Zoekresultaten

Experimental analysis of radially resolved dynamic inflow effects due to pitch steps

The dynamic inflow effect denotes the unsteady aerodynamic response to fast changes in rotor loading due to a gradual adaption of the wake. This does lead to load overshoots. The objective of the paper was to increase the understanding of that effect based on pitch step experiments on a 1.8 m diameter model wind turbine, which are performed in the large open jet wind tunnel of ForWind – University of Oldenburg. The flow in the rotor plane is measured with a 2D laser Doppler anemometer, and the dynamic wake induction factor transients in axial and tangential direction are extracted. Further, integral load measurements with strain gauges and hot-wire measurements in the near and close far wake are performed. The results show a clear gradual decay of the axial induction factors after a pitch step, giving the first direct experimental evidence of dynamic inflow due to pitch steps. Two engineering models are fitted to the induction factor transients to further investigate the relevant time constants of the dynamic inflow process. The radial dependency of the axial induction time constants as well as the dependency on the pitch direction is discussed. It is confirmed that the nature of the dynamic inflow decay is better described by two rather than only one time constant. The dynamic changes in wake radius are connected to the radial dependency of the axial induction transients. In conclusion, the comparative discussion of inductions, wake deployment and loads facilitate an improved physical understanding of the dynamic inflow process for wind turbines. Furthermore, these measurements provide a new detailed validation case for dynamic inflow models and other types of simulations.

Onderwijs en Innovatie: studiesucces

Presentatie / Pitch over onderzoekslijn Studiesucces van Hogeschool Inholland voor G5-bestuurders en lectorenoverleg

Investigation of the dynamic inflow effects due to collective and individual pitch steps on a wind tunnel setup

Dynamic inflow effects occur due to the rapid change of the rotor loading underconditions such as fast pitch steps. The paper presents a setup suitable for the investigation ofthose effects for non-axisymmetric rotor conditions, namely individual pitch steps. Furthermore, insights into the relevant phenomena are gathered. An individual pitch control capable model wind turbine is set up in a wind tunnel in order to conduct measurement under controllable conditions. During the execution of the collective and individual pitch steps, the loads and the operational parameters are recorded by the onboard sensors. Meanwhile, simulations engineering aeroelastic codes are run in order to evaluate their accuracy for predicting the relevant phenomena. Results show distinct behaviour of the rotor loads during an individual pitch step, which differs from the loads under collective steps. The free vortex wake simulations are able to predict the turbines’ response satisfactory while the blade element momentum tools show deviations from the measurements. The findings serve as a basis for discussion and future work.

Desk research PITCH project

Descriptive statistics Van Gogh PITCH

Social Media analysis Van Gogh PITCH