A Computational Assessment of the Pressure–Flow Rate Relationship Within the Spiral Casing of a Hydraulic Turbine

Safety, profitability, as well as energy and resource efficiency of hydropower plants require, among others, appropriate operation of hydraulic turbines, which involves reliable estimation and monitoring of water flow rate. In this work, computer simulation is used for investigation of water flow through the spiral casing of a hydraulic turbine under real operating conditions. The wall pressure at the pre-defined monitoring points in a radial plane, such as used in the Winter–Kennedy measurement method, is calculated for a range of water flow rates. The choice of the boundary-condition type downstream of the stay vanes and sensitivity to adopted turbulent-flow approach are also investigated. The numerical results agree well with the reference measurements. A relation is established between the computed monitoring pressure difference and the corresponding incoming flow rate. Having measured the static pressure at the given points, it can be used for continuous estimation of the water flow rate in the turbine under actual operating conditions.