Natural Cooling and Startup of Steam Turbines: Validity of the Over-Conductivity Function

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Gabriel Marinescu ◽  
Peter Stein ◽  
Michael Sell
Keyword(s):  
Experimental Investigation ◽  
Thermal Behavior ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Temperature Measurements ◽  
Measured Temperature ◽  
Steam Turbines ◽  
Optical Probes ◽  
The Real ◽  
Asme Paper

The temperature drop during natural cooling and the way in which the steam turbine restarts have a major impact on the cyclic lifetime of critical parts and on the cyclic life of the whole machine. In order to ensure the fastest startup without reducing the lifetime of the turbine critical parts, the natural cooling must be captured accurately in calculation and the startup procedure optimized. During the cool down and restart, all turbine components interact both thermally and mechanically. For this reason, the thermal analyst has to include, in his numerical model, all turbine significant parts—rotor, casings together with their internal fluid cavities, valves, and pipes. This condition connected with the real phenomenon lead-time—more than 100 hours for natural cooling—makes the analysis time-consuming and not applicable for routine projects. During the past years, a concept called “over-conductivity” was introduced by Marinescu et al. (2013, “Experimental Investigation Into Thermal Behavior of Steam Turbine Components—Temperature Measurements With Optical Probes and Natural Cooling Analysis,” ASME J. Eng. Gas Turbines Power, 136(2), p. 021602) and Marinescu and Ehrsam (2012, “Experimental Investigation on Thermal Behavior of Steam Turbine Components: Part 2—Natural Cooling of Steam Turbines and the Impact on LCF Life,” ASME Paper No. GT2012-68759). According to this concept, the effect of the fluid convectivity and radiation is replaced by a scalar function K(T) called over-conductivity, which has the same heat transfer effect as the real convection and radiation. K(T) is calibrated against the measured temperature on a Alstom KA26-1 steam turbine (Ruffino and Mohr, 2012, “Experimental Investigation on Thermal Behavior of Steam Turbine Components: Part 1—Temperature Measurements With Optical Probes,” ASME Paper No. GT2012-68703). This concept allows a significant reduction of the calculation time, which makes the method applicable for routine transient analyses. The paper below shows the theoretical background of the over-conductivity concept and proves that when applied on other machines than KA26-1, the accuracy of the calculated temperatures remains within 15–18 °C versus measured data. A detailed analysis of the link between the over-conductivity and the energy equation is presented as well.

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.

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.

Experimental Investigation Into Thermal Behavior of Steam Turbine Components—Temperature Measurements With Optical Probes and Natural Cooling Analysis

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Gabriel Marinescu ◽  
Wolfgang F. Mohr ◽  
Andreas Ehrsam ◽  
Paolo Ruffino ◽  
Michael Sell
Keyword(s):  
Steam Turbine ◽  
Numerical Procedure ◽  
Cyclic Fatigue ◽  
Temperature Measurements ◽  
Steam Turbines ◽  
Equivalent Conductivity ◽  
Cyclic Operation ◽  
Start Up ◽  
Higher Temperature ◽  
Fluid Conductivity

The steam turbine cooldown has a significant impact on the cyclic fatigue life. A lower initial metal temperature after standstill results in a higher temperature difference to be overcome during the next start-up. Generally, lower initial metal temperatures result in higher start-up stress. In order to optimize steam turbines for cyclic operation, it is essential to fully understand natural cooling, which is especially challenging for rotors. This paper presents a first-in-time application of a 2D numerical procedure for the assessment of the thermal regime during natural cooling, including the rotors, casings, valves, and main pipes. The concept of the cooling calculation is to replace the fluid gross buoyancy during natural cooling by an equivalent fluid conductivity that gives the same thermal effect on the metal parts. The fluid equivalent conductivity is calculated based on experimental data. The turbine temperature was measured with pyrometric probes on the rotor and with standard thermocouples on inner and outer casings. The pyrometric probes were calibrated with standard temperature measurements on a thermo well, where the steam transmittance and the rotor metal transmissivity were measured.

Experimental Investigation Into Thermal Behaviour of Steam Turbine Components: Part 1—Temperature Measurements With Optical Probes

2012 ◽  
Author(s):  
W. F. Mohr ◽  
P. Ruffino
Keyword(s):  
Steam Turbine ◽  
Combined Cycle ◽  
Temperature Measurements ◽  
Steam Turbines ◽  
Steam Temperature ◽  
Standard Temperature ◽  
Pressure Steam ◽  
Rotor Surface ◽  
Base Load

The first-in-time application of intensity pyrometry to measure in-situ the hot rotor surface temperature of a standard, combined cycle, intermediate pressure steam turbine is presented. The data cover a cold-start and cooling from base load. The pyrometric temperatures are compared to standard temperature measurements on static turbine parts and an upstream steam temperature measured on a thermo well. It is reported, how the applicability of pyrometry in steam turbines was assessed. Details are given about a newly developed USC autoclave, which was used to measure steam transmittance, and about the measurement of the emissivity of the rotor metal. Further the steps taken towards a steam-pyrometer are shown; how it was developed, validated in terms of its precision and lifetime in hot steam environment, and how its integration to a standard turbine was prepared.

Experimental Investigation Into Thermal Behavior of Steam Turbine Components: Part 3 — Startup and the Impact on LCF Life

2013 ◽  
Author(s):  
Gabriel Marinescu ◽  
Michael Sell ◽  
Andreas Ehrsam ◽  
Philipp B. Brunner
Keyword(s):  
Thermal Behavior ◽  
Steam Turbine ◽  
Low Cycle Fatigue ◽  
Numerical Procedure ◽  
Cyclic Fatigue ◽  
Low Flow ◽  
Steam Turbines ◽  
Early Loading ◽  
Start Up ◽  
The Impact

Steam turbine start-up has a significant impact on the cyclic fatigue life. Modern steam turbines are operated at high temperatures for optimal efficiency, which results in high temperature differences relative to the condition before start-up. To achieve the fastest possible start-up time without reducing the lifetime of the turbine components due to excessive thermal stress, the start-up procedure of cyclic turbines is optimized to follow the specific material low cycle fatigue limit. For such optimization and to ensure reliable operation, it is essential to fully understand the thermal behavior of the components during start-up. This is especially challenging in low flow conditions, i.e. during pre-warming and early loading phase. A two-dimensional numerical procedure is described for the assessment of the thermal regime during start-up. The calculation procedure includes the rotor, casings, valves and main pipes. The concept of the start-up calculation is to replace the convective effect of the steam in the turbine cavity by an equivalent fluid over-conductivity that gives the same thermal effect on metallic parts. This approach allows simulating accurately the effect of steam ingestion during pre-warming phase. The fluid equivalent over-conductivity is calibrated with experimental data. At the end of the paper the impact of ingested steam temperature and mass-flow on the rotor cyclic lifetime is demonstrated. This paper is a continuation of papers [1] and [2].

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.

Application of Numerical Simulations at Welding Multilayer Welds from the Material X22CrMoV12-2

2014 ◽  
Vol 1029 ◽  
pp. 31-36
Author(s):  
Jaromír Moravec ◽  
Marek Slováček
Keyword(s):  
Heat Treatment ◽  
Computational Model ◽  
Numerical Simulations ◽  
Steam Turbine ◽  
Input Data ◽  
Martensitic Steel ◽  
Steam Turbines ◽  
The Real ◽  
Set Up ◽  
Welding Procedure

Heat-resisting martensitic steel X22CrMoV12-1 is suitable to be used particularly for steam turbine components (e.g. blades or action wheels of steam turbines) and as parts of airplanes structural devices. The aim of this paper is to show how numerical simulations can help to optimize welding procedure of this very hardly weldable material. On the real multilayer weld will be described how to arrange whole experiment in order to obtain not only relevant input data but also verification data. As a result it will be possible to set up the computational model for this type of steel and consequently to use it for simulation computations of welding and heat treatment of real structure components.

Conserving Energy by the Efficient Use of the Industrial Gas Turbine

1982 ◽  
Author(s):  
D. M. S. Lightbody
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Market Forces ◽  
Specific Work ◽  
Steam Turbines ◽  
The Uk ◽  
Industrial Gas Turbine ◽  
Cycle Efficiency

The paper covers the basic thermodynamics of the combined cycle concept and illustrates that energy conservation is possible by coupling the Joule and Rankine cycles. It discusses the optimisation of steam conditions and outlines the concept of the unfired combined cycle. “Carnot efficiency” and “pinch points” are shown to be important as is the concept of “specific work” as it relates to the gas turbine in arriving at the best overall cycle efficiencies. The importance of the efficiency characteristic of the steam turbine is emphasised and it is shown that this characteristic will determine the overall cycle efficiency. It is suggested that steam turbine manufacturers should design and develop steam turbines to match the advanced gas turbines available to-day and so enchance the overall efficiency which can presently be obtained from to-day’s combined cycle. Market forces will tend to bring this about as evidenced by the growing interest being shown in this concept both in the UK and Europe.

The Combined Reheat Gas Turbine/Steam Turbine Cycle: Part I—A Critical Analysis of the Combined Reheat Gas Turbine/Steam Turbine Cycle

1980 ◽  
Vol 102 (1) ◽  
pp. 35-41 ◽  
Author(s):  
I. G. Rice
Keyword(s):  
Power Plant ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Critical Analysis ◽  
Pressure Ratio ◽  
Rankine Cycle ◽  
Steam Turbines ◽  
Gas Generator ◽  
World Energy

The reheat gas turbine cycle combined with the steam turbine Rankine cycle holds new promise of appreciably increasing power plant thermal efficiency. Apparently the cycle has been overlooked and thus neglected through the years. Research and development is being directed towards other gas turbine areas because of the world energy crunch; and in order to focus needed technical attention to the reheat cycle, this paper is presented, using logic and practical background of heat recovery boilers, steam turbines, gas turbines and the process industry. A critical analysis is presented establishing parameters of efficiency, cycle pressure ratio, firing temperature and output. Using the data developed, an analysis of an actual gas generator, the second generation LM5000, is applied with unique approaches to show that an overall 50 percent efficiency power plant can be developed using today’s known techniques and established base-load firing temperatures.

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