Method and device for manufacturing turbine blades

Abstract

A method and device for manufacturing turbine blades (5; 7; 28; 33) made of a metal alloy. Starting with aluminum and titanium alloy bar (10; 34) having a simple and/or axisymmetric shape, at least two mutually interlocking blanks (2; 3; 4; 8; 11) are produced in the bar (10; 34) by waterjet cutting (16) and then each one of the blanks (2; 3; 4; 8; 11) thus obtained is machined separately in order to obtain the blades (5; 7; 28; 33) having a final profile.

Claims

1. A method of manufacturing turbine blades (5; 7; 28; 33) in a metal alloy from a solid bar elongate about an axis and made of titanium aluminide comprising: making at least two blanks (2; 3; 4; 8; 11) imbricated in one another in said bar (10; 34) by water jet (16) cutting; separately machining each of said blanks (2; 3; 4; 8; 11) thus obtained to arrive at a blade (5; 7; 28; 33) with a definitive profile from each of said blanks.

2. The method as claimed in claim 1, characterized in that the imbricated blanks (2; 3; 4; 8; 11) are identical, produced facing one another, so that they are symmetric in pairs, respectively, with respect to a point (9), a straight line or a central plane (9).

3. The method as claimed in claim 1, characterized in that the titanium aluminide alloy is gamma TiAl.

4. The method as claimed in claim 1, characterized in that the blanks (2; 3; 4; 8; 11) are made from a cast bar (10; 34).

5. The method as claimed in claim 1, characterized in that the blanks (2; 3; 4; 8; 11) are made from an extruded bar (10; 34).

6. The method as claimed in claim 1, characterized in that the blanks (2; 3; 4; 8; 11) are made from a cylindrical bar (10; 34) and/or a bar having one or more external face(s) comprising only straight or convex surfaces.

Description

(1) The description refers to the accompanying drawings in which:

(2) FIG. 1 illustrates a side view of a parallelepipedal bar or billet from which three imbricated blanks for the production of turbine blades are made according to a first embodiment of the invention.

(3) FIG. 2 is a side view and a transverse view of another embodiment of a cylindrical bar in which two imbricated blanks/blades are made according to the invention.

(4) FIG. 3 is a view in cross section of two imbricated blade blanks according to another embodiment of the invention.

(5) FIG. 4 is a schematic diagram of a device for manufacturing a turbine blade according to one embodiment of the invention.

(6) FIG. 5 is a perspective view of a blade obtained using the method according to the invention more particularly described here.

(7) FIG. 6 is a perspective view of two imbricated vane blanks produced according to the method according to the invention.

(8) FIG. 7 schematically illustrates the steps of a method according to one embodiment of the invention.

(9) FIG. 1 schematically shows a side view of a solid parallelepipedal bar or billet 1 made of titanium aluminide from which are made three blanks 2, 3, 4 which are imbricated (in one another), and identical or substantially identical (taking optimizing of the imbricating into consideration) in order to produce turbine blades 5 according to one embodiment of the invention.

(10) The billet 1 is, for example, a 6 kg billet for producing three substantially 2 kg blanks from which three 1 kg blades will be extracted. The blades each have a core 5 and two ends 5 and 5 which are configured in a way known per se by machining.

(11) FIG. 2 is one embodiment of another bar 6 of simple geometry, elongate about an axis, in this instance cylindrical and capable of allowing the manufacture of two blades 7 from blanks 8 which are symmetric about a point of symmetry 9 belonging to the central plane 9.

(12) The blanks 2, 3 or 4 or 8 imbricated in one another are obtained by cutting from the same bar using a water jet as will be described hereinafter.

(13) FIG. 3 shows a view in cross section of a parallelepipedal bar 10 from which two identical blanks 11 imbricated, in this instance symmetrically with respect to an axis 12 obtained by the intersection of two planes 13 and 14 of symmetry of the parallelepipedal bar 10 are cut by a cutting gun.

(14) FIG. 4 more specifically shows one embodiment of a device 15 implementing the method for cutting the blank 10.

(15) This method uses a water jet 16 cutting gun 15 of the type known per se.

(16) The water, at a very high pressure (for example 3800 bar) is introduced at 17 into a collimating tube 18 and is then focused via a nozzle 19 in a mixing chamber 20 where it is mixed with an abrasive 21 introduced at 22 into the chamber situated in the body of the head 23 of the gun 15.

(17) The focusing gun 15 comprises an injector 24 which will attack the bar 10 at 25 in order to make the cut 26 along the cutting path desired by the designer of the blades and which has notably been optimized in terms of material consumption.

(18) A tightening nut 27 allows the injector of the focusing gun to be fixed to the head body 23.

(19) From the two blanks 11 obtained from the bar 10, and according to the embodiment of the method more particularly described here, each of said blanks 11 thus obtained is then machined separately to arrive at the blades 28 as depicted in FIG. 5.

(20) Such a cutting method was not used in the prior art because the person skilled in the art did not envision the benefit of imbricating blanks in one another but was seeking rather from the outset, given the complexity of the components to be obtained, to manufacture these one by one from a single bar of more complex shape.

(21) The intelligence therefore lay in the design of the casting mold.

(22) The device 15 moreover comprises a programmable controller 30 for controlling the gun 15, comprising a computer 31 programmed to produce simultaneously the two blanks 11 imbricated in one another in a way known per se. Once the blanks 11 have thus been obtained, machining means 32 which work by removing chips, or other known means such as electrochemical machining means comprising, for example, four-axis milling centers, precision electrochemical machining (PECM) machines, grinding centers, etc. are provided in order to obtain the blades 28 as described hereinabove.

(23) FIG. 6 depicts another embodiment of identical blades 33 obtained from a parallelepipedal bar 34 in chain line in the figure, cut along the curve 35 to obtain the blanks and programmed accordingly.

(24) One embodiment of the manufacture of a blade will now be described with reference to FIG. 7.

(25) Having chosen a solid bar, the method comprises a first step E1 in which the geometric parameters of the bar are input into the computer 31.

(26) The computer 31 creates a model of the bar on the basis of this information.

(27) In a second step E2, blade geometry parameters are input into the computer 31 which likewise creates models of blades for a determined use, for example for a vane positioned in the flow path along which a turbomachine air flow passes under determined aerodynamic conditions.

(28) The computer 31, which comprises programmed computation means, compares the bar and blade models in order therefrom to determine the optimum layout, i.e. the layout most economical in terms of material while at the same time complying with physical constraints.

(29) For example, a model is formed by a list of quadruplets. Each of the first three data elements represents one of the three coordinates of a Cartesian space, and the final one corresponds to whether or not this belongs to the component/bar modeled.

(30) The program contains an algorithm A1 which:

(31) determines a frame of reference in space,

(32) positions the model of the bar in this frame of reference,

(33) positions a number (for example three) of points of the determined blade model, and

(34) determines whether or not, as a function of the points of the blade model that are positioned in said frame of reference, the entirety of the model is contained within the bar and whether any point is superposed with another blade already positioned. This step is performed for example by comparing each model quadruplet by quadruplet.

(35) If a blade and the bar are compared and there is at least one blade quadruplet that has no equal in the bar model (scenario 1) then at least one point of the blade lies outside the bar,

(36) If two blades are compared and there is at least one quadruplet of each model that is the same as each other (scenario 2) then at least one point on each blade overlaps with each other.

(37) repeats the preceding step as long as scenario 1 or scenario 2 arises.

(38) If the algorithm finds no solution for combining the blades in a bar then the method returns via C1 to an earlier step E1 (or, in another embodiment, E2).

(39) This looping-back makes it possible to ensure that the imbrication is optimized, which imbrication is not a simple juxtaposition and therefore allows savings to be made on material and, in certain instances, reveals the benefit of reengineering the blades.

(40) The computer 31 may comprise display means (not depicted) that allow the various blades in the same bar to be viewed and possibly repositioned by an operator 31.

(41) Other parameters may also be included in the algorithm in order to optimize the positioning of the blades, for example the characteristics of the cutting water jet (width, depth, etc.) and data relating to the quality of the material at a given point.

(42) Finally, in a third step E3, the computer determines the cutting profile, for example a midline curve between the model of blades in the bar and steers the water jet accordingly in order to perform the cutting.

(43) As goes without saying and as is incidentally evident from the foregoing, the invention is not restricted to the embodiments more particularly described but on the contrary encompasses all variants thereof and notably those in which more than three blanks are obtained by simultaneous cutting, in which the profile of a bar is not straight but curved, or those in which the perimeters of the generatrix cross sections comprise a small and limited number (less than 25) of points joined together by straight lines or curves.