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    Experimental and CFD investigation of a multistage centrifugal pump including leakages and balance holes
    (DESALINATION PUBL, 2017) Babayigit, Osman; Ozgoren, Muammer; Aksoy, Muharrem Hilmi; Kocaaslan, Osman
    The aim of this study is to analyze numerically a multistage pump with some new approaches and compare the results with experimental data. A centrifugal pump, consisting of six backward curved blades, ten vane diffusers and two stages, was used. First, models of an impeller, a diffuser, suction and discharge sections of the centrifugal pump were separately designed by empirical equations. The flow volume of the pump was numerically solved by different turbulence models. Thus, the most accurate results in comparison with experimental data were obtained for the realizable k-epsilon turbulence model. For the purposes of this study, the effect of balance holes and leakages (clearances) on the performance was scrutinized. In most studies, it is not taken into consideration in computational fluid dynamics (CFD) analyses due to the difficulty of meshing these regions. The experimental studies were performed at a computer controlled pump test rig that was established according to the standard TS EN ISO 9906. The results of CFD/experimental analyses for the pump head, hydraulic efficiency and hydraulic power on the design point, having the flow rate of 80 m(3)/h and the revolution of 2,975 rpm, were found to be 81.47/80.70 m, 51.98%/51.42% and 17.94/17.77 kW, respectively. The obtained CFD and experimental results were found to be close agreement for the design flow rate as well as for all tested flow rates. Other characteristics of the pump such as velocity, static pressure, streamline patterns and turbulence kinetic energy were also investigated. In addition, the leakages and balance holes have significantly affected the pump characteristics, which must be considered in CFD analyses in order to find more precise results for true-to-life simulations.
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    Numerical identification of blade exit angle effect on the performance for a multistage centrifugal pump impeller
    (E D P SCIENCES, 2015) Babayigit, Osman; Kocaaslan, Osman; Aksoy, Muharrem Hilmi; Guleren, Kursad Melih; Ozgoren, Muammer
    Nowadays, single and multistage centrifugal pumps are widely used in industrial and mining enterprises. One of the most important components of a centrifugal pump is the impeller. The performance characteristics are related to the pump comprising the head and the overall efficiency rely a great deal on the impeller geometry. In this work, effects of blade exit angle change on hydraulic efficiency of a multi stage pump impeller are investigated via Ansys-Fluent computational fluid dynamics software for constant width impeller entrance and exit gates, blade numbers and blade thickness. Firstly, the flow volume of a centrifugal pump impeller is generated and then mesh structure is formed for the full impeller flow volume. Secondly, rotational periodic flow model are adopted in order to examine the effect of periodic flow assumption on the performance predictions. Corresponding to the available experimental data, inlet mass flow rate, outlet static pressure and rotation of impeller are taken as 0.02m(3)s(-1), 450 kPa and 2950 rpm, respectively for the water fluid. No slip boundary condition is exposed to all solid of surface in the flow volume. The continuity and Navier-Stokes equations with the k-epsilon turbulence model and the standard wall functions are used. During the study, numerical analyses are conducted for the blade exit angle values of 18 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees. In consequence of the performed analyses, it is determined that hydraulic efficiency of the pump impeller value is changed between 81.0-84.6%. The most convenient blade exit angle that yields 84.6% hydraulic efficiency at is 18 degrees. The obtained results show that the blade exit angle range has an impact on the centrifugal pump performance describing the pump head and the hydraulic efficiency.