Abstract
In order to investigate the effect of various impeller tip clearances on the pressure pulsation in a mixed-flow pump, the energy performance test and pressure pulsation experiment of a mixed-flow pump with different tip clearances are studied simultaneously. The pressure pulsation signals at impeller inlet, middle, and oulet are processed and analyzed by the wavelet transform. The results show that the change of tip clearance can affect the head and efficiency of mixed-flow pump. Under designed flow rate, when the tip clearance increases from 0.2 mm to 1.1 mm, the head and efficiency decrease by 18.1% and 11.6%, respectively. Due to the strong influence of blade passing frequency (BPF) at impeller middle, the period of pressure pulsation curve is about 1/4 of impeller rotation period. At impeller inlet, the low-frequency pulsation with energy concentration is the main disturbance frequency, and, with the increase of tip clearance, not only does the high-value region of wavelet spectrum expand to low-frequency direction but also it is easy to form second-order peaks in the time-averaged wavelet curve. At impeller outlet, affected by BPF and rotor-stator interaction (RSI), the high-frequency disturbance in RSI area decreases first and then increases. The wavelet coherence demonstrates the stable low-frequency disturbances in comparison to others and it will affect the flow field at impeller middle.
Highlights
The tip clearance size has a great business with the energy performance of mixed-flow pump
When the tip clearance is 0.8 mm or 1.1 mm, the pump head or efficiency decreases significantly. ese characteristics indicate that the tip clearance should be kept within 0.5 mm in this situation if the pump always operates under designed flow rate
The energy performance and pressure pulsation characteristics of a mixed-flow pump under different tip clearances are analyzed based on wavelet analysis; some findings are as follows: (1) e change of tip clearance can affect the head and efficiency of mixed-flow pump
Summary
E experimental measurements are conducted using Φ250 mm stainless steel closed test rig for mixed-flow pump in Research Center of Fluid Machinery Engineering and Technology, Jiangsu University. The pressure sensor (MPMtype) with 0.5% FS (full-scale) precision was equipped at the inlet and outlet of the mixed-flow pump to measure the pressure. E highfrequency pressure sensors are installed on the impeller end wall of different positions to measure the local pressure pulsation. All the following experimental procedures are applied to the experiment of mixed-flow pump with different kinds of tip clearance size. At the first procedure of experiment, all the experimental facilities are tested, and the supporting software of hydraulic machinery tester is debugged in order to record the pressure date successfully.
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