DESIGN ANALYSIS OF BULB TURBINE

Abstract

In view of increasing demand of energy and world's• depleting fossil fuel reserves, which provide the major source of energy, the development of renewable energy sources has got great importance. Small hydropower (SUP) is an important renewable energy source. There exists a large potential in the range of low head small hydropower schemes on canal falls and irrigation . dams. In low head hydropower schemes, energy per unit discharge is low and discharges to be handled are larger. Therefore the cost of civil structure and electromechanical equipment is higher. Due to higher cost previously sufficient attention was not paid to these low head power schemes but these days, increase in tariff rate and increasing energy demand necessitates to develop low head sites. Now several suitable low head turbines are being offered by manufacturers to make this sector attractive for development. In the present study, it is found that bulb turbine is more suitable for such conditions. Straight flow passage of bulb turbine leads to less hydraulic losses. In view of above, for low head hydroelectric power plant the major costs is the initial investment in the civil works structure and the electromechanical equipment. If the cost of the structure is reduced, more attractive small hydroelectric installations would be. In the present study, an attempt has been made to reduce the civil structure cost by reducing the intake structure cost because intakes for bulb turbines are the important structure from cost point of view as they are large in relation to their runner diameters. As the water velocity is low in the intake section of bulb turbine hence the losses are small. Due to this reason intake of bulb turbine can be simplified and shortened to lll decrease the civil structure cost. In the present study, possibilities for simplifying and shortening the intake have been investigated. For this purpose a typical power house having bulb turbine layout has been selected. The dimensions of various components are worked out in terms of runner diameter which is important parameter for deciding the sizing of components. Four intakes of different geometry has been designed. Head losses and capital cost of material is worked out for each type of intake. Due to simplifications and shortening of the intakes head loss is increases but capital cost is decreases. A study has been carried out by capitalizing the energy loss and comparing change in capital cost for different option of intakes. Based on the study carried out optimum intake selection is recommended. iv