Abstract: A device in fluid pressure generators comprising an annular casing which is peripherally mounted and driven in a through-flow channel. The inner face of said annular casing forms part of the wall of the through-flow channel. The annular casing is provided with a number of propeller blades which extend radially inwardly into the through-flow channel and which are rotationally mounted on their individual pin shafts by means of which propeller blades the magnitude of the thrust may be altered in a continuous manner and the direction of operation of said thrust in the through-flow channel be reset.