New Simulation Tool Cuts Computing Costs for Renewable Energy Turbines
Researchers have developed a faster way to predict dangerous vibrations and pressure spikes in hydroelectric turbines operating under variable loads—a growing problem as wind and solar power force grids to run these machines unpredictably. The method uses coarser computer models that run 3-5x quicker, potentially saving operators millions in design time and equipment failures.
Originaltitel: Numerical Analysis of Unsteady Pulsating Flows Using a Modified Wall-Function
Kraftverk med förnybar energiintegrering behöver klara kraftiga flödesvariationer som skapar tryckpulsationer och vibrationer i hydrauliska turbiner. Ett nytt väggmodellverktyg minskar beräkningskraven för simulering av dessa instabila flöden samtidigt det behåller precision. Forskare från Bukarest och Luleå testade Manhart-modellen tillsammans med k-ω SST-turbulensmodell på en geometri motsvarande turbindammens utloppskanal. Metoden tillåter grövre beräkningsnät (y+ upp till 5) än konventionella tillvägagångssätt, vilket reducerar simuleringstider utan att offra noggrannhet vid analys av virvelbildning och flödesinstabilitet. Studien använder den öppna programvaran Code_Saturne. För leverantörer av CFD-verktyg och turbinutvecklare utgör snabbare validering av dellastkonstruktioner en väsentlig kostnadsbesparare. Resultaten underlättar design av turbiner som tål ökad variabilitet från sol och vind.
<p>Nowadays, hydraulic turbines are more often operated under off-design conditions due to the increase in intermittent energy production (wind and solar). In these operating conditions, dynamic phenomena in hydraulic circuit are observed, such as flow instabilities, secondary flows, vortex rope developed in the draft tube etc. These phenomena can lead to pressure pulsations and structural vibrations of the hydraulic turbine structure, that affect the hydraulic turbine performance and its lifespan. In the present paper a wall model, developed by Manhart et al. (2008), is used with the k-ω SST turbulence model to study numerically the pulsating flows which can occur in a hydraulic turbine during part load operation. The Manhart wall model considers the adverse pressure gradient and has the advantage of being used on a coarser mesh (dimensionless distance, y+, can result in values up to 5), leading to smaller simulation time and computational demands when compared to the general approaches. The numerical analysis is carried on using the open-source software, Code_Saturne, and considers a geometry that is similar to the draft tube of a hydraulic turbine.</p>