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.

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.

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.

Conditioning of Leakage Flows in Gas Turbine Rotor-Stator Cavities

2020 ◽  
Author(s):  
P. W. Darby ◽  
A. W. Mesny ◽  
G. De Cosmo ◽  
M. Carnevale ◽  
G. D. Lock ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Outer Part ◽  
Engine Performance ◽  
Turbine Rotor ◽  
Flow Visualisation ◽  
Leakage Flow ◽  
Toroidal Vortex ◽  
Performance Measurements ◽  
Operating Cycle ◽  
Leakage Flows

Abstract Ingress is the penetration of hot mainstream fluid into the cavity formed between the turbine disc (rotor) and its adjacent casing (stator). Gas turbine engine designers use rim seals fitted at the periphery of the discs and a superposed sealant flow — typically fed through the bore of the stator — is used to reduce, or in the limit prevent, ingress. Parasitic leakage enters the cavity through pathways created between mating interfaces of engine components. Owing to the aggressive thermal and centrifugal loading experienced during the turbine operating cycle, the degree of leakage and its effect on ingress are difficult to predict. This paper considers the potential for leakage flows to be conditioned in order to minimise their parasitic effect on disc cooling, and ultimately engine, performance. Measurements of static and total pressure, swirl and species concentration were used to assess the performance of a simple axial clearance rim-seal over a range of non-dimensional leakage flow-rates. A computational model was used to provide flow visualisation to support the interpretation of flow structures derived from the experiments. Data is presented to investigate the effects of swirling the leakage flow in accordance with, and counter to, the disc rotation. The injected momentum from the leakage created a toroidal vortex in the outer part of the cavity. Co-swirl was found to improve the sealing effectiveness by up to 15% compared to the axially-introduced baseline and counter-swirled configurations. Varying the momentum of the leakage flow was considered by passing consistent mass-flows through a range of leakage outlet areas. Increasing the momentum was seen to increase the influence of the toroidal vortex on the flow structure in the cavity, which in turn influenced the sealing effectiveness.

Parametric Study of Vertical Axis Wind Turbine Rotor Configurations Using CFD

2017 ◽  
Author(s):  
John Keithley Difuntorum ◽  
Louis Angelo M. Danao
Keyword(s):  
Leading Edge ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Dynamics Modeling ◽  
Worst Case ◽  
Computational Fluid Dynamics Modeling ◽  
Baseline Case ◽  
Parametric Studies

Vertical axis wind turbines present several advantages over the horizontal axis machines that make them suitable to a variety of wind conditions. However due to the complexity of VAWT aerodynamics, available literature on VAWT performance in steady and turbulent wind conditions is limited. This paper aims to numerically predict the performance of a 5kW VAWT under steady wind conditions through computational fluid dynamics modeling by varying turbine configuration parameters. Two dimensional VAWT models using a cambered blade (1.5%) were created with open field boundary extents. Turbine configuration parameters studied include blade mounting position, blade fixing angle, and rotor solidity. Baseline case with peak Cp of 0.31 at tip speed ratio of 4 has the following parameters: mounting position at 0.5c, zero fixing angle, 3 blades (solidity = 0.3). Independent parametric studies were carried out and results show that a blade mounting position of 0.7c from the leading edge produces best performance with maximum Cp = 0.315 while worst case is a mounting position of 0.15c with peak Cp = 0.273. Fixing angle study reveals a toe-out setting of −1° producing the best performance with peak Cp of 0.315 and the worst setting at toe-in of 1.5° with peak Cp of 0.287. The solidity study resulted in a best case of 4 blades (solidity = 0.4) with peak Cp = 0.316 and worst case of 2 blades (solidity = 0.2) with peak Cp = 0.283.

scholarly journals Promoting Older Residents’ Social Interaction and Wellbeing: A Design Perspective

2020 ◽  
Vol 12 (7) ◽  
pp. 2834
Author(s):  
Cun Li ◽  
Kai Kang ◽  
Xu Lin ◽  
Jun Hu ◽  
Bart Hengeveld ◽  
...  
Keyword(s):  
Older Adults ◽  
Nursing Home ◽  
Social Interaction ◽  
Institutional Care ◽  
Interactive Systems ◽  
Structured Interviews ◽  
Design Considerations ◽  
Aging Society ◽  
The Status ◽  
Design Perspective

The aging society has arrived, and more and more older adults are living in a nursing home. However, institutional care settings are often described as places where residents suffer from social isolation. Under this context, we describe the process of translating into fieldwork into interactive systems facilitating elderly residents’ social interaction and wellbeing. Comprehensive semi-structured interviews with older residents and caregivers were first conducted in a Dutch nursing home, aiming at understanding the status of their social interaction. The context of a typical elderly resident’s social interaction was then generated, and based on which three interactive systems focusing on different aspects of their social interaction were designed and deployed. The paper finally concludes with design considerations for promoting social interaction and wellbeing of older adults living in the nursing home.

Combined Experimental and Numerical Approach for Linking Microstructure and Mechanical Properties on Different Length Scales for near γ–TiAl Alloys

2013 ◽  
Vol 750 ◽  
pp. 76-79 ◽  
Author(s):  
Mohammad Rizviul Kabir ◽  
Marion Bartsch ◽  
Liudmila Chernova ◽  
Janine Schneider ◽  
Klemens Kelm
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Computational Analysis ◽  
Numerical Approach ◽  
Tensile Behavior ◽  
Length Scale ◽  
Tial Alloys ◽  
Proper Understanding ◽  
Hardening Behavior ◽  
Meso Scale

At room temperature the macroscopic tensile behavior of TiAl alloys is extremely microstructure sensitive. In general the microstructures of TiAl alloys are heterogeneous at micro and meso scale. The materials micromechanisms that occur at different length scale have to be linked for a proper understanding of the macroscopic response. In order to explore those micromechanisms, methodologies combining advanced experimental and computational analysis have been proposed. Linking microstructure and properties using a two-scale numerical model we are able to explain the stress-strain and hardening behavior of this alloy.

scholarly journals Controlling Mixing at the Interaction Zone Through Systematic Variation of the Inlet Rotor Cavity Volume and Length Scale

2012 ◽  
Vol 4 (2) ◽  
pp. 17-24
Author(s):  
Konstantinos G. Barmpalias ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Toshio Hirano ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Systematic Variation ◽  
Length Scale ◽  
Cavity Volume ◽  
Interaction Zone

Unsteady Flow Interactions Within the Inlet Cavity of a Turbine Rotor Tip Labyrinth Seal

2003 ◽  
Author(s):  
A. Pfau ◽  
J. Schlienger ◽  
D. Rusch ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Cavity Flow ◽  
Fast Response ◽  
Labyrinth Seal ◽  
Turbine Rotor ◽  
Major Effect ◽  
Main Flow ◽  
Toroidal Vortex ◽  
Head Diameter ◽  
Flow Interactions ◽  
Axial Turbines

This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth seal of a 2 stage axial research turbine. Highly resolved, steady and unsteady 3-dimensional flow data are presented. The probes used here are a miniature 5 hole probe of 0.9mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth seal configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focussing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.

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