Robust design optimization of gas turbine compression systems

Gas turbine compression systems are required to perform adequately over a range of operating conditions. Complexity has encouraged the conventional design process for compressors to focus initially on one operating point, usually the most commonor arduous, to draw up an outline design. Generally, only as this initial design is refined is its offdesign performance assessed in detail. Not only does this necessarily introduce a potentially costly and timeconsuming extra loop in the design process, but it also may result in a design whose offdesign behavior is suboptimal. Aversion of nonintrusive polynomial chaos was previously developed in which a set of orthonormal polynomials was generated to facilitate a rapid analysis of robustness in the presence of generic uncertainties with good accuracy. In this paper, this analysis method is incorporated in real time into the design process for the compression system of a three-shaft gas turbine aeroengine. This approach to robust optimization is shown to lead to designs that exhibit consistently improved system performance with reduced sensitivity to offdesign operation.

El precio de la gasolina en España: distribución con restricciones verticales

[ES] Hemos realizado un análisis estructural del mercado de la gasolina en España para conocer la manera en la que se establecen los precios de la gasolina en comparación con los de la Unión Europea. Para ello analizamos la cadena de valor de las empresas más destacadas del mercado, así como las distintas barreras de entrada que limitan la competencia. Por último, destacamos las restricciones verticales que estas imponen a sus distribuidores minorista y su incidencia en el precio final del producto.

Study of thin-film SO2 gas sensors by photometric and ellipsometric methods

Pt-, Pd-, and Zr-doped SnO2 thin films and dopant-free VOx films were fabricated by planar magnetron sputtering. Tests for sensitivity to SO2 for all samples were conducted at 180 degreesC, and the sensitivities were investigated ex situ with photometric and ellipsometric methods at room temperature. It was found that the optical sensitivities as well as the sensitive wavelength region for SnO2 films could be tuned by doping. The Pd-doped SnO2 films had good sensitivity in the visible range, and the Zr-doped in the near IR. The dominant sensitive wavelength region for VOx films fell into the visible range, and the ratio of the sensitivity in the visible to that in the near IR increased with O-2/Ar in the depositing atmosphere. (C) 2001 society of Photo-Optical instrumentation Engineers .