EP-3274559-B1 - CERAMIC CORE FOR MULTI-CAVITIES TURBINE BLADE

Inventors

• PAQUIN, SYLVAIN
• Dujol, Charlotte, Marie
• ENEAU, PATRICE
• JOUBERT, Hugues, Denis
• ROLLINGER, Adrien, Bernard, Vincent

Dates

Publication Date

20260513

Application Date

20160322

Claims (6)

1. A ceramic core used for fabricating a hollow turbine blade for a turbine engine by using the lost-wax casting technique, the blade including leading edge and trailing edge cavities (28, 30, 32), at least one central cavity (20, 22), a first lateral cavity (24) arranged between said at least one central cavity and a suction side wall of the blade, and a second lateral cavity (26) arranged between said at least one central cavity and a pressure side wall of the blade, the core being shaped to constitute said cavities as a single element and, in order to feed the insides of said cavities jointly with cooling air, it includes core portions (60, 62) that are to form said first and second lateral cavities and that are connected to a core portion (44, 48) that is to form said at least one central cavity, firstly in the core root (46, 54) via at least two ceramic junctions (70), and secondly at various heights up said core via a plurality of other ceramic junctions (64, 66, 68) of positioning that defines the thickness of the internal partitions of the blade, while also ensuring additional cooling air for predetermined critical zones of said first and second lateral cavities, the ceramic core further including a core portion (59) for forming a bathtub (18) and connected to said core portion intended to form said leading edge and trailing edge cavities and at least one central cavity via ceramic junctions (57) of positioning that defines the thickness of said bathtub, while ensuring that cooling air is discharged at the blade tip.
2. A ceramic core according to claim 1, characterized in that said predetermined critical zones are selected from the zones of said first and second lateral cavities that are subjected to the greatest thermomechanical stresses.
3. A ceramic core according to claim 1, characterized in that said ceramic junctions are of section determined so as to ensure the mechanical strength of said internal partitions while casting the molten metal.
4. The use of a ceramic core according to any one of claims 1 to 3 for fabricating a hollow turbine blade for a turbine engine using the lost-wax casting technique.
5. A fabrication method for fabricating a hollow turbine blade for a turbine engine by using the lost-wax casting technique, the blade including leading edge and trailing edge cavities (28, 30, 32), at least one central cavity (20, 22), a first lateral cavity (24) arranged between said at least one central cavity and a suction side wall of the blade, and a second lateral cavity (26) arranged between said at least one central cavity and a pressure side wall of the blade, the method comprising a step of fabricating a single-element ceramic core corresponding to said leading edge and trailing edge cavities, to said at least one central cavity and to said first and second lateral cavities, core portions (60, 62) that are to form said first and second lateral cavities being connected to a core portion (42, 44, 48, 50, 52) that is to form said including leading edge and trailing edge cavities and said at least one central cavity, firstly in a core root (46, 54) via at least two ceramic junctions (70) so as to feed the insides of said cavities jointly with cooling air, and secondly, at various heights up said core via a plurality of other ceramic junctions (64, 66, 68) of positioning that defines the thickness of the internal partitions of the blade, while ensuring additional cooling air for predetermined critical zones of said first and second lateral cavities, the ceramic core a single-element further including a core portion (59) for forming a bathtub (18) and connected to said core portion intended to form said leading edge and trailing edge cavities and at least one central cavity via ceramic junctions (57) of positioning that defines the thickness of said bathtub, while ensuring that cooling air is discharged at the blade tip, the ceramic core as formed in this way being put into place in a casting mold and molten metal being cast in said mold.
6. A turbine engine including a hollow turbine blade fabricated using the fabrication method of claim 5.

Description

Scope of the invention The present invention relates to the general field of turbomachine turbine blades, and more particularly to turbine blades equipped with integrated cooling circuits produced by the lost-wax casting technique. Previous art As is well known, a turbomachine consists of a combustion chamber in which air and fuel are mixed before being burned. The gases produced by this combustion flow downstream of the combustion chamber and then power a high-pressure turbine and a low-pressure turbine. Each turbine has one or more rows of fixed blades (called distributors) alternating with one or more rows of moving blades (called runners), spaced circumferentially around the turbine rotor. These turbine blades are subjected to the very high temperatures of the combustion gases, which reach values far exceeding those that the blades, in direct contact with these gases, can withstand without damage, thus limiting their service life. To solve this problem, it is known to equip these blades with internal cooling circuits having high levels of thermal efficiency and aimed at reducing their temperature by creating, inside the blade, an organized circulation of this air (simple cavities with direct supply or paper clips for example) and, in the wall of the blade, perforations intended to generate a protective film for this blade. This technology, however, has several drawbacks. First, while paperclip cavity circuits maximize airflow through the circuit, they generate significant heating of the air, resulting in a decrease in the thermal efficiency of the holes at the ends of the paperclip. Similarly, configurations with leading-edge and trailing-edge cavities and direct feed do not provide an effective solution. to the high temperature levels typically observed at the blade tip. Furthermore, the various cavities are separated from the duct only by a wall of varying thickness depending on the blade area. Given the constraints on the flow rate allocated to blade cooling and the current trend of increasing duct air temperatures, it is not possible to efficiently cool the blade with this type of circuit without significantly increasing the air flow rate and negatively impacting engine performance. There figure 5 This illustrates a high-pressure turbine blade 10 of a gas turbine engine, comprising an aerodynamic surface or blade 12 extending radially between a root 14 and a blade tip 16. The blade root is shaped to allow the blade to be mounted on a rotor disk. The blade tip has a tub-shaped portion 18 consisting of a bottom transverse to the blade and a wall forming its edge in line with the wall of the blade 12. As shown in the cross-sectional view of the figure 6 In the example shown, the blade 12 comprises, for illustrative purposes only, a plurality of cavities 20, 22, 24, 26, 28, 30, 32. The first and second central cavities 20, 22 extend from the root to the tip of the blade, and two other cavities 24, 26 are arranged on either side of these central cavities, along the upper surface (extrados) between these central cavities and the upper surface (extrados) of the blade, and along the lower surface (intrados) between these central cavities and the lower surface (intrados) of the blade. Finally, a cavity 28 is located in the portion of the blade near the leading edge, and two cavities 30, 32 are arranged in a line in the portion of the blade near the trailing edge. The shape and number of cavities, as well as the position of the external holes 34, 36 and the geometry of the trailing edge slots 38, are given for illustrative purposes only; all these elements are generally optimized to maximize thermal efficiency in the areas most sensitive to the heat of the combustion gases in which these blades are immersed. The internal cavities are also often equipped with disruptors (not shown) to increase heat exchange. As described in the application FR2961552 On behalf of the plaintiff, high-pressure turbine blades are conventionally manufactured using the lost-wax casting method, with the geometry of the circuits being created, depending on its complexity, by positioning one or more elements in the mold. several ceramic cores whose outer surface forms the inner surface of the finished blade. In particular, cooling circuits with multiple cavities, such as those of figures 5 and 6 These processes require the assembly of several separate ceramic cores (designed to create the central cold cavities isolated from hot gases and the thin external cavities with separate air supplies) to ensure the necessary metal wall thicknesses before casting. This complex operation, manually assembled by joining the base and top of the ceramic cores, prevents the casting of the blade head's tub, necessitating a costly additional finishing operation that can compromise the blade's mechanical strength in this area (for example, adding the tub or sealing it by brazing). Object and summary of the invention The present invention therefore aims