Analysis of internal flow and hydraulic performance of bidirectional submersible tubular pump device
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Abstract:
Bidirectional submersible tubular pump device is a kind of mechatronics product combining diving motor and tubular pump technology, which has the advantages of high efficiency of tubular pump device and overcomes the technology problem of cooling, heat dissipation and sealing of traditional pump motor. It is more and more applied in the water conservancy project which combines urban water-logging drainage and water environment improvement.In order to clarify the inflow characteristics and hydraulic performance of the bidirectional submersible tubular pump device, bidirectional submersible tubular pump device in Yangzhou gate pumping station was taken as the research object. Based on SST C-C turbulence model, CFD software was used for numerical calculation of flow field of the full flow channel of bidirectional submersible tubular pump device. And the effectiveness of the numerical calculation was verified by the model test. It was found that, if the the pumping station is dominated by water-logging drainage and supplemented by water diversion, the best calculation scheme of pump device is to put the bulb in front in water-logging drainage condition and put the bulb rearward in water diversion condition. Based on the calculation scheme, the maximum efficiency was 58.41% when the bidirectional submersible tubular pump device was in reverse operation and the maximum efficiency was 59.29% in forward operation at the blade angle of 0° and at the blade adjustment angle of bilateral adjustable guide vanes of 0°. In the forward and reverse operation, the flow-head curve and flow-efficiency curve of the pump device predicted by numerical simulation and model test have the same trend, and the absolute difference of efficiency is within 5%. The high efficiency condition Q=303 L/s in forward operation and Q=237 L/s in reverse operation were selected for analysis: in forward operation, the streamlines in the inlet side of straight tube flow channel, diffusion guide vane and bulb were smooth, the flow pattern was good, and no vortex and other bad flow patterns were observed. While the streamlines in the outlet area of straight guide vane were disordered and flow patterns in the inlet area of outlet side of straight tube flow channel. In reverse operation, the streamlines in the inlet side of straight tube flow channel and inside of straight guide vane were smooth, while vortex cavity were apparently observed in the support of diffusion guide vane. The streamlines at the tail of bulb were also disordered and the flow patterns in the mid-front area of outlet side of straight tube flow channel were disordered; When the flow ranged in 220 to 350 L/s in forward operation, the mean value of axial velocity distribution uniformity in the outlet surface of straight tube flow channel was 92.92% and extreme difference was 2.24%. The mean value of velocity weighted average angle in the outlet surface of straight tube flow channel was 89.81° and extreme difference of each calculation condition was only 0.08%. When the flow ranged in 180 to 280 L/s in reverse operation, the mean value of axial velocity distribution uniformity in the outlet surface of straight tube flow channel was 93.92% and extreme difference was 1.1%. The mean value of velocity weighted average angle in the outlet surface of straight tube flow channel was 89.84° and extreme difference of each calculation condition was only 0.1%; In high efficiency condition, the area of the deviation angle of the water flow from the outlet surface of the straight guide vane to the inlet surface of the outlet conduit was gradually increased in the range of ?0.3° to 0.3° ; The axial force of the two-way impeller of the pump device decreased with the increase of the flow , and the change trend was consistent.Conclusions: (1) when the blade angle was 0°, the blade adjustment angle of bilateral adjustable guide vanes was 0° and the bulb was located on the outer river side, the maximum efficiency of the pump device was 59.29% in the water-logging drainage condition and 58.41% in the water diversion condition. (2) In different flow conditions, the impeller inlet side of the flow structure internal streamlines were smooth, and flow pattern were good; the impeller outlet side of the flow structure internal flow pattern was relatively disordered. In the two-way operation, The pressure on the pressure surface of the blade was uniform, and the flow analysis phenomenon was observed at the inlet edge of the suction surface of the blade. (3) In the two-way operation, the outlet surface of the straight tube inlet flow channel axial velocity distribution uniformity was greater than 92%, the average weighted velocity angle was greater than 89°, the straight tube inlet flow channel provided a good inflow velocity distribution for the impeller. In high efficiency condition, the deflection angle at the inlet of the outlet conduit of the pump device was lower than that at the outlet of the guide vane. The axial force on the impeller decreased with the increase of flow. The research results provided certain reference values for the structural optimization and efficient and safe operation of bidirectional submersible tubular pump device.
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