A spray jet discharging device comprising a centrifugal fan with an impeller rotating within a spiral housing, a hydraulic motor supplied with oil via a hydraulic circuit for driving the impeller in order to create an air stream, hydraulic piping for connection to a source of liquid, said piping having spray nozzles for spraying the liquid within the discharged air stream in order to create a spray jet beam and a support for mounting the fan, said device being characterized in that the fan support comprises: - a U-shaped base, the spiral housing being pivotally connected to said base at two points, located on the two arms of the "U" and defining an imaginable horizontal axis around which the spiral housing is rotatable, so that the inclination angle of the discharged spray jet beam in a vertical plane may be altered, in the upward or downward direction, - a rotatable support pillar, said pillar comprising a fixed internal trunk of a substantially cylindrical shape, an external jacket surrounding said trunk and being rotatably mounted thereon around an imaginable vertical axis, said jacket being fixedly connected to the U-shaped base, so that its rotation also entrains the centrifugal fan into rotation around said vertical axis, causing the discharged spray jet beam to rotate in a horizontal plane, to the left or to the right, wherein the fixed internal trunk is at the same time a central oil distributor, supplying oil to at least the impeller's hydraulic motor, and having at least two orifices at its bottom for connection to oil pipes coming from an oil supply pump, said orifices being the inlets to channels extending within the cylindrical trunk and letting out each one into a separate circular groove, said grooves being located on the cylinder circumference, each groove at a different axial height along the cylinder, so that the internal wall of the rotatable jacket in conjunction with the grooves of the cylindrical distributor and with seals provided at the lateral walls of the grooves define separate, leakproof annular oil chambers, two of said chambers forming part of the hydraulic circuit of said motor, one belonging to the supply line and the other to the return line, and wherein the external jacket has a radial through hole opposite each groove, said through holes having means for connection to oil hoses leading to the impeller's said hydraulic motor at least; so that said oil hose is enabled to follow the movements of said jacket during the device right-left rotation, without being twisted, while the oil circulation through the respective annular oil chamber is uninterrupted and wherein the maximum velocity of the spray jet, corresponding to the maximum rotational speed of the impeller motor, when measured at the centre of the device outlet, exceeds 400 km/h. - a U-shaped base, the spiral housing being pivotally connected to said base at two points, located on the two arms of the "U" and defining an imaginable horizontal axis around which the spiral housing is rotatable, so that the inclination angle of the discharged spray jet beam in a vertical plane may be altered, in the upward or downward direction, - a rotatable support pillar, said pillar comprising a fixed internal trunk of a substantially cylindrical shape, an external jacket surrounding said trunk and being rotatably mounted thereon around an imaginable vertical axis, said jacket being fixedly connected to the U-shaped base, so that its rotation also entrains the centrifugal fan into rotation around said vertical axis, causing the discharged spray jet beam to rotate in a horizontal plane, to the left or to the right,