An Optical Fiber Bundle Sensor for Tip Clearance and Tip Timing Measurements in a Turbine Rig

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions.

Performance of an Ocean Energy Conversion System with DFIG Sensorless Control

The 2009/28/EC Directive requires Member States of the European Union to adopt a National Action Plan for Renewable Energy. In this context, the Basque Energy Board, EVE, is committed to research activities such as the Mutriku Oscillating Water Column plant, OWC. This is an experimental facility whose concept consists of a turbine located in a pneumatic energy collection chamber and a doubly fed induction generator that converts energy extracted by the turbine into a form that can be returned to the network. The turbo-generator control requires a precise knowledge of system parameters and of the rotor angular velocity in particular. Thus, to remove the rotor speed sensor implies a simplification of the hardware that is always convenient in rough working conditions. In this particular case, a Luenberger based observer is considered and the effectiveness of the proposed control is shown by numerical simulations. Comparing these results with those obtained using a traditional speed sensor, it is shown that the proposed solution provides better performance since it increases power extraction in the sense that it allows a more reliable and robust performance of the plant, which is even more relevant in a hostile environment as the ocean.

Género y consumo

Curso on-line "Consumo responsable, consciente y transformador". Setem Hego Haizea

Generoa eta kontsumo

On-line ikastaroa "Kontsumo arduratsua, kontziente eta eraldatzailea". Setem Hego Haizea Traducción: Regina Laurrucea Aransolo

Hitzarmen kolektiboen ultraktibitatearen desagerpena

[EU]Lan erreforma indarrean sartu arte, hitzarmen kolektiboen negoziazioen porrotak, aurreko hitzarmenak indarraldia mantentzen jarraitzen zuela zekarren kontrako akordiorik egon ezean. Egun ordea, indarraldi hori urtebetera mugatu egiten da, eta hala, behin epe hori igarota eraginkortasuna galduko du, kontrako akordiorik ez badago, eta beraz, goragoko hitzarmena aplikatuko da (existitzen bada). Erreforma honek, hitzarmenen birnegoziazioa sustatzea eta lan baldintzen petrifikaziorik ez gertatzea du helburu. Baina, araudi berriak, interpretazio arazo ugari sortzen dituenez, lan honekin, eman daitezkeen erantzun posibleak landuko ditugu; eta auzitegiek zein irizpide jarraitu duten aztertuko da. Hitz gakoak: hitzarmen kolektiboa, ultraktibitatea, indarraldia, goragoko hitzarmen kolektiboa.

Precariedad laboral en Europa

[ES] Tras una primera visión del concepto de precariedad y acotación del término en el ámbito europeo, este trabajo trata, por un lado, de exponer los factores y el marco social en el que se crea dicha precariedad laboral y, por otro lado, de analizar mediante diversos indicadores de calidad del empleo la incidencia en el caso de la Unión Europea y España. Se exponen la flexibilidad laboral y otros cambios empresariales, reformas legales o transformaciones en el contexto del mercado del trabajo como causantes del aumento de empleos atípicos, los cuales tiendes a ser de peor calidad. En cuanto a los indicadores de calidad utilizados destacan las tasas de actividad, la temporalidad, la estructura de la renta y el salario mínimo, el porcentaje del trabajo a tiempo parcial con respecto al total o las malas condiciones de trabajo, entre otros. Además se hace referencia a la crisis comenzada en 2007 y al efecto agravatorio de esta en la situación, especialmente en el caso de los jóvenes. Por último, se mencionan ciertas propuestas y políticas laborales.

Detection of particles with a cloud chamber

Cloud chambers were essential devices in early nuclear and particle physics research. Superseded by more modern detectors in actual research, they still remain very interesting pedagogical apparatus. This thesis attempts to give a global view on this topic. To do so, a review of the physical foundations of the diffusion cloud chamber, in which an alcohol is supersaturated by cooling it with a thermal reservoir, is carried out. Its main results are then applied to analyse the working conditions inside the chamber. The analysis remarks the importance of using an appropriate alcohol, such as isopropanol, as well as a strong cooling system, which for isopropanol needs to reach −40ºC. That theoretical study is complemented with experimental tests that were performed with what is the usual design of a home-made cloud chamber. An effective setup is established, which highlights details such as a grazing illumination, a direct contact with the cooling reservoir through a wide metal plate, or the importance of avoiding vapour removal. Apart from that, video results of different phenomena that cloud chamber allow to observe are also presented. Overall, it is aimed to present a physical insight that pedagogical papers usually lack.