Numerical Simulation And V3V Measurements On Inlet Rotation Flow Of Vertical Axial-flow Pump

Axial flow pump system, as a mature type, has been applied widely by hundreds of large pumping stations. Compared to other types of pump system, it has advantages of more steady-operation, higher reliability, more convenient installation and reparation, lower investment and maintenance cost. Furthermore, it is much more experienced in design, manufacture, operation and management.The flow pattern at the inlet of impeller chamber of axial-flow pump has a great influence on the operation of large-scale low-head pumping station. Incorrect-designed intake structure of a pumping station may result in pre-swirl in the flow entering the pump and swirl in suction pipe even under no pump operation, which shall change flow condition, and affect adversely both pump performance and cavitation characteristics. Flow rotation problems in the past of axial flow pump unit inlet has done some research, but the content is not thorough, or a single research method, and can’t well reveal the mechanism of axial flow pump inleted vortex and law of development. For the further research of axial flow pump impeller chamber inlet flow not only has inletant theoretical significance, but also has inletant practical value.This paper adopts the numerical simulation combined with experimental research method of vertical axial flow pump unit inleted water flow to study the flow characteristics, especially for the bellmouth internal mechanism of vortex formation and the law of development are analyzed. Numerical simulation of axial flow pump unit is calculated first, and the calculated results are compared under the condition of three different kinds of inleted pump internal flow characteristics, analyzed the horn tube interior features of flow; Second external characteristic experiment was carried out to the axial flow pump unit, and pump assembly external characteristic experiment results are obtained and compared with the results of numerical calculation analysis; Finally uses the international advanced V3V non-contact 3D volume measurement technology of axial flow pump unit inleted the inner regions of the bellmouth, the measurement of flow field, and the measurement results and the numerical analysis results were analyzed.According to the results of numerical calculation, without rotation under the condition of inlets into the flow regime is good, assembly efficiency is highest, at 74.57%, clockwise rotation condition and anti-clockwise rotation inlet into water regime is poorer, under the condition of device efficiency is slightly lower, at 73.39% and 73.66% respectively; The highest efficiency is about 74.57%, the flow rate is about 32L/s and the head is about 2.21m; According to the characteristic test results, the device’s highest efficiency is about 74.51L/s, the flow rate is about 33.49L/s and the head is about 2.12m. The results of numerical calculation is close to the test measured data.No rotation inlet under the condition of water flow by inleted a smooth flow to the direction of the bellmouth, in pump sump there were two obvious along the flow direction of the central axis symmetry along into pool backflow region; Be rotation inlet conditions within the scope of operation condition can arise in pump sump surface vortex, and the stable submerged vortex occurs at the bottom of the bellmouth, surface vortex extends to the impeller chamber, And attached to the bottom of vortex enhanced spiral connection, along with the water into the impeller chamber, affect the pump assembly efficiency.No rotation inlet under the condition of the axial velocity distribution uniformity and The weighted average Angle speed is obviously better than clockwise rotation inlet conditions, no rotation inlet under the condition of the flow regime is better than that of clockwise rotation inlet under the condition of the flow regime, with tangential velocity of water flow into the impeller chamber, can produce adverse effect to the pump running; Be rotation inlet under the condition of fallopian tube internal in scope of small vortex and backflow, vortex tube position by the bellmouth cross section to the impeller chamber inlet section with the increase of the process, the present with the impeller rotating in the opposite direction of migration; Through the circulation near the vortex core analysis, the result shows that the circulation near the vortex core in the same horizontal section increases with the increase of circulation integral radius and the circulation at the same radius increase with increasing distance. V3V test results similar to the results of numerical calculation, found that the vortex in bellmouth is an inletant factor to reduce the operating efficiency of the pump system, to verify the accuracy of the numerical simulation results.