Study on the abnormal noise and control strategy in hydropower units

The structural complexity of hydropower units and the intricate nature of internal flow make it challenging to analyze and resolve abnormal noise issues in hydropower stations. This paper investigates an abnormal noise problem in a specific hydropower unit through a combination of tests and computational fluid dynamics simulations. By analyzing the on-site measured noise spectra, vibration spectra, and pressure fluctuation spectra, potential sources such as draft tube vortex, runner-stator interaction (RSI), inter-blade vortex, and air supply valve vibration were systematically excluded. The abnormal noise source was ultimately identified as resonance triggered by Karman vortex shedding from the turbine runner, based on the analysis of the locked-in phenomenon and the calculation of vortex shedding frequency. After thinning the trailing edges of the runner blades on site, the abnormal noise, along with the associated vibration and pressure fluctuation, was effectively eliminated. Noise and vibration near the runner were significantly reduced under all load conditions, with the maximum noise energy in the turbine chamber reduced by 95.2% and the vibration amplitude at the main frequency in the draft tube reduced to only 2% of its original value. This work provides a method for quickly analyzing and resolving flow-induced abnormal noise issues, offering theoretical and practical support for addressing abnormal noise problems in hydro-turbines.