Abstract: On the basis of the area ration principle, the calculation formulae of area ration for the centrifugal pump are deduced, which incarnate the relation between the area ration and the hydraulic parameter of the impeller and volute. The calculation method and formulae of the area ration and the eighth volute cross area for low specific speed centrifugal pump are proposed after increasing the flow-rate, which relate the area ration and the eighth volute cross area to the increasing coefficients of the flow-rate and the specific speed and the hydraulic parameter of the impeller and volute. It is resolved that design condition efficiency for low specific speed centrifugal pump is not the highest in terms of experiential statistical area ration value. The example indicates that the method proposed is practicable, which can enhance the efficiency of low-specific speed pump at design condition. The design theory of low specific-speed centrifugal pump is further enriched.

Key words: Area ration, Efficiency, Increasing coefficients, Low specific-speed centrifugal pump, Volute