The Effect of Head Inflow and Turbine Axis Angle Towards The Three Row Bladed Screw Turbine Efficiency

摘要

Archimedes screw applications as water turbine is being developed and researched in the past decade. This kind of turbine excellence is that it can operate at a low head (H <10 m) and does not require a penstock. The screw turbine performance is influenced by the turbine screw shape geometry and the flow characteristics in the screw turbine. This study aims to determine the screw turbine efficiency which is observed by the turbine rotation, turbine torque on a variable head inflow, water flow velocity and the turbine axis specific angle. In this research the screw turbine was made under a laboratory scale and made from flexi-glass. The turbine screw geometry was made of three starts rows screw groove under a 0.54 radius ratio with a 2.4 Ro pitch and a screw angle of 30°. The head inflow (ho) variation is 1/2 Ro, 2/3 Ro, 1 Ro with an incoming flow velocity (c_o) varied at 0.3 m/s, 0.4 m/s, and 0.5 m/s and an turbine axis angle (α) variation of 25°, 35°, and 45°. The highest efficiency found in this research is about 89%. This performance occurred on the condition of a 50 rpm turbine rotation, at a head in flow (ho) of 1 Ro, a water flow velocity of 0.5 m/s and at a 25° turbine axis angle. The highest turbine rotation on this experiment was 350 rpm, which was reached at a 45° turbine axis angle condition. The water inflow head (ho) and the turbine axis angle (α) variation would strongly affect the turbine efficiency. Because the smaller the head between blades Δh, the greater the ho/Δh ratio thus the higher the efficiency could be.