Flow phenomena leading to surge in a centrifugal compressor
2016 (English)In: Energy - The International Journal, ISSN ISSN: 0360-5442, Vol. 103, 572-587 p.Article in journal (Refereed) Published
Surge is a global flow instability occurring in centrifugal compressors at low mass-flow rate operation. Due to its violent nature, it is the limiting factor for operability. To enhance the operating range, understanding of the flow instability inception when approaching surge is essential. Therefore, the flow evolution along a speed line is analysed by performing unsteady, three-dimensional flow simulations using a centrifugal compressor geometry with ported shroud. A stable operating condition, at high mass-flow rates, is compared to lower mass-flow rate operating conditions close to and at surge. The particularities of the flow-fields are analysed and described. A smooth flow-field is observed for the stable operating condition, whereas flow reversal manifesting as tip leakage at the outer periphery of the impeller occurs for all off-design operating conditions. The reversed flow exhibits swirling motion in the impeller rotation direction. This induces a globally swirling flow upstream of the impeller, which influences the flow incidence angles at the blades and hence, their efficiency. Proper orthogonal decomposition and dynamic mode decomposition have been performed to analyse the flow structures appearing with surge more thoroughly. For the lowest mass-flow rate operating condition, low frequency modes describing the filling and emptying processes during surge have been found.
Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 103, 572-587 p.
Compressor flows, Large eddy simulation, Flow decomposition methods, Turbocharged engines, Turbomachinery
Fluid Mechanics and Acoustics
Research subject Engineering Mechanics
IdentifiersURN: urn:nbn:se:kth:diva-185756DOI: 10.1016/j.energy.2016.03.032ISI: 000376800200048ScopusID: 2-s2.0-84961644406OAI: oai:DiVA.org:kth-185756DiVA: diva2:923408
ProjectsCompressor Off-Design Operation at CCGEx
FunderSwedish Energy Agency
QC 201604272016-04-262016-04-262016-06-27Bibliographically approved