Study On The Numerical Simulation And 3D-LDV Measurement Of Tubular Pump

Tubular pump is the preference pump type for the pumping station with low head, and high discharge in the Eastern Route of South to North Water Diversion Project, especially the bulb tubular pump which suits to the large pumping station became a research focus on pump system of South to North Water Diversion Project. At present, study on the full passage simulation of different bulb tubular pumps and separate simulation of flow passage components was relatively less. In this paper, different types of bulb tubular pump were thoroughly studied by numerical simulation, model test and LDV flow measurement. Mainly in the following areas:Different turbulence models and their application range were compared in this paper, for the internal flow characteristics of tubular pump, it was determined to use RNG k-εturbulence model with consideration of flow separation and vortex effects to simulate the internal flow of tubular pump.The flow status of postpositive and prepositive bulb tubular pump under different conditions were analyzed and the external characteristics of both were calculated, the comparision results of the performance curves showed that best efficiency points of prepositive and postpositive bulb tubular pump system were in the same discharge, and the efficiency of postpositive bulb tubular pump system is about 1% higer than the prepositive one, but at the off-design condition the maximum difference between both was around 5%, the high efficiency area of postpositive bulb tubular pump was wider than the prepositive one.By calculating the hydraulic loss of each part of postpositive bulb tubular pump, it was found that the hydraulic loss of guide vane and bulb unit were in large proportion of the whole hydraulic loss. For this situation, focuses on the design parameters of guide vane, manhole, the bulb shape and the supporting shape which affect the performance of tubular pump, CFD technology was used to optimize the guide vane and the components of bulb unit. The results showed that all the main geometry parameters of the guide vane design, such as guide vane length, single edge diffusion angle, equivalent diffusion angle and so on, affect the performances of tubular pump, it should be chosen the parameters reasonably based on the actual situation. For the guide vane with determined blade shape and basic dimensions, the blade density will affect the hydraulic performance of whole pump. Too little blades will affect the recovery effect of circulation; the excessive number of guide vanes will increase the friction loss and crowding factor which influence the pump efficiency, so it should be consider the blade number of guide vane matches with the impeller blade number; according to the law of streamlined objects with minimum hydraulic resistance, change the componts (such as the tail of bulb, the manhole and the support, etc.) into streamline, choose the good frofile can push the separate point to posterior edge of the object, or even completely avoided the separated phenomenon.The 3D flow field in reversible bulb tubular pump with "S" airfoil impeller was analyzed. The pressure distribution on blade surface was similar at the two-way operating conditions, which indicating the symmetric aerofoil impeller with the same performance in both conditions. However, after adding the other parts to formed pump system, the performance of the two-way pump system became different between the positive condition and reverse condition because of the asymmetry structure in the inlet passage and outlet passage. The influence of bearing supporting on the two-way tubular pump was main studied, the results showed that the arrangement position of bearing supporting was certain influence the system performance in the positive and reverse condition. In the positive condition, the pump efficiency of the scheme that bearing supporting and bulb on both sides of the impeller was higher than the scheme that bearing supporting and bulb on the same side of the impeller, and in the reverse condition, the efficiency of same side scheme slightly higher than the both sides scheme. The positive operation efficiency was higher than the reverse one in two schemes.It is the first time to measure the internal 3D-flow of impeller exit and the guide vane by using 3D-LDV technique, and obtain the circumferential velocity, axial velocity and the radial velocity distribution. The CFD results were verified by the measurement results. The results of CFD and LDV in the distribution of circumferential velocity and axial velocity were close to each other. But the radial velocity diviation between the LDV results and the CFD ones was relatively large, the reasons of deviation were analyzed. The experimental results can be provided the reference for the hydraulic model design of tubular pump.