Solid-liquid two-phase turbulent flow simulation and wound experiment in axial flow pump with back swept blade and same external characteristics

Abstract: Demand for urban sewage treatment pumps is increasing annually, especially for sewage axial flow pumps. However, the current design of axial flow pump impeller is with the premise of using water medium, which will lead to serious impeller wear, impeller winding and flow blockage in the actual operation. So it is necessary for the existing axial flow pump impeller design to be modified to adapt to the requirements of the actual delivery of sewage medium. Under the same operation condition, the 40° and 60° back swept impellers were designed and manufactured. Through simulations and pump performance tests, we found that the head curve and efficiency curve of the 2 impellers were basically the same, which verified the reliability of the simulation. Particle model was used to simulate solid-liquid two-phase flow, and we found that solid volume fraction of 60° back swept blade was smaller than that of 40° back swept blade under the designed flow rate. Further, solid volume fraction on pressure surface of 60° back swept blade was 0.1% smaller than that of 40° back swept blade on average, and solid volume fraction on suction surface of 60° back swept blade was 0.2% smaller than that of 40° back swept blade on average. From the simulation results with different particle diameters, we found that with the increase of particle diameter, solid volume fraction of 60° back swept blade increased, and the solid phase concentrated areas were very similar. The radial flow trend of solid phase on the blade pressure surface was stronger and the axial flow trend was weaker; the stronger radial flow meant the solid volume fraction of blade pressure surface should be reduced, while the weaker axial flow trend meant the solid volume fraction of blade pressure surface should be increased. So with the increase of the particle diameter, the axial flow trend was the main factor to solid phase volume fraction on the blade pressure surface. Similarly, on the suction surface, when closer to the inlet, the axial flow trend would be more dominant. From the simulation results, we found with the increase of initial particle volume fraction, the solid volume fraction of 60° back swept blade increased. When the initial particle volume fraction was larger, its impact on the solid volume fraction of the blade pressure surface became smaller. Winding experiments were done with the 60° back swept blade, and we found that when the impeller rotated without sleeve, the anti-winding was strong, but when the impeller rotated with sleeve in water with much cotton, it was easy to block at the rim of the inlet. With different rotating speed, we also found that the faster the rotating speed of the impeller, the faster the cotton hanging on the import edge moved to the flange. This paper provides a reference for the study on anti-wear and anti-winding performance of axial flow pumps.