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Layout of spillway aerator air ventsand its effect on air supply
KTH, School of Engineering Sciences (SCI), Mechanics.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Utformning av luftinblandares utlopp i utskov och dess effekt på lufttillförseln (Swedish)
Abstract [en]

Chute aerators are constructed to protect spillways from cavitation damage.They function by launching the water ow as a jet and supplying airunderneath since having air entrained into the water is an eective way tomitigate cavitation. This report looks at Bergeforsen, a dam in northernSweden, and its spillway as a basis for investigating how altering the aerator'soutlet alters its performance. Five dierent designs are tested using CFD with ANSYS Fluent 17. The designs are evaluated with regard to totalair ow, air ow distribution, duct pressure distribution, cavity length, andair concentration in water jet.It was found that designs with more even duct pressure distribution, thattransported air further toward the spillway center, had somewhat reducedtotal air supply compared to designs that released more of its air in theearly part of the duct. Consequently there appear to be a trade o betweeneectively distributing the air and providing more air ow. The currentdesign used by Bergeforsen strikes this balance quite well, better than theother tested designs.

Abstract [sv]

Luftinblandare byggs för att skydda utskov från kavitationsskador. De fungerar genom att låta vattenströmmen bli en stråle under vilken luft tillsätts eftersom att blanda in luft i vattenströmmen är ett effektivt sätt att motverka kavitation. Den här rapporten undersöker Bergeforsen, en damm i norra Sverige, och dess utskov för att undersöka hur luftinblandarens utsläpp påverkar dess prestanda. Fem olika designer testas med hjälp av CFD i ANSYS Fluent 17. Designerna utvärderas med avsikt påtotalt luftflöde, fördelning av luftflöde, tryckfördelning i luftgången, längd pålufthålrum, samt luftkoncentration i vattenstrålen.

 Det upptäcktes att designer med mer jämn tryckfördelning i luftgången, som transporterade mer luft till utskovets mitt, hade något mindre total lufttillförsel jämfört med designer som släppte ut mer av luften tidigare ur luftgången. Det ser därför ut att krävas en kompromiss mellan effektiv fördelning och totalt luft flöde. Den design som används i Bergeforsen idag uppfyller den kompromissen ganska väl, bättre än de andra som testades.

Place, publisher, year, edition, pages
2017. , 27 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-208990OAI: oai:DiVA.org:kth-208990DiVA: diva2:1109484
External cooperation
Vattenfall AB
Supervisors
Examiners
Available from: 2017-06-14 Created: 2017-06-14 Last updated: 2017-06-14Bibliographically approved

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