Transient phenomena in the draft tube model of a Francis hydro-turbine

Abstract

This article is devoted to the study of pressure pulsations behind the runner of a hydro turbine model caused by the precessing vortex core (PVC). Pressure pulsations are investigated under conditions of stationary load and transient modes of the hydro-turbine operation. Studies were performed in model conditions on the aerodynamic setup. The map of pressure pulsations was built for stationary modes using acoustic sensors and served to find rotational speeds of the swirler and flow rates at which the PVC occurs. On the basis of the data presented by parametric dependences, the initial and final parameters of the transition process were chosen. In the article, a sudden (fast) transition from part-load regime to the best efficiency point and back was considered. The characteristic times for the formation of PVC and the establishment of the flow regime when changing the controlling parameters of the installation have been determined using a continuous wavelet transform.