Development of a novel numerical framework in OpenFOAM to simulate Kaplan turbine transients

Saeed Salehi,Håkan Nilsson,Eric Lillberg,Nicolas Edh

doi:10.1088/1755-1315/774/1/012058

Abstract

A novel numerical framework in OpenFOAM is proposed in this work, to simulate transient operation of Kaplan hydraulic turbines. Such transient operations involve a variation of both runner blade and guide vane angles, which also gives rise to a flow rate variation. A numerical simulation of such a process is very challenging, since it requires a deformation of both guide vane and runner meshes, with mesh slip conditions at arbitrarily shaped surfaces, at the same time that the runner mesh is rotating around the turbine axis. The currently available mesh morphing methodologies in OpenFOAM are not able to properly accomplish this. Thus a novel framework for OpenFOAM, including dynamic mesh solvers and boundary conditions, is developed to tackle this problem.The new framework is utilized to simulate the flow during transient operation of the U9-400 Kaplan turbine model. The guide vanes and runner blades are rotated individually around their own axes with a constant rotational speed, while the runner is rotating, and the flow rate is linearly changed with the guide vane angle. It is shown that the novel numerical framework can successfully be utilized to simulate the load change of Kaplan turbines.

Highlights

Renewable electric energy resources, such as solar and wind have been rapidly growing in recent years
The transient operation of Kaplan turbines involves a change of flow rate, change of guide vane angles, and change of runner blade angles while the runner is rotating
The computational meshes of the guide vane and runner domains are shown in Figure 5

Summary

Introduction

Renewable electric energy resources, such as solar and wind have been rapidly growing in recent years. The transient operation of Kaplan turbines involves a change of flow rate, change of guide vane angles, and change of runner blade angles while the runner is rotating. A special methodology is needed when the mesh is rotating at the same time as it is deforming, as is the case for Kaplan turbine runners. The numerical framework is utilized to simulate the flow in the U9-400 Kaplan turbine model, going from an operating condition close to the best efficiency point to a part load condition. 2. Developed numerical framework Transient operation of Kaplan turbines involves a variation of both guide vane and runner blade angles at the same time as the runner is rotating around the turbine axis. Simulations of the flow in Kaplan turbines during transient operation is very challenging and needs special developments that are described in the current section

Novel mesh morphing approach

Results and discussion

Conclusion