Abstract: A propulsion device for exerting thrust to a fluid comprises a central hub and at least two propulsive arrangements which protrude radially from the hub. Each propulsive arrangement comprises front and rear propulsive elements extending from a front inner end to a front outer end and from a rear inner end to a rear outer end, respectively. Inner and outer guide elements extend from the front end to the rear end. An elongate front distance member and an elongate rear distance member extend radially from the hub to the inner guide element. At least one intermediate propulsive element is arranged between the front and rear propulsive elements and extends radially from the inner guide element to the outer guide element. The inner guide element, the front distance member, the rear distance member and the periphery of the hub define an open space allowing free passage of the fluid.

Abstract: A propulsion device for exerting thrust to a fluid comprises a central hub and at least two propulsive arrangements which protrude radially from the hub. Each propulsive arrangement comprises front and rear propulsive elements extending from a front inner end to a front outer end and from a rear inner end to a rear outer end, respectively. Inner and outer guide elements extend from the front end to the rear end. An elongate front distance member and an elongate rear distance member extend radially from the hub to the inner guide element. At least one intermediate propulsive element is arranged between the front and rear propulsive elements and extends radially from the inner guide element to the outer guide element. The inner guide element, the front distance member, the rear distance member and the periphery of the hub define an open space allowing free passage of the fluid.