Numerical Investigation and Optimization of a Stator for a Radial Submersible Pump Stage With Minimum Stage Diameter

For radial multistage pumps with stationary vaned diffusers the diameter of the pump casing is much larger than the diameter of the impeller. In the case of submersible pumps, where just a limited space for installing the pump is available, smaller stator diameters need to be realized resulting in a loss in efficiency. Improving the design of these pumps and in order to save space and to decrease costs, alternative stators are being developed at the Institute of Turbomachinery and Fluid mechanics at University of Kaiserslautern. With respect to space, the optimum is a pump stage with a stage diameter equal to the outer impeller diameter. For realizing this concept, it is necessary for the flow to exit the radial impeller in axial direction before entering the stator. The advantage of this design is that when keeping the stage diameter constant, a much larger impeller diameter and thus a much higher hydraulic head can be realized. On the other hand, when keeping the hydraulic head or specific speed constant, the diameter of the pump casing can be much smaller. In this paper, the numerical calculation of the flow through the pump stage with minimum stage diameter is presented. Fully transient calculations with the sliding mesh method are performed. The numerical model consisting of the complete impeller with side gaps and stator is validated by measurements of characteristic curves and hot-wire data. After discussing the deficit of the initial stator layout, an optimized stator with a pump efficiency comparable to a conventional stator is presented. All results are compared to characteristic curves of a pump stage with conventional stator.