STATE OF THE ART IN TURBINE DESIGN

摘要

The paper describes the state of the art in Francis turbine design and focuses on the improvement of efficiency, cavitation performance and dynamic behaviour. Examples of theoretical analyses of the flow regime in runners are presented together with an explanation of the advantages obtained by splitter blades with an optimal shape. A discussion on the optimal use of geometry parameters by means of analysis based on classical potential theory is also included. A brief description is given of the philosophy behind pressure-balanced blades with skewed outlets that are made to stabilize dynamic behaviour and improve efficiency during off-design operation. An explanation is given about the possibility of avoiding cavitation with this design. Because of the reduced specific weight (Tonne & MW) through the introduction of high tensile strength steel, the working stresses have increased and critical material defects have decreased. A discussion on acceptable defects, necessary inspections, safety aspects and the lifetime of turbines is also given.