The effect of the opening ratio and location on the performance of a novel vertical axis Darrieus turbine

Generally speaking, the simulation results revealed that the power coefficient (CP) of a rotor with an opening is smaller than that of a rotor without an opening. However, the opening does increase the static torque coefficient (CTs) of the rotor, especially when the opening is located at the outer surface of the airfoil. Moreover, the inner opening has a fairly large negative effect on the ICT in the upwind zone. And the outer opening has a fairly small negative effect on the ICT in the upwind zone and has a greater negative effect on the ICT in downwind zone. It appears that the desirable rotors for inner opening are the rotors with 0.48 and 0.60 opening ratios. And the desirable rotors with an outer opening are the rotors with 0.72 and 0.84 opening ratios. They can be regarded as promising devices to replace the Savonius-Darrieus rotor considering the CP loss, CTs increase and SOICTs increase.