Rehabilitation of Francis Turbines of Power Plants with Computational Methods

Abstract

R ehabilitation of hydraulic turbines of existing power plants is an important topic because of the low performance, poor reliability, frequent maintenance intervals and undesirable cavitation properties of old turbines at the plants. Rehabilitation projects increased worldwide to improve turbine designs and to reach the desired performance characteristics, especially with the improvements in computational power and Computational Fluid Dynamics (CFD) technology. However, rehabilitation of old power plants is often more difficult than the design of the turbines for new power plants since most of the existing parts cannot be altered because some of the parts are buried and the space is limited with the size of the old turbine.Both experimental and numerical methods are common in the design [1] Su et al. [4] computed the three-dimensional turbulent flow in Francis turbines using Large Eddy Simulations (LES). They used unstructured meshes for the spiral case and the runner, while structured meshes were utilized for the remaining components. They found out that cavitation was observed at the suction side of the blade under partial load conditions. Patel et al.[5] also performed three-dimensional, unsteady CFD simulations for Francis turbines. They investigated the effect of partial loading on turbine performance. The A B S T R A C T R ehabilitation of existing hydroelectric power plants (HEPP) by redesigning the hydraulic turbines is usually more elaborate than designing a tailor-made turbine for a new plant. Some of the parts are buried and the space is limited with the size of the old turbine; therefore, this increases the number of constraints imposed on the design. This article presents a Computational Fluid Dynamics (CFD) based rehabilitation procedure involving the state of the art redesign of the turbine of a hydroelectric power plant for better performance at design and off-design conditions of several head and flow rates. Runner and guide vanes of the Francis turbine are designed per the design head and flow rates available for the turbine at the site. The simulations for the designed parts are performed both separately and using all turbine parts as full turbine analyses. Both the design and off-design conditions are simulated for the newly designed and existing turbines for comparison purposes. Cavitation performance of the new design is also determined. The proposed methodology is applicable to any Francis type turbine and any HEPP that needs rehabilitation.

Francis Type Turbine Runner Design and Comparison with Model Test Results

“…Celebioglu et al [9] worked on CFD based rehabilitation procedure involving the redesign of the turbine of a hydroelectric power plant with the help of ANSYS commercial software. The study was performed on the redesign of the turbine runner in the Kepez-1 hydroelectric power plant in Türkiye.…”

Roughness Coefficient of a Highly Calcinated Penstock

“…Efficiency and cavitation characteristics of runner is investigated and characteristics over operating region of the old Kepez turbine is determined by means of CFD [10] [12]. Design of the new turbine is significantly improved to better characterize the current operating regime [13]. The new turbine efficiency is obtained by means of both CFD [13] and model tests [14] performed at ETU HYDRO Turbine Design and Test Center.…”

“…Design of the new turbine is significantly improved to better characterize the current operating regime [13]. The new turbine efficiency is obtained by means of both CFD [13] and model tests [14] performed at ETU HYDRO Turbine Design and Test Center. Although these works give significant insight on the turbine performance, project requirements dictate comparison of efficiencies with in-situ site measurements.…”