Investigation of Transient Characteristics of a Vertical Axial-Flow Pump with Non-Uniform Suction Flow

Abstract

The aim of this paper is to study the influence of non-uniform suction flow on the transient characteristics of a vertical axial-flow pump device. The unsteady calculation is employed to forecast the unstable flow structure with three inlet deflection angles α, and the calculation accuracy under uniform inlet flow is verified by the external characteristic test. The results depict that a promotion in the α will increase the head and shaft power and thus improve the stress and fatigue failure risk of the impeller. At the impeller inlet, the pressure pulsation intensity (PPI) with α = 40° is lower than that with α = 0° caused by a decline in the axial velocity. The dominant frequency of the unsteady pressure signal is the blade-passing frequency (BPF), and the dominant frequency amplitude rises with the increase in α due to the improvement of the pre-rotation impact intensity. At the guide vanes inlet, the dominant frequency of the unsteady pressure signal at the guide vane inlet is also the blade-passing frequency. An improvement in α magnifies the angle between the trailing edge jet of the impeller and the leading edge of the guide vanes under 0.8Qdes and 1.0Qdes, while it diminishes the angle under 1.2Qdes. Thus, the PPI and dominant frequency amplitude with α = 40° are higher than that with α = 0° under 0.8Qdes and 1.0Qdes, but these are lower than that with α = 0° under 1.2Qdes.