Vortex generators for generating vortices upstream of a cascade of compressor blades

1. A blade assembly for a turbomachine compressor, said blade assembly comprising:

a plurality of individual devices acting on a principal flow, which axially flows through blades of said blade assembly, the plurality of individual devices being provided upstream of said blade assembly in a flow path of the principal flow and being formed at least so as to generate vortices; and

a shroud including a radial surface to which a blade of the blade assembly is attached and at least an upstream s face which is upstream of a leading edge of the blade and around which a recirculating flow passes, said flow coming from a cavity delimited by the shroud,

wherein each of said individual devices is arranged on said upstream surface, and wherein each of said individual devices is arrange at the place of said shroud where the recirculating flow is reinjected into the principal flow, in order that said individual devices act simultaneously on the principal flow and on the recirculating flow.

2. The assembly as claimed in claim 1 , wherein at least some of said devices comprise indentations which are formed in the upstream surface of the shroud around which said recirculating flow passes and at the place of said shroud where the recirculating flow is reinjected into the principal flow.

3. The assembly as claimed in claim 1 , wherein said devices are configured to guide at least said recirculating flow.

4. The assembly as claimed in claim 3 , wherein at least some of said devices comprise ribs which are arranged in the region of said upstream surface of the shroud around which said recirculating flow passes and at the place of said shroud where the recirculating flow is reinjected into the principal flow.

5. The assembly as claimed in claim 1 , wherein at least sonic of said devices are arranged between two successive blades.

6. The assembly as claimed in claim 1 , wherein at least some of said devices are arranged directly upstream of a blade.

7. The assembly as claimed in claim 1 , wherein said. assembly is a rectifier for a turbomachine compressor, said rectifier comprising:

an external shroud and an internal shroud which are coaxial;

the blades arranged adjacent to one another between said external and internal shrouds, the blades being connected thereto by ends thereof; and

the plurality of individual devices acting on the flow which are provided on the internal shroud, each of said devices being provided in the region of an upstream face of the internal shroud which is upstream of leading edges of the blades and around which a recirculating flow passes, said flow coining from a cavity delimited by the shroud, in a vicinity of a radially external side of the shroud, in order to act simultaneously on the principal flow and on the recirculating flow which corresponds to the flow of fluid passing below a radially internal side of the internal shroud, coming from a downstream face thereof.

8. The assembly as claimed in claim 7 , wherein said rectifier is formed from a plurality of individual structures assembled together, each comprising one of the blades.

9. The assembly as claimed in claim 8 , wherein said individual structures are each provided with a chamfer in the region of the edges and the adjacent chamfers each forms an indentation.

10. The assembly as claimed in claim 1 , wherein said assembly is a rotor for a turbomachine compressor, said rotor comprising:

an internal shroud and an external shroud which are coaxial;

the blades arranged adjacent to one another between said internal and external shrouds, the blades being connected thereto by ends thereof; and

the plurality of individual devices acting on the flow which are provided on the external shroud, each of said devices being provided in a region of an upstream face of the external shroud which is upstream of leading edges of the blades and around which a recirculating flow passes, said flow coming from a cavity delimited by the shroud, in order to act simultaneously on the principal flow and on the recirculating flow which corresponds to the flow of fluid passing on a radially external side of the external shroud, coming from a downstream face thereof.

11. A turbomachine compressor, comprising at east one blade assembly as claimed in claim 1 .

12. An aircraft turbojet engine, comprising at least one compressor as claimed in claim 11 .

13. The assembly as claimed in claim 1 , wherein the vortices generated by said individual devices transfer energy from the principal flow to boundary. layers so as to accelerate the boundary layers.

14. The assembly as claimed in claim 5 , wherein said at least sonic of said devices are arranged between two successive blades, one third of the distance along the inter-blade channel.

15. A blade assembly for a turbomachine compressor, said blade assembly comprising:

a plurality of individual devices acting on a principal flow, which axially flows through blades of said blade assembly, the plurality of individual devices being provided upstream of said blade assembly in a flow path of the principal flow and being formed at least so as to generate vortices; and

a shroud including a radial surface to which a blade of the blade assembly is attached and an upstream surface which is upstream of a leading edge of the blade,

wherein each of said individual devices is arranged on at least the upstream surface of the shroud around which a recirculating flow passes, circulating in a cavity delimited by the shroud, at the place where the recirculating flow is reinjected into the principal flow so that said individual devices act simultaneously on the principal flow and on the recirculating flow, and

wherein at least some of said devices comprise indentations which are formed in the upstream surface of the shroud around which said recirculating flow passes.

16. A blade assembly for a turbomachine compressor, said blade assembly comprising:

a plurality of individual devices acting on a principal flow, which axially flows through blades of said blade assembly, the plurality of individual devices being provided upstream of said blade assembly in a flow path of the principal flow and being formed at least so as to generate vortices; and

a shroud including a radial surface to which a blade of the blade assembly is attached and an upstream surface which is upstream of a leading edge of the blade,

wherein each of said individual devices is arranged on at least the upstream surface of the shroud around which a recirculating flow passes, circulating in a cavity delimited by the shroud, at the place where the recirculating flow is reinjected into the principal flow so that said individual devices act simultaneously on the principal flow and on the recirculating flow, and

wherein at least some of said devices comprise ribs which are arranged in the region of said upstream face of a shroud around which said recirculating flow passes.