No abstract

Regenerative pump is a low specific speed and rotor-dynamic turbomachine capable of developing high heads at low flow rates. In this paper, a numerical study has been carried out in order to investigate the effect of blade angle on the performance of a regenerative pump. Two groups of impellers were employed. The first type has symmetric angle blades with identical inlet/outlet angles of ±10°, ±30°, and ±50° and the second group has nonsymmetric angle blades in which the inlet angle was set to 0° and six different angles of ±10°, ±30°, and ±50° were designed for the outlet of the blades. A total of 12 impellers, as well as primary radial blades impeller, were investigated in this study. The results showed that all forward blades have higher head coefficients than radial blades impeller at design flow coefficient. It was found that regenerative pumps with symmetric angle forward blades have better performance than other types. Also, it is worth mentioning that the highest head coefficient and efficiency occur at angle+10<β<+30of symmetric angle blades. It was found that the maximum efficiency occurs at angle of +15.5° by curve fitting to the data obtained from numerical simulations for symmetric angle forward blades.

Purpose Regenerative flow pump (RFP) is a rotodynamic turbomachine capable of developing high pressure rise at low flow rates. This paper aims to numerically investigate the performance of a regenerative pump considering the modification in blade and casing geometry. Design/methodology/approach The radial blade shape was changed to the bucket form and a core is added to flow path. A parametric study was performed to improve the performance of the pump. Thus, the effect of change in blade angle, chord, height, pitch to chord ratio and also inlet port on the performance of RFP was investigated. Findings Results showed that the modified blade angle to achieve the maximum efficiency is about 41 degree. Also, the most efficient point occurs close to pitch/chord = 0.4 and by reducing the axial chord, efficiency of the pump increases. It was found that better efficiency will be achieved by increasing the “Arc of admission”, but there are limitations of manufacturing. It was observed that the performance curves shifted towards lower flow coefficients by reducing height of blades. Originality/value To improve the characteristics of regenerative pump, the blade shape changed to the bucket form (airfoil blades with identical inlet and outlet angle) and a core is added to flow path. A parametric study has been accomplished to see the influence of some important parameters on the performance of the pump.

Peristaltic flow of a viscoelastic fluid is numerically studied in a plane channel. The fluid is assumed to obey the Giesekus model as its constitutive equation, and the flow is assumed to be occurring under incompressible, laminar, and two-dimensional conditions. To simplify the equations of motion, use is made of the long-wavelength assumption together with the creeping-flow assumption. It is shown that for this particular fluid model, the governing equations are reduced to a system of coupled nonlinear ODEs, which are solved numerically using finite difference method. Numerical results show that the elastic behavior of a fluid can significantly decrease the pressure rise of peristaltic pumps. On the other hand, a radially-imposed magnetic field is shown to increase the pressure rise of the pump when the flow rate is less than a certain value. The results are interpreted in terms of the extensional-flow behavior of the fluid as represented by the fluid's mobility (or, extensional) factor.

Water hammer as a critical consequence of unsteadiness may take place in the penstock of the hydroelectric power plants. Hence, the unsteady flow analysis is important to identify undesirable pressure variations and to take preventive actions toward guaranteeing safe operation of the power plant. Chief among these actions are the installation of a surge tank and relief valve, and the transient flow behavior in the presence of protective devices is investigated herein. The method of characteristics is employed to numerically solve the equations governing the transient flow through channels. Also, in order to better resolve the transient behavior, unsteady friction effects have been considered. Validation of the developed computational code is carried out through comparison of the computed transient pressures with those measured at Karun-III Hydropower Plant. According to the results obtained for MONJ Hydropower Station, when only one turbine is in operation, the surge tank decreases the pressure rise within the spiral case and the turbine overspeed by 22% and 6%, respectively. While the percentages associated with employing a proper surge relief valves are accordingly 12% and 14%. This study substantiates how surge relief valves can be used instead of an expensive surge tank to relieve the transient response.