Blade with 3D platform comprising an inter-blade bulb

1. A blade for a turbomachine impeller, comprising:

an airfoil including a pressure surface, a suction surface, a trailing edge, and a leading edge; and

a platform extending at one of the ends of the airfoil in a direction which is globally Perpendicular to a longitudinal direction of the airfoil,

wherein the blade is adapted to be arranged with a plurality of substantially identical blades to form a ring around a ring axis and define therealong upstream and a downstream area, with the ring having the airfoils arranged substantially radially therein, and the adjacent blade platforms joining in pairs so as to form an inter-airfoil surface linking the pressure surface of an airfoil to the suction surface of the neighboring airfoil,

wherein in an upstream half of the airfoil, only a single boss is formed on the inter -airfoil surface, the boss being located closer to the pressure surface than to the suction surface, and a recessed passage is located between the boss and the pressure surface,

wherein the inter-airfoil surface comprises a part of revolution having a shape of revolution with respect to the ring axis, located on a side of the suction surface of the airfoil neighboring the boss,

wherein the boss is linked to the part of revolution by a radially descending surface, and

wherein the boss occupies a majority of the portion of the inter-airfoil surface which extends in a circumferential direction from the pressure surface of the airfoil to the suction surface of the neighboring airfoil and axially from 0% to 50% of an axial extent of the airfoil from the leading edge of the airfoil; wherein the boss includes an apex located axially between 0% and 25% of the airfoil on the upstream side.

2. The blade according to claim 1 , wherein the inter-airfoil surface has a profile located in a plane perpendicular to the ring axis and located axially in the upstream half of the airfoil, the recessed passage being immediately adjacent to the boss and immediately adjacent to the pressure surface of the airfoil.

3. The blade according to claim 1 , wherein the inter-airfoil surface comprises a part having a shape of revolution with respect to the ring axis and extending axially throughout the downstream half of the airfoil.

4. The blade according to claim 1 , wherein the boss is continued upstream or downstream of the inter-airfoil surface.

5. A turbomachine nozzle segment, comprising at least one blade according to claim 1 .

6. An impeller comprising a plurality of blades according to claim 1 .

7. A turbomachine comprising at least one impeller according to claim 6 .

8. The blade according to claim 1 , wherein the platform is located at a tip of the airfoil, on a side of the airfoil radially opposite the center of the ring.

9. The blade according to claim 1 , wherein the inter-airfoil surface has a profile located in a plane perpendicular to the ring axis and located axially in the upstream half of the airfoil, the profile successively comprising the recessed passage followed by the boss, starting from the pressure surface of the airfoil,

wherein the profile represents a cross-section of the inter-airfoil platform passing by an apex of the boss, and

wherein, in the profile, the apex is on a pressure surface side relative to the overall extent of the boss.

10. The blade according to claim 1 , wherein the boss includes an apex, and a slope of the boss on an upstream side of the apex is steeper than a slope of the boss downstream side of the apex.