Experimental Study And Numerical Simulation On The Characteristics Of Submersible Axial Flow Pump

Axial flow pump featuring large flow and low head is widely applied in many fields, such as agricultural irrigation, medium and large pumping stations, urban drainage, and industrial water. Submersible axial flow pump possesses even more simple structure, easy installation and high reliability comparing with regular axial flow pumps. Domestically, the existing advanced hydraulic models are generally used, but there is a paucity of applicable ones with synchronous speed,3000 r/min, and low specific speed. Therefore, the models for the comparatively high-speed axial flow pump need to be developed.As of such a type of pump mentioned above, the applicability of some commonly used impeller design methods is exhaustively discussed. The operating characteristics and internal flow fields of comparatively high-speed axial flow pump are investigated through experiment and numerical simulation, providing scientific evidence for developing high-performance hydraulic models.The main work and conclusions are as follows:1. Model pumps of ns=550 are designed by lifting coefficient method and arc method, respectively, and the guide vane by streamline method. The hub of pump was conically designed.2. The PEO/ENGINEER software are applied to design the axial-flow pump. Hydraulics professional software ICEM is used to generate unstructured grid of the interior fields. The internal flow fields of model pumps have been numerically computed with standard k-εturbulence model, using the ANSYS CFX software. The performances of the model pump are also evaluated. Sequentially, the flow 79 m3/h, the head 3.65 m and the efficiency 73.5% are the optimal performances of pump with lift coefficient method. The efficiency of 82.14% can be reached at the optimal condition, and the flow and head of pump,91.53 m3/h and 4.36 m, respectively by arc method. This part of study shows that the performance of the pump designed by arc method is much better.3. The experiments have been conducted on the performance of the model pump designed by arc method. The experimental results indicate that the efficiency of 82.14% can be reached at the optimal operating point, and the flow and head of pump,91.53 m3/h and 4.36 m, respectively, also coincide well with those of the design condition. Comparing the simulation results with experimental data, the discharge relative errors of-1.67%, shaft power relative error of 4.36%, the efficiency relative error of 1.18% are obtained on the design condition and the relative error are much bigger on the off design conditions. The high fidelity and accuracy of simulation results have reached to some extent.4. The performance experiments have been carried on in order to investigate the effects of rotating speed and thickness of blade on the performance of axial flow pump. The results suggest that the head and shaft power changes obviously as the speed varies, moreover, the optimal condition is shifted to the large flow and the maximum efficiency changes little. Consequently, it can be concluded that the variable speed performance adjustment is comparatively reasonable and effective. It should be mentioned that the thin blade, in comparison with the thick one, is well-performed in the large flow conditions, but the contrary is the case in the small flow conditions.5. Internal flow fields of the model pump in two conditions, i.e. variable speed and variable blade thickness, have been numerically simulated and analyzed. The conclusions are as follows:1) The static pressure of blade increase with the increasing of rotating speed and the pressure isoclines become sparse simultaneously.2) The pressure isoclines of thick blade are relatively concentrated at inlet and outlet areas in the design condition and large flow conditions. The big pressure gradient, flow disorder and big hydraulic losses are the main characteristics. While the pressure isoclines are relatively concentrating and the pressure isoclines twisted on the suction surface in the small flow conditions. The backflow and secondary flow are also generated. Those characteristics are more obvious on the thick blade.3) The characteristics of internal flow field are well agreed with the performances of pump.The working principle of submersible pump is similar to that of other regular pumps under backward working conditions, so the results can be applied to regular pumps.