Abstract:The objective of this paper is to develop the shape of an existing volute so that the radial forces in off-design condition become minimum. For this purpose 3-D inverse design method based on the 3-D viscous flow calculations was applied to re-design the geometry of the volute of a low specific speed pump. Various aspects of the geometry change independently to achieve the best one which produces less radial force in off design conditions. Measurements included time-averaged values of velocity and static press… Show more
“…7 showed that radial force depends on the geometry of the region where the gap between impeller and volute is small, including both tongue shapes and blade-tongue gap. More recently, Torabi and Nourbakhsh 8 studied the effects of volute geometrical factor variation on radial force. They observed that the gap between impeller and tongue severely affects the radial force.…”
In this study, we investigated the effects of volute tongue geometry variation on the head, efficiency, and radial force of a centrifugal pump. Numerical simulation modeling based on k À ! turbulence with automatic near wall treatments was used to simulate the turbulent flow. The effect of blade position with respect to the volute tongue on instantaneous pump characteristics was investigated. The parametric studies were done for cutwater gap, tongue shape, and volute tongue angle. Numerical results showed that the large cutwater gap caused lower radial force, especially at high flow rates. Investigations using various volute tongue shapes indicated that the short tongue volute decreased the radial force at design and low flow rates. Considering all aspects, the most satisfactory volute tongue angle was found to be 5 less than the outlet velocity angle of the impeller; yielding about 40% lower radial force than others at the design point.
“…7 showed that radial force depends on the geometry of the region where the gap between impeller and volute is small, including both tongue shapes and blade-tongue gap. More recently, Torabi and Nourbakhsh 8 studied the effects of volute geometrical factor variation on radial force. They observed that the gap between impeller and tongue severely affects the radial force.…”
In this study, we investigated the effects of volute tongue geometry variation on the head, efficiency, and radial force of a centrifugal pump. Numerical simulation modeling based on k À ! turbulence with automatic near wall treatments was used to simulate the turbulent flow. The effect of blade position with respect to the volute tongue on instantaneous pump characteristics was investigated. The parametric studies were done for cutwater gap, tongue shape, and volute tongue angle. Numerical results showed that the large cutwater gap caused lower radial force, especially at high flow rates. Investigations using various volute tongue shapes indicated that the short tongue volute decreased the radial force at design and low flow rates. Considering all aspects, the most satisfactory volute tongue angle was found to be 5 less than the outlet velocity angle of the impeller; yielding about 40% lower radial force than others at the design point.
“…In the case of manufacturing and cost analysis, the tangential diffuser is more suitable, and based on the latest study, the hydraulic forces created in the tangential diffuser are less than those of the radial one. 24 Figure 5.Parameters of volute with a tangential diffuser.…”
Section: Different Shapes Of Volute Cross-sectionmentioning
There is a misunderstanding about the volute casing of the centrifugal pump. Since it is a stationary part, it is assumed that the volute has a slight impact on the efficiency of the pump; however, this part has a considerable effect on the efficiency and is considered an important part converting the dynamic energy to static pressure. To authenticate this fact, in this article, main parameters of the volute which consist of the cross-section shape, theories of designing the volute (i.e., conservation of angular momentum and constant velocity), volute throat area, cutwater angle, cutwater diameter, base circle diameter, volute inlet width, diffuser length and outlet cross-section, and linear and quadratic diffusers are investigated. First, the performance curve has been obtained experimentally and numerically. In simulations, a proper turbulence model has been used and the continuity and the Navier–Stokes equations have been solved. Moreover, with the accurate analysis of contours, streamlines, and recirculation areas on the volute throat area and diffuser, all parameters have been optimized. According to the results, hydraulic efficiency and head of the circular cross-section are 87.6% and 14.55 m, respectively, which is the most efficient compared with the other shapes. The results also revealed that the most appropriate theory for designing the volute is the conservation of angular momentum, and the cutwater angle of 10° with the lowest possible cutwater diameter (3 mm) has the best efficiency (88.1%). Furthermore, the base circle diameter has the optimal value (220 mm, efficiency = 88.7%); otherwise, head loss of the volute increases. The volute inlet width of 23 mm has a hydraulic efficiency of 88.93%, and its head loss is the lowest. Increasing the length of the diffuser decreases its efficiency, and the length and diameter of the discharge area of the most appropriate one are 160 mm and 65 mm, respectively.
“…Their research showed that volute with round cross section gives more head and efficiency in comparison with trapezoidal and rectangular cross sections. More recently, Torabi and Nourbakhsh [9] studied the effects of some volutes geometrical factor variation on radial force. They found that the gap between impeller and tongue severely affects the radial force.…”
The effects of the volute geometry on the head, efficiency, and radial force of a low specific-speed centrifugal pump were investigated focusing on off-design conditions. This paper is divided into three parts. In the first part, the three-dimensional flow inside the pump with rectangular volute was simulated using three well-known turbulence models. Simulation results were compared with the available experimental data, and an acceptable agreement was obtained. In the second part, two volute design methods, namely, the constant velocity and the constant angular momentum were investigated. Obtained results showed that in general the constant velocity method gives more satisfactory performance. In the third part, three volutes with different cross section and diffuser shape were designed. In general, it was found that circular cross section volute with radial diffuser provides higher head and efficiency. Moreover, the minimum radial force occurs at higher flowrate in circular volute geometry comparing to rectangular cross section volute.
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