Study on performance of contra-rotating small hydro-turbine with thinner blade and longer front hub

Abstract There is a strong requirement to change fossil fuels into renewable energy in recent years because of the exhausted energy resources and the terrible environment pollution. Small hydropower is one of potential energy resource existing in our living environment and yet not been widely used. Small hydro-turbine can take advantage of this potential and unused energy while it still has some disadvantages, like performing low efficiency and easy to be out of control when there are foreign materials in the water. Thus we design this contra-rotating small hydro-turbine to increase its efficiency and stability. In this paper, a new kind of design method about the blade thickness, which can keep the blockage ratio of the blade constant, is adopted. In addition, a longer and arc chamfered front hub is also designed. The new test turbine is manufactured and the performance experiment is conducted. The numerical analysis is also carried out to investigate the internal flow condition. As the experimental and numerical results shown, the high efficiency area is moved closer to the designing flow rate area, the average efficiency of the new model becomes higher. The efficiency at flow rate Q  = 0.9 Q d and Q  = 0.95 Q d is increased about 1.7% and 2.9%, reaching to 53.2%and 61.2%. The highest efficiency is increased about 0.5%, reaching to 64.7%, and it is obtained at 1.15 Q d . The separation areas and vortex after the front blade and spokes become smaller, and the internal flow condition between the front rotor and rear rotor is improved.