Embalse El Nihuil: Características hidroquímicas, macro y microflora acuática y estado trófico

Both the physical chemical quality of the water and the primary plankton productivity and the presence of macrophytes are analyzed to assess the trophic status of the reservoir throughout its length and at different times of the year. To do this, electrical conductivity, total solids, anions and cations, among others, have been measured through quarterly sampling, as well as the content of chlorophyll a, phosphorus, nitrogen and Secchi transparency, all as established by the Standard Methods for the Examination of Water and Wastewater. Qualitative and quantitative analysis of phytoplankton has also been carried out, including biodiversity calculations and the estimation of the surface area occupied by macrophytes, as well as present submerged and aerial species. The results indicate calcium sulphated waters, with an average value of total solids around 1 g/L, with very low phytoplankton productivity in which diatoms predominate and a TN:TP ratio < 9, resulting in nitrogen limiting algal development. The trophic state indices (TSI) show a lake with oligotrophic waters in all its extension, even when the great development of macrophytes requires adequate measures for their control and better use of the lake for various purposes.Se analizan tanto la calidad físico química del agua como la productividad planctónica primaria y la presencia de macrófitas para evaluar el estado trófico del embalse en toda la extensión del mismo y en diferentes épocas del año. Para ello, mediante muestreos trimestrales se ha medido la conductividad eléctrica, sólidos totales, aniones y cationes, entre otros, así como el contenido de clorofila a, fósforo, nitrógeno y transparencia Secchi, todos según lo establecido por los Métodos Normalizados para el Análisis de Aguas Potables y Residuales. También se ha realizado el análisis cuali y cuantitativo del fitoplancton, incluyendo cálculos de biodiversidad y la estimación de la superficie ocupada por macrófitas, así como las especies tanto sumergidas como aéreas presentes. Los resultados indican aguas sulfatadas cálcicas con un valor medio de sólidos totales alrededor de 1 g/L, con muy baja productividad fitoplanctónica en la que predominan las diatomeas y una relación TN:TP< 9, resultando el nitrógeno limitante del desarrollo algal. Los índices de estado trófico (TSI) muestran un lago de aguas oligotróficas en toda su extensión, aún cuando el gran desarrollo de macrófitas requiera de medidas adecuadas para su control y mejor aprovechamiento del lago para diversos fines

La migración en México y el mundo

Plans to shut down nuclear power plants in some European countries as well as increased electricity production by wind and solar power will increase the work load on hydroelectric power plants in the future. Also, due to the power grid regulations, hydroelectric power plants undergo more frequent start-ups and shut-downs. During such transient periods, a large amplitude shaft motion can occur, especially in the power plants with vertical shafts. Large shaft motion is not desirable because it can lead to a machine failure. Furthermore, performance limitations of conventional white metal or babbitted bearings call for the development of new bearing designs. An outstanding tribological performance can be achieved by introducing compliant polymer liners. At the same time, bearings with compliant liners may alter rotor-bearing system dynamic behaviour compared to the systems with conventional white metal bearings. The research approach of this thesis is to employ nonlinear analysis to provide further understanding of the compliant bearing dynamic response to synchronous shaft excitation. Plain cylindrical journal bearings with different compliant liner thicknesses were analysed using a nonlinear approach. The numerical model was verified with an in-house developed code at steady state conditions. Results obtained by the numerical models showed good agreement. After verification of the numerical model for fixed geometry journal bearings, models for tilting pad journal bearings were developed. Results for the tilting pad journal bearing with three pads with line pivot geometry were compared with published data in dynamic conditions. A good agreement was obtained between the two numerical models. The effect of pad pivot geometry on bearing dynamic response was investigated. Vertical and horizontal shaft configurations were compared in terms of the effect of preload factor, pivot offset, tapers and pad inclination angles. Influence of the viscoelastic properties of compliant liners was also studied. All these factors significantly affect bearing dynamic response. It is shown how these factors should be selected to control the journal orbit sizes. It was also shown that the compliant liner provides lower maximum oil film pressure and thicker minimum oil film thickness in the bearing mid-plane in both static and dynamic operating conditions.QC 20120319Swedish Hydropower Centr