Blade for gas turbines with choke cross section at the trailing edge

• US 20010012484A1
• Filed: 12/19/2000
• Published: 08/09/2001
• Est. Priority Date: 12/27/1999
• Status: Active Grant

• Current Assignee: Ansaldo Energia IP UK Limited (Ansaldo Energia SPA)
• Original Assignee: Alstom Power AG
• Inventors: Nagler, Christoph, Beeck, Alexander, Schneider, Lothar, Semmler, Klaus, Ferber, Jorgen
• Granted Patent: US 6,481,966 B2
• Time in Patent Office: Days
• US Class Current: 416/97R
• CPC Class Codes: B22D 11/0405 Rotating moulds
• CPC Class Codes: F01D 5/187 Convection cooling
• CPC Class Codes: F05D 2240/122 related to the trailing edge of a stator vane
• CPC Class Codes: F05D 2240/304 related to the trailing edge of a rotor blade

Abstract

In a gas-turbine guide element (30) around which a hot air flow (23) flows and which, at least in a trailing edge region (21), in which the air flow (23) separates from the guide element (30), comprises at least two walls (10, 11) arranged essentially in parallel and connected to one another by ribs (16, 17, 20) in such a way as to form internal cooling passages (18, 19, 25, 26, 27), and which is cooled on the inside with cooling medium (28, 29) flowing through the cooling passages (18, 19, 25, 26, 27), the cooling medium discharging from the guide element (30) at the trailing edge (21) essentially parallel to and between the walls (10, 11), and in a method of producing it, easier reworking and less susceptibility to foreign particles are achieved owing to the fact that at least some of the ribs are arranged as choke ribs (24) so as to terminate essentially flush with the trailing edge (21).

Claims

1. A gas-turbine guide element (30) around which a hot air flow (23) flows and which, at least in a trailing edge region (21), in which the air flow (23) separates from the guide element (30), comprises at least two walls (10, 11) arranged essentially in parallel and connected to one another by ribs (16, 17, 20) in such a way as to form internal cooling passages (18, 19, 25, 26, 27), and which is cooled on the inside with cooling medium (28, 29) flowing through the cooling passages (18, 19, 25, 26, 27), the cooling medium discharging from the guide element (30) at the trailing edge (21) essentially parallel to and between the walls (10, 11), characterized in that at least some of the ribs (24) are arranged so as to terminate essentially flush with the trailing edge (21).

2. The guide element (30) as claimed in

claim 1

, characterized in that the rate of flow of cooling medium (28, 29) through the guide element (30) is essentially determined by the dimensioning of the outlet openings (25) arranged between the choke ribs (24).

3. The guide element (30) as claimed in

claim 2

, characterized in that the choke ribs (24) have a width (e) parallel to the trailing edge (21) and are arranged at a distance apart by in each case a rib spacing (f), and in that the ratio of width (e) to rib spacing (f) is within a range of 0.25 to 0.75.

4. The guide element (30) as claimed in one of the preceding claims, characterized in that the thickness (d) of the guide element (30) at the trailing edge (21) is within a range of 0.5 to 5 mm, in particular preferably within a range of 1.0 to 2.5 mm, and in that the slot thickness (c) of the cooling-air passages (25) between the walls (10, 11) at the outlet (21) is within a range of 0.3 to 2 mm, in particular within a range of 0.8 to 1.5 mm.

5. The guide element (30) as claimed in one of

claims 1

to

4

, characterized in that it is designed as a guide blade (30) arranged in front of a turbine rotor, and in that the cooling medium used is air.

6. The guide blade (30) as claimed in

claim 5

, characterized in that the guide blade is designed to be widened in its incident-flow region, and in the incident-flow region the cooling air flows in suction-side and pressure-side cooling passages around an inner, central, radially running insert (12), and in that the cooling air flows through between ribs (16) adjoining the insert (12), then between intermediate ribs (17), then between pins (20) between the walls (10, 11) before it discharges from the guide blade (30) through outlet openings (25) at the trailing edge.

9. The method as claimed in one of the preceding claims, characterized in that the casting process is a pressure casting process, in that the projecting length has a value (b) behind the trailing edge (21), in that the walls (10, 11) are kept at a distance apart at the outlet (21) by a slot thickness (c) of the cooling-air passages (25), and in that in particular the projecting length value (b) is 0.5 to 5 times, in particular preferably 1 to 3 times, as large as the slot thickness (c).

10. The method as claimed in one of the preceding claims, characterized in that the choke ribs (24) have a width (e) parallel to the trailing edge (21) and are arranged at a distance apart by in each case a rib spacing (f), in that the ratio of width (e) to rib spacing (f) is within a range of 0.25 to 0.75, in that the thickness (d) of the guide element (30) at the trailing edge (21) is within a range of 0.5 to 5 mm, in particular preferably within a range of 1.0 to 2.5 mm, and in that the slot thickness (c) of the cooling-air passages (25) between the walls (10, 11) at the outlet (21) is within a range of 0.3 to 2 mm, in particular within a range of 0.8 to 1.5 mm.

11. The method as claimed in one of the preceding claims, characterized in that the guide element is a guide blade (30) arranged in front of a turbine rotor, and in that the cooling medium used is air.

7. A method of producing a gas-turbine guide element (30) around which a hot air flow (23) flows and which, at least in a trailing edge region (21), in which the air flow (23) separates from the guide element (30), comprises at least two walls (10, 11) arranged essentially in parallel and connected to one another by ribs (16, 17, 20) in such a way as to form internal cooling passages (18, 19, 25, 26, 27), and which is cooled on the inside with cooling medium (28, 29) flowing through the cooling passages (18, 19, 25, 26, 27), the cooling medium discharging from the guide element (30) at the trailing edge (21) essentially parallel to and between the walls (10, 11), characterized in that the guide element (30) is produced by a casting process, in that the trailing edge region (21) is in this case cast with a projecting length extending the guide element (30) or its walls (10, 11) in the direction of flow, and in that the projecting length is removed after the casting in such a way that at least some of the ribs are arranged as choke ribs (24) so as to terminate essentially flush with the trailing edge (21).

8. The method as claimed in

claim 7

, characterized in that the rate of flow of cooling medium (28, 29) through the finished guide element (30) is essentially determined by the dimensioning of the outlet openings (25) arranged between the choke ribs (24).