Abstract: A turbomachine having a stationary housing and a rotatable rotor mounted therein and including a series of rotor blade rings carried by the rotor and a series of guide vane rings carried by the housing, the guide vane rings and the rotor blade rings being disposed in mutually alternating relationship, further includes means defining an annular space located forward of the first rotor blade ring of the series of rotor blade rings, flow medium supply means communicating with the annular space for supplying flow medium thereto, the annular space extending radially outwardly and along the entire periphery of the turbomachine for producing a torsional flow of the flow medium, the rotor having a shaft formed with a collar, and the series of rotor blade rings including a first blade ring mounted on the collar directly behind the annular space and having a diameter greater than that of the succeeding blade rings of the series, whereby the flow medium supplied to the annular space axially impinges directly on the firs