Resumo:
This work evaluates the local analyzes of the flow field (2D) in a Darrieus-H vertical
axis hydrokinetic turbine, through computational fluid dynamics - CFD, considering the
insertion of an upstream blocking plate, in order to improve its performance curve. This type
of configuration is easy to implement in existing Darrieus-H hydrokinetic turbines, allowing
to accelerate and to direct the flow over the advancing blade, creating a low energy zone
upstream of the retarding blade which, in turn, works as a starting mechanism system. This
work is divided into three parts. The first provides a method for predicting the performance
curve of Darrieus runners with a low computational cost. The second part evaluates through
CFD the Darrieus-H hydrokinetic turbine designed by Patel, Eldho, & Prabhu, (2019) in a free
flow, also in the blocking plate configuration (also called anteparo) with the best performance
analyzed by them, and with the addition of several geometries of blocking plates on the
advancing blade with variation of the inclination angle. In third and last part of this work, a
turbine with a blocking plate, like the developed one with the highest efficiency, is designed
for two points located over the San Juan River in the department of Chocó in Colombia and is
computationally evaluated under its flow conditions. As a result, CFD analyzes demonstrate
that it is possible to increase the efficiency obtained with the free runner up to ~26% by
adding a straight angle blocking plate. However, with the growth of turbulence generated by
the flow acceleration of the San Juan River and the increase in the size of the runner with
straight blocking plate predicted for generation in this river, the gain in efficiency decreased,
showing that in this type of configuration the efficiency gain for high Reynolds number is
reduced.
