Efficiency investigation of a helical turbine for harvesting wind energy

• Online Access: http://hdl.handle.net/2047/d20001223

In recent times, there has been an increased interest in wind energy due to concerns about the pollution caused by burning fossil fuels and their rising prices. Most wind turbines in use today are conventional wind mills with three airfoil shaped blades arraigned around a horizontal axis. These turbines must be turned to face into the wind and in general require significant air velocities to operate. Another style of turbine is one where the blades are positioned vertically or transverse to the axis of rotation. These turbines will always rotate in the same direction regardless of the fluid flow. Due to the independence from the direction of the fluid flow, these turbines have found applications in tidal and surface current flows. To see how effective this sort of turbine would be in air, a helical turbine based on the designs and patents of Dr. Alexander M. Gorlov was chosen. His turbine was developed to improve upon the design of Georges J. M. Darrius by increasing the efficiency and removing pulsating stresses on the blades, caused by the blades hitting their aerodynamic stall in the course of rotation, which often resulted in fatigue failure in the blades or the joints that secured them to the shaft. The turbine takes the Darrius type turbine, which has a plurality of blades arranged transverse to the axis of rotation, and adds a helical twist to their path, insuring that regardless of the position of the turbine, a portion of the blade is always positioned in the position that gives maximum lift. This feature reduces the pulsations that are common in a Darrius type turbine. In his investigations, Gorlov claims that his turbine is significantly more efficient than Darrius' and has achieved overall efficiencies between 30% and 35%. For this investigation, a helical turbine was tested inside and outside a wind tunnel using an electric generator (inside tests only) and a torque meter paired with a tachometer to measure the output power of the turbine and calculate its efficiency. In the end, the turbine did not come close to the claimed 30% efficiency, reaching at best an efficiency of around 0.35%. Further investigations should be made to determine why the results from this investigation were as low as they are.