Copy this text
Experimental measurements of a synchronized flow velocity and a marine current turbine power production
An experimental database has been obtained in order to study the correlation between the flow turbulence and the performances of a marine current turbine. To this aim, a model of a tidal three-bladed horizontal axis turbine (1:20 scale) has been used in the IFREMER wave and current flume tank. In order to understand better the influence of turbulence on the turbine behaviour, the torque and the flow velocity have been recorded simultaneously in two locations (upstream and downstream of the turbine). The power produced has been measured at moderate frequency and the flow velocity measured using a Laser Doppler Velocimeter (LDV) with a high frequency sampling rate over a long period of time (three hours). The objective of this study is to carry out a statistical analysis of the flow time series, the torque measurements, and to study their coherency.
The tests were carried out in the wave and current flume tank of IFREMER. The experimental working section is 4m wide by 2m deep and 18m long. The upstream intensity rate can be regulated by the use of flow straighteners. Two configurations are considered in this work with a mean upstream flow velocity of 0.8 m/s: configuration C1 with flow straighteners for a low turbulence rate of ~4 % and C2 without flow straighteners for a high turbulence rate of ~14 %. The flow velocity is measured at a distance of four times the turbine diameter D. These measurements are acquired successively at two locations, upstream and downstream of the turbine along is main axis (x direction). Furthermore, a second downstream measurement is taken at a distance D/2 in the y direction. The sensor device is a 2D Laser Doppler Velocimeter system that acquires point velocity values (u,v) related to (x,y) with an irregular sampling rate, that goes up to 800 or 900 Hz.
The model consists of a three-bladed horizontal axis turbine, which is D=0.7m in diameter. The rotor is connected to a motor-gearbox assembly consisting of a gearbox, a DC motor, a ballast load and a motor speed control unit, providing an active rotor speed control. The turbine blades are designed from a NACA 63-418 profile. A torque meter is placed between the rotor and the gearbox for torque measurements at 100Hz. The measurements are performed upstream at a distance of four times the diameter for TSR = 4 (which corresponds to the nominal operating point) and TSR = 2.5, with a view to studying the turbine model behaviour for various operation conditions.
In the article referenced below (Renewable Energy 2017), the experimental devices and the databases are presented. The turbulence and the flow scaling properties are characterized as well. The theoretical framework is the one of multi-fractal cascades and intermittency studies, a classical approach in fully developed turbulence. Non-linear and non-stationary methods such as Empirical Mode Decomposition (EMD) and Time Dependent Intrinsic Correlation (TDIC) have been used for correlation study.
50.729627N, 50.729627S, 1.597578E, 1.597578W