Simulação numérica da formação de vórtices em tomadas de água em hidrelétricas

Abstract

According to the 2011 National Energy Balance the contribution of hydro energy in the national energy matrix is approximately 88.8%. Despite the increasing trend of other energy sources, such as thermal, wind and solar power, everything indicates that hydropower will remain for many years the main source of electric power in Brazil. Before becoming electricity, hydropower must be transformed into kinetic energy that through a turbine is converted into mechanical energy. As a final element of the system, coupled to a generator turbine generates electricity which is distributed to consumers. The efficiency of a hydroelectric plant may be affected by conditions of water supply to it’s water intake. This operation should be stable, avoiding disturbances that can affect the system performance. The formation of vortices upstream of water intakes are causes of efficiency loss and can cause damage to the premises, causing unscheduled and unplanned downtime. Therefore, the formation of vortexes must be known and avoided. The objective of this work is to study the phenomenon of vortex and its formation at water intakes in a hydroelectric station. Obtaining results may be useful in guiding the design of new facilities, expansion of installed capacity of power plants in operation, and even to subsidizing the operations of plants that have characteristics that may favor the formation of vortices. This work is part of the research project: “Formation of vortices taken in water for hydroelectric plants”, with sponsorship and support from the Furnas Hydroelectric Hydraulics Laboratory of Experimental Furnas-LAHE and the Institute of Hydraulic Research -IPH/UFRGS. The studies is conducted using commercial software ANSYS CFX-analyzing several cases of submergence, water flow and turbulence model. The mathematical model composed by the mass and momentum equations as well as their respective boundary conditions is applied to a model of vertical water intake. The validation of the numerical results is obtained from literature data with existing studies on water intakes and vortex formation, as well as a verification of results found in the scale model of a vertical water intake developed by the Institute of Hydraulic Research UFRGS.