Thermal Engineering

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Browsing Thermal Engineering by Subject "air jet mechanism"

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    Design and Experimental Investigation of Savonius Wind Turbine with Air Jet mechanism
    (Addis Ababa University, 2021-02) Balcha, Tola; Abdulkadir, A. Hassen (PhD)
    The Savonius wind turbine is a type of wind turbine with a vertical axis that operates on the aerodynamic drag principle. It has potential to be developed as it has great advantages, such as simplicity in design and construction, full-capacity operation and production of energy in areas with low wind potential. However, because of its low performance compared to other turbines, the turbine is rarely used. The low efficiency of the turbine is due to the negative torque generated with this turbine. Several researchers have worked to reduce the negative torque generated by this turbine in a variety of ways. Most of them, however, are achieved by limiting the Omni-directional properties of this turbine, which is its main advantage and feature. In this work, we have developed a new feature called the air jet mechanism to reduce the negative torque of the turbine without omitting its Omni-directional properties. The air jet mechanisms have been developed with the capacity to receive wind from all directions and direct it to the useful area of the turbine blade. Due to its geometrical characteristics, the air jet mechanism also works as a venture to increase the speed of the incoming wind. In order to observe their size influence, three different sizes of air jet mechanisms are developed and labeled as longer air jet mechanism, medium air jet mechanism and shorter air jet mechanism and successively positioned around the conventional two-blade Savonius wind turbine with a diameter of 0.4 m and an aspect ratio of 1.5. The performance test of this specified turbine was performed in the laboratory by adding three different size air jet mechanisms around it and without air jet mechanisms (i.e. the bare turbine alone). The performance of the Savonius wind turbine tested under each air jet mechanism is compared with that of the bare Savonius wind turbine tested under the same conditions. When measured with a longer air jet mechanism at a tip speed ratio of 0.4, the power coefficient of the stated Savonius wind turbine increased from 0.05 to 0.11. The results of the investigation showed that an air jet mechanism could increase the efficiency of the conventional two-blade Savonius wind turbine without omitting the wind reception property from all directions.