Abstract: The QY90-4.4-1.5 submersible axial flow pump with specific speed 550 r/min and rotate velocity 2 900 r/min is developed. Through the experiment of type and the external characteristics of the variable rotational speed, performance curves such as qV-H、qV-Pa and qV-η are obtained. The conversion for qV-H、qV-Pa and the optimal condition among the variable rotational speed does not meet the proportion law of similar theory, and the affect between similar parabola of general characteristics and efficiency contour is larger. The internal flow fields on effect of the variable rotational speed are numerically simulated by computational fluid dynamics and both velocity distribution and static pressure distribution of blade surface at the various pump rotational speed are obtained. By analyzing the test data, the relation between the external characteristic and the internal flow is discussed, also the investigation results prove that the speed around the blade surface are improved with the increasing of rotational speed and the internal flow of pump can satisfy the assumptions of cylindrical flows without interference. Meanwhile it is showed that lift on the blade increases, the negative pressure on the blade suction surface further reduces and where the cavitation is prone to take place. A fact is demonstrated that viscous force and lift is changing irregularly among variable rotational speed conditions.

Key words: Axial flow pump, Computational fluid dynamics, Net positive suction head, Performance test, Variable speed