Determination of the Rational Number of Blades of the Centrifugal Wheel of a Submersible Pump

Abstract

The CAD/CAE/CAM method of end-to-end design of the impeller of a seven-stage submersible pump ODDESSEzentralasien –UPP 13-7/6 used for pumping sulfuric acid in hydrometallurgy is presented. The studies are conducted in order to increase the efficiency of the pump manufactured at the KARLSKRONA LC AB LLP plant (Kazakhstan). Computer calculations of the centrifugal wheel with 8 and 9 blades for strength were carried out in the NASTRAN top-level CAE system. The influence of the number of centrifugal wheel blades on the level of stresses arising in the sections of the blades of the cover and main centrifugal wheel discs is determined. The maximum stress in the sections of the wheel with 8 blades reached 319 MPa and the wheel with 9 blades 199 MPa. The influence of the number of blades on the dynamic characteristics of the rotor shaft is examined. To do this, design mechanical and computer schemes of dynamic calculation are simulated to determine the amplitude-frequency characteristics of the rotor shaft. The harmonics amplitudes at frequencies caused by liquid pulsation at the blade frequency of 400 Hz and 450 Hz reached 110 -4  m and 810 -4  m, respectively. Based on the results of computer modeling of static and dynamic problems, a model of the impeller of a centrifugal multistage pump with a rational number of 8 double curvature blades is developed. The choice of the number of blades meets the criterion of wheel strength and the dynamic criterion of the shaft-wheel system. For the production of the prototype wheel, an analysis of the process parameters of 3D printing in terms of surface roughness of finished products is carried out. Based on the analysis, stereolithography the technology is chosen and centrifugal wheels are printed for further bench hydrodynamic tests in a plant. The studies based on CAD/CAE/CAM computer modeling allow reducing the time and costs of developing a rational wheel geometry that meets the criterion of both the strength of the wheel itself and the criterion of vibration activity of the rotor shaft