In the previous paper, the optimum meridian profile of impeller and guidevane was obtained improving efficiency and cavitation performance. But, the meridian profile of impeller and guidevane is necessary to be decided by the consideration of various operative conditions for the practical use. In particularly, it is important that the separation flow in impeller and guidevane is suppressed in partial flow rate. In this paper, the optimum meridian profile of impeller and guidevane is calculated by considering the partial flow rate operative condition. That is, the optimum criteria are the efficiency, the cavitation performance and the partial flow rate operative condition. The partial flow rate operative condition is expressed by the limited condition of diffusion factor (e.g. Deq = 2). In the optimum procedure, the meridian profile is improved considering diffusion factor at partial flow rate in tip, mid-span and hub stream lines of impeller and guidevane become to the objective value (e.g. Deq = 2) in specified partial flow rate (e.g. Qpartial = 0.5Q). The equation of partial flow rate diffusion factor is expressed by partial inlet-outlet flow condition and additional term expressed by increase of attack angle at impeller inlet and at guidevane inlet. As the result, the optimum meridian profile considering partial flow rate operative condition is obtained.

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