Passageway between a shroud and a rotor platform in a turbine engine

1. A compressor assembly for a turbomachine, the assembly comprising:

an annular row of upstream vanes with trailing edges extending radially from an upstream support;

an annular row of downstream vanes with leading edges axially facing the trailing edges and extending radially from a downstream support; and

an annular passageway delimited by the upstream support and the downstream support;

wherein the downstream support comprises:

an outer surface with a profile, said profile comprising:

an upstream portion delimiting the annular passageway;

a downstream portion; and

a connecting arc connecting the upstream portion to the downstream portion, at least one of the leading edges being arranged upstream of the connecting arc;

wherein one of the annular rows of vanes is rotatable around an axis of rotation and the annular passageway, when seen in a transversal cross-section parallel to said axis of rotation, has a median axis forming an angle with the axis of rotation of between 15° and 45°; and

wherein each downstream vane has a chord line and an axial offset between the connecting arc and its leading edge, said axial offset being less than or equal to 10% of the length of the chord line.

2. The assembly according to claim 1 , wherein at least one of the leading edges has a radially inner end arranged upstream of the connecting arc.

3. The assembly according to claim 1 , wherein each downstream vane has a chord line and an axial offset between the connecting arc and its leading edge, said axial offset being greater than or equal to 5% of the length of the chord line.

4. The assembly according to claim 1 , wherein the upstream support and the downstream support comprise:

an abradable sealing device.

5. The assembly according to claim 1 , wherein the upstream support has an annular groove that is axially downstream open, the upstream portion being at least partially arranged into said annular groove.

6. The assembly according to claim 1 , wherein the length of the passageway is greater than or equal to the height of the passageway.

7. The assembly according to claim 1 , wherein the assembly comprises:

a drum or a disk supporting a third annular row of vanes arranged upstream of the upstream vanes.

8. The assembly according to claim 1 , further comprising:

an air bleed opening in fluidic communication with the annular passageway.

9. A compressor assembly for a turbomachine, the assembly comprising:

an annular row of upstream vanes with trailing edges extending radially from an upstream support;

an annular row of downstream vanes with leading edges axially facing the trailing edges and extending radially from a downstream support; and

an annular passageway delimited by the upstream support and the downstream support;

wherein the downstream support comprises:

an outer surface with a profile, said profile comprising:

an upstream portion delimiting the annular passageway;

a downstream portion;

a median axis forming an angle of between 15° and 45° with an axis of rotation; and

a connecting arc connecting the upstream portion to the downstream portion, at least one of the leading edges being arranged upstream of the connecting arc;

wherein one of the annular rows of vanes is rotatable around the axis of rotation and the annular passageway, when seen in a transversal cross-section parallel to said axis of rotation; and

wherein the downstream portion extends radially outwardly away from the connecting arc with respect to the axis of rotation.

10. A method for controlling the stability of a turbomachine compressor, the compressor including an assembly, the assembly comprising:

an annular row of upstream vanes with trailing edges extending radially from an upstream support;

an annular row of downstream vanes with leading edges axially facing the trailing edges and extending radially from a downstream support; and

an annular passageway delimited by the upstream support and the downstream support, wherein the downstream support comprises:

an outer surface with a profile, said profile comprising:

an upstream portion delimiting the annular passageway;

a downstream portion; and

a connecting arc connecting the upstream portion to the downstream portion, at least one of the leading edges being arranged upstream of the connecting arc;

wherein one of the annular rows of vanes is rotatable around an axis of rotation and the annular passageway, when seen in a transversal cross-section parallel to said axis of rotation, has a median axis forming an angle with the axis of rotation of between 15° and 45°;

the method comprising:

a step of operating the compressor during which a flow of air passes through the annular passageway in a direction inclined with respect to the downstream portion of an inclination that is less than or equal to 10°.

11. The method of claim 10 , wherein during the step of operating, the flow joins a boundary layer in contact with the outer surface; the flow and the boundary layer being inclined with respect to one another of less than 30°.

12. The method of claim 10 , wherein during the step of operating, the flow joins an annular flow passing axially through the compressor; the auxiliary flow and the annular flow being inclined with respect to one another of less than 20°.

13. The method of claim 10 , wherein the annular row of upstream vanes or the annular row of vanes downstream rotates during the step of operating, at a speed of at least 15000 rpm.

14. The method of claim 10 , wherein during the step of operating, the flow cools down the downstream support.