Improvement in the Rapid Startup Performance for the Solar Steam Turbine

2018 ◽  
Author(s):  
Peng Wang ◽  
Gang Chen ◽  
WenFu Li
Keyword(s):  
Steam Turbine ◽  
Cyclic Fatigue ◽  
Steam Turbines ◽  
Load Variations ◽  
Start Up ◽  
Reheat Steam ◽  
Startup Performance ◽  
Transient Thermal ◽  
Life Consumption ◽  
Operation Flexibility

In the latest several years, concentrated solar plants (CSP) have been rapidly developed. Steam turbines employed in these plants are subjected to daily start up and continuous load variations. There is a general increase in demand for operation flexibility and rapid start up capability for solar steam turbines. Accordingly, how to decrease the low cyclic fatigue life consumption during the daily start up process is a hot researched topic at present, and this greatly depends on the transient thermal stress. A number of studies show that the startup schemes and the unit’s structural form decide the LCF life consumption directly. In this paper, a 50MW double cylinder (HP and ILP Section) reheat solar steam turbine is studied, and it is operated continuously with inlet steam conditions of 540[°C], 140[bar], reheat steam conditions of 540[°C], 24[bar] and exhaust conditions of 41.5[°C], 0.08[bar]. A number of comparisons are made with the FEM numerical simulation, and some optimal designs which are applied to improve the rapid start up performance and decrease the LCF life consumption during the startup are presented.

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 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].

Experimental Investigation Into Thermal Behavior of Steam Turbine Components: Part 4 — Natural Cooling and Robustness of the Over-Conductivity Function

2014 ◽  
Author(s):  
Gabriel Marinescu ◽  
Peter Stein ◽  
Michael Sell
Keyword(s):  
Steam Turbine ◽  
Fluid Velocity ◽  
Numerical Procedure ◽  
Cyclic Fatigue ◽  
Theoretical Background ◽  
Fluid Temperature ◽  
Steam Turbines ◽  
Main Concept ◽  
Start Up ◽  
Conductivity Function

Steam turbine transient maneuvers have a significant impact on the cyclic fatigue life. Modern steam turbines are operated at high temperatures for optimal efficiency, which results in high time and space temperature gradients. A low initial metal temperature after standstill results in a high temperature difference to be overcome during the next startup and consequently a low lifetime at critical locations. To achieve the fastest possible start-up time without reducing the lifetime of the turbine components, the natural cooling must be captured accurately in calculation and the start-up procedure optimized. At the past two ASME conferences we presented three papers [1], [2], [3], about a 2D numerical procedure for the thermal regime calculation during natural cooling and startup. The analysis included the rotor, casings, valves and pipes. The main concept was to replace the thermal effect of the fluid convectivity by a fluid function K(T) called “over-conductivity”, which is calibrated vs. experimental data. The paper below shows: (a) the theoretical background of the over-conductivity function K(T) and (b) the equation of the correlation function f(T,p) between the fluid velocity and fluid temperature gradient. Both K(T) and f(T,p) are applicable for the flow within the large turbine cavities with negligible pressure gradient. The robustness of the K(T) function is verified on three different turbine configurations. For each machine a separate transient thermal model was built and the calculated temperatures were compared with the corresponding measured temperatures. At the end of the paper conclusions about the natural cooling features are presented.

Thermo-Structural Analysis of Steam Turbine Start-Up With and Without Integrated Pre-Warming System Using Hot Air

2020 ◽  
Author(s):  
Piotr Łuczyński ◽  
Lukas Pehle ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
Jan Vogt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Power Plants ◽  
Thermal Contact ◽  
Steam Turbines ◽  
Operating Modes ◽  
Hot Air ◽  
Start Up ◽  
Simulation Strategy ◽  
Transient Thermal

Abstract Motivated by the urgent need for flexibility and start-up capability improvements of conventional power plants in addition to extending their life cycle, General Electric provides its customers with a product to pre-warm steam turbines using hot air. In this paper, the transient thermal and structural analyses of a 19-stage IP steam turbine in various start-up operating modes are discussed in detail. The presented research is based on previous investigations and utilises a hybrid (HFEM - numerical FEM and analytical) approach to efficiently determine the time-dependent temperature distribution in the components of the steam turbine. The simulation strategy of the HFEM model applies various analytical correlations to describe heat transfer in the turbine channel. These are developed by means of extensive unsteady multistage conjugate heat transfer simulations for both start-up turbine operation with steam and pre-warming operation with hot air. Moreover, the complex numerical setup of the HFEM model also considers the thermal contact resistance (TCR) on the surfaces between vane and casing as well as blades and rotor. Prior to the analysis of other turbine start-up operating modes, the typical start-up turbine process is calculated and validated against an experimental data as a benchmark for subsequent analysis. In addition to heat transfer correlations, the simulation of a turbine start-up from cold state uses an innovative analytic pressure model to allow for a consideration of condensation effects during first phase of start-up procedure.

Experimental Investigation Into Thermal Behavior of Steam Turbine Components: Part 2—Natural Cooling of Steam Turbines and the Impact on LCF Life

2012 ◽  
Author(s):  
Gabriel Marinescu ◽  
Andreas Ehrsam
Keyword(s):  
Steam Turbine ◽  
Numerical Procedure ◽  
Cyclic Fatigue ◽  
Steam Turbines ◽  
Cyclic Operation ◽  
Start Up ◽  
Highly Sensitive ◽  
Higher Temperature ◽  
The Impact ◽  
Fluid Conductivity

Steam turbine cool-down 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. A two-dimensional numerical procedure is described 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 steam gross buoyancy during the gland steam ingestion phase by an equivalent fluid conductivity, that gives the same thermal effect on the metal parts. The fluid equivalent conductivity is calculated based on measurements. The approach is calibrated with experimental data. Finally, the highly sensitive nature of the cyclic lifetime to the predicted cooling evolution is demonstrated. This paper is complementary with the paper [1].

State of the Art Steam Turbine Automation for Optimum Transient Operation Performance

2007 ◽  
Author(s):  
Rainer Quinkertz ◽  
Edwin Gobrecht
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Operation Performance ◽  
Control Functions ◽  
Steam Power Plants ◽  
Start Up ◽  
Full Speed ◽  
Startup Performance

The growing share of renewable energies in the power industry coupled with increased deregulation has led to the need for additional operating flexibility of steam turbine units in both Combined Cycle and Steam Power Plants. Siemens steam turbine engineering and controls presently have several solutions to address various operating requirements: - Use of an automatic step program to perform startups allows operating comfort and repeatability. - 3 start-up modes give the operator the flexibility to start quickly to meet demand or slowly to conserve turbine life. - Several options for lifetime management are available. These options range from a basic counter of equivalent operating hours to a detailed fatigue calculation. - Restarting capabilities have been improved to allow a faster response following a trip or shutdown. - In addition to control of speed, load and pressure, special control functions provide alternative work split modes during transient conditions. - Optimum steam temperatures are calculated by the steam turbine control system to achieve optimum startup performance. - Siemens steam turbines are also capable of load rejection to house load, some even to operation at full speed, no load. Several plants are already equipped with these solutions and have provided data showing they are operating with shorter start-up times and improved load rejection capabilities. Finally Siemens of course continues to pursue future development.

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.

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.

A Simplified Analytical Approach for Calculating the Start-Up Time of Industrial Steam Turbines for Optimal and Fast Start-Up Procedures

2015 ◽  
Author(s):  
Wolfgang Beer ◽  
Lukas Propp ◽  
Lutz Voelker
Keyword(s):  
Steam Turbine ◽  
Analytical Approach ◽  
Three Dimensional ◽  
Steam Turbines ◽  
Time Step ◽  
One Dimensional ◽  
Start Up ◽  
Time Calculation ◽  
Fast Start ◽  
The One

New flexible operational regimes with fast start-ups and fast-changing load cycles for steam turbines require calculation procedures for determining optimal start-up times in order not to exceed the limits of thermal stress for the steam turbine parts. This work presents a start-up time calculation for various kinds of industrial steam turbines. An analytical approach for estimating the optimal thermal load of a turbine from quasi-steady or steady condition is developed. The geometry of the respective turbine components, the changing of the steam parameters and heat transfer effects during the start-up procedure are taken into account while observing the respective material properties and stress limits. The temperature distributions of the respective turbine parts are calculated with a one-dimensional numerical algorithm of Fourier’s heat conduction equation. Three-dimensional influences of the geometry and of the the heat flux are considered analytically by adjusting the numerical solutions of elementary bodies (e.g. one-dimensional plate). The start-up time calculation is performed in small time steps to guarantee the stability of the numerical solution. The unsteady stress analysis for the start-up procedure does not uniquely identify one critical component. The calculation must be repeated for each time step to identify the component which limits the start-up gradient. Other boundary conditions, such as restricted speed ranges of the rotor with minimum transients and time for synchronization with the electrical grid, are considered by the model too and can further limit the start-up gradient and lead to slower start-up procedures. The one-dimensional calculation models were verified with a three-dimensional FEA of the casing and a two axis symmetrical FEA of the rotor. The results for the temperature distribution are presented and compared to the one-dimensional results. The final result of the analytical approach for an optimized start-up time calculation is verified with two typical start-up calculations, one for a generator drive steam turbine and one for a mechanical-drive steam turbine.

Steam Turbine Hot Standby: Electrical Pre-Heating Solution

2019 ◽  
Author(s):  
Y. Kostenko ◽  
D. Veltmann ◽  
S. Hecker
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Steam Turbine ◽  
Power Plants ◽  
Heating System ◽  
Heating Process ◽  
Steam Turbines ◽  
Start Up ◽  
New Apparatus ◽  
General Aspects

Abstract Growing renewable energy generation share causes more irregular and more flexible operational regimes of conventional power plants than in the past. It leads to long periods without dispatch for several days or even weeks. As a consequence, the required pre-heating of the steam turbine leads to an extended power plant start-up time [1]. The current steam turbine Hot Standby Mode (HSM) contributes to a more flexible steam turbine operation and is a part of the Flex-Power Services™ portfolio [2]. HSM prevents the turbine components from cooling via heat supply using an electrical Trace Heating System (THS) after shutdowns [3]. The aim of the HSM is to enable faster start-up time after moderate standstills. HSM functionality can be extended to include the pre-heating option after longer standstills. This paper investigates pre-heating of the steam turbine with an electrical THS. At the beginning, it covers general aspects of flexible fossil power plant operation and point out the advantages of HSM. Afterwards the technology of the trace heating system and its application on steam turbines will be explained. In the next step the transient pre-heating process is analyzed and optimized using FEA, CFD and analytic calculations including validation considerations. Therefor a heat transfer correlation for flexible transient operation of the HSM was developed. A typical large steam turbine with an output of up to 300MW was investigated. Finally the results are summarized and an outlook is given. The results of heat transfer and conduction between and within turbine components are used to enable fast start-ups after long standstills or even outages with the benefit of minimal energy consumption. The solution is available for new apparatus as well as for the modernization of existing installations.

Sign in / Sign up

Export Citation Format

Share Document