then being divided into a plurality of partial channels nearest the pressure chamber 10 each guide vane is then formed with an end portion lying in an axial plane whereas surface portions lying at a larger distance from the pressure chamber 10 make an angle with the axis a a this angle increasing with the distance from the pressure chamber 10 the body 16 is preferably pointed at one end and substantially made in the form of a solid of revolution at its free end the connecting member 14 has an integrated portion substantially formed as a hollow truncated cone 18 39 which by its inner conical surface defines a coaxial channel 18 through which the space 19 surrounded by the hollow body is in communication with the collecting space 13 the external surface of the cone 18 39 defines radially inwardly an annular portion 20 of the space 19 at its outer periphery the annular portion 20 is connected to a tube 21 which is passed through a substantially circular cylindrical portion of an outer wall defining the annular portion 20 radially outwardly at least at the inlet end the tube 21 is substantially tangentially directed in relation to the circular cylindrical wall portion the free end of the tube is flanged to the supply conduit 11.