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Hole extension effect on transpiration flow efficiency

Lewandowski T., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2015

Vol. 19, No 2

121--128

The present analysis of the hole extension effect on the transpiration flow efficiency is a part of the research [1] which aims at defining a physical transpiration model of the flow through perforated plates. Perforated walls find a wide use as a method of flow control and effusive cooling. Some data on the L/D (hole length to diameter ratio) effect on the flow structure and mass flow rate may be found in the literature [2, 3], but all those works concern holes of a diameter at least one order of magnitude larger than those used in the simulations presented in this paper. Due to the size of the analyzed holes and their cylindrical shape, the only method of analysing the flow through such holes is the numerical method. In the conducted simulations, the holes were D = 0.6 mm, 0.3 mm and 0.125 mm in diameter and the perforation values were equal to 4%, 5%, 8% and 10%. The L/D ratio was changed between 0.25 and 8. The data bank of the flow through the cylindrical holes was produced. The hole extension has a significant influence on the obtained mass flow rate and, consequently, on the transpiration flow efficiency. In addition, entrance effects appear to be important.

Numerical analysis of eddy-current losses in the rotor of a high-speed synchronous machine

Kolondzovski Z., Belahcen A., Arrkio A.

Przegląd Elektrotechniczny

2007

R. 83, nr 7-8

115-118

In the paper eddy-current loss distribution is numerically estimated in the rotor parts of a high-speed permanent magnet (PM) synchronous machine. The machine under study is a high-speed PM motor designed for power P=130 kW and rotational speed n=31500 rpm. The analysis is performed with and without screen and for different L/D ratios for the rotor dimensions. It is shown that when using an aluminum screen the total rotor eddy-current losses are significantly reduced and the losses in the magnets are negligible.

W artykule przedstawiono oszacowanie rozkładu strat wiroprądowych w częściach wirnikowychwysokoobrotowego silnika synchronicznego z magnesami trwałymi. Badany silnik został zaprojektowany z następującymi parametrami: moc P=130 kW, prędkość obrotowa n=31500 rpm. Analiza przeprowadzona została z ekranem i bez ekranu dla różnych wielkości stosunku długości do średnicy wirnika L/D. Z przeprowadzonej analizy wynika, że użycie ekranu aluminiowego znacząco redukuje straty wiroprądowe a straty mocy w magnesach są pomijalne.