Design and testing of a contra-rotating tidal current turbine

Abstract

A contra-rotating marine current turbine has a number of attractive features: near-zero reactive torque on the support structure, near-zero swirl in the wake, and high relative interrotor rotational speeds. Modified blade element modelling theory has been used to design and predict the characteristics of such a turbine, and a model turbine and test rig have been constructed. Tests in a towing tank demonstrated the feasibility of the concept. Power coefficients were very high for such a small model and in excellent agreement with predictions, confirming the accuracy of the computational modelling procedures.High-frequency blade loading data were obtained in the course of the experiments. These show the anticipated dynamic components for a contra-rotating machine. Flow visualisation of the wake verified the lack of swirl behind the turbine. A larger machine is presently under construction for sea trials.

FEA – Finite Element Analysis

“…Turbine design is more fully described in [14][15]. In summary, an extension of conventional blade element momentum (BEM) theory was used to predict the geometry of the downstream rotor relative to the specified upstream rotor.…”

“…Performance predictions for the turbine are given in [15]; as in the original small model, provision is made for adjusting the blade pitch.…”

Development and In-Sea Performance Testing of a Single Point Mooring Supported Contra-Rotating Tidal Turbine

“…After successful proof of concept trials on a 0.9 m diameter contra-rotating turbine in a towing tank [1], a larger 2.5 m diameter prototype was constructed (see Figure 1). Sea trials in the Clyde estuary confirmed the inherent stability of the contra-rotating design and for the first time provided high-resolution measurements of blade bending moments, from strain gauges attached to blade roots on both rotors.…”

“…The 2 nd generation contra-rotating marine current turbine developed by the Energy Systems Research Unit (ESRU) at the University of Strathclyde has been widely reported and is now reasonably wellknown [1,2]. Two key features of the design, which uses two rotors with a dissimilar number of blades in close proximity, is: the increased relative shaft speeds enable the elimation of a gearbox in favour of a direct drive permanent magnet, contra rotating generator; and the ability to mitigate/ minimise the reactive torque transmitted to the supporting structure, permitting the use of relatively simple, economic mooring systems and allowing deployments in very deep water.…”

Investigating the Influence of the Added Mass Effect to Marine Hydrokinetic Horizontal-Axis Turbines Using a General Dynamic Wake Wind Turbine Code

“…More efficient MHK turbine designs help to reduce the cost of marine energy and make it more competitive with other forms of energy production. Recent studies of MHK devices [1][2][3][4] mainly focus on quasi-unsteady modeling techniques. Accurately modeling the unsteady effect of the rotor fluid dynamics is still a challenge.…”