Inducer is often used to improve the cavitation performance of pump. In order to study the cavitation characteristics of inducer under low flow condition of high-speed pump, high-speed photography technology was employed in this paper to carry out visual experiments on the inducer of a high-speed centrifugal pump. In low flow rates, Cavitation distribution and evolution among the inducer were captured. The experimental results revealed that a band-shaped backflow vortex in the inlet pipe would occur when the flow rate was less than 0.3 Qd. Moreover, the backflow vortex in the inlet pipe rotated with the inducer and the rotational speed of backflow vortex was approximately half of the inducer. The visualization test of 0.27 Qd was carried out: when the NPSH was greater than 6.72 m, the bubbles in the inlet pipe were asymmetrical; When the NPSH dropped to 5.41 m, the cavitation was becoming less asymmetrical; When NPSH dropped to 3.81 m, cavitation evolved to the deteriorating stage, plenty of bubbles entered into the main impeller, resulting in a rapid decline of pump performance. Furthermore, the cavitation performance was worse at an extreme flow rate, and the NPSH value of 0.27 Qd was 7.5% greater than that under design condition.

To research the effects of the blade outlet angle on the performance and the radial force of the marine pump, the unsteady numerical simulation of the four different models is carried out. The radial forces on the impeller and the blades are obtained under different flow rate conditions. The time and frequency domain characteristics of radial resultant force on the impeller and the blades are analyzed and those of the impeller torque are researched. The results show that the radial forces of the impeller and the blades increase with the increase of the blade outlet angle at the same flow rate. With the same blade outlet angle, the radial forces decrease with the increase of the flow rate. The roundness of radial force vector diagram becomes more obvious with the decrease of the blade outlet angle. The root mean square (RMS) of radial force on the blades is about 30% of that on the impeller. The main frequency of radial force on the impeller and the blades is the axial passing frequency (APF), and that of impeller torque is the blade passing frequency (BPF), and there are peaks at the blade frequency multiplier. At the same flow rate, the main frequency and maximum fluctuation amplitudes on the impeller and the blades increase with the increase of the blade outlet angle. Meanwhile, the impeller torque increases with the increase of the blade outlet angle. With the same blade outlet angle, the main frequency, maximum fluctuation amplitudes, and the impeller torque decrease with the increase of the flow rate. The amplitude difference decreases with the increase of the flow rate. The blade outlet angle has an obvious greater influence on the radial forces and fluctuation at the small flow rate. The vibration test shows that the vibration intensities of model 25 and model 35 are less than 2.5 mm/s, and the vibration intensity of model 25 is about 0.2 mm/s less than that of model 35.

Blade thickness is an essential parameter of the impeller, which has significant effects on the pump performance. The plastic pump generally adopts thick blade due to low strength of plastic. The effects of blade thickness on the internal flow and performance of a plastic centrifugal pump were discussed based on the numerical methods. Two kinds of blade profile, the constant thickness blade (CTB) and the variable thickness blade (VTB), were investigated. The results indicated that, for the CTB, when the blade thickness was less than 6 mm, the pump performance did not change significantly. When the blade thickness exceeded 6 mm, the pump head and efficiency decreased rapidly. The pump head and efficiency of CTB 10 decreased by 42.2% and 30% compared with CTB 4, respectively. For the VTB, with blade thickness in a certain range (6 mm–14 mm), the pump performance changed slightly with the increased of trailing edge thickness. The minimum blade thickness of the plastic centrifugal pump should be 4 mm based on the finite element analysis. A variable thickness blade (VTB 4-8-4) with the maximum thickness located at 60% chord length was proposed to improve the pump performance, and its efficiency was 1.67% higher than that of the CTB 4 impeller.