Experimental and numerical optimization of a centrifugal pump volute and its effect on head and hydraulic efficiency at the best efficiency point

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.