Method for producing a base body of a turbine blade

Abstract

A method for producing turbine rotor blades or the base bodies thereof includes a) providing the base body, which has, following one another along a longitudinal axis, a blade root, a blade platform and a blade airfoil, b) sensing a value of at least one parameter of the base body, at least one of the parameters representing a vibrational property of the base body, c) comparing the sensed value with a predetermined target interval, d) if the sensed value lies outside the target interval, reducing the mass of the base body, wherein the reduction of the mass takes place at the blade root and/or on the blade platform by introducing at least one recess and/or by reducing a dimension below the corresponding target value.

Claims

1. A method for producing a base body or a turbine rotor blade, comprising at least the successive steps of a) providing the base body, which comprises, following one another along a longitudinal axis, a blade root, a blade platform and a blade airfoil, b) sensing a value of at least one parameter of the base body, at least one of the parameters representing a vibrational property of the base body, c) comparing the sensed value with a predetermined target interval, d) if the sensed value lies outside the target interval, reducing the mass of the base body, wherein the reduction of the mass takes place at the blade root by introducing at least one recess and/or by reducing a dimension below the corresponding target value.

2. The method as claimed in claim 1, in which the reduction of the mass takes place at a region or regions of the blade root, and wherein the region concerned or the regions concerned lies or lie outside those regions of the base body that can be flowed over by a hot gas.

3. The method as claimed in claim 1, in which, before carrying out step b), at least most of the dimensions of the base body are brought to their target size.

4. A rotor turbine ring for a rotor of an axially flowed-through turbine, comprising: a number of turbine rotor blades, wherein the base bodies of which are produced by a method as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawing:

(2) FIG. 1 shows a flow diagram with the various production steps of a method according to the invention for producing a base body of a turbine rotor blade,

(3) FIG. 2 shows a flow diagram with further production steps and

(4) FIG. 3 shows a perspective view of an underside of a base body of a turbine rotor blade.

DETAILED DESCRIPTION OF INVENTION

(5) The method 10 according to the invention is represented in FIG. 1. The method 10 for producing a base body 30 (FIG. 3) of a turbine rotor blade comprises in a first step 12 the provision of the base body 30 of the turbine rotor blade. The base body 30 comprises, following one another along a virtual longitudinal axis 31, a blade root 32, a platform 34 and a blade airfoil 36.

(6) When its planar end face 38 is viewed perpendicularly, the contour of the blade root 32 is firtree-shaped and goes over via a so-called blade neck 40 into an underside 42 of the platform 34. Opposite from the underside 42, the platform has a hot gas side 44, which is monolithically adjoined by the blade airfoil 36. The latter is formed in the shape of a droplet and is aerodynamically curved to form a pressure side 46 and a suction side 48.

(7) The blade root 32 extends over a length L between the two planar end faces 38 lying axially opposite one another.

(8) In a second production step 14, a variable of at least one parameter of the base body 30 is sensed, at least one of the parameters representing a vibrational property of the base body. Usually, the resonant frequencies and the vibration modes are sensed by the usual methods.

(9) In a third production step 16, the sensed value or the sensed values is or are compared with a target interval (associated target interval). If the sensed values lie outside the associated target interval, according to the invention vibration-changing measures are carried out at the blade root 32 and/or on the underside 42 of the platform 36 as a fourth production step. These measures may be the introduction of one or more recesses 50 and/or the reduction of the previous dimensions, such as length, width or height, of certain features arranged there. For example, the length L of the blade root 32 may be shortened by several hundredths of a millimeter to a size that lies below the otherwise intended target value for the length L. The reduction of the mass of the base body 30 takes place in the region 49 that has been provided in particular for this. Consequently, the weight, and possibly the pressure-exerting surface, of the turbine rotor blade changes under centrifugal force, which has favorable effects on the vibrational property of the turbine rotor blade.

(10) In case of doubt, the second, third and fourth steps 14, 16, 18 are performed repeatedly as a series, to test the suitability of the base body 30. Only when the turbine rotor blades investigated satisfy the requirements with regard to the vibrational property are they passed on to the further production process.

(11) The base body 30 or the turbine rotor blade may also be a body or blade that is or is to be provided with a protective layer. The protective layer is in this case advantageously a corrosion protection layer of the type MCrAlY. Alternatively, a two-layer or multi-layer protective coating may also be provided, comprising a layer of the MCrAlY type as a bonding coat, on the outside of which a ceramic thermal barrier coat (TBC) has also been applied. By applying the protective layer, in particular a corrosion protection layer, the mass of the base body is further increased. The changing of the resonant frequency accompanying the increase in mass can be compensated by introducing recesses 50 at the blade root 32 or on the underside of the platform 34. It is in this case intended that recesses are introduced in sufficient numbers and with sufficient depths to make the turbine rotor blade satisfy the requirements for the resonant frequency. It may in this case be that the resonant frequency cannot be influenced strongly enough to satisfy the requirements in spite of applying the method according to the invention. In this case, the base body is not suitable for commercial use.

(12) The coating of the base body 30 may be performed before the second production step 14 is carried out for the first time or after the fourth production step 18 is carried out for the last time.

(13) By means of the recess 50 arranged on the end face in the blade root 32, a frequency shift of the resonant frequency takes place. The recesses 50 may be of any desired shape.

(14) FIG. 2 shows a second flow diagram for a further exemplary embodiment of a production method. According to the further exemplary embodiment, the production process comprises the previously mentioned steps 12, 14, 16, 18, supplemented by production steps 13 and 19 to be carried out in some cases in between. This has the effect on the one hand of supplementing the production step 13, in which the base body 30 is at least to the greatest extent produced to size. In other words: in this production step, the dimensions of the base body 30 that are affected by casting tolerances are brought to the planned target values, which for their part may similarly be affected by tolerances.

(15) In the production step 19, an until then uncoated base body 30 can be provided with an erosion and/or thermal barrier coating.

(16) Altogether, the invention consequently proposes a method for producing turbine rotor blades, or their base bodies 30, of which the frequency property can be adapted particularly easily to the required boundary conditions. For this purpose, it is provided that recesses 50 are introduced into the blade root 32 and/or a dimension is reduced below the corresponding target value if the base body 30 has insufficient vibrational properties. This provides a method by which the vibrational property of the turbine rotor blade can be set in a particularly easy and variable manner. As a result, the reject rate in the production of turbine rotor blades can be reduced.