Three groups of schemes were designed for different blade inlet angles of impellers to improve the efficiency and single-stage head of submersible well pumps. Furthermore, the hydraulic performance of the pumps was analysed using ANSYS CFX. As a result, the heads and efficiencies of the schemes were acquired. The internal flow fields of the schemes under different flow quantities were analysed, and the accuracy of the optimal scheme was experimentally verified. Results indicated that enlarging the inlet angle of the blade of submersible well pumps might improve the hydraulic performance to a certain degree. In comparison with the general design scheme with a fixed inlet angle that with an inlet angle was 26° at the front cover plate and 20° at the rear cover plate, and that in the middle was under uniform change. The incoming flow angle of the medium coincided with the inlet angle; thus, the discharge capacity of the pump had a high matching ratio with the actual discharge capacity. The head and efficiency improved remarkably relative to the initial model, and thus, the hydraulic performance of the pump improved.
Purpose
This paper aims to study the transient flow characteristics in a mixed-flow pump during the start-up period.
Design/methodology/approach
In this study, numerical calculation of the internal flow field in a mixed-flow pump using the sliding mesh method was carried out. The regulation of the pressure, streamline and the relative speed during the start-up period was analyzed.
Findings
The trend of the simulated head is consistent with the experimental results, and the calculated head is around 0.3 m higher than the experimental head when the rotation speed reached the stable stage, indicating that the numerical method for the start-up process simulation of the mixed-flow pump has a high accuracy. At the beginning, the velocity inside the impeller changes little along the radius direction and the flow rate increases slowly during the start-up process. As the rotation speed reached the stable stage, the flow inside the impeller became steady, the vortex reduced and transient effects disappeared gradually.
Originality/value
The study results have significant value for revealing the internal unsteady flow characteristics of the mixed-flow pump and providing the reference for the design optimization of the mixed-flow pump.
In order to study the shaft system vibration of mixed-flow pump under rotor–stator interaction, the unsteady pressure fluctuation characteristics are measured and the rotor axis orbit obtained based on the Bentley 408 data acquisition system. The relationship between pressure fluctuation and vibration characteristics of shaft system at the blade passing frequency is analyzed. The results show that the pressure fluctuation amplitude is the largest and the rotor–stator interaction effect is the most obvious in the middle of the impeller. Along the direction of the main stream, the velocity energy is converted into pressure energy, the rotor–stator interaction effect is gradually weakened, and the main frequency of the pressure pulsation gradually turns from the 4 X frequency to the 1 X frequency of the impeller rotation frequency. The hydraulic stirring vibration and other factors lead to jagged sharp corners on the original axis orbit. The axis orbit of 1 X frequency is an ellipse with little difference between long and short axis while the 2 X frequency is the opposite, from which the existence of arcuate rotary whirl and misalignment phenomenon of the rotor can be judged. Combined with time–frequency characteristics of pressure pulsation, it can be found that the hydraulic imbalance has a great influence on the vibration of the shafting, while the rotor–stator interaction at the blade passing frequency takes the second place, which is the main factor of inducing the 4 X frequency vibration of the axis orbit. This study targets is that providing practical guidance for improving operation stability and preventing the vibration failure of the mixed-flow pump.
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