further experimental research work on water current turbines

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It is clear from the readings taken and the corresponding graphs illustrated in chapter four, that the straight-cambered aerofoil blades give the maximum power (i.e. the product of torque and angular velocity), and this the experimental result obtained has rejected the hypothesis that the curved- cambered aerofoil would have given us the best results concerning the maximum power output, and this happens because the separation point moves extremely forward which helps the adverse pressure to build up. The hypothesis is based on the fact that curved surfaces will give high change in momentum according to its profile, but although these results are of trivial benefit in this junction, it creates opportunities for applications other than water-current turbine used for irrigation purposes. The extremely higher torques with lower speeds which have been obtained from the curved – cambered aerofoil can be of great usefulness in other engineering applications that need higher torques (for example grain mills, etc.). From the results obtained, it is clear that the straight-cambered aerofoil gives the best results concerning the torque and speed. The water-current turbine machine made in the Faculty of Engineering and Technology- Atbara needs some modifications in its design and consequently the manufacture of some major parts. It is noticed that the type of transmission used is the one which works with a flat belt and pulley system. It has the advantage of less costly, light in weight and easily manufactured and also it is durable and non-corrosive (the pulley is made of aluminium alloy), but it has relatively fair efficiency of transmission (i.e. not more than 75%) in comparison to gear transmission system which has a higher efficiency of 98%. Therefore, it is recommended to use gear transmission system with the necessary anti-corrosion protection needed. Also, another advantage of the gearing transmission system is that there is a possibility of increasing or decreasing the speed through several stages without a remarkable drop in the overall efficiency. It is also recommended that a compact design of the complete arrangement is required so as to lessen the machine size and consequently the working area. This could be attained by using a vertical shaft instead of a horizontal shaft or an inclined shaft. Consequently, testing of maximum power and efficiency may be carried out on aerofoil blades in the vertical positions which are expected to be greater than that of the inclined shaft. It is also recommended to study the effect of the thickness of the aerofoil section, the span length and chord length to the maximum power output and the overall efficiency of the system. Also, the effect of increasing and decreasing the number of blades must be studied.

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