Performance evaluation of a bulb turbine designed for ultra-low head applications

Abstract

Hydropower is one of the most common forms of clean source of electricity and forms an important source of power for a country like India. This paper is aimed to design mini-hydropower which utilizes ultra-low head and can be used for decentralized power generation and utilization for remote villages. In order to achieve this purpose an axial flow turbine without any guide vanes is designed. This design process is adopted because the presence of inlet guide vanes in the conventional bulb turbines may pose maintenance problem of clogging and also the design is not fish friendly. Another aspect of micro- or mini-hydropower is the non-availability of large reservoirs and there is likelihood that these turbines may be installed as a run-of-the-river type with some seasonal variation of flow rate. The turbine efficiency should be as much as insensitive to the variation in flow rate as possible. In our work, the turbine is expected to produce a relatively flat efficiency flow rate-curve over a range of flow rates. The peak efficiency obtained is about 74%. There is a need to improve the peak efficiency and hence loss analysis is carried out. It was found that the swirling flow in the draft tube downstream of the turbine contributes to a monotonic increase in loss with an increase in flow rate.