Experimental investigation of turbine stator well rim seal, reingestion and interstage seal flows using gas concentration techniques and displacement measurements

Gas turbine engine performance requires effective and reliable internal cooling over the duty cycle of the engine. Life predictions for rotating components subject to the main gas path temperatures are vital. This demands increased precision in the specification of the internal air system flows which provide turbine stator well cooling and sealing. This in turn requires detailed knowledge of the flow rates through rim seals and interstage labyrinth seals. Knowledge of seal movement and clearances at operating temperatures is of great importance when prescribing these flows. A test facility has been developed at the University of Sussex, incorporating a two stage turbine rated at 400 kW with an individual stage pressure ratio of 1.7:1. The mechanical design of the test facility allows internal cooling geometry to be rapidly re-configured, while cooling flow rates of between 0.71 CW, ENT and 1.46 C W, ENT, may be set to allow ingress or egress dominated cavity flows. The main annulus and cavity conditions correspond to in cavity rotational Reynolds numbers of 1.71×106< Reφ <1.93×106. Displacement sensors have been used to establish hot running seal clearances over a range of stator well flow conditions, allowing realistic flow rates to be calculated. Additionally, gas seeding techniques have been developed, where stator well and main annulus flow interactions are evaluated by measuring changes in gas concentration. Experiments have been performed which allow rim seal and re-ingestion flows to be quantified. It will be shown that this work develops the measurement of stator well cooling flows and provides data suitable for the validation of improved thermo-mechanical and CFD codes, beneficial to the engine design process. Copyright © 2011 by Rolls-Royce plc.

An investigation into numerical analysis alternatives for predicting reingestion in turbine disc rim cavities

Reliable means of predicting ingestion in cavities adjacent to the main gas path are increasingly being sought by engineers involved in the design of gas turbines. In this paper, analysis is to be presented that results from an extended research programme, MAGPI, sponsored by the EU and several leading gas turbine manufactures and universities. Extensive use is made of CFD modelling techniques to understand the aerodynamic behaviour of a turbine stator well cavity, focusing on the interaction of cooling air supply with the main annulus gas. The objective of the study has been to benchmark a number of CFD codes and numerical techniques covering RANS and URANS calculations with different turbulence models in order to assess the suitability of the standard settings used in the industry for calculating the mechanics of the flow travelling between cavities in a turbine through the main gas path. The modelling methods employed have been compared making use of experimental data gathered from a dedicated two-stage turbine rig, running at engine representative conditions. Extensive measurements are available for a range of flow conditions and alternative cooling arrangements. The limitations of the numerical methods in calculating the interaction of the cooling flow egress and the main stream gas, and subsequent ingestion into downstream cavities in the engine (i.e. re-ingestion), have been exposed. This has been done without losing sight of the validation of the CFD for its use for predicting heat transfer, which was the main objective of the partners of the MAGPI Work- Package 1 consortium. Copyright © 2012 by ASME.

Rim instability by solvent-induced dewetting

We study the condition of the occurrence of the rim instability in the solvent-induced dewetting process. Our experimental results show that the film thickness not only greatly influences the occurrence of the rim instability, but also influences the wavelength lambda as characterized by the undulation of the deformed contact line. The molecular weight of polymer does not almost influence the occurrence of the rim instability and the wavelength lambda. The wavelength lambda is proportional to the width of the rim in the rim instability region. The receding contact angle theta of polymer solutions on substrates in the dewetting process is an important factor to influence the rim instability in the solvent-induced dewetting.

Une nouvelle méthode de détection du glaucome par la mesure de l'asymétrie interoculaire : l’asymétrie du rapport de la surface neurorétinienne sur la surface du disque optique ou rim area to disc area asymmetry ratio (RADAAR)

Cette thèse constitue à la fois un apport de nature clinique et technologique dans l’approche diagnostique du glaucome. Plus précisément, nous nous proposons d’étudier une nouvelle façon de détecter le glaucome par la mesure de l’asymétrie du rapport de la surface de l’anneau neurorétinien et de la surface de la papille ou du disque optique ou rim to disc area asymmetry ratio (RADAAR). Pour atteindre cet objectif, nous avons recours à une base de données composée d’une population subdivisée en 4 différents groupes de diagnostic (normal, glaucome possible, glaucome probable et glaucome définitif). Les mesures du RADAAR sont calculées de différentes façons à partir des paramètres stéréométriques de la tête du nerf optique des sujets, produits par la microscopie confocale à balayage laser (Heidelberg Retina Tomograph (HRT) (Heidelberg Engineering, Germany)). Nous procédons à une analyse de données grâce au logiciel SPSS où nous mettons en exergue la distribution du RADAAR dans les différentes populations, sa validité et son utilité dans le dépistage du glaucome. Nous enrôlons donc 523 sujets dans cette étude avec 82 sujets atteints de glaucome définitif. La moyenne d’âge est de 62 ans. Il y a plus de femmes que d’hommes et plus de Caucasiens que d’Africains Caribéens. Nous trouvons que la distribution de la mesure du RADAAR est différente des sujets d’un groupe de diagnostic à l’autre. En termes de performance, la sensibilité de la mesure du RADAAR est très basse c'est-à-dire que sa capacité de détecter la maladie est basse. En revanche la mesure du RADAAR est plus spécifique c'est-à-dire que sa capacité d’identifier les sujets exempts de la maladie est plus grande. Elle tendrait à être aussi plus performante chez les Africains Caribéens que chez les Caucasiens. De même, elle serait plus sensible chez les hommes que chez les femmes. La mesure du RADAAR est utile si on l’associe à une autre méthode de diagnostic comme l’analyse de Régression de Moorfields (MRA) incluse dans le logiciel du HRT3 spécialement lors de la détection du glaucome dans la population à haut risque. En définitive, nous déterminons que la mesure du RADAAR se veut un outil d’aide au diagnostic. Elle est particulièrement intéressante dans le contexte de dépistage de glaucome.

Vegetation changes in a river oasis on the southern rim of the Taklamakan Desert in China between 1956 and 2000

The indigenous vegetation surrounding the river oases on the southern rim of the Taklamakan Desert has drastically diminished due to overexploitation as a source of fodder, timber and fuel for the human population. The change in the spatial extent of landscape forms and vegetation types around the Qira oasis was analyzed by comparing SPOT satellite images from 1998 with aerial photographs from 1956. The analysis was supplemented by field surveys in 1999 and 2000. The study is part of a joint Chinese-European project with the aim of assessing the current state of the foreland vegetation, of gathering information on the regeneration potential and of suggesting procedures for a sustainable management. With 33 mm of annual precipitation, plants can only grow if they have access to groundwater, lakes or rivers. Most of the available water comes into the desert via rivers in the form of seasonal flooding events resulting from snow melt in the Kun Lun Mountains. This water is captured in canal systems and used for irrigation of arable fields. Among the eight herbaceous and woody vegetation types and the type of open sand without any plant life that were mapped in 2000 in the oasis foreland, only the latter, the oasis border between cultivated land and open Populus euphratica forests and Tamarix ramosissima-Phragmites australis riverbed vegetation could be clearly identified on the photographs from 1956. The comparison of the images revealed that the oasis increased in area between 1956 and 2000. Shifting sand was successfully combated near to the oasis borders but increased in extent at the outward border of the foreland vegetation. In contrast to expectations, the area covered with Populus trees was smaller in 1956 than today due to some new forests in the north of the oasis that have grown up since 1977. Subfossil wood and leaf remnants of Populus euphratica that were found in many places in the foreland must have originated from forests destroyed before 1956. In the last 50 years, the main Qira River has shifted its bed significantly northward and developed a new furcation with a large new bed in 1986. The natural river dynamics are not only an important factor in forming the oasis’ landscape but also in providing the only possible regeneration sites for all occurring plant species. The conclusion of the study is that the oasis landscape has changed considerably in the last 50 years due to natural floodings and to vegetation degradation by human overexploitation. The trend towards decreasing width of the indigenous vegetation belt resulting from the advancing desert and the expansion of arable land is particularly alarming because a decrease in its protective function against shifting sand can be expected in the future.

The effect of thermal conductivity of RIM moulds in kinetics cure

Reaction Injection Moulding (RIM) is a moulding technology used for the production of large size and complex plastic parts. The RIM process is characterized essentially by the injection of a highly reactive chemical system (usually polyurethane) and fast cure, in a mould properly closed and thermally controlled. Several studies show that rapid manufacturing moulds obtained in epoxy resins for Thermoplastic Injection Moulding (TIM) affect the moulding process and the final properties of parts. The cycle time and mechanical properties of final parts are reduced, due to a low thermal conductivity of epoxy materials. In contrast, the low conductivity of materials usually applied for the rapid manufacturing of RIM moulds, increase the mechanical properties of final injected parts and reduce the cycle time. This study shows the effect of the rapid manufacturing moulds material during the RIM process. Several materials have been tested for rapid manufacturing of RIM moulds and the analysis of both, temperature profile of moulded parts during injection and the cure data experimentally obtained in a mixing and reaction cell, allow to determine and model the real effect of the mould material on the RIM process.

Five Little Monkeys Jumping on the Bed : En litteraturstudie om hur arbete med sång, rim och ramsor kan främja barns utveckling av engelska som främmande språk i grundskolans tidigare år.

Syftet med litteraturstudien är att undersöka hur arbete med sång, rim och ramsor kan främja yngre elevers språkutveckling i engelska som främmande språk. Detta görs genom att fokusera på främjandet av barns språkinlärning, hur lärare bör arbeta med sång, rim och ramsor inom engelska som främmande språk, samt lärares attityder till ett sådant arbetssätt. Arbetet genomfördes som en systematisk litteraturstudie innehållande en bakgrund med relevant teori, samt analys av fem vetenskapliga studier rörande ämnet. Dessa gav möjlighet till en bred bild av området, då länder och perspektiv varierade. Studierna valdes ut genom sökning i databaser efter relevans och tillförlitlighet. I studiernas resultat framgick att majoriteten av tillfrågade lärare och elever var positivt inställda till arbete med sång och ramsor i engelskundervisning, och den språkutveckling dessa metoder innebar. Genom arbete med läraren som förebild motiverades eleverna. Dock fanns en avsaknad av material och kunskap för att kunna genomföra och bedöma undervisning innehållande sång och ramsor. En avsaknad av rim i de studier som analyserats berörs även i studien, likaså en brist på svenska studier. Sammanfattningsvis verkar sång och ramsor enligt de granskade studierna ha ett värde i engelskundervisning. Dock finns det behov av mer forskning och kunskap för att få starkare underlag för användning av dessa metoder i undervisning.

Sånger, rim och ramsor inom engelskundervisning : Lärares attityder till användning av sånger, rim och ramsor för att gynna elevers engelska språkutveckling i årskurs F-3

Syftet med detta arbete är att få en ökad insikt i vad svenska lärare har för attityder till arbete med sång, rim och ramsor i engelskundervisning för grundskolans tidigare år. Frågeställningarna är: 1. Vad har lärarna i studien för attityder till arbete med sång, rim och ramsor inom engelskundervisning? 2. Hur arbetar lärarna i studien med sång, rim och ramsor inom engelskundervisning? 3. Hur ser lärarna i studien på vikten av sin egen roll i arbetet med sång, rim och ramsor i engelskundervisning? I studien utfördes sex stycken semi-strukturerade intervjuer med lärare som arbetar eller nyligen arbetat med engelskundervisning för årskurserna F-3 i en mellanstor kommun i sydvästra Sverige. I resultatet framkom att det finns betydande skillnader i hur individuella lärare arbetar med och ser på arbete med sång, rim och ramsor. Även flertalet likheter framkom, som i sin tur liknade de resultat från tidigare forskning som tas upp i bakgrunden. Flera lärare har en mycket positiv attityd till arbete med sång, rim och ramsor i engelskundervisningen, men det råder stora skillnader i hur lärarna upplever det faktiska värdet för engelskundervisningen och elevernas språkutveckling. Hur lärarna arbetar med sång, rim och ramsor varierar också stort mellan olika lärare, men återkommande knöt lärarna dessa moment till de teman och övriga ämnen som behandlades i undervisningen. Gemensamt var också en bredd i material och medieringsmetoder, samt ett multimodalt arbete som ofta kombinerade ljud, bild och rörelser. Gällande lärarnas roll var de helt eniga i att lärarens engagemang och deltagande hade en stor inverkan på hur arbetet med sång, rim och ramsor mottogs av eleverna. Enligt intervjusvaren deltog alla lärarna i dessa moment, och lät sig inte hindras av faktorer som självförtroende eller bristande kunskaper. Som vidare forskning föreslås mer djupgående studier i lärares attityder, kombinerat med fältstudier och elevintervjuer, för att på så vis uppnå en mer heltäckande bild av arbete med sång, rim och ramsor i svensk kontext.