Unconventional oil-free high-speed bearing for orc turbogenerator.

Obecnie w małych nowoczesnych systemach produkcji energii najczęściej stosowane są mikroturbiny o mocy rzędu od 1 do 20 kW. Niezwykle istotny jest rozwój niezawodnej technologii łożyskowania wirników tych miniaturowych maszyn przepływowych. Prezentowany w artykule układ wirujący turbogeneratora podparto w bezolejowych łożyskach foliowych. Podatne łożyska foliowe są rodzajem łożysk hydrodynamicznych, które wykorzystują gaz z otoczenia jako czynnik smarujący, co znacząco upraszcza ich konstrukcję.In modern low-power generation systems, microturbines of the power output ranging between 1 and 20 kW are applied. The development of reliable bearing technology for high-speed small turbomachinery could be essential to these power-generating devices. Therotating system presented in the paper is supported in oil-free, airfoilbearings. Compliant surface foil gas bearings are a class of hydrodynamicbearings that use the ambient gas as their working fluid and, thus, require no dedicated lubrication systems, which makes their design much simpler

Crystal size and crystalline volume fraction effects on the Erbium emission of nc-Si:Er grown by r.f. sputtering

Erbium-doped low-dimensional Si films with different microstructures were grown by reactive magnetron sputtering on glass substrates by varying the deposition parameters. Their structure and chemical composition were studied by micro-Raman and Rutherford backscattering spectrometry, respectively. In this contribution the Erbium emission is studied as a function of nanocrystalline fraction and average crystal sizes and also as a function of the matrix chemical composition. We discuss the temperature dependence of the Er3+ emission as well as the possible explanations of the low Er active fraction.FCT (POCTI/CTM/39395) and INTAS Project #03-51-6486

Model of the gas journal bearing dynamics with a exibly supported foil.

The work is devoted to an analysis of the journal bearing dynamics employing a numerical model which takes into account factors related to motion and friction of non{rotating elements of the sleeve. This model yields the basis for simulations carried out in order to determine correctly dynamic characteristics of an oil{free machine rotating system at the early stage of its design and during its operation. On the basis of those simulations, the thickness of gas lm was determined as well as the pressure distribution in the bearing and its lift capacity. Moreover, the numerical program led to an analysis of proper vibrations and forced vibrations of the system under consideration. It was possible to obtain attenuation of the force and to visualize a journal trajectory for the dynamic harmonic input function. The FFT (Fast Fourier Transform) analysis of vibrations was implemented. In the spectrum, only a frequency of the input function was observed, whereas and a lack of subsynchronous frequencies pointed to the stable operation of the bearing

Structural and photoluminescence studies of erbium implanted nanocrystalline silicon thin films

Hydrogenated amorphous and nanocrystalline silicon thin films deposited by Hot Wire (HW) and Radio-Frequency Plasma-Enhanced (RF) Chemical Vapor Deposition were Er-bium-implanted. Their pre-implantation structural properties and post-implantation optical properties were studied and cor-related. After one-hour annealing at 150ºC in nitrogen atmos-phere only amorphous films showed photoluminescence (PL) activity at 1.54 μm, measured at 5 K. After further annealing at 300oC for one hour, all the samples exhibited a sharp PL peak positioned at 1.54 m, with a FWHM of ~5 nm. Amorphous films deposited by HW originated a stronger PL peak than corresponding films deposited by RF, while in na-nocrystalline films PL emission was much stronger in sam-ples deposited by RF than by HW. There was no noticeable difference in Er3+ PL activity be-tween films implanted with 1x1014 atoms/cm2 and 5x1015 at-oms/cm2 Er doses.FCT for a post-doctorate grant (SFRH/BPD/14919/2004

Photoluminescence of nc-Si:Er thin films obtained by physical and chemical vapour deposition techniques: The effects os microstructure and chemical composition

Erbium doped nanocrystalline silicon (nc-Si:Er) thin films were produced by reactive magnetron rf sputtering and by Er ion implantation into chemical vapor deposited Si films. The structure and chemical composition of films obtained by the two approaches were studied by micro-Raman scattering, spectroscopic ellipsometry and Rutherford backscattering techniques. Variation of deposition parameters was used to deposit films with different crystalline fraction and crystallite size. Photoluminescence measurements revealed a correlation between film microstructure and the Er3+ photoluminescence efficiency.FCT Project POCTI/CTM/39395/2001INTAS Project #03-51-648