scholarly journals Preheating procedure for fast start-up of a steam turbine from a cold state

2019 ◽  
Vol 137 ◽  
pp. 01024
Author(s):  
Wojciech Kosman ◽  
Andrzej Rusin
Keyword(s):  
Steam Turbine ◽  
Thermal State ◽  
Initial Period ◽  
Electric Heater ◽  
Cold State ◽  
Hot Air ◽  
Start Up ◽  
Maximal Stress ◽  
Fast Start ◽  
Start Ups

The paper describes a procedure that allows to start up a steam turbine in a significantly shorter period. The procedure is developed for start-ups that begin from a cold state, when the temperature of the parts of the turbine is close to the ambient temperature. The pre-heating rises the parts temperature before the actual start-up begins. It changes the thermal state of the turbine and causes smaller maximal stress during the initial period of the start-up. The procedure involves a pre-heating of the turbine with a hot air generated in an electric heater. The paper describes the requirements of the process. It presents the possible configurations of the flow in the turbine and the analysis of the thermal and the strength state of the turbine during the pre-heating.

Model-Based Analysis of the Start-Up Improvement of a CCPP due to Steam Turbine Warm-Keeping With Air

2019 ◽  
Author(s):  
Dennis Toebben ◽  
Tobias Burgard ◽  
Sebastian Berg ◽  
Manfred Wirsum ◽  
Liu Pei ◽  
...  
Keyword(s):  
Power Plant ◽  
Steam Turbine ◽  
Power Plants ◽  
Cold Start ◽  
Nox Emissions ◽  
Data Set ◽  
Water Steam ◽  
Hot Air ◽  
Start Up ◽  
Low Load

Abstract Combined cycle power plants (CCPP) have many advantages compared to other fossil power plants: high efficiency, flexible operation, compact design, high potential for combined heat and power (CHP) applications and fewer emissions. However, fuel costs are relatively high compared to coal. Nevertheless, major qualities such as high operation flexibility and low emissions distinctly increase in relevance in the future, due to rising power generation from renewable energy sources. An accelerated start-up procedure of CCPPs increases the flexibility and reduces the NOx-emissions, which are relatively high in gas turbine low load operation. Such low load operation is required during a cold start of a CCPP in order to heat up the steam turbine. Thus, a warm-keeping of the thermal-limiting steam turbine results in an accelerated start-up times as well as reduced NOx-emissions and lifetime consumption. This paper presents a theoretical analysis of the potential of steam turbine warm-keeping by means of hot air for a typical CCPP, located in China. In this method, the hot air passes through the steam turbine while the power plant is shut off which enables hot start conditions at any time. In order to investigate an improved start-up procedure, a physical based simplified model of the water-steam cycle is developed on the basis of an operation data set. This model is used to simulate an improved power plant start-up, in which the steam turbine remains hot after at least 120 hours outage. The results show a start-up time reduction of approximately two-thirds in comparison to a conventional cold start. Furthermore, the potential of steam turbine warm-keeping is discussed with regards to the power output, NOx-emissions, start-up costs and lifetime consumption.

scholarly journals X-Ray Measurements in a Cavitating Centrifugal Pump During Fast Start-Ups

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
G. Bois
Keyword(s):  
Centrifugal Pump ◽  
Rocket Engine ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
X Ray ◽  
Speed Increase ◽  
Start Up ◽  
Fast Start ◽  
Start Ups

The start-up of rocket engine turbopumps is generally performed in a few seconds or even less. It implies that these pumps reach their nominal operating conditions after a few rotations only. During the start-up, the flow evolution within the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed increase. Significant pressure fluctuations, which may result in the development of cavitation, are observed. A centrifugal impeller whose transient behavior during start-ups has been detailed in a previous publication is considered. Three different cases of fast start-ups have been identified according the final operating point (Duplaa et al., 2010, “Experimental Study of a Cavitating Centrifugal Pump During Fast Start-Ups,” ASME J. Fluids Eng., 132(2), p. 021301). The aim of this paper is to analyze the evolution during the start-ups of the local amount of vapor in the blade to blade channels of the pump by fast X-ray imaging. This technique has enabled to calculate the time-evolution of the fluid density within the pump, which appears to be correlated with pressure time-evolutions. For each investigated start-up, X-ray measurements have been performed at three different sections of the impeller height. For each investigated start-up and section tested, measurements have been performed for several initial positions of the impeller, to estimate the measurement uncertainty, and to obtain records from different beam angles, like in tomography.

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.

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

2021 ◽  
Author(s):  
Piotr Luczynski ◽  
Lukas Pehle ◽  
Manfred Wirsum ◽  
Jan Vogt ◽  
Wolfgang F. D. Mohr ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Steam Turbine ◽  
Hot Air ◽  
Start Up

Utilization of a Thermo-Mechanical Model Coupled With Multi-Objective Optimization to Enhance the Start-Up Process of Solar Steam Turbines

2018 ◽  
Author(s):  
Monika Topel ◽  
Andrea Vitrano ◽  
Björn Laumert
Keyword(s):  
Steam Turbine ◽  
Solar Power ◽  
Low Cycle Fatigue ◽  
Steam Turbines ◽  
Multi Objective Optimization ◽  
Concentrating Solar Power ◽  
Multi Objective ◽  
Start Up ◽  
Turbine Component ◽  
Start Ups

The need to mitigate the climate change has brought in the last years to a fast rise of renewable technologies. The inherent fluctuations of the solar resource make concentrating solar power technologies an application that demands full flexibility of the steam turbine component. A key aspect of this sought steam turbine flexibility is the capability for fast starts, in order to harvest the solar energy as soon as it is available. However, turbine start-up time is constrained by the risk of low cycle fatigue damage due to thermal stress, which may bring the machine to failure. Given that the thermal limitations related to fatigue are temperature dependent, a transient thermal analysis of the steam turbine during start process is thus necessary in order to improve the start-up operation. This work focuses on the calculation of turbine thermo-mechanical properties and the optimization of different start-up cases in order to identify the best solution in terms of guaranteeing reliable and fast start-ups. In order to achieve this, a finite element thermal model of a turbine installed in a concentrating solar power plant was developed and validated against measured data. Results showed relative errors of temperature evolutions below 2%, making valid the assumptions and simplifications made. Since there is trade-off between start-up speed and turbine lifetime consumption, the model was then implemented within a multi-objective optimization scheme in order to test and design faster start-ups while ensuring safe operation of the machine. Significant improvements came up in terms of start-up time reduction up to 30% less than the standard start-up process.

Numerical Investigation of the Heat Transfer and Flow Phenomena in an IP Steam Turbine in Warm-Keeping Operation With Hot Air

2017 ◽  
Author(s):  
Dennis Toebben ◽  
Piotr Łuczyński ◽  
Mathias Diefenthal ◽  
Manfred Wirsum ◽  
Stefan Reitschmidt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Steam Turbine ◽  
Flow Structure ◽  
Conjugate Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Hot Air ◽  
Start Up ◽  
Flow Phenomena

Nowadays, steam turbines in conventional power plants deal with an increasing number of startups due to the high share of fluctuating power input of renewable generation. Thus, the development of new methods for flexibility improvements, such as reduction of the start-up time and its costs, have become more and more important. At the same time, fast start-up and flexible steam turbine operation increase the lifetime consumption and reduce the inspection intervals. One possible option to prevent these negative impacts of a flexible operation is to keep the steam turbine warm during a shut down and a startup. In order to do so, General Electric has developed a concept for warm-keeping respectively pre-warming of a high-pressure (HP) / intermediate-pressure (IP) steam turbine with hot air: After a certain cool-down phase, air is passed through the turbine while the turbine is rotated by the turning engine. The flow and the rotational direction can be inverted to optimize the warming operation. In order to fulfill the requirements of high flexibility in combination with reduced costs and thermal stresses during the start-up, a detailed investigation of the dominant heat transfer effects and the corresponding flow structure is necessary: Complex numerical approaches, such as Conjugate Heat Transfer (CHT), can provide this corresponding information and help to understand the physical impact of the flow phenomena. The aim of the present work is thus to understand the predominant heat transport phenomena in warm-keeping operation and to gain detailed heat transfer coefficients within the flow channel for blade, vane and shrouds. A multitude of steady-state simulations were performed to investigate the different warm-keeping operation points. Data from literature was recomputed in good agreement to qualitatively validate the numerical model in windage operation. Furthermore, the steady-state simulations were compared with transient Computational Fluid Dynamics (CFD) simulations to verify that the flow in warming operation can be simulated with a steady-state case. The transient calculations confirm the steady-state results. A variation of the mass flow rate and the rotational speed was conducted to calculate a characteristic map of heat transfer coefficients. The Conjugate Heat Transfer simulations provide an insight into the flow structure and offer a comparison with the flow phenomena in conventional operation. In addition, the impact of the flow phenomena on the local heat transfer was investigated.

High Steam Turbine Operating Flexibility Coupled With Service Interval Optimization

2003 ◽  
Author(s):  
Artur Ulbrich ◽  
Edwin Gobrecht ◽  
Michael R. Siegel ◽  
Erich Schmid ◽  
Pamela K. Armitage
Keyword(s):  
Steam Turbine ◽  
Service Time ◽  
Power Plants ◽  
Economic Calculation ◽  
Stress Monitoring ◽  
Time Consumption ◽  
Start Up ◽  
Fast Start ◽  
The Impact ◽  
Base Load

Historically steam turbine operations were designed for a market that was typically either base load or intermediate duty load operation. The optimal steam turbine start-up profile was established using the maximum allowable component stress and therefore optimizing service time consumption. Over the last few years, the market requirements have changed significantly. The market requires plant start-up flexibility with the ability to accurately predict start-up time, and reliably meet the start-up time. Applying the historical steam turbine start-up philosophy either limits the operating flexibility of the plant or exceeds steam turbine allowable stresses increasing service time consumption. Innovative concepts are being presented on how steam turbines can achieve reduced start-up times while minimizing service time consumption thereby improving availability. These concepts allow the customer to be able to accurately predict start-up times and reliably meet the dispatch bid. Therefore, an economic calculation may be performed to determine the most effective start-up mode. This economic calculation will evaluate the impact to service life (inspection and test intervals) versus the benefits of power generation. The new concepts provide one solution for base load, intermediate duty load operation, and plants requiring fast start up capability. The new market needs for flexible operation including fast start-up times require plant operability enhancements [1]. Some of the operability enhancements that can be implemented include: • steam turbine stress controller and stress monitoring systems which allow a selection of the start-up mode determining the start-up time, thermal stress and service time consumption; • high level of plant automation; • plant systems designed to provide steam conditions necessary for selected start-up mode. The benefit of these solutions will be presented by means of examples from recently modified power plants. It is possible to achieve a significant improvement in the plant operation and start-up with low costs.

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

2021 ◽  
Author(s):  
Piotr Luczynski ◽  
Lukas Pehle ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
Jan Vogt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Thermal Contact ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Operating Modes ◽  
Hot Air ◽  
Start Up ◽  
Simulation Strategy ◽  
Transient Thermal

Abstract In this paper, the transient thermal and structural analyses of a 19-stage IP steam turbine in various start-up operating modes are discussed. The research 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 analytical correlations to describe heat transfer in the turbine channel. These are developed by means of unsteady multistage conjugate heat transfer simulations for both start-up turbine operation with steam and pre-warming operation with hot air. Moreover, the numerical setup of the HFEM model 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 analytic pressure model to allow for a consideration of condensation effects during first phase of start-up procedure. Finally, the presented thermal investigation focuses on the comparison of transient temperature fields in the turbine for different start-up scenarios after pre-warming with hot air and provides the subsequent structural investigation with boundary conditions. As a result, the values of the highest stress are numerically determined and compared to the values obtained by means of cold start-up simulation.

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.

Comparison of Steam Turbine Pre-Warming and Warm-Keeping Strategies Using Hot Air for Fast Turbine Start-Up

2021 ◽  
Author(s):  
Lukas Pehle ◽  
Piotr Luczynski ◽  
Taejun Jeon ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Hot Air ◽  
Start Up
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