An experimental study of improvement of a micro hydro turbine performance
The thesis includes a literature survey of small hydraulic turbines, incorporating a historical review. The possible role of "micro hydros" in generating power in various parts of the world, and particularly in Iran, is discussed. The theory of turbo machinery, particularly with regard to axial flow turbines, is presented next. This is followed by some details on the design of guide vanes, runner blades and draft tube of axial flow turbines, these components being usually regarded as areas which have major impact on the performance of hydraulic turbines. The next chapter gives the details of the test circuit that was constructed. This could provide water volume flow rates of up to 0.15 m3/s at heads of up 25m. The two dynamometers that were used could adsorb pores to up to 25 kw and 50 kw respectively. An existing micro-turbine, the Agnew turbine, was selected for examination and possible improvement. The first possible improvement was the introduction of guide vanes upstream of the turbine runner (this inclusion necessitated a second support for the main shaft). It was found that this gave significant improvements - efficiency raised by over 20% in some cases. The domain of high efficiency working was considerably extended. It was observed that instability (with fall in power output) could occur after a period of running. This seemed to be associated with an accumulation of air bubbles at the highest point in the casing of the machine. Introduction of a vent from this point was found to relieve this problem and ensure stable operation.