Radiale und diagonale bidirektionale Luftturbinen für den Einsatz in Wellenenergiekraftwerken

This thesis addresses novel bidirectional reaction turbines of radial and mixed flow types which promise several advantages compared to the axial Wells turbines usually installed in present-day oscillating water column (OWC) wave energy converters. Based on the blade element momentum (BEM) method, a design tool for the rotor blades has been developed. Different casing designs were investigated under bidirectional flow and design criteria were developed. Empirical models were employed to estimate specific losses and efficiencies already during the design process. By use of RANS simulations and flow field measurements insights into the air turbines’ fundamental flow phenomena have been gained. One radial and three mixed flow turbines were designed, manufactured and precisely measured at the specially developed bidirectional air turbine test facility at University of Siegen. The functionality of both radial and mixed flow turbines has been demonstrated in experiments. The mixed flow turbines have been proven to be particularly advantageous. Compared to some state of the art Wells turbines, the characteristic curves of the best investigated mixed flow turbine demonstrated a significantly increased power density and a considerably extended operating range at a high efficiency and without hysteresis effects. The peak efficiency as well as the specific noise emission are of similar magnitude as for well-designed axial Wells turbines.