Effect of Steam Injection on Last-Stage Blade Temperature of Low Pressure Steam Turbine at Low Volume Flow Condition

2017 ◽  
Author(s):  
Can Ma ◽  
Jun Wu ◽  
Yuansheng Lin
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Steam Injection ◽  
Low Pressure ◽  
Volume Flow ◽  
Pressure Steam ◽  
Last Stage ◽  
Low Volume

In the nuclear power plant, the last stage of the low pressure steam turbine is characterized by long blades. These long blades operate under severe working conditions with wet steam flow and strong mechanical stress. At the start up and shut down operating condition where the volume flow is extremely low, the last stage blades operate in ventilation conditions where there is significant reverse flow in the exhaust and the last stage. In such a condition, the reverse flow would cause significant increase in the blade temperature. In addition, the rotating reverse flow would increase the vibration of the rotor blade. Such temperature increase and enhanced vibration can cause blade damage and force the machine to be shut down. In previous work, the steam injection in the last stage has been proposed as a promising method to decrease the reverse flow at low volume flow conditions, which reduces the stall cell size in the last stage blade. This work investigates the effect of the steam injection process on the blade temperature distribution by conducting three-dimensional flow simulations. Various steam injection configurations are compared in this work and the major consideration to be noted in the design process is discussed.

Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine

2014 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Arne Graßmann
Keyword(s):  
Steam Turbine ◽  
Design Process ◽  
Energy Demand ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Pressure Steam ◽  
Last Stage

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.

On the Prediction and Theory of the Temperature Increase of Low Pressure Last Stage Moving Blades During Low Volume Flow Conditions, and Limiting it Through Steam Extraction Methods

2014 ◽  
Author(s):  
Adam Beevers ◽  
Said Havakechian ◽  
Benjamin Megerle
Keyword(s):  
Steam Turbine ◽  
Temperature Increase ◽  
Low Pressure ◽  
Volume Flow ◽  
Flow Conditions ◽  
Steam Extraction ◽  
Last Stage ◽  
Low Volume ◽  
Critical Regions ◽  
Ventilation Conditions

During extreme low volume flow conditions, the last stages of a low pressure steam turbine operate in ventilation conditions that can cause a significant temperature increase of critical regions of the last stage moving blade. Under some conditions, the blade temperature may rise above a safe operating temperature, requiring the machine to be shut down. Limiting the heating effect on the last stage moving blade increases the allowable operating range of the low pressure turbine. One common method is to spray water droplets into the low pressure exhaust. As the length of last stage moving blades continues to increase, this method reaches its limit of practical operating effectiveness due to the amount of water required and its impact on the erosion of the LSB. An investigation into complimentary solutions to limit the temperature increase was conducted using CFD. An appropriate CFD setup was chosen from a sensitivity study on the effect of geometry, mesh density, turbulence model and time dependency. The CFD results were verified against steam turbine data from a test facility. The proposed complimentary solutions to limit the temperature increase include low temperature steam extraction, targeted for critical regions of the moving blade. From the test turbine and CFD results, the drivers of the temperature increase during ventilation conditions are identified and described.

On the Prediction and Theory of the Temperature Increase of Low Pressure Last Stage Moving Blades During Low Volume Flow Conditions, and Limiting it Through Steam Extraction Methods

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Adam Beevers ◽  
Said Havakechian ◽  
Benjamin Megerle
Keyword(s):  
Steam Turbine ◽  
Temperature Increase ◽  
Low Pressure ◽  
Volume Flow ◽  
Flow Conditions ◽  
Steam Extraction ◽  
Last Stage ◽  
Low Volume ◽  
Critical Regions ◽  
Ventilation Conditions

During extreme low volume flow conditions, the last stages of a low pressure steam turbine operate in ventilation conditions that can cause a significant temperature increase of critical regions of the last stage moving blade (LSB). Under some conditions, the blade temperature may rise above a safe operating temperature, requiring the machine to be shut down. Limiting the heating effect on the LSB increases the allowable operating range of the low pressure turbine. One common method is to spray water droplets into the low pressure exhaust. As the length of LSBs continues to increase, this method reaches its limit of practical operating effectiveness due to the amount of water required and its impact on the erosion of the LSB. An investigation into complimentary solutions to limit the temperature increase was conducted using CFD. An appropriate CFD setup was chosen from a sensitivity study on the effects from geometry, mesh density, turbulence model, and time dependency. The CFD results were verified against steam turbine data from a scaled test facility. The proposed solutions include low temperature steam extraction, targeted for critical regions of the moving blade. From the test turbine and CFD results, the drivers of the temperature increase during ventilation conditions are identified and described.

scholarly journals Failure Analysis in Lacing Wire Of Last Stage Low Pressure Steam Turbine Blade

2021 ◽  
Vol 1096 (1) ◽  
pp. 012097
Author(s):  
A M Kongkong ◽  
H Setiawan ◽  
J Miftahul ◽  
A R Laksana ◽  
I Djunaedi ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Steam Turbine ◽  
Turbine Blade ◽  
Low Pressure ◽  
Pressure Steam ◽  
Steam Turbine Blade ◽  
Last Stage

Some Aspects of CFD Modeling in the Analysis of a Low-Pressure Steam Turbine

2007 ◽  
Author(s):  
Filippo Rubechini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Stefano Cecchi ◽  
Federico Dacca`
Keyword(s):  
Steam Turbine ◽  
Computational Cost ◽  
Three Dimensional ◽  
Low Pressure ◽  
Design Tool ◽  
Cfd Modeling ◽  
Navier Stokes ◽  
Sources And Sinks ◽  
Leakage Flows ◽  
Pressure Steam

A three-dimensional, multistage, Navier-Stokes solver is applied to the numerical investigation of a four stage low-pressure steam turbine. The thermodynamic behavior of the wet steam is reproduced by adopting a real-gas model, based on the use of gas property tables. Geometrical features and flow-path details consistent with the actual turbine geometry, such as cavity purge flows, shroud leakage flows and partspan snubbers, are accounted for, and their impact on the turbine performance is discussed. These details are included in the analysis using simple models, which prevent a considerable growth of the computational cost and make the overall procedure attractive as a design tool for industrial purposes. Shroud leakage flows are modeled by means of suitable endwall boundary conditions, based on coupled sources and sinks, while body forces are applied to simulate the presence of the damping wires on the blades. In this work a detailed description of these models is provided, and the results of computations are compared with experimental measurements.

Sensors and Methods for Blade Damage Operational Assessment in Low-Pressure Steam Turbine Stages

2013 ◽  
Vol 569-570 ◽  
pp. 726-733 ◽  
Author(s):  
Pavel Procházka ◽  
František Vaněk
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Residual Life ◽  
Turbine Blades ◽  
Low Pressure ◽  
Mutual Position ◽  
Static Characteristics ◽  
New Approach ◽  
Pressure Steam

The study deals with the opportunities for the assessment of damage to blades in low-pressure steam turbine stages under operation. So far existing methods are based on measurements and evaluation of blade vibrations. Calculations of fatigue cycles are used as a basis for an estimate of the residual life of the blades. A new approach using the analysis of impulse blade signals generated by non-contact stator sensors was applied. Basis for the assessment of blade damage are static characteristics and mutual position of blades. Geometrical and mechanical characteristics of blades change due to creation and progress of a crack. The presence of the crack leads to a change in position between adjacent blades. This method has been applied and verified by long-term measurements at the nuclear power plant Temelin. Other static methods based on blade untwisting and elongation are suggested for monitoring the state of turbine blades.

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