RU2800747C2 - Blade of aircraft gas turbine engine and method of its manufacture by means of casting using smelted wax models - Google Patents

Abstract

FIELD: aircraft.

SUBSTANCE: blade (102) of an aircraft gas turbine engine, wherein the blade comprises at least one internal cavity (100) for circulation of the ventilation air flow, whereas the cavity has a wall (104) that comprises the first protruding elements (106) oriented in the first direction and forming elements of perturbation of the air flow, and this wall additionally comprises at least one second protruding element (108), oriented at least in a second direction different from the first direction, and this second element and at least one of the first elements overlap each other in one zone, characterized in that the first element or each first element that overlaps the second element has a height (H2, H4') greater than the height (H1) of the second element in said zone and which exceeds the height (H3) of the other first wall elements, to maintain its function as an element of perturbation throughout its length.

EFFECT: efficiency of blade cooling.

9 cl, 8 dwg

Description

The field of technology to which the invention belongs

The present invention relates to an aircraft gas turbine engine blade and to a method for manufacturing the same by means of lost wax casting.

State of the art

The prior art is represented, inter alia, by FR-A1-2 874 186 filed in the applicant's name and EP-A1-3 450 683, US-A1-2016/208620, EP-A2-0 945 595, CN-B -104 493 081 and US-A1-2011/016717.

The blades of a gas turbine engine, and in particular a turbine, are subjected to increased thermal stresses and contain internal cavities for the circulation of a ventilation fluid, typically air in the case of a gas turbine engine.

Typically, these blades are made by lost wax casting. This technique consists in making a model in wax or other equivalent temporary material for the part to be cast. The model is surrounded by a ceramic shell mold. This mold is made by successively dipping the model into a slurry containing ceramic material, and by smearing the resulting layer between each immersion. The mold is dried, the wax contained in it is removed by a first heat treatment at an appropriate temperature, then the mold is heated to a high temperature to give it the strength needed for casting. In this case, the model is displayed in the form of a cavity into which molten metal is poured. After cooling, the mold is destroyed to extract the part. After that, the latter is subjected to simple finishing.

If the blade contains cavities for circulation of the cooling air flow, one or more cores must be included in the model. This phase of the method comprises first separately manufacturing the rod or rods by molding a ceramic material reinforced with a binder, if necessary joining them and placing the rod or rods in a wax mold. Thus, the model is molded by injecting wax into a wax mould. The model forms a replica of the manufactured part.

In FIG. 1, in a section perpendicular to the axis of the part, a wax mold 10 is shown, the inner wall of which is a representation of the part being made. In this case, this form consists of two parts 10A and 10B. A rod 12 was placed in this mold. In this case, the rod 12 consists of a plurality of branches 12A-12G, parallel to each other and connected to a common base. The branches form spaces between them, which subsequently form partitions after pouring the metal. Spacers 14, for example, made of platinum, are provided to secure the rod 12 inside the mold. The function of these spacers is to maintain space between the walls of the stem 12 and the inner wall 16 of the mold, and possibly even between the legs 12A-12G of the stem. When injecting wax, this avoids the unevenness of the layer and the formation of partitions due to accidental displacement of the rod.

As shown in FIG. 2, the aforementioned spacers 14 are placed in the hollow impressions of the shaft wall. These impressions can be obtained at the time of core molding or by mechanical processing. Typically, the spacers 14 are elongated in the form of a pin or needle, and are placed on a rod, laid in the direction of length (running along the longitudinal axis of the blade, which is essentially radial with respect to the longitudinal axis of the gas turbine engine in which it is installed). These hollow impressions are thus arranged in a particular direction.

In addition, the shaft 12 contains other hollow impressions 18 on its wall, which extend in the other direction to provide fluid flow disturbance elements in the blade cavity. As shown in FIG. 2, in some cases the perturbation hollow impressions 18 and spacer pockets 14 coincide or at least overlap.

At the next stage, a ceramic mold is formed around the model obtained after it was removed from the mold 10. After that, the wax is removed from the mold and molten metal is poured into the mold, which fills the space between the walls of the mold and the walls of the rod. After appropriate processing, the elements forming the rod are removed to obtain cavities. This produces a part, and in particular the blade 20 shown in FIG. 3.

The molten metal is designed to fill the spaces between the branches 12A-12G and between the rod and the mold in order to obtain partitions and walls of the cavities 22, as well as to fill the voids of the hollow impressions of the rod in order to obtain protruding elements 24 on these walls of the cavities (see Fig. 3) . As mentioned above, given the overlap of some of the hollow impressions of the rod, some protruding elements overlap each other in the cavities of the blade.

However, in these overlap zones, the perturbation elements lose their function and do not create turbulences in the ventilation air flow, which seriously affects the cooling efficiency of the blade, significantly reducing the heat transfer coefficient between the blade and this flow.

The object of the invention is to solve this problem in such a way that the function of the disturbance elements in the blade cavity is not impaired by the presence and overlap of other protruding elements of this cavity.

Disclosure of invention

The object of the invention is an aircraft gas turbine engine blade, wherein the blade comprises at least one internal ventilation air flow circulation cavity, the cavity having a wall that contains first protruding elements oriented at least in the first direction and forming air flow disturbance elements, moreover this wall further comprises at least one second protruding element oriented in at least a second direction different from the first direction, this second element and at least one of the first elements overlapping each other in one zone, characterized in that the first element or each first element that overlaps the second element has a height greater than the height of the second element in said zone and which is greater than the height of the other first wall elements in order to maintain its function as a perturbation element throughout its length.

In the present application, the height of the protruding element should be understood as the size of this element, measured along the direction normal to the surface on which it protrudes.

Thus, it is understood that although the first and second elements may overlap, the first elements are always taller than the second element and therefore always protrude into the cavity while retaining their function as a flow disturbing element.

The claimed blade may have one or more of the following features, considered separately from each other or in combination with each other:

- the directions of the first and second elements are essentially perpendicular to one another or one relative to the other;

- the directions of the first and second elements are inclined relative to each other;

- the first element or each first element and/or said second element has a common elongated shape;

- only one of the first elements overlaps the said second element and forms a cross with it;

- two of the first elements overlap said second element and form branches on two opposite sides of this second element;

- the first element or each first element that overlaps said second element has a height that varies and is maximum in said zone.

The subject of the present invention is also a ceramic rod for manufacturing the above-described blade by means of a manufacturing method by lost wax casting, this rod having a part configured to mold said cavity and containing, on the one hand, first hollow impressions oriented along at least in the first direction and configured to mold said protruding elements, and, on the other hand, at least one second hollow impression oriented in at least a second direction different from the first direction and forming a spacer socket, this second the print and at least one of the first prints overlap each other in one zone, characterized in that the first print or each first print that overlaps the second print has a depth greater than the depth of the second print in said zone.

In the present application, the depth of a hollow impression should be understood as the size of this impression, measured along the direction normal to the surface of the bottom of this impression.

The subject of the invention is also a method for manufacturing the above-described blade by means of a manufacturing process by lost-wax casting using the above-described ceramic rod.

Brief description of the figures

Other features and advantages of the invention will become more apparent from the following detailed description with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-sectional view of a mold and a ceramic core for manufacturing a blade by lost wax casting.

Fig. 2 is a schematic axial sectional view of a mold and a ceramic core for manufacturing a blade by lost wax casting.

Fig. 3 is a schematic cross-sectional view of a gas turbine engine blade.

Fig. 4 is a partial schematic view of a turbine engine blade cavity illustrating an embodiment of the invention.

Fig. 5 is a schematic view illustrating the embodiment shown in FIG. 4.

Fig. 6 is a partial schematic perspective view of a turbine engine blade cavity illustrating another embodiment of the invention.

Fig. 7 is a schematic view illustrating the embodiment shown in FIG. 6.

Fig. 8 is a partial schematic perspective view of hollow impressions of the cavity rod of the embodiment shown in FIG. 6.

Detailed description of the invention

Fig. 1-3 are described above and illustrate the prior art. They also illustrate the invention insofar as the description of these figures is applicable to the invention.

In FIG. 4 and 5 show a first embodiment of the invention. In FIG. 4 shows the cavity 100 of the blade 102, which is only partially visible and can be considered similar to the blade shown in FIG. 3.

Cavity 100 has an overall elongated shape and is formed by a rod, as discussed above and known to those skilled in the art of blade manufacturing by lost wax casting. The cavity 100 includes a wall 104 on which protruding elements 106, 108 are located.

In the present application, the first protruding element, indicated by the position 106, should be understood as an element configured to form an element of perturbation of the air flow. The air flow F that passes in the cavity will have to go around this element, which will create turbulence in the air flow and thus facilitate heat exchanges between this air flow F and the wall 104 (FIG. 5).

The element 106 generally has an elongated shape and may be in the form of a parallelepiped, a cylinder, and so on.

The element 106 extends in a particular direction, and the elements 106 of the same cavity 100 may be parallel to each other.

As a rule, they run in a direction perpendicular or oblique with respect to the direction of the air flow F in the cavity 100, and form obstacles to this flow.

In this application, the second protruding element, indicated by the position 108, should be understood as an element obtained during the manufacture of the blade 102 and having no special function inside the cavity 100.

This second element 108 is oriented in a second direction different from the first direction and generally parallel to the direction of the air flow F in the cavity.

As seen in the drawings and as mentioned above, elements 106, 108 may overlap each other.

In the embodiment shown in FIG. 4 and 5, only one of the first elements 106 overlaps the second element 108 substantially in its middle, forming a cross. Thus, in the example shown, the directions of the first and second elements 106, 108 are substantially perpendicular.

The second element 108 has a height H1 which is constant. The first element 106 overlapping the second element 108 has a height H2 that is greater than H1. The height H2 of the first element 106 is also constant. In FIG. 4 it can be seen that the height H2 may exceed the height H3 of the other first cavity elements which do not overlap the second element. In addition, the height of H3 may be similar to H1.

In FIG. 6 and 7 show a second embodiment of the invention. In FIG. 6 shows the cavity 100 of the blade 102, which is also partially visible.

The cavity 102 is similar to the cavity of the previous embodiment and includes on its wall 104 a second protrusion 108 which is also similar to the second protrusion described above.

In addition, the wall 104 includes first protrusions 106a, 106b different from the protrusions 106 described above.

Each element 106a, 106b has an overall elongated shape and may be in the form of a parallelepiped, cylinder, etc.

The members 106a, 106b extend in oblique directions with respect to the direction of the member 108. In addition, the members 106a, 106b are inclined relative to each other in such a way that they form a chevron even if they are not adjacent to each other and therefore spaced apart in the illustrated example.

In this case, the elements 106a, 106b are located on both sides of the element 108 and thus form the side branches of the element 108. The element 106a is inclined and reaches the upper end of the element 108, while the element 106b is inclined and reaches the lower end element 108.

The second element 108 has a constant height H1. The heights H4, H4' of the elements 106a, 106b may vary. The maximum height H4' of the elements 106a, 106b is at the level of the ends of these elements which are in the overlap zones, while the height H4 is the height of the opposite ends of these elements.

In this case, the elements 106a, 106b are made in the form of inclined ramps. The height H4 may be equal to the height of other first cavity elements that do not overlap the second element.

The last figure partially shows the ceramic rod 200 for manufacturing the blade 103 and, in particular, the cavity 100 of this blade according to the second embodiment described above.

This rod 200 includes a portion 202 configured to form a cavity 100 and includes, on the one hand, first hollow impressions 206a, 206b, oriented in the first directions and configured to form elements 106a, 106b, and, on the other hand, at least at least one second hollow impression 208 oriented in a second direction different from the first directions and forming a seat for the spacer 14.

This second impression 208 and the first impressions 206a, 206b overlap each other in one zone, and these first impressions 206a, 206b have a depth greater than that of the second impression 208 in said zone. Thus, it is understood that the first impressions 206a, 206b recede more (are deeper) than the second element 208, and that this depth difference is determined in such a way as to obtain a difference in height of the protruding elements 106a, 106b, 108 inside the cavity of the manufactured blade .

During the manufacture of the blade by lost wax casting, the molten metal poured into the mold will occupy the empty spaces left by the wax and the spacers 14. Thus, the molten metal will occupy the space of the hollow impressions 206a, 206b, 208 to form the projections 106a, 106b, 108 shown in FIG. 5 and 6.

Claims (9)

1. A blade (102) of an aircraft gas turbine engine, containing at least one internal cavity (100) for circulating a ventilation air flow, while the cavity has a wall (104) that contains the first protruding elements (106, 106a, 106b) oriented at least at least in the first direction and forming elements of the perturbation of the air flow, and the wall additionally contains at least one second protruding element (108) oriented at least in a second direction different from the first direction, the second element and at least one of the first elements overlap each other in one zone, characterized in that the first element or each first element that overlaps the second element has a height (H2, H4') greater than the height (H1) of the second element in said zone and which exceeds the height (H3) of the others first wall elements in order to maintain its function as a perturbation element throughout its length. 2. Blade (102) according to claim 1, characterized in that the directions of the first and second elements (106, 108) are substantially perpendicular to each other. 3. Blade (102) according to claim 1, characterized in that the directions of the first and second elements (106a, 106b, 108) are inclined relative to each other. 4. Blade (102) according to one of the preceding claims, characterized in that the first element or each first element (106, 106a, 106b) and/or said second element (108) has a common elongated shape. 5. Blade (102) according to one of the previous claims, in which only one of the first elements (106) overlaps said second element (108) and forms a cross with it. 6. Blade (102) according to one of the previous claims, in which two of the first elements (106a, 106b) overlap said second element (108) and form branches on two opposite sides of the second element. 7. Blade (102) according to one of the previous claims, in which the first element or each first element (106a, 106b) that overlaps said second element (108) has a height (H4, H4') that varies and is maximum in the said zone. 8. A ceramic rod (200) for manufacturing a blade (102) according to one of the previous paragraphs using a manufacturing method by lost wax casting, the rod containing a part configured to form said cavity (100) and containing, with one side, the first hollow impressions (206a, 206b) oriented at least in the first direction and configured to form said projecting elements (106a, 106b), and, on the other hand, at least one second hollow impression (208) oriented in at least a second direction different from the first direction and forming a socket for the spacer, wherein the second impression and at least one of the first impressions overlap each other in one zone, characterized in that the first impression or each first impression that overlaps the second the imprint has a depth exceeding the depth of the second imprint in the mentioned zone. 9. A method of manufacturing a blade according to one of paragraphs. 1-7 using lost-wax casting using a ceramic rod according to item 8.

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