Design of a Turbine That Utilizes the Energy in Spill Water of Large Ships
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In this master thesis, a Straflo turbine prototype used for energy recovering in large ships was tested, evaluated, and redesigned. The main goals were first to evaluate the performance of the prototype based on efficiency measurements from tests, and secondly to design a new improved turbine and evaluate the design. The prototype turbine was provided by the turbine development company QRRNT AS, and was designed for the circulation system of the fish tanks on a well boat. To map its performance at different operation points, a test rig was set up in the Waterpower laboratory to perform efficiency measurements. Based on experiences from these tests, another turbine was designed for a different ship. Then, CFD-simulations was performed to evaluate and optimize the turbine design. During the prototype testing, some challenges occurred due to the poor mechanical design of the turbine, which caused the runner to detach from the shroud and then the generator magnets to loosen. However, measurements showed that the prototype turbine was able to generate a maximum of 17-18 kW at an efficiency of approximately 72 % and a partly performance chart was created. To enhance future models, improvements include using runner blade modules and improving the hub and runner blade design. The new turbine was designed and optimized according to these findings, and simulations predicted a hydraulic efficiency of 88.3 %, which is higher than the simulated and measured performance of the prototype turbine. The goals of this thesis were therefore achieved, although unplanned events limited the performance mapping of the prototype. Future work includes finding a solution to re-attach the magnets to the shroud and pursuing the performance mapping and performing additional CFD-simulations of the new turbine to optimize its blade thickness and study its transient behavior.