Sökning: "pulsations"

Visar resultat 21 - 25 av 42 avhandlingar innehållade ordet pulsations.

1. 21. A New Paradigm for Large Brushless Hydrogenerators : Advantages Beyond the Static System

   Författare :Jonas Kristiansen Nøland; Urban Lundin; Phil Mellor; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Brushless exciters; Rotating exciters; Permanent Magnet Machines; Synchronous Generator Excitation; Thyristor Rectifiers; Chopper Rectifiers; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

   Sammanfattning : The grid code, FIKS, from the Norwegian transmission system operator (TSO), Statnett, states that synchronous generators > 25MVA, must have a static excitation system. However, an improved brushless excitation system is in operation on some commercial power plants (36MVA, 93.75rpm & 52MVA, 166. LÄS MER

3. 22. Fluid Dynamics of Fluidized Bed Reactors: Experiments and Simulations with System Interactions

   Författare :Srdjan Sasic; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Air-supply system; Interaction; Fluidized bed; Pressure waves; Pressure fluctuations;

   Sammanfattning : This thesis is a study of the interaction between the fluidized-bed dynamics and the pressure and flow pulsations from the air-supply system. The interaction has been identified as a key process to understand in order to correctly formulate inlet boundary conditions in numerical modelling of fluidized beds, operated under industrial conditions. LÄS MER

4. 23. Fast-response rotating brushless exciters for improved stability of synchronous generators

   Författare :Jonas Kristiansen Nøland; Urban Lundin; Oskar Wallmark; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; synchronous generators; permanent magnet machines; excitation systems; power electronic interfaces; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

   Sammanfattning : The Norwegian Network Code FIKS from the Norwegian Transmission System Operator (TSO) Statnett, states that synchronous generators ≥ 25 MVA must have a static excitation system. It also includes requirements on the step time response and the available field winding ceiling voltage of the excitation system. LÄS MER

5. 24. Turbulence-resolving Simulations of Swirling Flows

   Författare :Ardalan Javadi; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Swirling Flow; URANS; Hydropower; Hybrid URANS-LES; SAS; Flow Control; Turbulence Modeling; Vortex Breakdown; DDES; LES;

   Sammanfattning : A series of numerical investigations is undertaken using a wide range of turbulence mod-els including conventional and non-conventional URANS models, hybrid URANS-LESmethods and LES to capture a large variety of physical mechanisms that produce pres-sure pulsations in the swirling flows. The available knowledge about these pulsations,which are usual in hydropower, are still far from complete. LÄS MER

7. 25. Inside Pulsating White Dwarfs: Clues from time-resolved spectroscopy

   Författare :Rubina Kotak; Astronomi - Genomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; pulsating white dwarfs; convection; asteroseismology; Astronomi; Astronomy; spectroscopy; Fysicumarkivet A:2002:Kotak;

   Sammanfattning : Several analyses using time-resolved optical spectrocopy of pulsating white dwarfs are presented. The data have been put to a number of uses. First, line-of-sight velocities associated with the pulsations have been measured in three hydrogen-atmosphere white dwarfs (DAVs), bringing the total number of such measurements up to five. LÄS MER