Analýza rozpadu paprsku peltonovy turbíny s využitím vlastní ortogonální dekompozice experimentálně získaného souboru snímků

Analysis of Pelton Turbine Jet Decay Using a Proper Orthogonal Decomposition of Experimentally Obtained Image Ensemble

abstrakt

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The decay of the jet produced by the Pelton turbine nozzle is analyzed using the proper orthogonal decomposition of image ensemble obtained from a high speed camera. The ensembles of images were recorded with frequency of 1000Hz and frame size 800x600 pixels, where only the part with a boundary between jet and air is considered. The spatio-temporal behavior of the jet decay is carried out for several flow regimes depending on head and nozzle opening. The first comparison is performed for constant nozzle opening and various heads, while the second one for constant head and various nozzle openings. The nozzle was supplied by a centrifugal pump controlled by a frequency convertor. An image processing, proper orthogonal decomposition and graphical representations are performed using a self-written script in MATLAB software. The effort is to extract main unsteady frequencies and assign them to the behavior of the jet decay – longitudinal and transverse fluctuations. Noticeable is redistribution of spatio-temporal shape of modes when the nozzle operating conditions are changed. One of the jet regimes is also influenced by the frequency of centrifugal pump. Presented results of this work show how the potential undesirable frequency of the jet can be determined when the Pelton turbine is operated.

Rozpad paprsku produkovaného tryskou peltonovy turbíny je analyzován s využitím vlastní ortogonální dekompozice souboru snímků získaných z vysokorychlostní kamery. Soubor snímků byl zaznamenáván s frekvencí 1000Hz a velikosti snímků 800x600 pixelů, kde pouze část obsahující rozhraní paprsku a okolního prostředí byla uvažována. Prostorově-časové chování rozpadu paprsku byla vyhodnocena pro různé režimy v závislosti na spádu a otevření dýzy.

The decay of the jet produced by the Pelton turbine nozzle is analyzed using the proper orthogonal decomposition of image ensemble obtained from a high speed camera. The ensembles of images were recorded with frequency of 1000Hz and frame size 800x600 pixels, where only the part with a boundary between jet and air is considered. The spatio-temporal behavior of the jet decay is carried out for several flow regimes depending on head and nozzle opening. The first comparison is performed for constant nozzle opening and various heads, while the second one for constant head and various nozzle openings. The nozzle was supplied by a centrifugal pump controlled by a frequency convertor. An image processing, proper orthogonal decomposition and graphical representations are performed using a self-written script in MATLAB software. The effort is to extract main unsteady frequencies and assign them to the behavior of the jet decay – longitudinal and transverse fluctuations. Noticeable is redistribution of spatio-temporal shape of modes when the nozzle operating conditions are changed. One of the jet regimes is also influenced by the frequency of centrifugal pump. Presented results of this work show how the potential undesirable frequency of the jet can be determined when the Pelton turbine is operated.

Jet decay, POD, fluctuations, Pelton turbine, nozzle

08.09.2013

Ecole polytechnique fédérale de Lausanne, Laboratory for Hydraulic Machines

Lausanne, Switzerland

Book of Abstract, 5th International Workshop on Cavitation and Dynamic Problems in Hydraulic Machinery

48