Design and Test of a Micro Turbine in the Water Power Laboratory
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The Norwegian company Deep River which specialises in small scale hydro power has developed the concept of a simple and portable micro propeller turbine, delivering 16 kW at a head of 5 meter and a discharge of 400 l/s. In cooperation with the Polish turbine design and producer Male Elekrownie Wodne (MEW) a turbine unit has been designed, produced and sent to the water power laboratory at NTNU for efficiency testing. Several tests have been conducted on the turbine with the purpose of establishing the best efficiency point and maximum power output. All of the tests has been preformed after IEC standards. Due to limitations at the laboratory, most of the tests was preformed with an effective head of approximately 8 meter. The highest efficiency at an effective head of 8.37 meter was found to be 78.10 %, with an uncertainty of +/- 0.87 %. This efficiency was measured having a propeller blade angle of 18 degrees. Assuming a constant efficiency at all the effective heads, the results have been down scaled to an effective head of 5 meter. The maximum power output for an effective head of 5 meter was estimated to be 8.10 kW, this with a propeller blade angle of 22 degrees. The turbine delivered lower discharges than stated from the producers, and at high discharges the efficiency was relative low. Reasons for this is discussed to be the size of the runner and the spiral casing design. Because of the low power output of the turbine, a new turbine unit, consisting of a runner, spiral casing and guide vanes has been designed. The new design is fully theoretical and no CFD has been included during the design process. In order to increase the discharge, the runner diameter is increased by 100 mm. The blades are desiged for a discharge at 400 l/s. For getting an higher hydraulic efficiency, the propeller blade length is increased. The size of the spiral casing is also larger than the original design, in order to decrease the flow velocities into the runner. The new turbine unit is modelled with 3D CAD software and is ready for CFD testing.