Quantitative investigation of the head-hump of large-scale vaned-voluted centrifugal pump

Abstract

In this study, the three-dimensional incompressible flow in a large-scale vaned-voluted centrifugal pump was numerically studied based on the Reynolds-averaged Navier–Stokes (RANS) method. As the flow rate increases, the vortices suddenly appear and disappear. These alternating vortices cause the instability region on the Q-H curve. Therefore, the local entropy production rate (LEPR) is analyzed for a better understanding. The LEPR method will provide a visualization of the energy change in unit and make it easier to understand the reasons of head-hump. Large-scale vaned-voluted centrifugal pumps are often used in large-scale water diversion projects. Long-time operation and frequent changes of conditions require the stability of pump performance, and the head-hump is an important factor that affects the stability of centrifugal pumps. The hump characteristics must be studied and the hump region should be avoided. Under small flow rate condition, six typical high LEPR situations in stay vanes are summarized. It is found that the vortex itself will not produce a large energy loss, the vortex causing high LEPR interacts with surrounding flow or wall. The flow interaction dominates LEPR in impeller and stay vanes. Zonal proportion of LEPR in impeller accounts for a higher proportion than stay vane. This study provides an effective way in understanding the mechanism of flow energy loss in the large-scale vaned-voluted centrifugal pump and can be referred to other similar turbomachinery cases.