Improvement of the suction performance is also important for the general purpose pumps. The method of improvement is investigated on the centrifugal impeller with splitter blade. Many design alternatives are studied by using CFD. The optimum design of the splitter blade is proved to improve the suction performance of both the centrifugal impeller alone and the pump with centrifugal impeller and inducer.

Cavitation erosion is one of the serious problems because it relates to performance reduction and lifetime reduction of fluid machinery, and a breakage of the component. However, the relationship between cavitation inception and cavitation erosion has not been investigated. In this study, cavitation erosion tests of SUS304 and 9Cr steel were carried out in various liquids by the vibratory apparatus. The test results were evaluated in terms of mean depth of erosion rate (MDER). The effect of vibratory amplitude on erosion rate was discussed. High speed video camera was used to obtain cavitation bubble behaviors.

Small hydropower generation is one of important alternative energy, and potential of small hydropower is great. Efficiency of small hydroturbines is lower than that of large one, therefore there are demands for small hydroturbines to keep high performance. Then, we adopt contra-rotating rotors, which can be expected to achieve high performance. Efficiency of the contra-rotating small hydroturbine is high in pico-hydroturbine and high efficiency can be kept in wide flow rate range. On the other hand, the relatively large loss occurs at the spokes which should be installed for this small hydroturbine to support the rotors. Then, the new spoke to increase its performance is proposed in this research. In the present paper, the performance of the contra-rotating small hydroturbine using different spoke geometry is shown by the numerical results. Further, internal flow condition between the front and rear rotors are investigated.