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Study on Air Injecting Hydrofoil: Improving Aerating Runners Technology

Author(s): Gregoire Recchia; Leila Dhar; Florentin Anne; Cedric Beguin; Stephane Etienne; Laurent Bornard; Philippe Cote

Linked Author(s): Michel Sabourin

Keywords: Two-phase flow; Hydrofoil; Pressure losses; Air injection; Hydroturbines

Abstract: An air injecting NACA0015 hydrofoil allows investigating previously uncharted two-phase flow areas with high volumetric quality (up to 12 %) in high-speed water crossflows. This work focuses on the pressure losses and pressure evolution at three levels: the losses at the injection, the evolution around the hydrofoil and finally the evolution downstream of the hydrofoil. Varying multiple parameters such as water’s velocity, hydrofoil’s angle of attack toward the cross-flow, injection orientation and mass airflow rate allows a robust study for this specific category of two-phase flows. Pressure sensors located around, downstream of the hydrofoil and inside the internal air chamber portray the pressure profile of the flow and its evolution in cases ranging from a pure water crossflow up to highly aerated two-phase flow. First, adaptation for two-phase flow of pressure loss equations, based on existing literature, yield good results. In the case of an aerating hydrofoil injection, an adequate correction is proposed to match single-phase and two-phase flows. Injecting a significant amount of air on one hydrofoil’s side reduces the pressure difference between both sides for non-zero angles of attack, thus contributing to reduce the global hydrofoil’s lift. Finally, a predictive model allows linking the pressure losses downstream of the flow with controlled and known parameters. All the correlations and models developed here are required for the development of a new generation of aerating runners.


Year: 2023

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