Abstract
Downsizing is one of the considerations in various engineering technologies at present because of the energy and environmental problem in the future global society. To promote it in hydraulic machinery, we have been engaged in a basic study to develop a high performance mini-pump, the impeller of which diameter is 34mm. One of the design concepts for mini-impeller is to choose larger exit blade-angle. For the test impeller, we use 50°. The experimental result shows that the internal efficiency of more than 60% is achievable. But the unstable Q-H curve was observed in the low flow region. To improve this curve, we introduced the method to return some amount of flow bypassed from the pump exit to the suction pipe. From the experimental results so far, it is examined that the unstable performance can be improved to some extent by using the proposed method.
