Reconstruction of the blade model of the Francis GAMM runner using a smoothed numerical blade

Abstract

The blade of a hydraulic turbine is the critical element of the energy conversion process in a hydroelectric plant; therefore, numerous blade reconstruction techniques are based on stacking cross-sections along the flow streamlines generated inside the runner passage. The uneven distribution along the spanwise direction causes surfaces with a lower degree of uniformity and continuity, especially in highly twisted and re-flexed blades. To solve this problem, the researchers often stack many cross-sections, causing a proportional increase in the number of parameters and points that define each section, which is detrimental when performing hydrodynamic optimization or numerical machining of the runner. In consequence, in this paper, we created the Smoothed Numerical Blade (SNB), a blade that is computationally cheap and defined with the lowest number of well-defined cross-sections placed orthogonality on a grid instead of following the fluid trajectory. The quantitative and qualitative analysis developed in the model test of the Francis GAMM turbine shows that the runner created by SNB achieves a high degree of smoothness and continuity on the blade surfaces, thereby maintaining the GAMM turbine performance of the original parameters.

Keywords

• Blade reconstruction
• Francis runner
• Reverse engineering
• Smooth surfaces
• CAD
• CFD