Method and device for reducing the noise of turbo-machines

In a turbo-machine which includes an elongated, hollow, stationary outer wall, a rotatable rotor ring mounted centrally inside of said outer wall and comprising an elongated rotor shaft and a number of radial rotor blades extending from said rotor shaft towards said stationary outer wall, and a stationary stator ring having a number of radial stator vanes extending towards said stationary outer wall, the improvement wherein said turbo-machine includes an apparatus for reducing the noise generated by the interaction of the rotating rotor blades and the stationary stator vanes by creating a counter-noise of opposed phase, this apparatus comprising:

• a cylindrical screen integrally connected to the tips of said rotor blades at the ends thereof opposite the ends connected to said rotor shaft, said cylindrical screen being mounted so as to extend coaxially with said rotor shaft,
• a circumferential surface encircled by said cylindrical screen, said circumferential surface forming a part of said stationary outer wall, the annular space formed between the cylindrical screen and the circumferential surface including an annular injection chamber,
• a plurality of injection orifices located in said stationary outer wall and distributed around the circumference thereof, the number of injection orifices being equal to the number of vanes in said stator ring,
• a plurality of injection pipes, each injection pipe interconnecting a respective injection orifice with a corresponding point along the circumference of said annular injection chamber,
• means forming a toroidal manifold surrounding said cylindrical screen,
• means for supplying a constant flow of fluid to said toroidal manifold,
• a peripheral opening in said cylindrical screen of a width which varies cyclically as it extends around said cylindrical screen, the outer mouth of said opening facing said toroidal manifold and the inner mouth facing said annular injection chamber so as to move, as said cylindrical screen rotates, near the mouths of said injection pipes and control the frequency of fluid passed to said injection orifices from said toroidal manifold, and
• a phase regulator ring positioned to be coaxial with the cylindrical screen and to be axially slidably positioned in said annular space between said cylindrical screen and said mouths of said injection pipes, said phase regulator having a plurality of identical, regularly spaced radial holes for controlling communication of fluid passing from the toroidal manifold through the peripheral opening in the rotating cylindrical screen to the mouths of the injection pipes, said phase regulator being angularly adjustable so as to modulate the phase of the fluid passed to said injection orifices.