Numerical Simulation And Experimental Study On The Inner Flow Of The Submersible Sewage Volute Type Axial Flow Pump

Axial flow pumps are vane pumps with high specific speed, because of simple structure, convenient operation; axial flow pumps are widely used in various fields of the national economy, especially in the large flow and low lift situations. The submersible axial flow pump with the spiral case has the advantages of high flow capacity, convenient installation, and cost saving and so on. At present, there are little researches on the volute type axial flow pump, especially on using computational fluid dynamics(CFD) methods and tests for volute type axial flow pumps hydraulic optimization of the internal flow characteristics, structural characteristics, as well as the pump pressure fluctuation trends.Based on the theoretical analysis; numerical simulation was carried out on the hydraulic model of the volute type axial flow pump. The hydraulic model had been optimized after analyzing the results of numerical simulation. And the internal pressure pulsations at monitoring points were timely and frequency analyzed, and the structure of the pump was also analyzed. Finally, production and testing pump were done.The steady flow in the volute type axial flow pump was numerically simulated by using ANSYS CFX software. Three key hydraulic parameters of volute of cross section, base diameter and volute inlet width were optimized. The optimization results show that the performance characteristics of the volute 3 section are better than the original scheme and the volute 2, the flow distributions in volute 3 are better and smoother than others as well. the head and the efficiency when base diameter is180 mm were higher than that when the base diameter is 190 mm or 170 mm. The inlet width of the volute has little influence on the outer characteristics of the axial flow pump, when the inlet width of the volute is 100 mm, the whole external performance is better. The guide vane type axial flow pump and the volute type axial flow pump are compared with the same impeller. Compared by the results, the head and efficiency of the guide vane type axial flow pump are obviously higher than that of the volute type axial flow pump. At the design flow rate, the head of the guide vane type axial flow pump is higher than the he volute type axial flow pump about 0.7m, the efficiency of the guide vane type axial flow pump is higher than the volute type axial flow pump about 6.2%.The unsteady numerical simulation of the axial flow pump was carried out. The pressure fluctuation characteristics at the monitoring points on the inlet and outlet of the impeller and on the different sections of volute were studied; the axial force of the impeller in a cycle and radial force are studied at the same time. It is found that the monitoring points at radial impeller import and export and the volute in a cycle have certain regulations. The radial force and axial force of the impeller in the 0.8Qopt, 1.0Qopt and 1.2Qopt three conditions are obvious, the trends are the same and the amplitudes are different.Based on the fluid solid coupling technique, the stress distributions and the structural deformations of the three structures under different working conditions were calculated and analyzed. The results show that the fluid loads play an important role in the force and deformation of the impeller, and the distribution of the deformation of the impeller under the fluid loads is asymmetrical, and the asymmetry is more obvious as the flow increasing. The impeller deformations increase with the increasing of the radius, the maximum is in the outer edge of the impeller. Under different flow rate conditions, the stress distributions and deformations rules of the volute are almost the same. Axial stress distributions are of uniform, there is no stress concentration phenomenon. The deformations of the shaft section near the impeller are larger, and the strength meets the requirements in the design condition.Mould for making impeller and volute was manufactured through 3D printing rapid prototyping technology, after machining, finally volute type axial-flow model was assembled. The outer characteristics tests of the volute type axial flow pump were carried out. Tested flow- lift curves and flow- efficiency curve trends are consistent with those of the numerical simulation results. The pressure fluctuations tests of the axial flow pump were carried out. The results show that, under the design conditions, the pressure fluctuations at each monitoring point is obvious, and the main frequency of the 4 monitoring points is near the 134 Hz.