Effects of Design Variations of Rotor Entry Cavity Geometry on Shrouded Steam Turbine Performance

2010 ◽  
Author(s):  
K. G. Barmpalias ◽  
A. I. Kalfas ◽  
R. S. Abhari ◽  
Toshio Hirano ◽  
Naoki Shibukawa
Keyword(s):  
Steam Turbine ◽  
Constant Width ◽  
Main Flow ◽  
Volume Reduction ◽  
Efficiency Gain ◽  
Cavity Volume ◽  
Turbine Performance ◽  
Baseline Case ◽  
Stage Performance ◽  
Stage Efficiency

This paper presents an experimental study of the effect of geometry variations of the rotor entry cavity on shrouded steam turbine performance. A series of experiments was carried out where different configurations of the geometry of the entry cavity were tested. Blade geometry and tip clearance remained unaltered for all cases examined. Interactions between cavity and main flow are carefully investigated and their consequences on shrouded steam turbine stage efficiency are examined. Geometry variations of the entry cavity were installed in a pre-existing ‘baseline’ case of high efficiency. Five different test cases were examined. For the first two of these cases a ring having a constant width of 2mm and 4mm in radial direction is used. The next two cases employ a non-uniform, wavy insert and for the last case a backwards slanted insert is used that covers most of the inlet to cavity area, maintaining a safety distance of 2mm from the downstream rotor. The cases are divided into two groups, based on the same inlet cavity volume. The first group of three cases has a cavity volume reduction of 14% compared to the baseline case, whereas in the second group two cases are examined which maintain a 28% cavity volume reduction compared to the baseline case. Stage performance and flow field data were acquired and analyzed. Strong interactions between cavity and main flow are observed for all cases, not only at the location where the variations were installed. An observed effect can also be seen downstream of the rotor affecting the stage performance. Measurements were performed with the use of miniature probes ensuring minimum blockage effects especially within the cavity, both at rotor inlet as well as downstream of the second rotor. The use of a uniform geometry variation for the inlet rotor cavity in both groups proved to be the best in terms of stage efficiency. Although more complex and non-uniform variations were also used, the simple design of uniform geometry caused the least disturbance in the flow downstream of the 2nd rotor, having at the same time a moderate positive influence at the exit of the 2nd stator. The use of a constant width insert ring (thickness = 2mm) showed an efficiency gain of at least 0.3% from cases with 14% cavity volume reduction, whereas in the cases with 28% cavity volume reduction the use of a uniform ring of 4mm width produced a marginal efficiency gain of 0.1% at the operational point.

Design Considerations for Axial Steam Turbine Rotor Inlet Cavity Volume and Length Scale

2011 ◽  
Author(s):  
Konstantinos G. Barmpalias ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Toshio Hirano ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Turbine Rotor ◽  
Volume Reduction ◽  
Length Scale ◽  
Toroidal Vortex ◽  
Cavity Volume ◽  
Design Considerations ◽  
Baseline Case ◽  
Design Perspective ◽  
Reduction Case

In this paper we examine the interaction between the cavity and main flows of three different rotor cavities. For each of the three rotor cavities, the cavity inlets differ in their axial cavity lengths, which are modified by extending the upper casing stator platform. The three cavity volumes are comprised of a baseline case, along with a 14% and a 28% volume reduction relative to the baseline case. Measurements show that there is an increase in efficiency of 0.3% for the 14% cavity volume reduction case (relative to the baseline case), whereas a further volume reduction of 28% (relative to the baseline case) decreases the efficiency. Computational analysis highlights the break-up of a toroidal vortex within the cavity as the primary factor explaining the changes in efficiency. The dominant cavity vortex originally present in the baseline case firstly broken up into two smaller vortices for the 14% cavity volume reduction case and secondly, completely replaced with a strong radial jet for the 28% volume reduction case. From a design perspective, reducing the cavity volume by extending the upper casing stator platform yields improvements in efficiency provided that the cavity vortex is still present. The design considerations, analysis and the associated aerodynamics are discussed in detail within this paper.

Design Considerations for Axial Steam Turbine Rotor Inlet Cavity Volume and Length Scale

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Konstantinos G. Barmpalias ◽  
Reza S. Abhari ◽  
Anestis I. Kalfas ◽  
Toshio Hirano ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Turbine Rotor ◽  
Volume Reduction ◽  
Length Scale ◽  
Toroidal Vortex ◽  
Cavity Volume ◽  
Design Considerations ◽  
Baseline Case ◽  
Design Perspective ◽  
Reduction Case

In this paper we examine the interaction between the cavity and main flows of three different rotor cavities. For each of the three rotor cavities, the cavity inlets differ in their axial cavity lengths, which are modified by extending the upper casing stator platform. The three cavity volumes are comprised of a baseline case, along with a 14% and a 28% volume reduction relative to the baseline case. Measurements show that there is an increase in efficiency of 0.3% for the 14% cavity volume reduction case (relative to the baseline case), whereas a further volume reduction of 28% (relative to the baseline case) decreases the efficiency. Computational analysis highlights the breakup of a toroidal vortex within the cavity as the primary factor explaining the changes in efficiency. The dominant cavity vortex originally present in the baseline case firstly broken up into two smaller vortices for the 14% cavity volume reduction case and secondly, completely replaced with a strong radial jet for the 28% volume reduction case. From a design perspective, reducing the cavity volume by extending the upper casing stator platform yields improvements in efficiency provided that the cavity vortex is still present. The design considerations, analysis and the associated aerodynamics are discussed in detail within this paper.

Efficiency Improvements in an Industrial Steam Turbine Stage: Part 1

2016 ◽  
Author(s):  
Srikanth Deshpande ◽  
Marcus Thern ◽  
Magnus Genrup
Keyword(s):  
Steam Turbine ◽  
Total Pressure ◽  
Rotor Blades ◽  
Efficiency Improvement ◽  
Turbine Stage ◽  
Design Modification ◽  
Ansys Cfx ◽  
Baseline Case ◽  
Profile Losses ◽  
Stage Efficiency

The present work approaches the idea of increasing the efficiency of an industrial steam turbine stage. For this endeavor, an industrial steam turbine stage comprising of prismatic stator and rotor is considered. With the velocity triangles as input, airfoil design is carried out. Firstly, the rotor is redesigned to take care of any incidence issues in the baseline case. In rotor blades, the peak Mach number is reduced in blade to blade flow passage and hence, efficiency of stage is increased. Rotor is made front loaded. After finalizing the rotor, the stator is redesigned. Stator is made more aft-loaded when compared to the baseline case. By making the stator aft-loaded, the efficiency increased by reducing profile losses. This design modification also showed advantage in secondary losses. The total pressure loss in the stator was reduced by a delta of 0.15. When creating an airfoil for stator or rotor, MISES was used in order to evaluate profile losses. The design verification for the stage was numerically done using commercial CFD software ANSYS CFX. Steady state RANS simulations were carried out. The stator and the rotor still being prismatic, only by virtue of airfoil design, the total to total stage efficiency improvement of 0.33% was predicted.

Maintaining steam turbine performance

1933 ◽  
Vol 52 (11) ◽  
pp. 748-751
Author(s):  
C. R. Soderberg
Keyword(s):  
Steam Turbine ◽  
Turbine Performance

Experience in the Use of a Digital Computer for Predicting Steam-Turbine Performance

1964 ◽  
Vol 179 (1) ◽  
pp. 307-342
Author(s):  
R. U. McCrae ◽  
A. Montague ◽  
M. Douglass
Keyword(s):  
Energy Balance ◽  
Steam Turbine ◽  
Turbine Generator ◽  
Design And Optimization ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Experienced Programmer ◽  
Turbine Design ◽  
Considerable Detail

This paper describes a number of programmes for digital computers that have been developed by the authors' firm to eliminate many of the tedious hand calculations which are encountered in the preliminary stages of steam-turbine and condenser design. By their use a considerable amount of the designers' time is saved and fatigue is reduced. These programmes also eliminate mistakes and inaccuracies which may occur in long calculations made by hand. The programmes described have been chosen as being representative of the range of programmes used in preliminary turbine design and optimization and are as follows: a programme to enable steam properties to be calculated, based on the formulae given in the Keenan and Keyes Steam Tables; a programme which can be used to determine the efficiency of small industrial turbines; a feed-heating programme which will carry out the calculations necessary to determine the preliminary energy balance for a feed-heating cycle; a detailed energy-balance programme incorporating turbine-efficiency calculations; a condenser-optimization programme for determination of the ideal parameters to be used in the design of a condenser. The programmes are arranged so that unskilled operators can run them on the computer without the help of an experienced programmer. Facilities are also made available for writing programmes in a simplified form called ‘autocode’ which can be used by an engineer after the briefest of trainings. Some programmes are described in considerable detail to assist others who may wish to write a similar programme or to compare them with programmes of their own. All these programmes have been in regular use for more than three years and have greatly enlarged the scope of investigations which may be carried out in the project stage of the design of a steam-turbine generator and associated power-station equipment.

Numerical Analysis of the Effects of Non-Uniform Surface Roughness on Compressor Stage Performance

2010 ◽  
Author(s):  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Mauro Venturini
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Traditional Approach ◽  
Fluid Dynamic ◽  
Turbine Blades ◽  
Compressor Stage ◽  
Turbine Performance ◽  
Performance Map ◽  
Overall Performance ◽  
Stage Performance

Gas turbine performance degradation over time is mainly due to the deterioration of compressor and turbine blades, which, in turn, causes a modification of the compressor and turbine performance maps. Since detailed information about the actual modification of the compressor and turbine performance maps is usually unavailable, component performance can be modeled and investigated (i) by scaling the overall performance map, or (ii) by using stage-by-stage models of the compressor and turbine and by scaling each single stage performance map to account for each stage deterioration, or (iii) by performing 3D numerical simulations, which allow to both highlight the fluid-dynamic phenomena occurring in the faulty component and grasp the effect on the overall performance of the component. In this paper, the authors address the most common and experienced source of loss for a gas turbine, i.e. compressor fouling. With respect to the traditional approach, which mainly aims at the identification of the overall effects of fouling, authors investigate a micro-scale representation of compressor fouling (e.g. blade surface deterioration and flow deviation). This allows (i) a more detailed investigation of the fouling effects (e.g. mechanism, location along blade height, etc.), (ii) a more extensive analysis of the causes of performance deterioration and (iii) the assessment of the effect of fouling on stage performance coefficients and on stage performance maps. The effects of a non-uniform surface roughness on both rotor and stator blades of an axial compressor stage are investigated by using a commercial CFD code. The NASA Stage 37 test case was used as the baseline geometry. The numerical model already validated against experimental data available in literature was used for the simulations. Different non-uniform combinations of surface roughness levels on rotor and stator blades were imposed. This makes it possible to highlight how the localization of fouling on compressor blades affects compressor performance, both at an overall and at a fluid-dynamic level.

The Impact of Rotor Inlet Cavity Volume and Length Scale on Efficiency

2012 ◽  
Author(s):  
Konstantinos G. Barmpalias ◽  
Reza S. Abhari ◽  
Anestis I. Kalfas ◽  
Naoki Shibukawa ◽  
Takashi Sasaki
Keyword(s):  
Experimental Work ◽  
Computational Analysis ◽  
Cavity Length ◽  
Cavity Wall ◽  
Length Scale ◽  
Cavity Volume ◽  
Turbine Stage ◽  
Flow Interactions ◽  
The Impact ◽  
Stage Efficiency

The interaction between the cavity and the main flows accounts for a considerable amount of the overall aerodynamic losses in axial turbomachinery. Experimental work supplemented by a computational analysis is presented in this paper on the impact of rotor inlet cavity volume and length scale on turbine stage efficiency. Inlet cavity volume and geometry have been systematically varied. The flow interactions occurring at the cavity inlet between the cavity and main flows and their subsequent impact on efficiency were studied. Five different configurations have been examined within this study. The radial cavity wall has been shortened by 13% and 25% compared to the initial cavity length. Cavity volume has been reduced by 14% and 28% respectively. An additional rounding introduced at the upper right corner of the cavity generated two more variations. Efficiency was increased by 1.1% and 1.6% for the 14% and 28% cavity volume reductions, respectively. The rounding introduced led only to efficiency deficits as the strengthening of the cavity vortex caused increased interaction at the cavity inlet area.

A Study of the Heat Transfer in Winglet and Squealer Rotor Tip Configurations for a Non-Cooled HPT Blade Based on CFD Calculations

2013 ◽  
Author(s):  
Lucilene Moraes da Silva ◽  
Jesuino Takachi Tomita
Keyword(s):  
Rotor Blade ◽  
Energy Transfer Process ◽  
Main Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Hot Gas ◽  
Turbine Performance ◽  
Blade Row ◽  
The Common

HPT operate at high pressure and temperatures. One of the most important loss sources is the tip leakage flow on the rotor tip region. The flow that leaks in this region does not participate in the energy transfer process between the hot gas and rotor blade row. Hence, the main flow suffers a penalty to maintain the energy conservation. To try decreasing this mass flow leakage some techniques can be applied. The most common are the winglet and squealer rotor tip configuration. These techniques improve the turbine performance, but some attention should be taken into account because the temperature distribution changes on this region for different tip configurations. In this work, the winglet and squealer tip geometries are compared with the common flat tip configuration. The analysis was performed for design and off-design conditions. The HPT developed in the E3 program was used as baseline turbine to explore the differences of the flowfield on the rotor tip region. The results are compared and discussed in detail.

Unsteady Steam Turbine Optimization Using High Fidelity CFD

2020 ◽  
Author(s):  
Vahid Iranidokht ◽  
Ilias Papagiannis ◽  
Anestis Kalfas ◽  
Reza Abhari ◽  
Shigeki Senoo ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Computational Cost ◽  
Flow Distribution ◽  
Fast Response ◽  
Test Facility ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Efficiency Gain ◽  
Flow Angle ◽  
Computational Optimization

Abstract This paper presents the computational methodology, and experimental investigations accomplished to enhance the efficiency of a turbine stage by applying non-axisymmetric profiling on the rotor hub wall. The experimental setup was a two-stage axial turbine, which was tested at “LISA” test facility at ETH Zurich. The 1st stage was considered to create the flow history for the 2nd stage, which was the target of the optimization. The hub cavity of the 2nd stage was designed with large dimensions as a requirement of a steam turbine. The goal was to optimize the interaction of the cavity leakage flow with the rotor passage flow to reduce the losses and increase efficiency. The computational optimization was completed using a Genetic Algorithm coupled with an Artificial Neural Network on the 2nd stage of the test turbine. Unsteady time-accurate simulations were performed, using in-house developed “MULTI3” solver. Besides implementing all geometrical details (such as hub and tip cavities and fully 3D blade geometries) from the experimental setup into the computational model, it was learned that the unsteady upstream effect could not be neglected. A novel approach was introduced by using unsteady inlet boundary conditions to consider the multistage effect while reducing the computational cost to half. The importance of this implementation was tested by performing a steady simulation on the optimized geometry. The predicted efficiency gain from steady simulations was 4.5 times smaller (and negligible) compared to the unsteady approach. Excluding the cavity geometry was also assessed in a different simulation setup showing 3.9% over-prediction in the absolute efficiency value. Comprehensive steady and unsteady measurements were performed utilizing pneumatic, Fast Response Aerodynamic (FRAP), and Fast Response Entropy (FENT) probes, on the baseline and profiled test cases. The end-wall profiling was found to be successful in weakening the strength of the hub passage vortex by a 19% reduction in the under-over turning. As a result, the blockage was reduced near the hub region leading to more uniform mass flow distribution along the span. The flow angle deviations at the higher span position were also corrected due to better control of the flow angles. Furthermore, the improvements were confirmed by reductions in entropy, Secondary Kinetic Energy, and pressure unsteadiness. The accurate computational implementations led to an excellent agreement between the predicted and measured efficiency gain.

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