Method and cooling system for cooling blades of at least one blade row in a rotary flow machine

Abstract

A method and a cooling system for cooling blades of at least one blade row in a rotary flow machine includes an axial flow channel which is radially limited on the inside by a rotor unit and at the outside by at least one stationary component, the blades are arranged at the rotary unit and provide a shrouded blade tip facing radially to said stationary component. Pressurized cooling air is fed through from radially outside towards the tip of each of said blades in the at least one blade row, and the pressurized cooling air enters the blades through at least one opening at the shrouded blades' tip.

Claims

1. A method for cooling blades of at least one blade row in a rotary flow machine, comprising an axial flow channel which is radially limited on the inside by a rotor unit and at the outside by at least one stationary component, said blades are arranged at the rotary unit and provide a shrouded blade tip facing radially to said stationary component, wherein the pressurized cooling air is fed through from radially outside towards the tip of each of said blades in the at least one blade row, and said pressurized cooling air enters the blades through at least one opening at the shrouded blade tip.

2. The method according to claim 1, wherein the pressurized cooling air is fed through the stationary component surrounding said at least one blade row radially and entering a cavity enclosed by the stationary component and shrouded tips of the blades in the at least one blade row.

3. The method according to claim 2, wherein the pressurized cooling air is fed into the cavity through at least one stationary component sided opening such that a static pressure prevails within said cavity which is higher than a total relative pressure of a flow in the axial flow channel at a leading edge of the blades in the at least one blade row.

4. A cooling system for cooling blades of at least one blade row in a rotary flow machine comprising an axial flow channel which is radially limited on the inside by a rotor unit and at the outside by at least one stationary component, said blades are arranged at the rotary unit and provide a shrouded blade tip facing radially to said stationary component, wherein at least one opening is arranged at the stationary component facing radially towards the shrouded tips of the blades of the at least one blade row, said at least one opening is an exit port of a cooling channel inside the stationary component, each of the blades provides at least one aperture at its shrouded blade tip, and said aperture is an entrance port of a cooling channel inside the blade.

5. The cooling system according to claim 4, wherein the shrouded tips of the blades are designed and arranged such that the shroud of each blade provides an upstream and a downstream edge relative to an axial flow direction through said axial flow channel of the rotary flow machine, and along said up- and downstream edge at least one fin is arranged arising radially beyond a shroud surface extending between both fins.

6. The cooling system according to claim 5, wherein the shrouded tips of the blades are designed and arranged such that shrouds of two neighbouring blades adjoin each other in a circumferential direction, so that the shrouds of all blades in the at least one blade row combine to form at least one a radially outwardly directed annular shaped inter fin cavity bordered radially by the stationary component.

7. The cooling system according to claim 5, wherein the opening contour of the aperture provides a funnel shaped cross-section in radially and circumferentially direction, said funnel shaped cross-section has an assigned funnel axis tending into circumferential direction of rotation.

8. The cooling system according to claim 7, wherein each aperture of the shrouded blade tip provides an opening contour having an extension in axial, radial and circumferential direction such that a flow cross-section of said aperture becomes larger in flow direction of the cooling air entering the aperture.

9. The cooling system according to claim 7, wherein the opening contour of each aperture extends between two or more neighbouring blades.

10. The cooling system according to claim 4, wherein the exit port of the at least one opening has an assigned axis which is orientated radially.

11. The cooling system according to claim 4, wherein the rotary flow machine is a gas or steam turbo machine or a compressor unit.

12. A rotary flow machine comprising an axial flow channel which is radially limited on the inside by a rotor unit and at the outside by at least one stationary component, and blades within at least one blade row being arranged at the rotary unit and provide a shrouded blade tip facing radially to said stationary component, characterized in that at least one opening is arranged at the stationary component facing radially towards the shrouded tips of the blades of at least one blade row, said at least one opening is an exit port of a cooling channel inside the stationary component, each of the blades provides at least one aperture at its shrouded blade tip, and said aperture is an entrance port of a cooling channel extending within the blade.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention shall subsequently be explained in more detail based on exemplary embodiment in conjunction with the drawing. The drawing

(2) FIG. 1a shows a side view of a blade inside a rotary flow machine,

(3) FIG. 1b shows a schematically top view of two shrouded blade tips within one blade row and

(4) FIG. 1c shows a sectional view along cut line BB through the head part of to neighboring shrouded blades in circumferential direction of a blade row.

DETAILED DESCRIPTION

(5) FIG. 1 shows a side view of a blade 1 mounted in a blade row of a rotary flow machine. The rotary flow machine comprises a flow channel 2 which is radially limited on the inside by rotor unit 3 and the outside by at least one stationary component 4. Typically the stationary component 4 is a heat shield component which is mounted at the inner wall of a casing surrounding said rotary flow machine. Each blade 1 of the blade row comprises a shovel foot 5 which is detachably connected to the rotor unit 3, an air foil 6 extending radially through the axial flow channel 2 and being exposed to the hot gas flow passing the axial flow channel, and finally a shroud 7 at the blade tip's end.

(6) For cooling purpose of the blade 1 it is inventively suggested to feed cooling air 8 radially outward from the stationary component into the blade 1 through an opening 9 at the shrouded blade tip. By radial cooling air supply to the blade 1 from radially outside through at least one stationary component 4 complex designed cooling channels inside the rotor unit, as described above, can be avoided. The cooling air supply to the stationary component 4 can be designed and arranged very easy so that constructive and financial expense for realizing cooling of the blades 1 can be reduced significantly.

(7) To ensure that no hot gases will enter the opening 9 of the cooling channel inside the blade 1 the shroud 7 provides an upstream edge 7′ and a downstream edge 7″ relative to the axial flow direction through the axial flow channel 2 illustrate by the arrow F in FIG. 1a which is directed from the left to the right. Along the upstream edge 7′ a first fin 10 and along the downstream edge 7″ a second fin 11 are arranged, both fins 10, 11 arise radially beyond the shroud surface 12 extending between both of fins 10, 11. Due to the shroud design and the arrangement of the blade 1 relative to the stationary component 4 the shroud 7 encloses an inter fin cavity 13 together with the stationary component 4 into which cooling air 8 is fed through the opening 14 of the stationary component which is an exit port of a cooling channel system inside the stationary component not shown. The pressurized cooling air 8 is fed into the inter fin cavity 13 such that a static pressure previous within said cavity 13 is higher than a total relative pressure of flow in the axial flow channel 2 at a leading edge 15 of the blade 1 in the at least one blade row. In this way it can be avoided that hot gases can enter the inter fin cavity 13.

(8) The at least one opening 14 inside the stationary component 4 is arranged in radially projection to the shrouded blade tips and the number of such openings 14 depends on the desired cooling effect in the blades. If the cooling air supply cannot be met by just one opening more openings can be arranged in circumferential direction around the blade row inside the stationary component.

(9) FIG. 1b shows a schematically top view on two neighboring shrouded blade tips with an indicated profile of the airfoil of each blade. Each shroud 7 provides an upstream edge 7′ along which fin 10 and an downstream edge 7″ along which fin 11 are arranged each extending beyond the shroud surface 12 extending axially between both fins 10, 11. In FIG. 1b it is assumed that the fins 10, 11 arise beyond the drawing plain.

(10) Further it is shown that the shrouds 7 of two neighboring blades adjoin each other in the circumferential direction R which corresponds to the movement of rotation of the rotary flow machine, so that the shrouds 7 of all blades in the at least one blade row combine to form a radially outwardly directed annular shaped inter fin cavity 13 which is seen in FIG. 1b from the top view.

(11) Each blade provides at its shroud 7 at least one opening 9 at the shroud surface 12 which is an entrance port of a cooling channel 17 inside the blade 1. See also FIG. 1c which shows a sectional view along a cut line BB as indicated in FIG. 1b. Each opening 9 has an overlap to at least one neighboring shroud and provides an opening contour having an extension in axial and in circumferential direction such that in radial protection onto the shroud 7 as illustrated in FIG. 1b, the aperture 9 corresponds to a bottle neck shape with a smallest axial width 16 directed in circumferential direction of rotation R. Such shape of aperture sustains an inflow of cooling medium into the cooling channel 17 of the blade 1. Especially the cross section design of each aperture 9 which is illustrated in FIG. 1c supports an inflow of cooling air into the cooling channel 17, due to a funnel shaped cross section in radially and circumferentially direction of the opening contour of the opening 9 which has a funnel axis 18 tending into circumferential direction R of rotation.

(12) As indicated in FIG. 1a the top of each fin 10, 11 is arranged very close to the inner surface of the stationary part 4 which is, as explained before a heat shield component preferably, so that a leakage of cooling air escaping from the inter fin cavity 13 into the flow path 2 can be reduced significantly. In preferred embodiment the fins 10, 11 and the heat shield component are arranged and designed to realize a labyrinth sealing.