The starting phase for pumps in water transportation pipelines is crucial and has significant transient characteristics which merit further study in order to evaluate the operational stability of the pumping system. This paper presents the results of a study in which the relative steady operating conditions and starting period of a large double-suction centrifugal pump were monitored in real time, including pressure fluctuations, shaft run-out and vibration at the bearing. The transient characteristics of a double-suction centrifugal pump under different operating conditions have been analyzed using fast Fourier transform (FFT) and continuous wavelet transform (CWT). Results indicate broadband frequency components within the spectrum of pressure fluctuations in the volute casing under all test conditions, and the central frequency of the broadband frequency gradually decreases as flow rate increases and approaches the blade frequency, which is the primary reason for an increase in blade-frequency amplitude. This may produce a vibration frequency that is similar to the natural frequency of a certain part of the double-suction centrifugal pump during the starting period, which causes the resonance phenomenon. The radial force is also large during the starting period, which causes eccentric wear of the seal ring at the impeller inlet.

The pulsating characteristics in turbulent flow are very important physical quantities. There are many studies focused on the temporal characteristics of pulsation. However, the spatial distribution of temporal states with pulsations rarely receives attention. Therefore, the pulsation tracking network (PTN) method is proposed to track the pulsating characteristics of turbulence. Based on the computational fluid dynamics (CFD) simulation result, the PTN is arranged in a specific region of the flow domain. The fast Fourier Transform (FFT) method is used for time-frequency conversion. As shown in the example of trailing-edge vortex-shedding flow over NACA0009 hydrofoil, important pulsation quantities, including the total pulsation intensity, dominant frequencies, amplitude of frequencies, and the phase and phase difference, can be obtained with a high spatial resolution. The source, reason and attenuation of the vortex-shedding frequency f_vs and the 2 f_vs frequency caused by vortex-interaction are well indicated. The dominant regions of f_vs and 2 f_vs are shown and analysed. The propagation and attenuation of vortex-shedding induced pulsation are understood in detail. Based on the comparison against traditional analysis, PTN is found to function as a good supplement for the CFD post-processing by tracking unknown temporal and spatial characteristics. These findings represent a potential breakthrough in terms of solving actual pulsation-excited flow problems.

A large-scale, vaned-voluted centrifugal pump can be applied as the key component in water-transfer projects. Pressure pulsation will be an important factor in affecting the operation stability. This paper researches the propagation and spatial distribution law of blade passing frequency (BPF) and its harmonics on the design condition by numerical simulation. Experimental and numerical monitoring is conducted for pressure pulsation on four discrete points in the vaneless region, which shows that the BPF is dominant. The pulsation tracking network (PTN) is applied to research propagation law and spatial distribution law. It provides a reference for frequency domain information and visualization vaned diffuser. The amplitude of BPF and its harmonics decays rapidly in the vaneless region. BPF and BPF’s harmonics influence each other. BPF has local enhancement in the vaneless region when its harmonics attenuate. In the vaned diffuser, the pulsation amplitude of BPF attenuates rapidly, but the local high-pressure pulsation amplitude can be found on the vane blade concave side because of obstruction and accumulation of the vaned diffuser. In the volute, the pulsation amplitude of BPF is low with the decelerating attenuation. This study provides an effective method for understanding the pressure pulsation law in turbomachinery and other engineering flow cases.

Canned motor pump is widely used in the transportation of chemical industry. The common failure component of the pump is the sliding bearing. The service life of the bearing will be directly reduced if it bears too much axial force. Thus, it has higher requirements on the axial force balance of the impeller. In this study, the axial force and the axial force self-balance position of the canned motor pump impeller were calculated and analyzed by numerical calculation and experimental verification. By deducing the theoretical formula of the clearance, the relationship between the total axial force of the impeller and the size of the axial clearance is obtained, which can be concluded simply to a functional equation. Based on the principle of curve fitting, an iterative asymptotic strategy is proposed to solve the self-balance position. This method successfully avoids the problem that the axial clearance falls into “solving interval traps.” The results show that the axial force is sensitive to axial clearance at a special interval. The axial clearance size decreases with the flow rate increasing. This study is of great significance for solving the axial force balance state of impeller.