Evaluation of the flow velocity distribution in the intake structure of a small hydropower plant

Abstract

Intake structures are an important part of small hydropower plants, which affect the water flow, turbine operation and total power of power plant. The flow quality is significantly influenced by the flow homogeneity in the intakes, as the inhomogeneous flow velocity distribution has a negative impact to the operation of the hydropower plants, such as uneven load on the mechanical parts which leads to decrease in efficiency and faster aging of turbine parts. The paper describes the flow assessment in the intake structures of a low-pressure small hydropower plant (the Stará Ľubovňa small hydropower plant) with respect to the flow homogeneity. The River2D, 2D numerical modelling software, has been used for evaluation of flow in the intakes. Flow simulations for the current state of operation have been modelled. In assessing the current situation of intake structure, scenarios were modelled. The boundary conditions were changed to approximate the various variants of hydropower plant operation. The simulations proved the negative impact of the construction solution for the flow conditions in the intakes. This appears mostly in profiles of coarse racks and screenings where is a significant unequal distribution of flow and significant deviation in flow velocities from the recommended values. The simulations results were evaluated in turbine intake profiles (profile of screenings), where the distribution of flow velocities was evaluated. The flow velocities in this profile were compared with the average flow velocity in the turbine intake profile. In order to optimize the velocity distribution in the intake structure, the modification of the intake shapes has been proposed. The subject of the proposal was to improve flow parameters. Simulations were created for the modification that were subsequently reviewed. The modification was compared to the current situation of the intakes.