Exhaust pipe integrated into a central ventilation pipe

Description

[0001] The present invention relates to a central ventilation tube of a turbomachine.

[0002] A turbomachine, for example a turbojet, may include an exhaust system configured to extract and channel pressurizing air from the bearing housings and eject it to the atmosphere. The exhaust system typically includes a central ventilation tube, in which is positioned an inner tubular structure that forms a constriction within the central ventilation tube.

[0003] Vibrations and temperature differences can cause cracks between the central tube and the inner tubular structure, resulting in damage to the exhaust system. The tube and the inner tubular structure are two independent parts that are in contact. Static and vibrational stresses can lead to cracking of the inner tubular structure in the area of ​​contact with the central ventilation tube, resulting in damage to the exhaust system.

[0004] Documents FR 2995634 A1 and US 2011 / 146224 A1 present prior art systems.

[0005] The present invention therefore provides an air exhaust system with improved integration of the inner tubular structure within the central ventilation tube as well as a method of manufacturing the system. The proposed exhaust system integrates the central ventilation tube and the inner tubular structure into a single part. STATEMENT OF THE INVENTION

[0006] It is therefore an object of the present invention to provide an upstream part (40) of an air evacuation system (20) for a turbomachine (30), comprising: a tube (70) with an upstream end (50) and a downstream end (60), an inner tubular structure (10) located inside (80) said tube (70) and configured to form a narrowing of its section (170), the inner tubular structure (10) being integral with the tube (10) at the downstream end (60) of the tube and freely suspended at the upstream end (50) of the tube.

[0007] Said upstream portion may comprise a free space (90) being formed between the tube (70) and the inner tubular structure (10) such that the tube and the inner tubular structure are connected only at the downstream end, the tube and the inner tubular structure preferably being connected only along a circumference of the downstream end.

[0008] Alternatively, said tube and the inner tubular structure may be separated by an annular slot (100) at the upstream end such that the inner tubular structure is freely suspended at the upstream end, the annular slot preferably having a size of 1.5 mm or more.

[0009] A wall (110) of the tube may include at least one opening (120) configured to allow removal of unmelted powder located between the tube and the interior tubular structure.

[0010] Said tube (70) may have a cylindrical shape, with a longitudinal axis (220) and a first angle (140) between a wall of the inner tubular structure (10) and the longitudinal axis may be 50° or less.

[0011] A wall thickness (150) of the pipe and the inner tubular structure may be between 0.8 mm and 1.2 mm.

[0012] The invention also relates to an air evacuation system comprising said upstream part and an extension tube (160), the extension tube being connected to the downstream end of the tube (70) so as to form an extension thereof and to form a downstream part of the air evacuation system, the extension tube being connected to the tube (70) preferably by a weld (180).

[0013] In said air evacuation system the extension pipe may comprise a material different from the material of the upstream part.

[0014] The present invention also relates to a turbomachine with a device (200) for evacuating air from the bearing enclosures, the air being conducted to the outside of the turbomachine by an air evacuation system as presented above.

[0015] The invention also relates to a method of manufacturing an upstream part of an air evacuation system as presented previously, by laser fusion on a powder bed.

[0016] During said manufacturing process, laser melting may take place from the upstream end to the downstream end.

[0017] The invention also relates to a method of manufacturing the air evacuation system presented above, the method comprising the steps presented above and a step of assembling the extension pipe to the upstream part by a welding method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be better understood on the basis of the following description and the attached drawings in which: there figure 1 shows a turbomachine comprising a device (200) for evacuating air from the bearing enclosures, the figure 2 shows a central ventilation tube located inside the ejection cone, the Figures 3a, 3b and 3c show a section of the upstream part of the central ventilation tube, the Figures 4a and 4b show a section of the upstream portion of the central ventilation tube with a manufacturing support. DETAILED PRESENTATION OF SPECIFIC IMPLEMENTATION METHODS

[0019] There figure 1 shows a turbomachine comprising a device (200) for evacuating air from the bearing enclosures.

[0020] A turbomachine, for example a turbofan, comprises an air inlet comprising a fan whose outlet air flow is divided into an air flow which enters the engine and forms a hot flow or primary flow, and an air flow which flows around the engine and forms a cold flow or secondary flow.

[0021] The engine typically comprises, from upstream to downstream, in the direction of gas flow, at least one compressor, a combustion chamber, at least one turbine, and an ejection device in which the combustion gases leaving the turbine and forming the primary flow are mixed with the secondary flow.

[0022] At its downstream end, the turbomachine comprises an ejection cone (190) for the primary flow, or even for the primary flow-secondary flow mixture. This cone has an elongated shape, the upstream end of which has a larger diameter and is fixed to an element of the turbomachine, such as a casing.

[0023] A central ventilation tube (20) passes longitudinally through the ejection cone (190). The function of this central ventilation tube (20) is to extract and channel the air discharged from the oil by the oil separators of the turbomachine and to eject it into the atmosphere through the downstream end of the tube (20), located substantially at the downstream end of the ejection cone (190). Thus, air from the bearing enclosures of the turbomachine is conducted to the outside through the central ventilation tube (20).

[0024] The central ventilation tube contains an inner tubular structure (10), which has a constriction (170), or in other words a reduced diameter section (170), in order to cause a Venturi effect for the air circulating in the inner tubular structure. A nozzle (300) brings purge air to this constriction (170), which creates a low pressure suction by the Venturi effect, pulling the purge air from the nozzle and then ejecting it to the outside. In this figure, as in figure 2 , the direction of the air flow, from upstream to downstream in the turbomachine in operation, is indicated by an arrow 230.

[0025] There figure 2 shows the central ventilation tube (20) located inside the ejection cone (190). This tube comprises an upstream part (40) followed, downstream, by an extension tube (160), the inlet of which is indicated by the arrow 280. The upstream part (40) itself comprises an upstream end (50) and a downstream end (60).

[0026] The upstream portion comprises a tube (70), preferably cylindrical in shape, having a longitudinal axis (220). The inner tubular structure (10) is located inside this tube (70) and forms the narrowing (170) there.

[0027] The extension tube (160) is connected to the downstream end (60) of the upstream portion (40) so as to form an extension of the tube (70). The extension tube may be connected to the upstream portion (40) by a weld (180). In this case, the extension tube may comprise a material different from the material of the upstream portion. For example, the latter may comprise a material particularly well suited for manufacturing by laser powder bed fusion or another additive manufacturing process. The extension tube may comprise a material suitable for manufacturing by other methods.

[0028] It is also possible to manufacture the upstream part and the extension tube in one piece, for example by a laser powder bed fusion process or another additive manufacturing process.

[0029] There Figure 3a shows a section, in a plane which contains the longitudinal axis (220) of the tube (70), of the upstream part (40) of the central ventilation tube (20) of the figure 2 . In this figure, we also see the end (280) of the extension tube as well as the upstream part (40), comprising the tube (70) between the upstream end (50) and the downstream end (60). The tube can have a diameter of 78 mm. The inner tubular structure (10) forms the narrowing (170) inside (80) of the tube. In other words, air entering through the upstream end (50) to exit through the downstream end must pass through a passage whose section, relative to the diameter of the tube, first contracts to expand further. Advantageously, as illustrated in Figure 3a , the narrowing (170) is asymmetrical with respect to the longitudinal axis (220) of the tube, more precisely the narrowing is eccentric with respect to the longitudinal axis (220). In other words, the air entering through the upstream end (50) is deflected from the longitudinal axis (220) by the asymmetrical narrowing. The asymmetrical shape has the advantage of avoiding oil retention upstream of the narrowing area, which ensures a permanent flow of oil towards the outside.

[0030] There Figure 3cshows an enlargement of the downstream end (60) of the inner tubular structure and the tube. The inner tubular structure is integral with the tube at the downstream end (60). Generally speaking, by a first part "integrated" with a second part, it is understood that the first part and the second part are made integrally and in a single piece. In other words, the inner tubular structure and the tube are made integrally, or else, at the downstream end, there is continuity of material between a wall of the tube and a wall of the inner tubular structure. Preferably, the inner tubular structure is integral with the tube over an entire circumference at the downstream end. In this way, the inner tubular structure and the tube are connected in a reliable and durable manner and the service life of the central ventilation tube is ensured.

[0031] There Figure 3bshows an enlargement of the upstream end (40) of the central ventilation tube. The inner tubular structure is freely suspended at this end. In other words, at the upstream end, the inner tubular structure is not bonded to the tube. The tube and the inner tubular structure are only bonded at the downstream end so as to leave a free space (90) between a wall (110) of the tube and the inner tubular structure. The tube and the inner tubular structure can be bonded only along the circumference of the downstream end. At the upstream end there is a gap of a size d between the inner tubular structure and the tube, as shown in Figures 3a and 3b. This space may form an annular slot (100) at the upstream end so that the inner tubular structure is freely suspended therein. The annular slot may have a size of 1.5 mm or more. The free space (90) is in communication with the outside through the space left between the inner tubular structure and the tube or through the annular slot (100). The upstream portion (40) is, in this way, particularly well suited to single-piece manufacturing by a laser powder bed fusion process. Following this formation of the upstream portion, the free space (90) is filled with powder that has not been fused to form the walls (110) and other parts of this upstream portion (40). This powder may be discharged to the outside through the space of size d, or the annular slot (100), as illustrated in Figures 3a and 3b. The tube and the inner tubular structure which are integral at the downstream end and free at the upstream end are thus particularly well suited to single-piece manufacturing, by laser fusion on a powder bed. Advantageously, the wall (110) of the tube may comprise one or more lateral opening(s) (120) configured to allow the removal of unmelted or unfused powder.

[0032] The thickness (150) of the wall (110) of the tube and the inner tubular structure may be 0.8 mm or 1 mm or 1.2 mm. It is also possible to have a thickness that varies between 0.8 mm and 1 mm or between 1 mm and 1.2 mm or between 0.8 mm and 1.2 mm. It is thus possible to choose one or more thicknesses for the upstream part of the central ventilation tube. A thickness between 0.8 mm and 1.2 mm is particularly well suited for manufacturing by laser powder bed fusion. The length (130) of the upstream part (40) of the central ventilation tube may be 600 mm or less, which is compatible with easy manufacturing on a large number of laser powder bed fusion installations.

[0033] THE Figures 4a and 4b show a section along the same plane as the Figure 3a. These figures also show a powder (250), located between the tube and the inner tubular structure, as well as a manufacturing support (260), which is not part of the central ventilation tube. Reference 140 designates a first angle (140) of orientation of the wall of the inner tubular structure relative to the longitudinal axis (220). Reference 240 designates an angle of orientation of the wall of the inner tubular structure relative to an axis perpendicular to the longitudinal axis (220).

[0034] The manufacturing support (260) may be flat and support the manufacture of a flange (90) at the upstream end of the tube. During the formation of the flange, by powder fusion, the support provides support to the material forming the flange, until it stiffens. Generally, the support (260) facilitates the start of the construction of the part. The support (260) may be in material continuity with the part. In this case, the first grains of powder which form the flange are fused with the material of the support (260). In this case, the support must be separated from the part at the end, for example by machining.

[0035] Preferably, the first angle (140) between the wall and the longitudinal axis is 50° or less. In other words, since the sum of the first angle and the second angle is 90°, the second angle between the wall and a vertical axis is 40° or more. A first wall angle or a second wall angle within this range of values ​​is particularly well suited for laser powder bed fusion manufacturing. Said range of values ​​is advantageous because a wall having a first angle of 50° or less with the longitudinal axis can be manufactured without an addition of material (270) between the part and the support (260), as shown in the Figure 4b .

[0036] The material addition (270) becomes necessary for a first angle of more than 50°. It is formed on the air inlet side and stabilizes the part or wall during powder melting. The material addition is then machined to form the wall. This block of material forming the material addition (270) can be manufactured in material addition manufacturing, such as by powder melting. The material addition can have parameters different from those of the part, such as for example a lower density. The lower density of the material addition compared to the part facilitates machining, for example to form the wall.

[0037] Thus the entire part can be manufactured in one piece, including the additions of material. In summary, a distinction must be made between the manufacturing support (260) allowing the entire part to be supported from the start of manufacturing and the addition(s) of material (270) which may be necessary for the manufacture of certain parts of the part because the manufacturing angle is too small.

[0038] The manufacturing method comprises manufacturing the upstream part (40) in a single piece by laser powder bed fusion. Advantageously, this additive manufacturing by laser fusion begins with the formation of the upstream end and ends with the manufacturing of the downstream end. The flange (90) can thus be easily manufactured at the start of the process, by resting on the support (260). Alternatively, the manufacturing can take place from the downstream end (60) towards the upstream end (50).

[0039] At the end of the laser melting process, powder (250) remains in the free space (90) and must be removed. This is powder not used for forming the walls. This powder can be removed (210) through the space provided between the tube and the inner tubular structure, located at the upstream end. The unmelted powder can be removed through the annular gap (100). Advantageously, powder can also exit through the opening(s) (120) in the wall (110) of the tube.

[0040] The tube and the inner tubular structure are thus manufactured in one piece by an additive process, preferably laser powder bed fusion as described above.

[0041] The upstream part by laser powder bed fusion can be made of "Inconel 718" (registered trademark). In a particular form, Iconel 718 can comprise, in mass percentage, 50-55% Ni, 17-21% Cr, 15-21% Fe, 4.75-5.5% Nb, 2.8-3.3% Mo, 0.65-1.15% Ti and 0.2-0.8% Al. This material is particularly well suited for manufacturing by laser powder bed fusion.

[0042] The extension tube may also be made of Inconel 718. Alternatively, the extension tube may be made of "Inconel 625" (registered trademark). In a particular form, Inconel 625 may comprise, in mass percentage, Ni 58% or more, Cr 20-23%, Fe 5% or less, Mo 8-10%, Nb 3.15-4.15, Co 1% or less, Mn 0.5% or less, Al 0.4% or less, Ti 0.4% or less, Si 0.5% or less, C 0.1% or less, S 0.015% or less and P 0.015% or less.

Claims

1. Upstream part (40) of an air-discharge system (20) for a turbomachine (30), comprising: - a tube (70) with an upstream end (50) and a downstream end (60), - an internal tubular structure (10) located in the interior (80) of said tube (70) and configured to form therein a narrowing of its cross section (170), characterized in that the internal tubular structure (10) is made in one piece with the tube (70) at the downstream end (60) of the tube and freely suspended at the upstream end (50) of the tube.

2. Upstream part according to claim 1, wherein: a free space (90) is formed between the tube (70) and the internal tubular structure (10) so that the tube and the internal tubular structure are connected solely at the downstream end. the tube and the internal tubular structure preferably being connected solely along a circumference of the downstream end.

3. Upstream part according to claim 1 or 2, wherein: the tube and the internal tubular structure are separated by an annular slot (100) at the upstream end so that the internal tubular structure is freely suspended at the upstream end, the annular slot preferably having a size of 1.5 mm or more.

4. Upstream part according to one of claims 1 to 3, wherein: a wall (110) of the tube comprises at least one opening (120) configured to make it possible to remove any non-molten powder located between the tube and the internal tubular structure.

5. Upstream part according to one of claims 1 to 4, wherein: - the tube (70) has a cylindrical shape, with a longitudinal axis (220) and - a first angle (140) between a wall of the internal tubular structure (10) and the longitudinal axis is 50° or less.

6. Upstream part according to one of claims 1 to 5, wherein: a thickness (150) of the wall (110) of the tube and of the internal tubular structure is between 0.8 mm and 1.2 mm.

7. Air-discharge system, comprising - and upstream part according to one of claims 1 to 6 and - an extension tube (160), the extension tube being connected to the downstream end of the tube (70) so as to form an extension thereof and to form a downstream part of the air-discharge system, the extension tube being connected to the tube (70) preferably by a weld (180).

8. Air-discharge system according to claim 7, wherein: the extension tube comprises a material different from the material of the upstream part.

9. Turbomachine with a device (200) for discharging air from the bearing chambers, the air being conducted towards the outside of the turbomachine by an air-discharge system according to one of claims 7 or 8.

10. Method for manufacturing an upstream part of an air-discharge system according to one of claims 1 to 6, by powder bed laser fusion.

11. Manufacturing method according to claim 10, the laser fusion taking place from the upstream end towards the downstream end.

12. Method for manufacturing an air-discharge system according to claim 7 or 8, the method comprising the steps according to one of claims 10 or 11 and a step of assembling the extension tube at the upstream part by a welding method.