Model test with sensor equipped Francis runner for Part Load Operation

Abstract

With the need for flexible operation Francis runners are exposed to various operating conditions outside the traditional operating range. These machines have to be designed for long time Part Load Operation to meet hydraulic and structural requirements. Deep Part Load Operation mainly consists of stochastic loads on the blades. Calculation methods for the dynamic stress at Full Load Operation are well established, whereas the calculation of the dynamics during low load operation are in the focus of the current research to increase the predication accuracy. Through a model test of a Francis runner with multiple sensors in the rotating frame, knowledge is gained about low load operating conditions. The sensors consist of both pressure transducers and strain gauges. On the basis of the results for multiple operating conditions a comparison between pressure sensors and strain gauges is made and connected to flow phenomena. Prototype strain gauge data is utilized to prove the feasibility of the data gained in model size.