Search

The hydraulic design of a pump is a challenging optimization problem. It has multiple conflicting objective functions based on computationally very expensive (16–20 hours) numerical simulations, and simulation failures, meaning that simulation calls can be unsuccessful. In this article, a surrogate-assisted evolutionary interactive multiobjective optimization method is applied to designing a pump stator. A decision maker's preferences are iteratively incorporated into the solution process and the advantages of an interactive method are demonstrated in two areas: (1) reducing the computation time; and (2) finding a preferred solution that reflects the decision maker's preferences with a low cognitive load. The decision maker was satisfied with the interactive solution process and the final solution reflected his preferences well. Additionally, because he was familiar with the domain of the problem, the preferences he provided guided the search in directions where no failed simulations were encountered. Importantly, the applied method could save days of computation time. [ABSTRACT FROM AUTHOR]

Presented paper deals with the numerical investigation of a flow in a complete hydraulic system of a pump station. The station uses a recently developed high-efficiency axial-flow pump with the specific speed ns=680 min-1. The pump is vertically mounted in the suction object with the free water level and equipped with the suction bell and the suction cone with one rib. For the numerical simulations, the lowest possible water level is considered. Such scenario is the most limiting for the pump station design and need to be analysed properly. The unsteady multiphase numerical simulations were focused on the creation of the complex vortical structures at the suction part of the mentioned axial-flow pump. This phenomenon strongly influences the pump performance (hydraulic efficiency, delivery and suction head, etc.) and operation (especially the vibrations and noise) characteristics. The unsteady flows inside the investigated domains are simulated using Ansys Fluent with appropriate solver settings. The Scale Resolving Simulations (SRS) are used to model large vortices and the interaction between stationary and rotating parts.

The phase transition of austenitic stainless steel of commercial label CL20ES and zinc ferrite nanoparticles was studied in an oxidative atmosphere of dry air to develop a low-cost, effective technique for covering-layer fabrication. CL20ES powder and zinc ferrite powder were mechanically mixed. This mixture was studied in an atmosphere of dry air at different annealing temperatures from room temperature to 900 °C. The employed characterization techniques are X-ray powder diffraction, Mössbauer spectroscopy in the transmission geometry, and scanning electron microscopy with elemental mapping. The fabricated layers were also characterized by surface-specific techniques such as conversion electron Mössbauer spectroscopy and grazing incidence X-ray powder diffraction. The analyzed powder mixture shows resistance against oxidation in dry air and high temperatures. These results were employed to produce zinc ferrite covering layers on 3D-printed cylinders of CL20ES. The results show a predisposition of zinc ferrite to be recrystallized at temperatures above 350 °C without the production of corrosive substances on steel. The zinc ferrite layers were analyzed by an ultrasonic hardness tester as well, which proved the hardness enhancement. [ABSTRACT FROM AUTHOR]