable of reaching significantly higher efficiency compared to the standalone fuel cell system. An important observation is that FCCC systems may result in economically competitive power production units, comparable with contemporary fossil power stations.

Clearance and Seals Design for New Heat™ Steam Turbine

2006 ◽  
Author(s):  
Bernard A. Couture ◽  
Leslie B. Keeling ◽  
Mark W. Kowalczyk
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
High Efficiency ◽  
Labyrinth Seal ◽  
Mechanical Analysis ◽  
Advanced Technology ◽  
Speed Test ◽  
Steady State Operation ◽  
Thermal Mechanical Analysis ◽  
Abradable Coatings

The HEAT™ (High Efficiency Advanced Technology) steam turbine utilizes high reaction technology [1], which is significantly influenced by the effectiveness of sealing between the stages. The thermal-mechanical analysis based clearance design and the combination of labyrinth sealing with abradable coatings offer an effective solution to minimize bucket and nozzle tip leakage through transient and steady state operation of the turbine. The aim of this paper is to describe the clearance design process and the development of abradable-labyrinth seal configurations. The paper describes extensive testing and detailed analysis conducted to evaluate seal properties and behaviors. Properties investigated included corrosion, erosion and in particular, rub characteristics. Rub behavior is investigated in a high temperature, high speed test apparatus designed to simulate clearance changes during transient periods of start-up, shutdown and hot re-start which often result in interference between the sealing components. This paper will discuss the method to predict differential rotor to stator movements and the resulting abradable incursion during the various operating transients. The seal tooth to coating contact is then simulated with component testing for multiple incursion modes (i.e. radial, axial and a combination of the two) and rates. The discussion will also include the application of the clearance design and sealing technology to a reaction type steam turbine.

Creep Deformation of High Pressure Steam Turbine Part

2015 ◽  
Vol 732 ◽  
pp. 187-190
Author(s):  
František Straka ◽  
Pavel Albl ◽  
Pavel Pánek
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Steam Turbine ◽  
Creep Deformation ◽  
Steam Turbines ◽  
High Pressure Turbine ◽  
High Pressure Steam ◽  
Pressure Steam ◽  
Temperature Levels ◽  
Steam Parameters

Steam turbines are complex rotating machines working at high pressure and high temperature levels. Their high-pressure parts, which are subjected to the highest steam parameters, are most affected by these conditions and may suffer from creep deformation. Permanent changes in geometry become visible in high-pressure turbine casings when they are disassembled after certain time in operation.

Manufacturing Experience in an Advanced 9%CrMoCoVNbNB Alloy for Ultra-Supercritical Steam Turbine Rotor Forgings and Castings

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Rod Vanstone ◽  
Ian Chilton ◽  
Pawel Jaworski
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Creep Strength ◽  
Stainless Steels ◽  
First Generation ◽  
Turbine Rotor ◽  
Steam Turbines ◽  
Martensitic Stainless Steels ◽  
Operating Temperatures ◽  
New Generation

Advanced 9–12%Cr martensitic stainless steels to enable extension of steam turbine operating temperatures beyond 565 °C have been under development since the 1980s. Steam turbines with operating temperatures approaching 600 °C based on the first generation of these improved alloys, which exploited optimized levels of Mo, W, V, Nb, and N, entered service in the 1990s. Around the same time, a second generation of advanced alloys was developed incorporating additions of Co and B to further enhance creep strength. These alloys have recently been exploited to enable steam turbines with operating temperatures of up to 620 °C, and this new generation of steam turbines is now beginning to enter service. This paper describes the background to the development of these alloys and the experience gained in their application to the manufacture of high temperature rotor forgings and castings.

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