Analysis aerodynamics diffuser-augmented wind turbines

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A complete and consistent, one-dimensional momentum theory is derived for the aero-dynamics of slotted diffuser-augmented wind turbine (sDAWT). This theory does not require empirical relations. It results in a set of three-parameter relations for aerodynamic characteristics such as power coefficient Cp, rotor resistance k, rotor axial force coefficient CT, axial induction factor , wake-expansion factor ß, duct axial force coefficient CT,duct and slot mass flux. The theory predicts that the maximum achievable power coefficient Cp of (s)DAWT's increases monotonically with increasing ß, surpassing the Betz limit of open-rotor wind turbines (ORWT's), already for modest (>2) ß's. The slot of an sDAWT feeds outside air into the diffuser, which for given ß decreases the flow through the rotor and therewith Cp . However, the flow through the slot delays the onset of flow separation in the diffuser, increasing the maximum achievable ß and therewith the power coefficient of sDAWT's beyond that of DAWT's. Based on a vortex model of the (s)DAWT, an expression is derived for the velocity induced at the rotor plane by the diffuser and for the corresponding circulation of the diffuser. The derived three-parameter relations for sDAWT's reduce to two-parameter relations for DAWT's and the familiar one-parameter relations for ORWT's.

Original languageEnglish
Article number042008
Number of pages11
JournalJournal of physics: Conference series
Issue number4
Publication statusPublished - 22 Sep 2020
EventScience of Making Torque from Wind 2020, TORQUE 2020 - Virtual, Online, Netherlands
Duration: 28 Sep 20202 Oct 2020


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