Abstract
This study was conducted theoretically with the aim of investigating the effect of the straight blade angle change on the aerodynamic performance of the vertical axis wind rotor (VAWR). The work was done within the blade angle range of 25°–85° with an angular gradient of 20°. A special name has been given to the VAWR concerned in this paper, where it was called Straight Slant Blades (SSBs). The so-called multi-stream tube (MST) model was modified to be suitable for SSBs. MST is an aerodynamic model, which was previously used to work on what is known as Darrieus and H-Darrieus vertical axis wind turbines. A computer program is designed and developed using Microsoft Visual Basic to be consistent with the objectives of this research. As for verifying the effectiveness of this program, its theoretical results were compared with previous laboratory results from other research studies as it proved its effectiveness in achieving satisfactory results commensurate with the objective of this study. This study is applied to four groups of different engineering designs for the SSB rotor, where each group is concerned with one of the geometric variables confined to the rotor height 2H, the rotor radius R, the number of rotor blades N, and the airfoil C. The results obtained are displayed as rotor power coefficient curves as a function of blade tip speed ratio. As it resulted in the ideal range for the angle of the blade between 45° and 65°, according to the rotor in this range, the value of maximum power coefficient CpMAX is at its maximum and the range of tip speed ratios is the highest in addition to the diminution of the problem of self-movement.
Highlights
Relative velocity (W) is one of the most important components of wind velocity adjacent to the wind rotor due to its direct link with the angle of attack (α), where this relative velocity (W) arises as a result of a difference between the rotor’s rotational velocity and the velocity of the wind passing on it (V) at a certain value of the rotor rotation angle (θ)
By connecting the two facts mentioned above, we find that λ0 or ωR/V has a direct and strong influence on the value of the L/D force ratio of rotor blade
The aerodynamic performance of the vertical axis wind turbines (VAWTs) is poor in both the high and low ranges ωR/V1 with the reason being different in both cases
Summary
Relative velocity (W) is one of the most important components of wind velocity adjacent to the wind rotor due to its direct link with the angle of attack (α), where this relative velocity (W) arises as a result of a difference between the rotor’s rotational velocity (ωR) and the velocity of the wind passing on it (V) at a certain value of the rotor rotation angle (θ). METHOD To achieve the main objective of this research, which is to conclude the effect of changing the geometric dimensions of the SSB rotor on its general performance, the choice of the multi-stream tube (MST) analytical model was the most appropriate due to its excellent ability to predict the power output in general, in addition to the ease and speed of its use. This allows a large number of configurations to be studied in a relatively short time.
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