Bidirectional Impulse Turbine Research Articles

0518 潮流発電用の往復流型ディフューザーの数値解析

The bi-directional impulse turbine and the bi-directional diffuser for tidal energy conversion is investigated in this paper. The bi-directional impulse turbine with fixed guide vanes is adopted because the turbine has a large efficiency and an advantage of maintenance. The turbine characteristics is obtained experimentally by the air turbine test rig. As a bi-directional diffuser suitable for the bi-directional impulse turbine, the diffuser geometry is proposed, which has a straight part and a semicircular brim part. By using a CFD analysis, the diffuser geometries are selected for the water flow turbine. Numerical results showed that the install of the brim can reduce the flow resistance.

Multiple surrogate based optimization of a bidirectional impulse turbine for wave energy conversion

Oscillating water column based wave energy extracting system has a low efficiency due to the poor performance of its principal power extracting component, the bidirectional turbine. In the present work, flow over a bidirectional impulse turbine was simulated using CFD technique and optimized using multiple surrogates approach. The surrogates being problem dependent may produce unreliable results, if a wrong surrogate is selected. Hence, multiple surrogates such as response surface approximation, radial basis function, Kriging and weighted average surrogates were incorporated in this problem. Same design points were used to generate multiple optima via multiple surrogates to enhance the robustness of the optimization process. Numbers of guide vanes and rotor blades were chosen as the design variables, and the objective was to maximize the blade efficiency. Reynolds-averaged Navier–Stokes equations were solved for analyzing the flow physics. The computed results were used to train the surrogates and find the optimal points via hybrid genetic algorithm. The surrogates were further applied to find the optimal flow parameters by changing flow velocity and turbine speed. The relative efficiency enhancement through our present approach was about 16%. Detailed methodologies, analysis of the results and surrogate applicability have been presented in this paper.

Analysis of Flow through Ocean Energy Harvesting Bidirectional Impulse Turbine

Oscillating water column based wave energy device uses bi-directional flow impulse turbine. In this paper, a computational analysis of an impulse turbine has been performed using Ansys-CFX 14.0 code. Initially, a CAD model was prepared and unstructured meshing strategy was implemented in the flow domain. Reynolds-averaged Navier Stokes equations were solved to analyse the fluid flow properties. The efficiency, torque coefficient and input coefficient were compared for the evaluations. The flow features through the turbine shows that the flow separation occurs near the trailing edge of the suction surface of the blade.