Numerical Investigation of Steam Turbine Exhaust Diffuser Flows and Their Three Dimensional Interaction Effects on Last Stage Efficiencies

2014 ◽  
Author(s):  
Tadashi Tanuma ◽  
Yasuhiro Sasao ◽  
Satoru Yamamoto ◽  
Yoshiki Niizeki ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Steam Turbine ◽  
Numerical Investigation ◽  
Large Scale ◽  
Three Dimensional ◽  
Interaction Effects ◽  
Steam Turbines ◽  
Three Dimensional Flow ◽  
Flow Type ◽  
Last Stage

The purpose of this paper is to present the methodology for high accurate aerodynamic numerical analysis and its design application of steam turbine down-flow type exhaust diffusers including their three dimensional flow interaction effects on last stage efficiencies. Down-flow type exhaust diffusers are used in large scale steam turbines from 200MW to 1400MW class units for power generation plants mainly. The axial length of typical 1000MW class large scale steam turbines is about 30–40m and its four low pressure (LP) down-flow type exhaust diffusers occupy a large amount of space. The axial lengths and diameters of these exhaust diffusers contribute significantly to the size, weight, cost, and efficiency of the turbine system. The aerodynamic loss of exhaust hoods is nearly the same as that of stator and rotor blading in LP steam turbines, and there remains scope for further enhancement of steam turbine efficiency by improving the design of LP exhaust hoods. In the design process of last stages, the average static pressure in the last stage exit is introduced accurately using numerical analysis and experimental data of model steam turbines and model diffusers. However the radial and circumferential unsteady aerodynamic interaction effects between last stages and their exhaust diffusers are still need to be investigated to increase the accuracy of the interaction effect on the last stage efficiencies. This paper presents numerical investigation of three dimensional wet steam flows including three dimensional flow interaction effects on last stage efficiencies in a down-flow type exhaust diffuser with non-uniform inlet flow from a typical last stage with long transonic blades designed with recent aerodynamic and mechanical design technology.

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.

Numerical Investigation of Three-Dimensional Wet Steam Flows in an Exhaust Diffuser With Non-Uniform Inlet Flows From the Turbine Stages in a Steam Turbine

2012 ◽  
Author(s):  
Tadashi Tanuma ◽  
Yasuhiro Sasao ◽  
Satoru Yamamoto ◽  
Yoshiki Niizeki ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Numerical Investigation ◽  
Evaluation Method ◽  
High Efficiency ◽  
Mechanical Design ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Steam Turbines ◽  
Wet Steam ◽  
Low Pressure Turbine

The purpose of this paper is to present a numerical evaluation method for the aerodynamic design and development of high-efficiency exhaust diffusers in steam turbines, as well as to present the comparison between the numerical results and measured data in an actual real scale development steam turbine. This paper presents numerical investigation of three-dimensional wet steam flows in a down-flow-type exhaust diffuser that has non-uniform inlet flows from a typical last turbine stage. This stage has long transonic blades designed using recent aerodynamic and mechanical design technologies, including superimposed leakages and blade wakes from several upstream low pressure turbine stages. The present numerical flow analysis showed detail three-dimensional flow structures considering circumferential flow distributions caused by the down-flow exhaust hood geometry and the swirl velocity component from the last stage blades, including flow separations in the exhaust diffuser. The results were compared with experimental data measured in an actual development steam turbine. Consequently, the proposed aerodynamic evaluation method was proved to be sufficiently accurate for steam turbine exhaust diffuser aerodynamic designs.

Aerodynamic Interaction Effects From Upstream and Downstream on the Down-Flow Type Exhaust Diffuser Performance in a Low Pressure Steam Turbine

2013 ◽  
Author(s):  
Tadashi Tanuma ◽  
Yasuhiro Sasao ◽  
Satoru Yamamoto ◽  
Yoshiki Niizeki ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Low Pressure ◽  
Interaction Effects ◽  
Wet Steam ◽  
Inlet Flow ◽  
Flow Type ◽  
Diffuser Flow ◽  
Aerodynamic Interaction ◽  
Pressure Steam ◽  
Last Stage

The purpose of this paper is to explain aerodynamic interaction effects from upstream and downstream on the down-flow type exhaust diffuser performance in a low pressure steam turbine. To increase exhaust diffuser performance, design data related to the aerodynamic interaction effects from upstream turbine stages and downstream exhaust hood geometry on the exhaust diffuser performance would be very useful. This paper presents numerical investigation of three dimensional wet steam flows in a down-flow type exhaust diffuser with non-uniform inlet flow from a typical last stage with long transonic blades designed with recent aerodynamic and mechanical design technology. Previous studies show that small scale model tests and CFD analyses of exhaust diffusers with uniform inlet flow conditions are not enough to investigate diffuser efficiency and detail diffuser flow mechanism because inlet flow structures including tip leakage flows and blade wakes superimposed from a last stage and several other upstream turbine stages in low pressure turbines affect flow separations that reduce the exhaust diffuser performance. Recent studies by the authors show that the introduction of radial distributions of velocities and flow angles at the inlet section of exhaust diffuser measured in a full scale development steam turbine increased the accuracy of numerical analysis of diffuser flow. In the present study, the computational domain was enhanced and the method of boundary condition definition was improved to increase the accuracy of boundary layer separation and separation vortex generation in wet steam flows. Using the improved method, the calculation results explained the aerodynamic interaction effects from upstream and downstream on the down-flow type exhaust diffuser performance.

scholarly journals EXPERIMENTAL AND NUMERICAL ASSESSMENT OF A LAST STAGE ST BLADE DAMPING AT LOW LOAD OPERATION

2018 ◽  
Vol 20 ◽  
pp. 16-28
Author(s):  
Andrea Bessone ◽  
Luigi Carassale ◽  
Roberto Guida ◽  
Zdeněk Kubín ◽  
Antonio Alfio Lo Balbo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Steam Turbine ◽  
Software Tool ◽  
Test Plant ◽  
Steam Turbines ◽  
Aerodynamic Damping ◽  
Numerical Assessment ◽  
Low Load ◽  
Last Stage

As LP steam turbines are requested to work at strong part-loads, LSB stalled and unstalled flutter may occur. Testing on a downscaled steam turbine in T10MW test plant have been carried out to measure LSB aggregated damping at low load. Also numerical analysis to predict aerodynamic damping have been performed and results have been compared to experimental data, allowing software tool validation at low load.

Numerical Investigation on the Flow in Tip Clearance of the Last Three Stages of Industrial Steam Turbine

2014 ◽  
Vol 721 ◽  
pp. 78-81
Author(s):  
Zhao Jun Sha ◽  
Rong Xie ◽  
Xiao Fang Wang ◽  
Xu Dong Ding ◽  
Yong Feng Sui
Keyword(s):  
Steam Turbine ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Internal Flow ◽  
Tip Clearance ◽  
Wet Steam ◽  
Three Dimensional Flow ◽  
Two Phase ◽  
Computational Flow Dynamics ◽  
Three Stages

Numerical investigation was conducted on the full-three-dimensional flow in the last three stages of steam turbine using by the commercial computational flow dynamics software CFX. And the equilibrium condensation model was adopted to describe the wet steam two phase flows. This article analyzes the internal flow of the turbine with tip clearance and the structure of the leakage flow.

Investigation of Tip Clearance Flow Effects on an Open 3D Steam Turbine Flutter Test Case

2017 ◽  
Author(s):  
Tianrui Sun ◽  
Paul Petrie-Repar ◽  
Di Qi
Keyword(s):  
Steam Turbine ◽  
Large Scale ◽  
Numerical Models ◽  
Leading Edge ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Steam Turbines ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Last Stage

Blade failure caused by flutter is a major problem in the last stage of modern steam turbines. It is because rotor at this stage always has a large scale in spanwise, which provides low structural frequency as well as supersonic tip speeds. Since most of the unsteady aerodynamic work is done in the tip region, transonic tip-leakage flow that influences the tip region flow could have a remarkable effect on the aerodynamic stability of rotor blades. However, few research had been done on the tip-leakage flow influence on flutter characteristic based on full-scale steam turbine numerical models. In this paper, an open 3D steam turbine stage model designed by Durham University was applied, which was widely analyzed and representative for the last stage of modern industrial steam turbines. The average Mach number at the rotor outlet is 1.1. URANS simulation carried by both numerical software CFX and LUFT code is applied, and the two solvers show an agreement on steady and unsteady results. The numerical results indicate that the influence of tip leakage flow on blade stability is based on two types of flow mechanisms. Both mechanisms act on the suction side of near tip region. The first type of mechanism is produced by the reduction of passage shock near the leading edge, and the other type of mechanism at the rear of blade is caused by the interaction between tip leakage vortex and trailing edge shock of the neighbor blade. In conclusion, tip leakage flow has a significant influence on steam turbine flutter boundary prediction and requires further analysis in the future.

Non-Equilibrium Homogeneously Condensing Flow Analyses as Design Tools for Steam Turbines

2002 ◽  
Author(s):  
Shigeki Senoo ◽  
Yoshio Shikano
Keyword(s):  
Flow Pattern ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Design Stage ◽  
Steam Turbines ◽  
Three Dimensional Flow ◽  
Pattern Design ◽  
Flow Calculation ◽  
Dimensional Flow ◽  
Non Equilibrium

In order to get the details of flow fields in steam turbines, three-dimensional turbulent flow calculations are useful. However in a design procedure, three-dimensional flow calculations are only possible in the last design stage, because they need in-depth boundary conditions of both geometries and flows. At such a late time in the procedure, it is difficult to go back and change main design parameters, such as flow area and stage load. Both three-dimensional flow patterns and non-equilibrium condensation caused by rapid expansions of steam have important roles with respect to steam turbine performance particularly in low-pressure sections. The steam turbine internal efficiency can be improved by taking account of these effects in the early design stage, especially in flow pattern design. This paper describes a multi-stage through-flow calculation technique including both three-dimensional flow efffects and phase changes from vapour to small droplets. To compute the high-speed two phase steam flow, a flux-splitting procedure including non-equilibrium homogeneously condensation is introduced. Three-dimensional blade forces are calculated by using angles of both blade camber and radial lean. The blade camber lines can be decided without in-depth blade geometries. Therefore this computational technique is applicable in the flow pattern design. The calculation results agree well with fully three-dimensional flow calculation and the calculation can predict supersaturating states and Wilson lines which are defined as the maximum supercooling.

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 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.

Numerical Analysis of the Deterministic Stresses Associated to Impeller-Tongue Interactions in a Single Volute Centrifugal Pump

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
J. M. Fernández Oro ◽  
J. González ◽  
R. Barrio Perotti ◽  
M. Galdo Vega
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Centrifugal Pump ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Relevant Information ◽  
Three Dimensional Flow ◽  
Deterministic Analysis ◽  
Starting Point ◽  
Flow Features

In this paper, a deterministic stress decomposition is applied over the numerical three-dimensional flow solution available for a single volute centrifugal pump. The numerical model has proven in previous publications its robustness to obtain the impeller to volute-tongue flow interaction, and it is now used as starting point for the current research. The main objective has been oriented toward a detailed analysis of the lack of uniformity in the flow that the volute tongue promotes on the blade-to-blade axisymmetric pattern. Through this analysis, the fluctuation field may be retrieved and main interaction sources have been pinpointed. The results obtained with the deterministic analysis become of paramount interest to understand the different flow features found in a typical centrifugal pump as a function of the flow rate. Moreover, this postprocessing tool provides an economic and easy procedure for designers to compare the different deterministic terms, also giving relevant information on the unresolved turbulence intensity scales. Complementarily, a way to model the turbulent effects in a systematic way is also presented, comparing their impact on the performance with respect to deterministic sources in a useful framework, that may be applied for similar kinds of pumps.

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