Blade with non-axisymmetric platform
View Patent ↗A blade for a turbomachine impeller including an airfoil and at least one platform at one end of the airfoil, the blade configured to be arranged with a plurality of substantially identical blades so as to form a ring, the platform surface having a suction surface profile and a pressure surface profile respectively along the suction surface and the pressure surface. In the blade, the pressure surface profile including a pressure surface recessed part is located axially in an upstream half of the airfoil. Due to this configuration, efficiency of the blade is improved.
1. A blade for a turbomachine impeller, comprising:
an airfoil including a pressure surface, a suction surface, a trailing edge, a leading edge; and
a platform extending at one of ends of the airfoil in a direction that is globally perpendicular to a longitudinal direction of the airfoil; wherein
the blade is configured to be arranged with a plurality of substantially identical blades to form a ring around a ring axis and define therealong upstream and downstream directions, with the ring having the airfoils arranged substantially radially therein;
adjacent portions of platform surfaces of two adjacent blades located between their respective airfoils define an inter-airfoil surface;
a suction surface profile is projected on the platform surface at a constant distance from the suction surface;
a pressure surface profile along the pressure surface is projected on the platform surface at a constant distance from the pressure surface;
the pressure surface profile includes a pressure surface recessed part, at least 90% of said pressure surface recessed part being contained within a downstream half of the airfoil and at most 10% of said pressure surface recessed part lying in an upstream half of the airfoil;
most of the inter-airfoil surface is a surface with a shape corresponding to a motion from upstream to downstream of a line segment in a direction parallel to the ring axis, the line segment having a first end point on the suction surface profile and a second end point on the pressure surface profile, and presenting an angle relative to the ring axis; and
the angle is between 60 and 120 degrees.
2. The blade according to claim 1 , wherein the suction surface profile includes a suction surface recessed part located axially in the upstream half of the airfoil, and a suction surface boss-like part, located axially downstream of the suction surface recessed part.
3. The blade according to claim 2 , wherein the suction surface recessed part is located axially between 0 and 40% of the airfoil.
4. The blade according to claim 3 , wherein a bottom point of the suction surface recessed part is located axially between 12% and 35% of the airfoil.
5. The blade according to claim 2 , wherein the suction surface boss-like part is located axially between 40 and 80% of the airfoil.
6. The blade according to claim 2 , wherein when such blades are assembled into a ring, sections of the platform surfaces of the assembled blades in a vicinity respectively upstream and downstream of the airfoils define an upstream median circle and a downstream median circle, these sections being perpendicular to the ring axis;
the circles define a cone coaxial to the ring axis and containing the circles;
the suction surface recessed part is depressed with respect to the cone; and the suction surface boss-like part protrudes with respect to the cone.
7. The blade according to claim 6 , wherein the pressure surface recessed part is depressed with respect to the cone.
8. The blade according to claim 6 , wherein the pressure surface profile further includes a pressure surface boss-like part, located axially mainly in an upstream half of the airfoil, and which is further protruding with respect to the cone.
9. The blade according to claim 1 , wherein the pressure surface profile further includes a pressure surface boss-like part, located axially mainly in an upstream half of the airfoil.
10. The blade according to claim 9 , wherein the pressure surface boss-like part is axially extending over more than three quarters of the airfoil.
11. The blade according to claim 9 , wherein the pressure surface boss-like part is located axially between 0 and 50% of the airfoil.
12. The blade according to claim 1 , wherein the recessed part continues downstream of the inter-airfoil surface.
13. The blade according to claim 1 , wherein the platform surface further includes a portion shaped as a surface of revolution with respect to the ring axis, close to the pressure surface of the airfoil and located axially at about 75% of the airfoil.
14. The blade according to claim 1 , wherein the platform surface includes a portion shaped as a surface of revolution with respect to the ring axis and located close to a trailing edge of the airfoil.
15. A turbomachine nozzle segment, comprising at least one blade according to claim 1 .
16. An impeller comprising a plurality of blades according to claim 1 .
17. A turbomachine comprising at least one impeller according to claim 16 .
18. The blade according to claim 1 , wherein at least three quarters of said inter-airfoil surface has said shape corresponding to said motion of said line segment, and wherein said motion of said line segment includes a motion of the end points of the line segment in a same direction along the suction surface profile and the pressure surface profile.
19. The blade according to claim 1 , wherein the platform is located at a head of the airfoil, radially opposite a center of the turbomachine impeller.