Experimental and Numerical Analysis of the Dynamical Behavior of a Small Horizontal-Axis Wind Turbine under Unsteady Conditions: Part I

Abstract

An efficient and reliable exploitation of small horizontal-axis wind turbines (HAWT) is a complex task: these kinds of devices actually modulate strongly variable loads with rotational speeds of the order of hundreds of revolutions per minute. The complex flow conditions to which small HAWTs are subjected in urban environments (sudden wind direction changes, considerable turbulence intensity, gusts) make it very difficult for the wind turbine control system to optimally balance the power and the load. For these reasons, it is important to comprehend and characterize the behavior of small HAWTs under unsteady conditions. On these grounds, this work is devoted to the formulation and realization of controlled unsteady test conditions for small HAWTs in the wind tunnel. The selected test case is a HAWT having 3 kW of maximum power and 2 m of rotor diameter: in this work, this device is subjected to oscillating wind time series, with a custom period. The experimental analysis allows therefore to characterize how unsteadiness is amplified moving from the primary resource (the wind) through the rotor revolutions per minute to final output (the power), in terms of delay and amplitude magnification. This work also includes a numerical characterization of the problem, by means of aeroelastic simulations performed with the FAST software. The comparison between experiments and numerical model supports the fact that the fast transitions are mainly governed by the aerodynamic and mechanical parameters: therefore, the aeroelastic modeling of a small HAWT can be useful in the developing phase to select appropriately the design and the control system set up.

The Yawing Behavior of Horizontal-Axis Wind Turbines: A Numerical and Experimental Analysis

“…A full-scale three-bladed HAWT having 2 m of rotor diameter has been selected as a test case for this work, also on the ground of previous studies (Scappaticci [29], Castellani [31], Castellani [32]) characterizing its design, control and vibration behavior under steady and unsteady conditions. A measurement campaign has been conducted in the wind tunnel of the University of Perugia and the experimental conditions have been replicated using two simulation frameworks: the aeroelastic software FAST, developed at the NREL, and an ad hoc developed code based on Blade Element Momentum Theory.…”

“…The test case is a three-bladed horizontal-axis wind turbine HAWT having two meters of rotor diameter: this prototype has been selected because it has been possible to employ it for full-scale tests in the wind tunnel of the University of Perugia. Furthermore, previous studies had been conducted about the dynamical behavior of this wind turbine, especially as regards vibrations and control (Scappaticci [29], Castellani [30], Castellani [31], Castellani [32]). Sideways, the study of the control and of the performance of small HAWT technology has recently been attracting attention in the scientific literature, especially as regards the interaction with complex ambient conditions (as, for example, urban environment: see Battisti [33], Balduzzi [34], Bianchi [35], Balduzzi [36]).…”

Effect of Wind Tunnel Blockage on the Performance of a Horizontal Axis Wind Turbine with Different Blade Number

“…The turbine was located 1.5 m down exit convergence, and the hub height was 1.2 m from the floor of the test chamber (see Figure 3). Blades had a constant pitch angle with varying rotational speed from 100-700 RPM (see [26][27][28]). This study investigated different inlet velocities of 6, 7, and 8 m/s.…”

Functional Investigation of Geometrically Scaled Drive Components by X-in-the-Loop Testing with Scaled Prototypes

“…The general structure of this virtual coupling is shown in Figure 2. Studies with scaled subsystems also exist in the field of mechatronic systems and wind turbines [16][17][18][19][20][21]. For practical testing and validation activities, it is important to integrate the system under investigation into the overall system.…”