Flow characteristics and influence associated with inter-blade cavitation vortices at deep part load operations of a Francis turbine

K Yamamoto,C Landry,A Müller,A Favrel,F Avellan

doi:10.1088/1742-6596/813/1/012029

K Yamamoto, C Landry + Show 3 more

Open Access

https://doi.org/10.1088/1742-6596/813/1/012029

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Abstract

At a deep part load operation, Francis turbines are subject to the formation of inter-blade cavitation vortices inside blade channels, however its characteristics are not fully understood yet. The present study aims to investigate the development of the inter-blade vortex as well as the flow characteristics associated with the vortex formation inside the blade channel, by using the unsteady RANS simulation. The velocity survey reveals the appearance of the back flow region in the vicinity of the hub near the trailing edge, which seems closely linked with the inter-blade vortex development. Furthermore, the local influence of the inter-blade vortex is evaluated by the specific energy loss calculated from the rothalpy in the blade channel. The comparison of the different operating conditions evidences the impact of the inter-blade vortex presence on the energy dissipation through the blade channel.

Highlights

It is well known that Francis turbines are subject to a various type of cavitation flows depending on its operating condition [1, 2]
The simulated vortex structure is compared to the visualization results for the validation, the structure of the flow inside the blade channel associated with the inter-blade vortex development is investigated
The specific energy loss is evaluated by the integration of the specific rothalpy through the blade channel, and the influence of the inter-blade vortex on the energy dissipation is investigated by comparison of different operating conditions

Summary

Introduction

It is well known that Francis turbines are subject to a various type of cavitation flows depending on its operating condition [1, 2]. In the framework of the HYPERBOLE research project, experiments and numerical simulations for the inter-blade cavitation vortex at deep part load operation have been conducted and reported, contributing to a better comprehension of its characteristics [7, 8, 9]. The present study aims to demonstrate the numerical investigations about the development and the characteristics of the inter-blade vortex by the unsteady RANS simulation.

Results

Conclusion