| Bi-directional submersible cross-flow pump is a pump device with large flow rate and low lift.It meets the requirements of bi-directional operation through the forward and reverse operation of impellers with reasonable flow passages.It has the characteristics of compact structure,easy installation,easy maintenance and so on.Therefore,it is often applied to bi-directional pumping stations that give consideration to irrigation and drainage.However,when the pump device is running,there is a large difference between the forward and reverse running performance.In order to further study the causes of the large difference and put forward reasonable optimization suggestions,this paper will use CFD to carry out three-dimensional full-flow numerical simulation of the two-way submersible tubular pump device,analyze its internal flow characteristics and hydraulic performance,and reveal its internal flow rules.The results show that the hydraulic loss of the inlet passage and the guide cone section of the two-way submersible tubular pump device is small and its hydraulic performance is good.Under the design condition,the guide vane and bulb body support play a better role in recovering the annulus,making the flow pattern in the outlet passage smoother.Generally speaking,the hydraulic performance of the pump device is better when it is running in the forward direction.When the pump device runs in the reverse direction,the impeller reverses,the water inlet direction is opposite to the forward direction,and the rear bent guide vane changes into the front bent guide vane.As the bent guide vane plays a pre-rotating role,the flow velocity uniformity at the inlet of the impeller is affected,and the work of the impeller is affected.Secondly,there is no guide vane recovery loop at the outlet of the impeller,so that the water flow in the outlet passage is spiral,and the hydraulic loss increases,thus deteriorating the overall performance of the pump device.In this paper,the curved guide vane in the original device is replaced by the straight guide vane of NACA airfoil.Orthogonal experimental design is carried out on its four main design parameters:the number n of guide vane blades,the chord length L of guide vane blades,the relative thickness ? of guide vane,and the distance D between guide vanes to analyze its influence on the performance of the pump device.The research shows that the difference between the forward and reverse performance of the two-way submersible tubular pump device becomes smaller after the adoption of the straight guide vane,in which the reverse performance is obviously improved and the forward performance is somewhat reduced.With the change of the design parameters of the straight guide vane,the forward performance of the pump device fluctuates greatly while the reverse performance fluctuates slightly.Among many factors,the relative thickness ? of the guide vane has the greatest influence on the performance of the pump device.The single factor analysis of the relative thickness of the guide vane shows that when the pump device is running in the forward direction,the relative thickness of the guide vane has a great influence on the performance of the pump device,and with the increase of the relative thickness of the guide vane,the flow separation on the suction surface of the straight guide vane is improved,and the performance of the pump device is improved first and then decreased.The relative thickness of the guide vane has an optimal value,and an appropriate relative thickness of the guide vane can be selected according to the actual situation to improve the forward performance of the bidirectional submersible tubular pump using straight guide vanes.When the pump device runs in reverse direction,although the performance of the pump device decreases with the increase of the relative thickness of the guide vane,the improvement of reverse efficiency is still obvious compared with the bent guide vane scheme.Therefore,when designing a two-way submersible tubular pump equipped with straight guide vanes,the positive efficiency can be improved by selecting the appropriate relative thickness of guide vanes.In this paper,the pump device model is optimized by the structure of the straight guide vane,and the parameters of the optimal scheme are ?=15%,n=4,d=0.098D,L=130 mm.Under the design conditions,the forward efficiency of the sche3me is 70.47%,the forward lift is 2.55m,the reverse efficiency is 66.09%,and the reverse lift is 3.53m.Compared with the curved guide vane scheme,the forward performance of the pump device is reduced,the efficiency is reduced by 3.1%,the lift is reduced by 0.12m,and the reduction range is not large.The reverse performance is obviously improved,the efficiency is increased by 7.8%,the lift is increased by 1.33m,and the difference between the forward and reverse performance of the pump device and the deviation of the optimal operating point are reduced. |
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