The Effects of a Parametric Variation of the Rim Seal Geometry on the Interaction Between Hub Leakage and Mainstream Flows in High Pressure Turbines

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Ivan Popović ◽  
Howard P. Hodson
Keyword(s):  
Large Scale ◽  
Full Range ◽  
Flow Uniformity ◽  
Linear Cascade ◽  
Parametric Variation ◽  
Optimum Geometry ◽  
Parametric Studies ◽  
Mass Flow Rates ◽  
Rotor Disk ◽  
Computational Fluid Dynamics Cfd

The objective of this work was to assess and understand the effects of a parametric variation performed on a typical overlapping rim seal geometry. The datum geometry has been the focus of a detailed experimental investigation employing a large-scale linear cascade subjected to a range of the mass flow rates and swirl velocities of the leakage air. The parametric variations described in this paper were examined using validated computational fluid dynamics (CFD). As a part of the parametric studies, both the axial and the radial seal clearance between the rotor fin (angel wing) and stator platform were varied as well as the length of the overlap between stator and rotor platforms. In addition, the effects of forward and backward facing annulus steps were also investigated. It has been found that a backward-facing annulus step was detrimental for all conditions considered, while a forward-facing step offered improvements for smaller step heights and/or lower leakage fractions. Tightening of the seal clearances closer to the annulus line improved the sealing effectiveness but often at the expense of increased losses. On the other hand, increasing the overlap length led to improvements in the sealing effectiveness with very small effects on the overall losses. Moving the rim seal away from the blade-leading edges reduced the pressure asymmetry at the rim seal and increased the flow uniformity of the leakage air. However, this led to an increased cross-passage flow (more negative skew) and higher losses at all but lowest leakage fractions. The results presented in this paper highlight the fact that there may not be an optimum rim seal solution that would offer an improvement for the full range of leakage fractions and that, for different rim sealing flows, there may be a different optimum geometry. In addition, rotor disk movements in radial and axial directions at various off-design conditions should be considered as a part of the design process. Based on the presented results, it may be of a benefit to the turbine designer to consider rotor disk designs that would be more biased towards the upstream and outward disk movements, which would result in tightening of the seal clearances and avoidance of a backward-facing annulus step.

The Effects of a Parametric Variation of the Rim Seal Geometry on the Interaction Between Hub Leakage and Mainstream Flows in HP Turbines

2012 ◽  
Author(s):  
I. Popović ◽  
H. P. Hodson
Keyword(s):  
Large Scale ◽  
Full Range ◽  
The Other ◽  
Flow Uniformity ◽  
Flow Rates ◽  
Linear Cascade ◽  
Parametric Variation ◽  
Optimum Geometry ◽  
Parametric Studies ◽  
Mass Flow Rates

The objective of this work was to assess and understand the effects of parametric variation performed on a typical overlapping rim seal geometry. The datum geometry has been focus of a detailed experimental investigation employing a large-scale linear cascade subjected to a range of the mass flow rates and swirl velocities of the leakage air. The parametric variations described in this paper were examined using validated CFD. As a part of the parametric studies, both the axial and the radial seal clearance between the rotor fin (angel wing) and stator platform were varied as well as the length of the overlap between stator and rotor platforms. In addition, the effects of forward and backward facing annulus steps were also investigated. It has been found that a backward facing annulus step was detrimental for all conditions considered, while a forward facing step offered improvements for smaller step heights and/or lower leakage fractions. Tightening of the seal clearances closer to the annulus line improved the sealing effectiveness, but often at the expense of increased losses. On the other hand, increasing the overlap length led to improvements in the sealing effectiveness with very small effects on the overall losses. Moving the rim seal away from the blade leading edges reduced the pressure asymmetry at the rim seal and increased the flow uniformity of the leakage air. However, this led to an increased cross-passage flow (more negative skew) and higher losses at all but lowest leakage fractions. The results presented in this paper highlight the fact that there may not be an optimum rim seal solution that would offer an improvement for the full range of leakage fractions and that for different rim sealing flows there may be a different optimum geometry. In addition, rotor disc movements in radial and axial directions at various off-design conditions should be considered as a part of the design process. Based on the presented results it may be of a benefit to the turbine designer to consider rotor disc designs which would be more biased towards the upstream and outward disc movements that would result in tightening of the seal clearances and avoidance of a backward facing annulus step.

Analysis of Late Phase Severe Accident Phenomena in CANDU Plant

2017 ◽  
Vol 3 (2) ◽  
Author(s):  
D. Dupleac
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Late Phase ◽  
Severe Accident ◽  
Ansys Fluent ◽  
Water Depletion ◽  
Sources Of Uncertainty ◽  
Parametric Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Containment Pressure

The paper overviews the analytical studies performed at Politehnica University of Bucharest on the analysis of late phase severe accident phenomena in a Canada Deuterium Uranium (CANDU) plant. The calculations start from a dry debris bed at the bottom of calandria vessel. Both SCDAPSIM/RELAP code and ansys-fluent computational fluid dynamics (CFD) code are used. Parametric studies are performed in order to quantify the effect of several identified sources of uncertainty on calandria vessel failure: metallic fraction of zirconium inside the debris, containment pressure, timing of water depletion inside calandria vessel, steam circulation in calandria vessel above debris bed, debris temperature at moment of water depletion inside calandria vessel, calandria vault nodalization, and the gap heat transfer coefficient.

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 of the viaducts for the Line 3 of the Riyadh Metro LRT in Saudi Arabia

2018 ◽  
Author(s):  
Paul-Emile Durand ◽  
Lucas Wise ◽  
Emmanuel Joy ◽  
Alain Rossetto
Keyword(s):  
Saudi Arabia ◽  
Large Scale ◽  
Parametric Design ◽  
Full Range ◽  
Design Approach ◽  
Construction Site ◽  
Box Girder ◽  
Construction Engineering ◽  
Long Span ◽  
Metro Project

<p>In June 2013, three consortia were awarded the three construction packages that constitute the whole Riyadh Metro Project in Saudi Arabia for a total of 6 lines and 180 kilometres.</p><p>International Bridge Technologies was in charge, as a subconsultant of Idom, of the complete structural scope of services for the 25.6 km of elevated viaduct that Riyadh Metro Package 2 comprises (Line 3, around 41.6 km, out of which 25.6 km are elevated). This scope consisted of the full range of services from conceptual tender design to final detailed design, including shop drawings production, construction engineering and construction site support.</p><p>The Line 3 elevated viaduct consists of a three-cells precast segmental box-girder with typical simply-supported spans of 37 m and special continuous spans of 50 m. Six long span structures with spans varying from 60 m to 95 m were required for the special crossings over existing interchanges. Typical and continuous spans are erected span-by-span with an overhead truss while long spans are erected in balanced cantilever with cranes on the ground or lifting frames on the deck.</p><p>The present paper is centred on the design of the elevated viaduct and presents the different structures with key features and how they were constructed to permit large scale standardisation and speed of construction. Some key design aspects are developed, in particular the design approach for the 3-cells box-girder as the most effective solution to satisfy the imposed aesthetic criteria. This paper also exposes the design approach adopted to produce a “design-for-demand” by relying as much as practically possible on a realistic modelling of the alignment and by limiting parametric design. This allowed for an optimisation of material quantities.</p>

Self-Undermining Rhetoric in the Past and Present

2015 ◽  
Author(s):  
Adam Seth Levine
Keyword(s):  
Collective Action ◽  
Policy Change ◽  
Large Scale ◽  
Political Change ◽  
Political Action ◽  
Full Range ◽  
Economic Insecurity ◽  
The Past ◽  
Broad Concept ◽  
The Face

This chapter considers the prospects for political change in the face of communicative barriers to collective action. It begins to address this question by identifying several of the most well-known historical and recent moments in which there was large-scale mobilization on some economic insecurity issues. This discussion, in concert with the empirical findings in this book, helps clarify the prospects for political action (and policy change) on these issues. The chapter then uses the findings from the book to identify three types of people that are most likely to become active. It also talks about the implications of having this (narrower) set of people active as opposed to the full range of people that find the issues to be important. It concludes by reiterating how self-undermining rhetoric is a broad concept that can apply in many different situations beyond those considered herein.

Analytical bow waves for fine ship bows with rake and flare

2011 ◽  
Vol 55 (01) ◽  
pp. 1-18
Author(s):  
Francis Noblesse ◽  
Gérard Delhommeau ◽  
Patrick Queutey ◽  
Chi Yang ◽  
Hyun Yul Kim
Keyword(s):  
Parametric Study ◽  
Rake Angle ◽  
Wave Profile ◽  
Wave Crest ◽  
Bow Waves ◽  
Bow Wave ◽  
Hydrodynamic Calculations ◽  
Parametric Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Analytical Relations

The bow wave generated by a steadily advancing ship is considered for a family of fine ruled ship bows with rake and flare. This family of ship bows is defined in terms of four parameters: the ship draft D, the entrance angles a and a' at the top and bottom waterlines, and the rake angle 8. The corresponding bow wave similarly depends on four parameters: the draft-based Froude number F and the three angles a, a', and 8. An extensive parametric study, based on thin-ship theory, is performed to explore the variations of the water height Z0 at the ship stem X = 0, the location X0 (measured from the ship stem) of the intersection of the bow-wave profile with the mean free-surface plane Z = 0, and the bow-wave profile, with respect to the four parameters F, a, a', and 8. This parametric study extends the previously reported similar study of the height Zb of the bow wave and the location Xb of the bow-wave crest. These two complementary parametric studies yield simple analytical relations, which extend relations given previously for wedge-shaped ship bows without rake or flare. In spite of their remarkable simplicity, the analytical relations given here yield bow waves that are comparable to computational fluid dynamics (CFD) waves given by Euler-flow calculations. The analytical relations, which explicitly account for the influence of the four primary parameters F, a, a', and 8, can be used immediately—without hydrodynamic calculations—for ship design, notably at early design stages when the precise hull geometry is not yet known. The study also provides insight for ship bow design. Specifically, it suggests that a bow with positive rake and negative flare may be beneficial, and that a bulb located aft of the stem and integrated with the hull may be an advantageous alternative to a traditional bulb protruding ahead of the bow, in agreement with the results of a hull-form optimization analysis.

scholarly journals Throw variations and strain partitioning associated with fault-bend folding along normal faults

2019 ◽  
Author(s):  
Efstratios Delogkos ◽  
Muhammad Mudasar Saqab ◽  
John J. Walsh ◽  
Vincent Roche ◽  
Conrad Childs
Keyword(s):  
Large Scale ◽  
Full Range ◽  
Quantitative Model ◽  
Normal Faults ◽  
Strain Partitioning ◽  
Fault Surface ◽  
Irregular Geometries ◽  
Surface Irregularities ◽  
Fault Bend ◽  
Constant Displacement

Abstract. Normal faults have irregular geometries on a range of scales arising from different processes including refraction and segmentation. A fault with an average dip and constant displacement on a large-scale, will have irregular geometries on smaller scales, the presence of which will generate fault-related folds, with major implications for across-fault throw variations. A quantitative model has been presented which illustrates the range of deformation arising from movement on fault surface irregularities, with fault-bend folding generating geometries reminiscent of normal drag and reverse drag. The model highlights how along-fault displacements are partitioned between continuous (i.e. folding) and discontinuous (i.e. discrete displacement) strain along fault bends characterised by the full range of fault dip changes. Strain partitioning has a profound effect on measured throw values across faults, if account is not taken of the continuous strains accommodated by folding and bed rotations. We show that fault throw can be subject to errors of up to ca. 50 % for realistic fault bend geometries (up to ca. 40°), even on otherwise sub-planar faults with constant displacement. This effect will provide apparently more irregular variations in throw and bed geometries that must be accounted for in associated kinematic interpretations.

scholarly journals STH/CFD Coupled Simulation of the Protected Loss of Flow Accident in the CIRCE-HERO Facility

2020 ◽  
Vol 10 (20) ◽  
pp. 7032 ◽  
Author(s):  
Pucciarelli Andrea ◽  
Galleni Francesco ◽  
Moscardini Marigrazia ◽  
Martelli Daniele ◽  
Forgione Nicola
Keyword(s):  
Thermal Stratification ◽  
Outlet Section ◽  
Experimental Conditions ◽  
Ansys Fluent ◽  
Internal Loop ◽  
Fuel Pin ◽  
Mass Flow Rates ◽  
Computational Fluid Dynamics Cfd ◽  
The University ◽  
Good Agreement

The paper presents the application of a coupling methodology between Computational Fluid Dynamics (CFD) and System Thermal Hydraulic (STH) codes developed at the University of Pisa. The methodology was applied to the CIRCE-HERO facility in order to reproduce the recently performed experimental conditions simulating a Protected Loss Of Flow Accident (PLOFA). The facility consists of an internal loop, equipped with a fuel pin simulator and a steam generator, and an external pool. In this coupling application, the System code RELAP5 is adopted for the simulation of the internal loop while the CFD code ANSYS Fluent is used for the sake of simulating the pool. The connection between the two addressed domains is provided at the inlet and outlet section of the internal loop; a thermal coupling is also performed in order to reproduce the observed thermal stratification phenomenon. The obtained results are promising and a good agreement was obtained for both the mass flow rates and temperature measurements. Capabilities and limitations of the adopted coupling technique are discussed in the present paper also providing suggestions for improvements and developments to be achieved in the frame of future applications.

Natural Ventilation Design and Optimization of Large-Scale Industrial Workshop

2014 ◽  
Vol 1065-1069 ◽  
pp. 2137-2140
Author(s):  
Xiao Hu Yang ◽  
Yan Long ◽  
Ling Zhao Meng ◽  
Yu Hui Jin
Keyword(s):  
Large Scale ◽  
Natural Ventilation ◽  
Thermal Environment ◽  
Orthogonal Experiment ◽  
Structure Design ◽  
Iron And Steel ◽  
Design And Optimization ◽  
Experiment Method ◽  
Orthogonal Experiment Method ◽  
Computational Fluid Dynamics Cfd

In this paper, we used orthogonal experiment method and Computational Fluid Dynamics (CFD) technology to simulate the thermal environment of the iron and steel workshop. By comparing and analyzing the temperature distribution and air flow of workshops with different window structures, we obtained an optimization of natural ventilation design for industrial workshop. The research results can be used for the structure design or reformation of industrial workshops as reference.

scholarly journals Scaling Up Intervention Studies to Investigate Real-Life Foreign Language Learning in School

2019 ◽  
Vol 39 ◽  
pp. 161-188 ◽  
Author(s):  
Detmar Meurers ◽  
Kordula De Kuthy ◽  
Florian Nuxoll ◽  
Björn Rudzewitz ◽  
Ramon Ziai
Keyword(s):  
Language Learning ◽  
Large Scale ◽  
Intervention Studies ◽  
Full Range ◽  
Real Life ◽  
Foreign Language Learning ◽  
Time Frame ◽  
Field Trials ◽  
Web Based ◽  
Gold Standard Method

AbstractIntervention studies typically target a focused aspect of language learning that is studied over a relatively short time frame for a relatively small number of participants in a controlled setting. While for many research questions, this is effective, it can also limit the ecological validity and relevance of the results for real-life language learning. In educational science, large-scale randomized controlled field trials (RCTs) are seen as the gold standard method for addressing this challenge—yet they require intervention to scale to hundreds of learners in their varied, authentic contexts.We discuss the use of technology in support of large-scale interventions that are fully integrated in regular classes in secondary school. As an experimentation platform, we developed a web-based workbook to replace a printed workbook widely used in German schools. The web-based FeedBook provides immediate scaffolded feedback to students on form and meaning for various exercise types, covering the full range of constructions in the seventh-grade English curriculum.Following the conceptual discussion, we report on the first results of an ongoing, yearlong RCT. The results confirm the effectiveness of the scaffolded feedback, and the approach makes students and learning process variables accessible for the analysis of learning in a real-world context.

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