Signature analysis of characteristic frequencies in a Francis turbine

Abstract

The present work investigates the unsteady pressure fluctuations in a model Francis turbine that are observed during steady state operation. Focus of the present study is to correlate pressure fluctuations between stationary and rotating components in the turbine. It is challenging and expensive to perform pressure measurements inside the rotating parts of the turbine. Pressure measurements at the runner upstream and downstream can help to understand the signature of pressure pulsations in the blade passages. To this end, one pressure sensor in the vaneless space, four pressure sensors in the runner and two pressure sensors in the draft tube cone were integrated to acquire pressure data. Detailed analysis of the acquired pressure data is carried out including statistical analysis, spectral analysis and coherence analysis. Further, stochastic and deterministic analysis of the pressure fluctuations in the turbine is carried out. The results showed that pressure data in the vaneless space and the draft tube could be used to understand the signature of pressure fluctuations existed in the runner.