Abstract
In order to reveal the relationship between rotor‐stator interaction‐induced unsteady flow and the shaft vibration of the mixed‐flow pump, PIV (particle image velocimetry) and axis orbit experiments were carried out synchronously in a mixed‐flow pump under designed flow rate (1.0Qdes) and the partial load conditions (0.4Qdes and 0.2Qdes). The distribution of the relative velocity and the vorticity in the rotor‐stator interaction region at a certain position of the mixed‐flow pump impeller was captured; the axis orbit diagram and the time‐domain diagram of shaft system were acquired as well. Besides, the waterfall diagrams of the frequency spectrum under different flow rate conditions were compared. The results show that the backflow and the flow separation phenomenon appear in the rotor‐stator interaction flow field under the partial load condition, indicating the flow instability. The medium‐frequency exciting force and high‐frequency exciting force induced by these unstable flows resulting from the rotor‐stator interaction are the main factors to intensify the shaft vibration at the power frequency. The rotor‐stator interaction under partial load condition is the main reason for the deterioration of shaft system vibration. The 2X frequency also affects the axis orbit in a low level, while other frequencies have less influence on the shaft vibration. The research results can provide the reference and theory instruction for revealing the operating characteristic of mixed‐flow pump when it operates under partial load conditions and to reduce or to prevent the deterioration of vibration of shaft system.
Highlights
In order to reveal the relationship between rotor-stator interaction-induced unsteady flow and the shaft vibration of the mixedflow pump, particle image velocimetry (PIV) and axis orbit experiments were carried out synchronously in a mixed-flow pump under designed flow rate (1.0Qdes) and the partial load conditions (0.4Qdes and 0.2Qdes). e distribution of the relative velocity and the vorticity in the rotor-stator interaction region at a certain position of the mixed-flow pump impeller was captured; the axis orbit diagram and the time-domain diagram of shaft system were acquired as well
In order to get hold of the relationship between the rotorstator interaction and the shaft system vibration, the PIV experiment and axis orbit collection of a mixed-flow pump model were carried out under the design flow rate condition and the partial load conditions. e flow fields in the impeller interaction zones were developed based on the PIV technology, and the shaft vibration was measured using the Bentley 408 data acquisition system
The shaft movements induced by the unsteady rotor-stator interaction flow fields are related to the axis orbit of mixed-flow pump leading to the following conclusions: Under the partial load conditions, the secondary flow such as the backflow, flow separation, and the unsteady flow of vortexes at various scales appear in the rotor-stator interaction flow field of the mixed-flow pump. us, the medium-frequency exciting force and high-frequency exciting force induced by these unstable flows resulting from the rotor-stator interaction are the main factors to worsen the shaft vibration at the power frequency, which causes the imbalance of the shaft system increasing and the rise on the level of the shaft vibration
Summary
2.1. Experimental Model. e model of the mixed-flow pump in this study is shown in Figure 1. Figure 1(a) shows the impeller of the mixed-flow pump and the hub and blades are painted with black pigment. Figure 1(b) shows the impeller chamber wrapping the impeller and guide vane, which was made of transparency poly methyl methacrylate and its refractive index is close to the water in order to observe clearly.
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