Banca de DEFESA: GUILHERME TABATINGA MEDEIROS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GUILHERME TABATINGA MEDEIROS
DATE: 17/02/2023
TIME: 09:00
LOCAL: Plataforma Microsoft Teams
TITLE:

Experimental study on the influence of rotor height in relation to the ground and terrain roughness on the performance of horizontal axis unimpeded turbines.

KEY WORDS:

horizontal-axis turbines; tower height; ground roughness; experimental methods; wind tunnel; hot-wire anemometry

PAGES: 80
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

In horizontal-axis wind turbines, two elements that influence energy conversion are the height of the rotor in relation to the ground and the roughness of the terrain. The present work presents an experimental study on the influence of these two factors on the power curve of small-scale models of horizontal axis free turbines. The experiments were carried out in the wind tunnel of the Laboratory of Energy and Environment at UnB. Three different heights and two surface roughness conditions are evaluated. The hot wire anemometry technique is used to determine the mean longitudinal velocity and turbulence intensity in specific regions of interest in the flow. To simulate a rough terrain, chains were installed over the originally smooth surface of the wind tunnel test section. Experiments were carried out on the smooth surface and on the rough surface. We have noticed that, for the smooth surface, two competing mechanisms which alter power generation by the rotor take place: the partial confinement of the flow, observed as the rotor approaches the surface, with a tendency to increase the power coefficient; and the velocity deficit in the boundary layer over the tunnel surface, which tends to reduce the power coefficient. It was identified that when the height of the turbine is close to the minimum possible height in relation to the surface, the partial confinement of the flow increases the average velocity through the rotor, resulting in an expressive power coefficient elevation, compared to the case in which the turbine is in the far field from the ground. On the other hand, at intermediary heights, the flow velocity deficit in the boundary layer overcame the flow confinement and leads to a reduction of the power coefficient. The study considering a rough ground surface indicated that roughness can significantly change the dynamics observed in a situation where the surface is smooth. When there is roughness, the power elevation observed for the case with lower height does not occur at the same levels. All results are discussed in conjunction with fields of flow average velocity and turbulence intensity upstream and downstream rotor. The present study leads to the conclusion that using very high towers to isolate the rotor from the ground’s influence is not necessarily beneficial when only energy generation is considered.

BANKING MEMBERS:
Interno - 404142 - ANTONIO CESAR PINHO BRASIL JUNIOR
Externo à Instituição - JERSON ROGERIO PINHEIRO VAZ - UFPA
Externo ao Programa - 3295206 - RAFAEL CASTILHO FARIA MENDES
Presidente - 3375759 - TAYGOARA FELAMINGO DE OLIVEIRA