Analyses of the spatial and temporal features of the blade pressure‐side cavitation in a pump‐turbine runner in the pump mode

Abstract

AbstractIn the pump mode of pump‐turbine, cavitation usually happens in runners because of the local pressure drop on the blade leading‐edge. At over‐load, pressure drop and cavitation occur on the runner blade pressure side. In conventional studies, the spatial and temporal features of the blade pressure‐side cavitation are difficult to understand. In this study, the runner blade pressure‐side cavitation is studied in a pump‐turbine in pump mode at over‐load. Local low pressure and cavitation are found on runner blade pressure‐side at leading‐edge near shroud. Moreover, small‐scale gathering cavitation is also observed on the blade suction‐side with connecting the large‐scale pressure side cavity. As a breakthrough in flow analysis, the pulsation tracking network (PTN) method is applied to track the spatial and temporal features of cavitation. The time‐accumulated intensity, pulsation amplitude, frequency, and phase are analyzed for cavitation based on PTN. The stably‐gathering strong‐intensity cavitation sites are indicated by time‐accumulated intensity. Based on the pulsation amplitude contour, strong pulsating cavitation is found on the edges of the gathering strong cavities. Frequency and phase analyses indicate the cavitation propagation along the blade‐to‐blade direction and reveal the reason of the connecting cavitation phenomenon. The spatial and temporal features of cavitation is well investigated.