METHOD FOR PRODUCING A ROTOR BLADE

Abstract

A method for producing a rotor blade for a gas turbine, the blade having a fastening region and a platform, on which a blade ending in a blade tip is arranged. The method is designed to facilitate a particular high efficiency of the gas turbine with a particularly resource-saving manner of production. The method includes: production of a reinforcement; casting of a first part of the rotor blade about at least one portion of the reinforcement; and construction of a second part of the rotor blade by a 3D-printing method.

Claims

1. A method for producing a rotor blade for a gas turbine, the blade having a fastening region and a platform, on which a blade airfoil ending in a blade tip is arranged, the method comprising: production of a reinforcement; casting of a first part of the rotor blade around at least one part of the reinforcement; and buildup of a second part of the rotor blade by a 3-D printing method.

2. The method as claimed in claim 1, wherein the reinforcement comprises a stay, which extends from a region of the rotor blade tip to the platform.

3. The method as claimed in claim 2, wherein the reinforcement comprises a stay, which extends from the region of the rotor blade tip to the fastening region.

4. The method as claimed in claim lone of the preceding claims, wherein the first part comprises the fastening region.

5. The method as claimed in claim 4, wherein the first part comprises the platform.

6. The method as claimed in claim 4, wherein the first part comprises a sheath for at least some of the stays of the reinforcement in one region of the blade airfoil.

7. The method as claimed in claim 1, wherein the reinforcement is manufactured from steel.

8. The method as claimed in claim 1, wherein the second part comprises one region of the blade airfoil.

9. The method as claimed in claim 8, wherein cooling ducts are arranged in the region of the blade airfoil during the buildup of the second part.

10. The method as claimed in claim 1, wherein selective laser fusion is used as the 3-D printing method.

11. A rotor blade for a gas turbine, produced by the method as claimed in claim 1.

12. A rotor blade for a gas turbine, comprising a reinforcement arranged in the interior.

13. A gas turbine comprising: a rotor blade as claimed in claim 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Illustrative embodiments of the invention are explained in greater detail by means of a drawing, in which:

[0022] FIG. 1 show a partial longitudinal section through a gas turbine,

[0023] FIG. 2 shows a reinforcement for a rotor blade,

[0024] FIG. 3A shows the reinforcement with a cast blade root in section,

[0025] FIG. 3B shows the reinforcement with a cast blade root and partial sheathing of the reinforcement, and

[0026] FIG. 4 shows a section through the rotor blade.

DETAILED DESCRIPTION OF INVENTION

[0027] In all the figures, identical parts are provided with the same reference signs.

[0028] FIG. 1 shows a gas turbine 100 in a partial longitudinal section. A turbine is a continuous flow machine which converts the internal energy (enthalpy) of a flowing fluid (liquid or gas) into rotational energy and ultimately into mechanical driving energy.

[0029] In the interior, the gas turbine 100 has a rotor 103, which is mounted so as to rotate about an axis of rotation 102 (axial direction) and which is also referred to as a turbine rotor. Situated one after the other along the rotor 103 are an intake casing 104, a compressor 105, a toroidal combustion chamber 110, in particular an annular combustion chamber 106, having a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust casing 109.

[0030] The annular combustion chamber 106 communicates with an annular hot gas duct 111. There, four turbine stages 112 arranged in series, for example, form the turbine 108. Each turbine stage 112 is formed by two blade rings. When viewed in the flow direction of a working medium 113, a guide blade row 115 is followed in the hot gas duct 111 by a row 125 formed by rotor blades 120. The blades 120, 130 have a slightly curved profile, similar to an aircraft wing.

[0031] In this case, the guide blades 130 are fastened on the stator 143, whereas the rotor blades 120 of a row 125 are mounted on the rotor 103 by means of a turbine disk 133. The rotor blades 120 thus form component parts of the rotor or turbine wheel 103. A generator or a machine (not shown) is coupled to the rotor 103.

[0032] During the operation of the gas turbine 100, air 135 is drawn in and compressed by the compressor 105 through the intake casing 104. The compressed air supplied at the turbine end of the compressor 105 is passed to the burners 107 and is mixed there with a fuel. The mixture is then burnt in the combustion chamber 110 to form the working medium 113. From the combustion chamber, the working medium 113 flows along the hot gas duct 111, past the guide blades 130 and the rotor blades 120.

[0033] Some of the internal energy of the fluid flow is removed by the—as far as possible—eddy-free laminar flow of the turbine blades 120, 130, and this energy is transferred to the rotor blades 120 of the turbine 108. This then imparts rotation to the rotor 103, as a result of which, first of all, the compressor 105 is driven. The useful power is output to the machine (not shown).

[0034] During the operation of the gas turbine 100, the components exposed to the hot working medium 113 are subject to thermal loads. Apart from the heat shield blocks lining the annular combustion chamber 106, the guide blades 130 and rotor blades 120 of the first turbine stage 112, as viewed in the flow direction of the working medium 113, are subject to the highest thermal loads. The high loads render materials capable of bearing extreme loads necessary. The turbine blades 120, 130 are therefore manufactured from titanium alloys, nickel super alloy or tungsten-molybdenum alloys. The blades are protected by coatings against corrosion (MCrAlX; M=Fe, Co, Ni, rare earths) and heat (heat insulation layer, e.g. ZrO2, Y2O4-ZrO2) to ensure greater resistance to temperature and erosion, such as pitting. The heat shield coating is referred to as a thermal barrier coating or TBC for short. Further measures for making the blades more resistant to heat consist in sophisticated cooling duct systems. This technique is used both in the guide blades and in the rotor blades 120, 130.

[0035] Each guide blade 130 has a guide blade root (not shown here) facing the inner casing 138 of the turbine 108 and a guide blade head situated opposite the guide blade root. The guide blade head faces the rotor 103 and is fixed on a sealing ring 140 of the stator 143. In this arrangement, each sealing ring 140 surrounds the shaft of the rotor 103. Each rotor blade 120 likewise has a rotor blade root of this kind, as illustrated in the following figures, but ends in a rotor blade tip.

[0036] FIG. 2 shows a reinforcement 144 for a rotor blade 120 of this kind. The reinforcement 144 has an upper transverse stay 146.

[0037] A total of four longitudinal stays 148, 150 point downward from the upper transverse stay 146 at equal spacings from one another, extending away from one another slightly in a radiating pattern. The two central longitudinal stays 148 are somewhat longer than the outer longitudinal stays 150. They are of equal length and are connected at the end thereof by a lower transverse stay 152. At the end of the outer longitudinal stays 150, which are likewise of equal length, said stays are connected to one another and to the central longitudinal stays 150 by a further transverse stay 154. Between the further transverse stay 154 and the upper transverse stay 146, all the longitudinal stays 148, 150 are connected to one another by central transverse stays 156 arranged at regular spacings.

[0038] The arrangement of the longitudinal and transverse stays 146, 148, 150, 152, 154, 156 which is shown in FIG. 2 is only illustrative. In further alternative embodiments, it is, of course, possible to choose the number, orientation and distribution of the stays to match the forces which occur.

[0039] The longitudinal and transverse stays 146, 148, 150, 152, 154, 156 thus form a stable reinforcement 144, which can be arranged in the interior of a rotor blade 120. The process for producing the rotor blade 120 is explained with reference to the following figures. First of all, the reinforcement 144 is produced as described. It consists of a high-strength steel alloy and remains stable in the casting process shown in FIGS. 3A and 3B.

[0040] In a first illustrative embodiment of the method, only the rotor blade root 158 is cast, as shown in FIG. 3A. This root comprises a platform 160 for sealing off the inner regions of the rotor 103 from the hot gas in the hot gas duct 111 and comprises a fastening region 162, which has a tongue on both sides, which is formed for a tongue and groove joint on the rotor. As can be seen, the transverse stay 154 is situated in the platform 160 here. Those regions of the central longitudinal stays 148 which extend downward beyond the transverse stay 154, and the lower transverse stay 152, are situated in the fastening region 162.

[0041] In a second illustrative embodiment of the method, sheaths 164 for each longitudinal stay 150, 152 are cast in addition to the rotor blade root 158, as shown in FIG. 3B. These sheaths can be of cylindrical design, for example, with the longitudinal stay 150, 152 as an axis. In both illustrative embodiments, a comparatively simple, reusable mold can be used in casting.

[0042] Finally, FIG. 4 shows the finished rotor blade 120. The remaining parts of the body of the rotor blade 120 have been produced by means of selective laser fusion, starting from the component shown in FIGS. 3A and 3B. The part produced in this way comprises the blade airfoil 166, in particular, wherein the upper transverse stay 146 of the reinforcement 144 is arranged in the region of the rotor blade tip 167.

[0043] The blade airfoil 166 has a relatively complex geometry: its profile resembles that of an aircraft wing. It has a rounded profile nose 168 and a profile rear edge 170. Extending between the profile nose 168 and the profile rear edge 170 are a concave pressure-side wall and a convex suction-side wall of the rotor blade 120. A plurality of cooling air ducts (not shown specifically) are introduced in the interior, between the pressure-side wall and the suction-side wall.

[0044] The complex geometry described can be built up in a particularly simple manner by means of 3-D printing, starting from the partially cast rotor blade 120. The structural weaknesses of the material produced by 3-D printing are compensated by the reinforcement 144.