A selected literature review of efficiency improvements in hydraulic turbines

Knowing the efficiency of a hydraulic turbine has important operational and financial benefits to those who operate a plant. Historical efficiency and other data on turbine performance are essential for the informed selection and use of turbines. So having such a database from different manufactures is attractive. However, at present it is almost impossible to get a universal database to reflect the turbine characteristics. This paper reviewed a set of empirical equations to replacefull database which defines the peak efficiency and shape of the efficiency curve as a function of the commissioning date for the unit, rated head, rated flow and other main design parameters. Since the design theories, methods and tools of turbines are relatively mature, and the majority of turbine manufacturers have reached a level of know how which enables them to carry out hydraulically and structurally correct units to product high-performance turbines. This paper paid more attention to the design factors, which could influence the value of the practically attainable overall turbine efficiency. To quantify the effects of these factors, this paper investigated the influence of roughness and gap clearances on the internal leakage flow rate. Testing and CFD are the most two important tools in different design stages. This paper reviewed some key ideas and issues on the efficiency research in both. At last, improvement measures based on these above mentioned design factors were provided.