Aerodynamic Optimization of the Nozzle for the Last Stage of Steam Turbine

2015 ◽  
Author(s):  
Aleš Macálka ◽  
Jaroslav Synáč ◽  
Jana Váchová ◽  
Miroslav Hajšman
Keyword(s):  
Design Process ◽  
Energy Demand ◽  
Cfd Simulation ◽  
Latin Hypercube Sampling ◽  
Optimized Design ◽  
Steam Turbines ◽  
Aerodynamic Optimization ◽  
Transient Time ◽  
Low Pressure Turbine ◽  
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 of a low pressure turbine (LP). This paper focuses on aerodynamic study by compound lean, axial sweep and hub end-wall of nozzle. The objective function is to maximize efficiency and minimize the leaving losses under the assumption of constant mass flow rate. The aerodynamic design process involves commercial 3D CFD tools. The maximization of the objective functions is achieved by means of a Design of Experiment (DoE) method “Optimal Space Filling” based on “Latin Hypercube Sampling”. Finally, the optimized design is analyzed by a transient (Time Transformation) CFD simulation. Furthermore, the detailed flow pattern of the optimized and the initial design is analyzed and compared.

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.

Vibration Investigation for Low Pressure Turbine Last Stage Blade Failure in Steam Turbines of a Power Plant

2012 ◽  
Author(s):  
Jyoti K. Sinha ◽  
W. Hahn ◽  
K. Elbhbah ◽  
G. Tasker ◽  
I. Ullah
Keyword(s):  
Power Generation ◽  
Power Plant ◽  
Steam Turbines ◽  
Cause Analysis ◽  
Low Pressure Turbine ◽  
Root Cause ◽  
Turbo Generator ◽  
Last Stage ◽  
Blade Failure

West Burton Power Plant, UK owned by EDF energy has 4 steam turbo-generator (TG) units for power generation. These units were installed and commissioned between 1967 and 1969 and have since operated smoothly without any major problems up to 2007. In 1995 and 1996, two TG sets, namely units 2 and 3, were retrofitted with the new design LP rotors and in 2005, retrofitting of HP rotor for all four TG units was commenced. The retrofitting was done without changing the foundation, but only with the aim to enhance the power output by 20MW (10 MW through LP retrofit and 10MW through HP retrofit). Cracking of the last stage blades of LP1 and LP2 turbine, steam-end blades has been observed in TG units 2 and 3 only. Hence the in-situ vibration measurements have been carried out on TG unit 3 and compared with healthy TG unit 1 to understand the dynamics of both units. This paper presents observations made on the dynamics of TG units 1 and 3, and results from the root cause analysis which may possibly lead to the solution to the blade failure problem in TG units 2 and 3.

Aerodynamic Optimization of the Diffuser Towards Improving the Performance of Turbine and Exhaust Hood

2014 ◽  
Author(s):  
Jing-Lun Fu ◽  
Jian-Jun Liu ◽  
Si-Jing Zhou
Keyword(s):  
Kinetic Energy ◽  
Aerodynamic Performance ◽  
Steam Turbines ◽  
Exhaust Hood ◽  
Aerodynamic Optimization ◽  
Operational Conditions ◽  
Flow Interactions ◽  
Overall Performance ◽  
Last Stage ◽  
End Wall

Exhaust hood of large steam turbines is designed to recover the leaving kinetic energy of the last stage turbine while guiding the flow from the turbine to the condenser, which is of great importance to the overall performance of the steam turbine. The influences imposed by the strong flow interactions between the last stage turbine and the non-axisymmetric exhaust hood have not been taken into account properly in the current exhaust hood design approaches. The purpose of this paper is to optimize the diffuser in order to guarantee the aerodynamic performance of the turbine and the exhaust hood under the operational conditions. Considering the flow interactions between the turbine and the exhaust hood, the profiles of the diffuser end-wall were improved. The coupled turbine and exhaust hood calculations and the experiments were carried out to validate the effects of the optimization. It’s found that the redesigned diffuser can enhance the pressure recovery ability of the exhaust hood and increase the power output of the last stage turbine.

Survey of Twisted Blading Development in Steam Turbines

1969 ◽  
Vol 184 (1) ◽  
pp. 449-474 ◽  
Author(s):  
A. Smith
Keyword(s):  
Steam Turbine ◽  
Low Pressure ◽  
Scale Model ◽  
Steam Turbines ◽  
Power Station ◽  
Low Pressure Turbine ◽  
Last Stage ◽  
Turbine Blading

The development of steam turbine blading with high tip to hub diameter ratios over the last 50 years has been traced with particular emphasis on the reasons for adopting twisted blading in low pressure turbines. The aerodynamic concepts of the more generally accepted design bases for twisted blading are discussed and comparisons made between the efficiencies of selected twisted designs and straight blading. Current methods in the development of transonic low pressure blading for large 3000 rev/min central power station units are also described and the paper concludes by comparing the theoretical and measured steam angles across the last stage of a one-third scale model of a 136-in tip diameter low pressure turbine.

A Novel Evaluation Procedure for the Prediction and Assessment of Diffuser Humming in Steam Turbines

2018 ◽  
Author(s):  
Johannes Tusche ◽  
Christian Musch
Keyword(s):  
The Other ◽  
Evaluation Procedure ◽  
Steam Turbines ◽  
Test Rig ◽  
Basic Principles ◽  
Fluctuating Pressure ◽  
Low Pressure Turbine ◽  
Blade Row ◽  
Comprehensive Test ◽  
Last Stage

The mechanical integrity of turbine blade rows might be compromised by transient aerodynamic effects that occur in interaction with the diffuser. Effectively addressing this issue requires the prediction of the effects and the creation of a basis for their evaluation. This paper focuses on the specific case of diffuser humming in steam turbines. The paper describes the results obtained from two turbine diffusers with different pulsation frequencies calculated and tested under identical conditions. One diffuser forced a resonance of the last-stage blade row, while the other diffuser ensured the absence of resonance. The basic principles are described that allow estimating and quantifying the pulsation frequencies of the fluctuating pressure. To evaluate the developed approach comprehensive test runs were conducted using a Siemens low-pressure turbine test rig. These measured results are shown to provide validation of the calculation method.

Development of Highly Efficient and Robust Ultra-Long Last Stage Blade for High Backpressure

2019 ◽  
Author(s):  
Ondrej Novak ◽  
Marek Bobcik ◽  
Vaclav Slama ◽  
Bartolomej Rudas ◽  
Josef Kellner ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Operating Conditions ◽  
Thermodynamic Efficiency ◽  
Steam Turbines ◽  
Supersonic Wind Tunnel ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Blade Shape ◽  
Last Stage ◽  
Very High

Abstract For modern steam turbines with large operating range and enhanced efficiency an ultra-long last stage rotor blade in a low pressure turbine part for high backpressure and 50 Hz fixed speed operation have been developed. An advanced design approach was used to create the blade shape with a high thermodynamic efficiency, high natural frequencies and a very high safety factor of average radial static stress in the blade span. Furthermore, the tip section of the bucket was improved to decrease a static tension and the hub section was refined to simplify the assembly. Tip and hub airfoils were experimentally validated in a supersonic wind tunnel. An advanced in-house procedure using numerical analysis to predict a potential danger of unstalled flutter was carried out for wide range of operating conditions.

Modeling of a Steam Turbine Including Partial Arc Admission for Use in a Process Simulation Software Environment

2011 ◽  
Author(s):  
Eric Liese
Keyword(s):  
Steam Turbine ◽  
Process Simulation ◽  
Process Model ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Simulation Software ◽  
State Variables ◽  
Steam Turbines ◽  
Software Environment ◽  
Last Stage

A dynamic process model of a steam turbine, including partial arc admission operation, is presented. Models were made for the first stage and last stage, with the middle stages presently assumed to have a constant pressure ratio and efficiency. A condenser model is also presented. The paper discusses the function and importance of the steam turbines entrance design and the first stage. The results for steam turbines with a partial arc entrance are shown, and compare well with experimental data available in the literature, in particular, the “valve loop” behavior as the steam flow rate is reduced. This is important to model correctly since it significantly influences the downstream state variables of the steam, and thus the characteristic of the entire steam turbine, e.g., state conditions at extractions, overall turbine flow, and condenser behavior. The importance of the last stage (the stage just upstream of the condenser) in determining the overall flowrate and exhaust conditions to the condenser is described and shown via results.

Development of a Last Stage Blade Row Coupled by Damping Elements: Numerical Assessment of its Vibrational Behavior and its Experimental Validation During Spin Pit Measurements

2017 ◽  
Author(s):  
Christian Siewert ◽  
Frank Sieverding ◽  
William J. McDonald ◽  
Manish Kumar ◽  
James R. McCracken
Keyword(s):  
Structural Integrity ◽  
Mechanical Design ◽  
Vibration Response ◽  
Dynamic Loads ◽  
Steam Turbines ◽  
Response Level ◽  
Vibrational Behavior ◽  
Blade Row ◽  
Calculation Results ◽  
Last Stage

Last stage blade rows of modern low pressure steam turbines are subjected to high static and dynamic loads. The static loads are primarily caused by the centrifugal forces due to the steam turbine’s rotational speed. Dynamic loads can be caused by instationary steam forces, for example. A primary goal in the design of modern and robust blade rows is to prevent High Cycle Fatigue caused by dynamic loads due to synchronous or non-synchronous excitation mechanisms. Therefore, it is important for the mechanical design process to predict the blade row’s vibration response. The vibration response level of a blade row can be limited by means of a damping element coupling concept. Damping elements are loosely assembled into pockets attached to the airfoils. The improvement in the blade row’s structural integrity is the key aspect in the use of a damping element blade coupling concept. In this paper, the vibrational behavior of a last stage blade row with damping elements is analyzed numerically. The calculation results are compared to results obtained from spin pit measurements for this last stage blade row coupled by damping elements.

Development of 1500-r/min 75-Inch Ultra-Long Last Stage Blades for Nuclear Steam Turbine

2017 ◽  
Author(s):  
Deqi Yu ◽  
Jiandao Yang ◽  
Wei Lu ◽  
Daiwei Zhou ◽  
Kai Cheng ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Large Scale ◽  
Vibration Monitoring ◽  
Steam Turbines ◽  
Element Analysis ◽  
Rotating Blade ◽  
Lifetime Analysis ◽  
Computational Fluid Dynamics Cfd ◽  
Last Stage

The 1500-r/min 1905mm (75inch) ultra-long last three stage blades for half-speed large-scale nuclear steam turbines of 3rd generation nuclear power plants have been developed with the application of new design features and Computer-Aided-Engineering (CAE) technologies. The last stage rotating blade was designed with an integral shroud, snubber and fir-tree root. During operation, the adjacent blades are continuously coupled by the centrifugal force. It is designed that the adjacent shrouds and snubbers of each blade can provide additional structural damping to minimize the dynamic stress of the blade. In order to meet the blade development requirements, the quasi-3D aerodynamic method was used to obtain the preliminary flow path design for the last three stages in LP (Low-pressure) casing and the airfoil of last stage rotating blade was optimized as well to minimize its centrifugal stress. The latest CAE technologies and approaches of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and Fatigue Lifetime Analysis (FLA) were applied to analyze and optimize the aerodynamic performance and reliability behavior of the blade structure. The blade was well tuned to avoid any possible excitation and resonant vibration. The blades and test rotor have been manufactured and the rotating vibration test with the vibration monitoring had been carried out in the verification tests.

Design Optimization of a Low Pressure Steam Turbine Radial Diffuser Using an Evolutionary Algorithm and 3D CFD

2012 ◽  
Author(s):  
Tom Verstraete ◽  
Johan Prinsier ◽  
Alberto Di Sante ◽  
Stefania Della Gatta ◽  
Lorenzo Cosi
Keyword(s):  
Design Optimization ◽  
Steam Turbine ◽  
Differential Evolution Algorithm ◽  
Low Pressure ◽  
Pressure Recovery ◽  
Strong Impact ◽  
Optimized Design ◽  
Steam Turbines ◽  
Recovery Coefficient ◽  
Lp Turbine

The design of the radial exhaust hood of a low pressure (LP) steam turbine has a strong impact on the overall performance of the LP turbine. A higher pressure recovery of the diffuser will lead to a substantial higher power output of the turbine. One of the most critical aspects in the diffuser design is the steam guide, which guides the flow near the shroud from axial to radial direction and has a high impact on the pressure recovery. This paper presents a method for the design optimization of the steam guide of a steam turbine for industrial power generation and mechanical drive of centrifugal compressors. This development is in the frame of a continuous effort in GE Oil and Gas to develop more efficient steam turbines. An existing baseline exhaust and steam guide design is first analyzed together with the last LP turbine stage with a frozen rotor full 3D Computational Fluid Dynamics (CFD) calculation. The numerical prediction is compared to available steam test turbine data. The new exhaust box and a first attempt new steam guide design are then first analyzed by a CFD computation. The diffuser inlet boundary conditions are extracted from this simulation and used for improving the design of the steam guide. The maximization of the pressure recovery is achieved by means of a numerical optimization method that uses a metamodel assisted differential evolution algorithm in combination with a 3D CFD solver. The profile of the steam guide is parameterized by a Bezier curve. This allows for a wide variety of shapes, respecting the manufacturability constraints of the design. In the design phase it is mandatory to achieve accurate results in terms of performance differences in a reasonable time. The pressure recovery coefficient is therefore computed through the 3D CFD solver excluding the last stage, to reduce the computational burden. Steam tables are used for the accurate prediction of the steam properties. Finally, the optimized design is analyzed by a frozen rotor computation to validate the approach. Also off-design characteristics of the optimized diffuser are shown.

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