The specific revolutions are derived from the similar laws of hydraulics to distinguish the similarities of hydraulic characteristics of centrifugal pumps. In centrifugal pumps, often than the number of revolutions understood as: the pump is operating at maximum efficiency, resulting in lm head, flow rate 0.075m ² / s consumed power of 0. 735kW, it must have the number of revolutions. It has the following meanings: 1. Centrifugal pumps of similar geometry have similar operating conditions at the highest point of efficiency; 2. Centrifugal pumps with different specific rotational speeds must have different geometrical shapes; pumps with the same number of revolutions, whose geometry The shape must be similar, but it does not rule out the case of geometric shapes are not similar. The following factors related to the specific speed. Centrifugal pump than the size of the liquid and the nature of liquid transport has nothing to do with the shape of the impeller and the performance curve of the pump are closely related. The pump with a higher specific speed corresponds to a larger flow at the highest efficiency and a smaller head, whereas a pump with a lower specific speed does the opposite and is suitable for smaller flows and higher heads. When the outlet diameter of the pump is the same, if the flow of two pumps is similar, the lift smaller than the number of revolutions is small, and the shaft power consumption is also large. In general, centrifugal pump smaller than the number of revolutions, the impeller exit narrow width, large diameter, the blade formed by the narrow and long flow path. If the ratio is relatively large, the impeller exit wide, small diameter, the short and wide flow channel.
