Estimation of blade loads for a variable pitch vertical axis wind turbine from particle image velocimetry

Bruce Leblanc,Carlos Ferreira

doi:10.1002/we.2674

Abstract

AbstractThis paper presents the flow fields and aerodynamic loading of a two bladed H‐type vertical axis wind turbine with active variable pitch for load and circulation control. Particle Image Velocimetry is used to capture flow fields at six azimuthal positions of the blades during operation, three upwind and three downwind. Flow phenomena such as dynamic stall and tower shadow are captured in the flow fields. The phase‐averaged velocity fields and their time and spatial derivatives are used to calculate the normal and tangential loading at each position for each pitching configuration using the Noca formulation of the flux equations. The results show the effect of load shifting from the upwind to downwind region of the actuator using pitch and the effects of dynamic stall on the blades. The results also provide an unique database for model validation.

Highlights

The blades of a vertical axis wind turbine undergo a variety of complex aerodynamic loading fluctuations throughout each rotation: large angle of attack swings, unsteady flow, dynamic stall, blade vortex interaction, and tower shadow to name a few known examples
In order to provide better insight into these phenomena, a set of flow field measurements through Particle Image Velocimetry were conducted using the PitchVAWT active pitch turbine at Delft University of Technology. This paper presents these flow fields as well as the aerodynamic forces acting on the VAWT blade mid-span section for several upwind and downwind azimuthal positions
A set of studies was performed by Ferreira,[7] which presented an array of simulations and particle image velocimetry measurements which focused on the near wake of the turbine and characterized dynamic stall and blade loading with studies using the velocity data captured through both CFD and PIV

Summary

| INTRODUCTION

The blades of a vertical axis wind turbine undergo a variety of complex aerodynamic loading fluctuations throughout each rotation: large angle of attack swings, unsteady flow, dynamic stall, blade vortex interaction, and tower shadow to name a few known examples This leads to many inherent difficulties for designers to properly characterize the loads and performance of these turbines, especially in understanding fatigue. Research interest has increased in the areas of active variable pitch for improving power extraction, controlling the direction of the wake, or minimizing loads.[1,2,3,4,5] In order to provide better insight into these phenomena, a set of flow field measurements through Particle Image Velocimetry were conducted using the PitchVAWT active pitch turbine at Delft University of Technology This paper presents these flow fields as well as the aerodynamic forces acting on the VAWT blade mid-span section for several upwind and downwind azimuthal positions. All data cited in this work are available in online in a dataset collection hosted by 4TU.ResearchData.[18]

| METHODS

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| RESULTS AND DISCUSSION

| CONCLUSIONS