The world is now facing a serious energy problem. Mass consumption of fossil fuel such as oil and coal causes global warming and the environmental problems due to acid rain. To deal with this problem, the hydropower should occupy the attention of the electric power generation systems as clean and cool energy sources with highest density. However, suitable turbine type is not determined yet in the range of micro hydropower(less than 100kW) and it is necessary to study for the effective turbine type.
According to the recent study results related to the small hydropower development, wasted energy by pressure reducing valve at the end of the pipeline can be extracted by using a small hydropower turbine. Main concept of using the small hydropower turbine is based on using the different water preassure levels in pipe lines. A propeller type hydropower turbine, which is called as tubular turbine, has been used in order to use this renewable differential pressure energy.
Conventionally, tubular turbine has been used in the range of relatively low head of below 10m. However, in order to widen the operating range of the turbine, the purpose of this study is focused on the developing a new design method of the tubular turbine which can be used in the range higher than the head of 10m.
Moreover, this study is aimed to propose a optimum design method which can be applied to the design of the tubular turbine using differential pressure in the water supply system. The reliability of the proposed design method can be acquire by theoretical analysis , CFD analysis and experiment for a tubular turbine model.
According to the present study, the results are obtained as followings.
(1) Operational range of tubular turbine head using differential pressure in the water supply system can be extended to over 10m by the adoption of variable vane angle of the turbine runner.
(2) Best turbine efficiency by an opening angle of the runner vane, which is estimated by optimum design method, agrees well with the result of CFD analysis for the tubular turbine efficiency.
(3) In the head range over 10m, optimum operational condition can be obtained by using 4 pieces of runner vane according to the present design method.
(4) Similarity law of the tubular turbine performance can be confirmed by the two turbines, which are designed by the present optimum design method. The design points of the turbines are flow rate Q=0.215㎥/_(S), effective head H=15m for the actual sized turbine and flow rate Q=0.1043㎥/_(s), effective head H=2.59m for the turbine model.
(5) Application of servo motor for the variation of runner vane opening angle allows to extend the operational condition of the tubular turbine for the expected small hydropower resources.