Mathematical simulation of nonlinear oscillations of viscoelastic pipelines conveying fluid

Improving the cavitation inception performance of a reversible pump-turbine in pump mode by blade profile redesign: Design concept, method and applications

Design optimization of a backward-curved blades centrifugal pump with specific speed of 150 has been performed to improve hydraulic performance of the pump using surrogate modeling and three-dimensional steady Reynolds-averaged Navier-Stokes analysis. The shear stress transport model was used for the analysis of turbulence. Four geometric variables defining the blade hub inlet angle, hub contours, blade outlet angle, and blade angle profile of impeller were selected as design variables, and total efficiency of the pump at design flow rate was set as the objective function for the optimization. Thirty-six design points were chosen using the Latin hypercube sampling, and three different surrogate models were constructed using the objective function values calculated at these design points. The optimal point was searched from the constructed surrogate model by using sequential quadratic programming. The optimum designs of the centrifugal pump predicted by the surrogate models show considerable increases in efficiency compared to a reference design. Performance of the best optimum design was validated compared to experimental data for total efficiency and head.

High-efficiency design optimization of a centrifugal pump †

Small fans with powerful performance are being developed recently, reflecting the trends of the times in which electrical home appliances are becoming smaller and smaller. In order to develop high-performance, high-efficiency fans, an analysis of the effects of design parameters and an optimum design process are essential. This study was conducted to analyze the effects of design parameters of the diffuser in a small, high-speed centrifugal fan, and to derive an optimum model based on the results. Six design parameters (independent variables) were considered for this study: the number of Guide vanes (GVs), the meridional plane length of the GV(rear), the crosssectional area of the Leading edge (LE) in the GV(rear), the beta angle of the Trailing edge (TE) in the GV(rear), the maximum thickness of the airfoil in the GV(rear), and the maximum thickness position of the airfoil in the GV(rear). In addition, the dependent variables were fan performance (vacuum and fan efficiency), and the results were converted to dimensionless values. For screening design, the 26-1 fractional factorial design method was used. To check the existence of the curvature effect, the center point was added. For optimum design, the central composite design method of the Response surface methodology (RSM) was used for two design variables. P-value and T-value were used to determine whether each compounded factor was appropriate for the analysis object of the design of experiments. The results of the screening design were expressed by Pareto chart and main effects plot, and the results of the optimum design by surface plot, overlaid contour plot, and Response optimization. The reliability of the Computational fluid dynamics (CFD) was verified through a comparison between the experiment results and CFD results of the optimum model. As a result of the screening design, the design parameter that had the greatest influence on fan performance was the beta angle of the TE in the GV(rear), followed by the number of the GV(rear) and the maximum thickness of airfoil in the GV(rear). It was judged that the vacuum increase was determined by the beta angle of the TE in the GV(rear), and that the main cause of the vacuum decrease was the increase of pressure loss due to the decreasing cross-sectional area between the GVs and the generation of a vortex at the hub of TE in the GV(rear).

Optimum design of diffuser in a small high-speed centrifugal fan using CFD & DOE

As a single-channel pump is used for wastewater treatment, this particular pump type can prevent performance reduction or damage caused by foreign substances. However, the design methods for single-channel pumps are different and more difficult than those for general pumps. In this study, a design optimization method to improve the hydrodynamic performance of a single-channel pump impeller is implemented. Numerical analysis was carried out by solving three-dimensional steady-state incompressible Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. As a state-of-the-art impeller design method, two design variables related to controlling the internal cross-sectional flow area of a single-channel pump impeller were selected for optimization. Efficiency was used as the objective function and was numerically assessed at twelve design points selected by Latin hypercube sampling in the design space. An optimization process based on a radial basis neural network model was conducted systematically, and the performance of the optimum model was finally evaluated through an experimental test. Consequently, the optimum model showed improved performance compared with the base model, and the unstable flow components previously observed in the base model were suppressed remarkably well.

Optimization of a Single-Channel Pump Impeller for Wastewater Treatment

In double-suction centrifugal pumps, it was found that cavitation instabilities occur with vibration and a periodic chugging noise. The present study attempts to identify cavitation instabilities in the double-suction centrifugal pump by the experiment and Computational Fluid Dynamics (CFD). Cavitation instabilities in the tested pump were classified into three types of instabilities. The first one, in a range of cavitation number higher than breakdown cavitation number, is cavitation surge with a violent pressure oscillation. The second one, in a range of cavitation number higher than the cavitation number of cavitation surge, is considered to be rotating cavitation and causes the pressure oscillation due to the interaction of rotating cavitation with the impeller. Last one, in a range of cavitation number higher than the cavitation number of rotating cavitation, is considered to be a surge type instability.

http://koreascience.or.kr:80/article/JAKO201431454589567.pdf

Shusaku Kagawa

Papers

Study of Cavitation Instabilities in Double-Suction Centrifugal Pump

Flow Characteristics in a V-shaped Region of a Suction Performance Curve in a Double-suction Centrifugal Pump

New Centrifugal Pump in Very Low Specific Speed Range

Numerical Study of One Dimensional Pipe Flow Under Pump Cavitation Surge

Cavitation CFD analyses considering the pressure wave propagation within the piping systems