Abstract
In engineering, the highest operating head of the pumping station is usually controlled to be slightly lower than the lowest saddle bottom head of the axial-flow pump. However, in the practical operation, it is found that the highest operating head of the pumping station is obviously lower than the saddle bottom head of the pump device, which leads to the reduction of the operating range of the pumping station. To investigate the difference of lowest saddle bottom head between axial flow pump and axial flow pump device and apply it correctly, the energy performance tests of the TJ04-ZL-06 hydraulic model and its corresponding pump device were carried out to obtain the external curves, and numerical simulation was carried out to analyze and compare the internal flow field and pressure distribution. The results show that when the flow rate decreases, the first saddle-shaped region of the axial-flow pump and the saddle-shaped region of the pump device are caused by the decrease of the lift coefficient due to the increase of the attack angle between flow and blade. When the flow rate is less than 0.32Qd, the influence range of backflow in the inlet pipe is large, which leads to the high-pressure zone near the wall of the inlet pressure measurement section during the pump performance test, and hence the second saddle-shaped region of the axial-flow pump is essentially a measurement illusion. It is suggested that the inlet pressure measurement section should be set at least 4Dp away from the inlet flange of the impeller when testing the performance of the axial-flow pump under the condition of small flow rate, and the first saddle bottom head of the axial-flow pump or the saddle bottom head of the corresponding pump device can be considered as the control value of the highest head of the pumping station.
Highlights
Axial-flow pumps play significant roles in irrigation, urban water supply, and flood control [1,2,3]
It can be found that at different blade angles, the first saddle bottom head of the pump is close to the saddle bottom head of the corresponding pump device, while the second saddle bottom head is obviously lower than the saddle bottom head of the corresponding pump device
The energy performance tests of the TJ04-ZL-06 hydraulic model and its corresponding pump device were carried out to obtain the external curves, and numerical simulation was carried out. e conclusions are as follows: (1) ere are two saddle-shaped regions of the axial-flow pump, while there is only one saddle-shaped region of the corresponding device. e first saddle bottom head of the axial-flow pump is close to the saddle bottom head of the corresponding pump device, while the second saddle bottom head is obviously lower than the saddle bottom head of the corresponding pump device
Summary
Axial-flow pumps play significant roles in irrigation, urban water supply, and flood control [1,2,3]. In addition to a large number of studies on the operation of the axial-flow pump and axial-flow pump device under optimal conditions [4,5,6,7], some scholars have studied the operation and harm in the saddle-shaped region. It is found that there is vibration and noise when the axial-flow pump works in saddle-shaped region, which reduces the life of the pump and affects the safety of the pumping station [8,9,10]. Erefore, when selecting a pump for an axial-flow pumping station, the highest head of the pumping station must be lower than the lowest saddle bottom head of the axial-flow pump [11]. The first saddle bottom head of the pump is close to
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