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Optimization of a draft tube using statistical techniques - DOE and 2D computational fluid dynamic analysis
Author(s): Antonio Carlos Barkett Botan, Ramiro Gustavo Ramirez Gustavo, Geraldo Lucio Tiago Filho, Edna Raimunda da Silva
Keywords: CFD analysis, Design of experiments, Draft tube, Bulb turbine, MOSA, Optimization
The draft tube is one of the main components that integrate a turbine, since it has the function of recovering the residual kinetic energy after the runner by the pressure energy. The search for a draft tube design that increases the efficiency of the turbine is always an engineering challenge. The hydromechanics components geometry optimization can be accomplished through the integration of optimization methods and CFD tools. In this work, the geometric optimization of a double diffuser draft tube of a Bulb turbine, applied to ultra-low heads will be presented, with the objectives of maximizing the pressure recovery coefficient, Cp, and increasing the hydraulic efficiency of the turbine, ηh. These improvements would make it possible to reduce the longitudinal length of the draft tube, thereby, making an easier insertion of this kind of turbines in water transport systems, with pressures around 3 mH2O. The optimization methodology was performed in the meridional plane, using twelve geometric variables in the draft tube through the integration of optimization methods and computational fluid dynamics. The results were extended to the 3D flow analysis, where the optimized machine showed efficiency gains of 82% to 84%, considering that its total length was reduced and its geometry simplified, resulting in a more compact and versatile equipment.

Journal of Applied Fluid Mechanics

The Journal of Applied Fluid Mechanics (JAFM) is an international, peer-reviewed journal which covers a wide range of theoretical, numerical and experimental aspects in fluid mechanics. The emphasis is on the applications in different engineering fields rather than on pure mathematical or physical aspects in fluid mechanics. Although many high quality journals pertaining to different aspects of fluid mechanics presently exist, research in the field is rapidly escalating.

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