COMBUSTION CHAMBER OF A TURBOMACHINE

Abstract

Combustion chamber assembly (10) of an aircraft turbomachine comprising a housing (11) and a tubular mounting device (23) for a spark plug (22) on the housing (11), the tubular mounting device (23) comprising: - a first annular portion (24) in which the spark plug (22) is able to be sealed, - and a second annular portion (25) sealed to the housing (11), the tubular mounting device (23) further comprising a vibration damping means (30) connecting the first annular portion (24) to the second annular portion (25). Figure 3

Description

Title of the invention: COMBUSTION CHAMBER OF A TURBOMACHINE

[0001] This disclosure relates to a combustion chamber of a turbomachine comprising a crankcase, a spark plug and a tubular device for fixing the spark plug to the crankcase. Previous technique

[0002] A turbomachine combustion chamber generally comprises an annular chamber bottom wall connected to two substantially cylindrical of revolution and coaxial shells extending downstream, and a fairing or cowling fixed to the chamber bottom and extending upstream.

[0003] The fairing guides the airflow supplied by the turbomachine compressor and divides it into a central stream that feeds the combustion chamber and into two peripheral streams that bypass the combustion chamber.

[0004] The air from the compressor is brought into the combustion chamber and mixed with fuel, the combustion of the mixture being initiated by at least one spark plug mounted on an external casing and passing through an opening in the external shell.

[0005] To mount the spark plug onto the crankcase, it is known to mount a spark plug retaining device in the opening, in the form of a tubular device, this device receiving and securing the spark plug to the crankcase. This device thus ensures the guidance and securing of the spark plug to the crankcase as well as the sealing of the combustion chamber at the level of this opening.

[0006] However, it has been observed that the operation of the turbomachine can cause damage to the spark plug, for example by cracking. This is due in particular to the vibrations generated by the operation of the turbomachine. These vibrations are transmitted to the spark plug via the outer skin of the housing and are then amplified at the mounting device and its interface with the spark plug.

[0007] The purpose of this disclosure is, in particular, to provide a solution to the problem of damage encountered by the spark plug, and thus to provide a solution for preserving and increasing the lifespan of a spark plug for a combustion chamber. Summary

[0008] To this end, a combustion chamber assembly for an aircraft turbomachine is proposed, comprising a casing and a tubular device for attaching a spark plug to the casing, the tubular attachment device comprising: - a first annular section in which the spark plug is suitable for mounting in a sealed manner, - and a second annular part fixed to the casing with a seal, the tubular fixing device further comprising a vibration damping means connecting the first annular part to the second annular part, the vibration damping means comprising an elastomeric annular piece, the first annular part comprising a first annular face and the second annular part comprising a second annular face, the elastomeric annular piece being arranged between, and in contact with, the first annular face and the second annular face.

[0009] The vibration damping device reduces the transmission of vibrations from the second annular portion, in contact with the crankcase, to the first annular portion, in contact with the spark plug. The spark plug is thus subjected to attenuated vibrations compared to the vibrations present on the outer skin of the crankcase. The spark plug is therefore better protected from vibrational stresses and can thus expect a longer service life.

[0010] In addition, the tubular fixing device can be formed in one piece and include an annular wall having a corrugated shape, along a plane including a longitudinal axis.

[0011] The corrugated shape provides a degree of flexibility to the tubular fastening device. The corrugated shape acts overall like a spring and has the advantage of allowing the tubular fastening device to be formed from a single piece. This eliminates the need for additional parts or damping means, which could lead to sealing problems and thus necessitate, for example, the addition of gaskets, tightening, or precise adjustments between the first and second annular sections.

[0012] The first annular part may further include a first radial annular rim comprising the first annular face, extending radially, the second annular part may further include a second radial annular rim which includes an annular portion radially curved inwards, and presenting the second annular face, oriented radially, the second radial annular face being arranged longitudinally opposite the first radial annular face.

[0013] The vibration damping means may further include a longitudinal gap arranged between the second radial annular rim and the first radial annular rim.

[0014] The elastomeric annular piece may further comprise a longitudinal dimension and a radial dimension defined between an inner diameter and an outer diameter of the elastomeric annular piece, the longitudinal dimension being at least 1.5 times smaller than the radial dimension.

[0015] In addition, the elastomer annular piece can be arranged radially between, and in contact with, the first annular face and the second annular face, the second annular face being arranged radially outside with respect to the first annular face.

[0016] The second annular part may comprise a first portion and a second portion, the first portion having a threaded portion which cooperates with a threaded portion of the second portion, the elastomer annular piece being arranged radially between the first annular part and the second portion, the first annular part being arranged radially inside with respect to the second portion, and the second portion being arranged radially inside with respect to the first portion.

[0017] Alternatively, the elastomeric annular piece may comprise a longitudinal dimension and a radial dimension defined between an inner diameter and an outer diameter of the elastomeric annular piece, the longitudinal dimension being at least three times greater than the radial dimension.

[0018] The housing may further include an opening, and the assembly may further include the spark plug extending along a longitudinal axis and passing through the opening of the housing.

[0019] This disclosure further relates to an aircraft turbomachine, such as for example a turbojet or a turboprop, comprising an assembly as described above. Brief description of the drawings

[0020] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0021] [Fig.1] Fig.1 is a schematic cross-sectional view of a combustion chamber comprising a tubular fixing device and a spark plug according to the known technique; Fig. 2

[0022] [Fig.2] The [Fig.2] is a schematic perspective view of the combustion chamber of the [Fig.1]. Fig. 3

[0023] [Fig.3] The [Fig.3] is a schematic cross-sectional view of an example embodiment according to this disclosure. Fig. 4

[0024] [Fig.4] The [Fig.4] is a schematic cross-sectional view of an example embodiment according to this disclosure. Fig. 5

[0025] [Fig. 5] Fig. 5 is a schematic cross-sectional view of an example embodiment according to this disclosure. Fig. 6

[0026] [Fig.6] Fig.6 is a schematic cross-sectional view of an example embodiment according to this disclosure. Description of the implementation methods

[0027] Figures 1 and 2 illustrate a combustion chamber 10 of a turbomachine. The combustion chamber 10 comprises a casing 11. The casing 11 is external to the combustion chamber 10. The casing 11 includes an opening 12. The combustion chamber 10 also includes an outer ring 13 of revolution. The opening 12 extends to an opening in the outer ring 131 within the outer ring 13, which has a downstream annular flange for mounting on the casing 11. The combustion chamber 10 further includes an inner ring 14 of revolution having a downstream annular flange for mounting on an inner casing, and a chamber bottom 15 on which fairings 16 extending upstream are mounted.

[0028] Fuel injection lances 17, distributed around the axis of the turbomachine, open into the bottom of chamber 15, through injection heads 18. Mixers 19 are arranged around each injection head 18.

[0029] The airflow supplied by the turbomachine compressor is guided by the fairings 16 and divided into a central stream intended to supply the combustion chamber 10 and into two peripheral streams 21 intended to bypass the combustion chamber.

[0030] The mixers 19 form a swirling incoming airflow into a primary combustion zone 20 of the combustion chamber 10. This air is mixed with the fuel sprayed by the injection heads 18, the mixture being ignited by at least one spark plug 22.

[0031] The spark plug 22 is generally cylindrical in shape with a circular cross-section. The spark plug 22 is mounted, by its outer end, in a tubular mounting device 23, fixed to the outer housing 11. The inner end of the spark plug 22 passes through the outer ferrule opening 131, until it is flush with the inner surface of the outer ferrule 13. The outer end of the spark plug includes a bearing face 26. The bearing face 26 may be annular and extend radially with respect to the longitudinal axis L22 of the spark plug 22.

[0032] The tubular mounting device 23 is adapted to fix the spark plug 22 to the housing 11. For this purpose, the tubular mounting device 23 extends along a longitudinal axis L23. The longitudinal axis L22 and the longitudinal axis L23 coincide. The The tubular fixing device 23 comprises a first annular part 24 and a second annular part 25. The first annular part 24 is radially external with respect to the axis of the turbomachine and with respect to the second annular part 25, which is arranged radially internal with respect to the axis of the turbomachine.

[0033] The first annular portion 24 may include a first internal thread. The spark plug 22 is inserted into the tubular mounting device 23. The spark plug 22 may further include a threaded portion 28, cooperating with the first internal thread of the first annular portion 24. The mounting of the spark plug 22 in the tubular mounting device 23 may further be completed by the bearing surface 26 pressing against the first annular portion 24. The spark plug is thus sealed in the tubular mounting device 23, the bearing surface 26 being in seal contact with the first annular portion 24.

[0034] The second annular part 25 is fixed to the housing 11. The fixing of the second annular part 25 to the housing 11 is sealed. For example, the second annular part 25 is fixed to the housing 11 by means of two screws via a flange of the second annular part 25, and the seal is achieved by a sealing washer or ring 27, interposed radially between the second annular part 25 and the housing 11, at the opening 12 of the housing.

[0035] By mounting the spark plug 22 in the tubular mounting device 23 described above, it is understood that the spark plug is in contact only with the first annular portion 24 of the mounting device. The spark plug thus does not have any contact or support with the second annular portion 25.

[0036] A combustion chamber 10 according to the present disclosure is shown in Figures 3 to 6. This differs from the combustion chamber 10 shown above in that the tubular mounting device 23 further includes a vibration damping means 30. The vibration damping means 30 connects the first annular portion 24 to the second annular portion 25. The vibration damping means 30 reduces the transmission of vibrations from the second annular portion 25, which is fixed to the housing 11 and therefore in contact with it, to the first annular portion 24, which is in contact with the spark plug 22. Since the spark plug 22 is in contact with the tubular mounting device 23 only via the first annular portion 24, the spark plug 22 is subjected to the vibrations generated by the combustion chamber only through the first annular portion 24.Since the vibrations are dampened between the second annular section 25 and the first annular section 24, the spark plug 22 is thus subjected to reduced vibrations compared to the vibrations present on the outer skin of the crankcase. The spark plug is therefore better protected from vibrational stresses and can thus expect a longer service life.

[0037] By vibration damping means 30, it must be understood that the vibration damping means 30 can have a vibration damping coefficient, for example, two to ten times greater than the vibration damping coefficient of the first and second annular parts.

[0038] According to an example illustrated in [Fig. 3], the tubular fastening device 23 is formed from a single piece. By "a single piece," it is understood that the fastening device does not comprise several elements assembled together to form said device. The tubular fastening device is therefore formed from a single piece, or, as otherwise described, from a single block of material. Furthermore, the material of the tubular fastening device 23 is identical throughout said device.

[0039] According to this example in [Fig. 3], the vibration-damping means 30 of the tubular fastening device 23 comprises an annular wall 303 having a corrugated shape. The annular wall extends and is connected, on the one hand, to the first annular portion 24, and on the other hand, to the second annular portion 25. The corrugated shape of the annular wall 303 is defined along a plane including the longitudinal axis L23 of the tubular fastening device 23. As can be seen in [Fig. 3], the corrugated shape takes the form of waves, folds, or undulations, the troughs 31 of which are oriented radially inward with respect to the longitudinal axis L23, and the crests 32 of which are oriented radially outward with respect to the longitudinal axis L23. The corrugated shape provides flexibility to the tubular fastening device 23.

[0040] Furthermore, the annular wall 303 may have a variable thickness. More specifically, the annular wall 303 may comprise, between a first end of the annular wall 32, arranged at the level of the first annular portion 24, and a second end of the annular wall 33, arranged at the level of the second annular portion 25, a wall thickness that may vary depending on its position between the first end of the annular wall 32 and the second end of the annular wall 33. For example, the annular wall 303 may have a greater thickness towards the first end of the annular wall 32 than towards the second end of the annular wall 33, or vice versa. According to another example, the annular wall 303 may have a greater thickness in its central portion than at the ends of the annular wall 32, 33.

[0041] According to the embodiments shown in Figures 4, 5, and 6, the vibration damping means 30 comprises an annular elastomer part 301. An elastomer part provides specific elasticity, damping, and stiffness properties that differ from those of a metallic alloy. An elastomer part can thus provide a different (for example, in terms of its dimensions) or complementary damping solution to that provided by the metallic material of the vibration damping means.

[0042] In particular, according to the embodiment shown in [Fig. 4], the first annular portion 24 may include a first radial annular rim 36. The first radial annular rim 36 extends radially with respect to the longitudinal axis L32. The first radial annular rim 36 has a first annular face 34, extending radially with respect to the longitudinal axis L32. The first annular face 34 is oriented towards the first annular portion 24, i.e., the first annular face 34 faces the first annular portion 24. Furthermore, the second annular portion 25 may include a second radial annular rim 37. The second radial annular rim 37 extends radially with respect to the longitudinal axis L32. The second radial annular rim 37 further comprises an annular portion 38, radially curved inwards with respect to the longitudinal axis L23. The annular portion 38 has a second annular face 35.The second annular face 35 is oriented radially along the longitudinal axis L23. Furthermore, the second annular face 35 is arranged opposite the first annular face 34. In particular, this opposite orientation is longitudinal, along the longitudinal axis L23. Moreover, along the axis of the turbomachine, the second annular face 35 is radially external to the first annular face 34. In other words, the second annular rim 37 radially surrounds the first radial annular rim 36, and in particular its first annular face 34. The second annular rim 37 can be described as an annular hook, defining a space in which the elastomer annular piece 301 and the first annular face 34 are arranged.With reference to the axis of the turbomachine, the most radially internal element is the first annular face 35, and the most radially external element is the second annular face 35, the elastomeric annular piece 30 being arranged between, and in contact with, the first annular face 34 and the second annular face 35. In other words, the elastomeric annular piece 301 is interposed between the first annular face 34 and the second annular face 35.

[0043] Furthermore, as shown in [Fig. 4], the elastomer annular piece 301 comprises, along the longitudinal axis L23, a longitudinal dimension E301 and a radial dimension R301. The radial dimension R301 is defined as the difference between the inner diameter DI and the outer diameter D2 of the elastomer annular piece 301. The longitudinal dimension E301 is, for example, at least one and a half times smaller than the radial dimension R301.

[0044] Furthermore, still according to the example in [Fig. 4], the vibration damping means further comprises a longitudinal clearance 302 of the tubular fixing device 23. The longitudinal clearance 302 allows displacement along the longitudinal axis L23 between the first annular portion 24 and the second annular portion 25. The longitudinal clearance 302 is arranged in the space delimited by the second inner rim, between radially inwards, along the axis of the turbomachine, the second annular rim 37 and radially outwards the first radial annular rim 36.

[0045] In the example of [Fig.4], the vibration damping means thus mainly provides damping along the longitudinal axis L23.

[0046] According to the embodiment shown in [Fig. 5], the first annular portion 24 comprises a first annular face 34. In this configuration, unlike the example described above, the first annular face 34 is cylindrical in revolution and extends along the longitudinal axis L23. The second annular portion 25 also comprises a second annular face 35. The second annular face 35 is cylindrical in revolution and extends along the longitudinal axis L23. With respect to the longitudinal axis L23, the second annular face 35 is arranged radially outside the first annular face.

[0047] According to [Fig.5], the elastomer annular piece 301 is arranged radially between, and in contact with, the first annular face 34 and the second annular face 35. In other words, and as can be seen in [Fig.5], the second annular part 25 includes an annular notch in a portion facing the first annular face 34 to define a space between the second annular face 35 and the first annular face, this to receive the elastomer annular piece 301.

[0048] In this example, the longitudinal dimension E301 of the elastomer annular part 301 is, for example, at least three times greater than the radial dimension R301 of said elastomer annular part 301.

[0049] With reference to the example described in [Fig.5], and according to an alternative, it can be provided that the annular faces 34 and 35 are not cylindrical of revolution but slightly frustoconical, with a section decreasing towards the outside of the turbomachine, this for better centering of the spark plug 22.

[0050] In the example of [Fig.5], the vibration damping means thus mainly provides radial damping along the longitudinal axis L23.

[0051] According to the embodiment shown in [Fig. 6], the second annular portion 25 comprises a first portion 41 and a second portion 42. The first portion 41 and the second portion 42 may be cylindrical. The first portion 41 may include an internal thread 43 cooperating with an external threaded portion 44 of the second portion 42. In other words, the first portion 41 cooperates with the second portion 42 by screwing the second portion 42 into the first portion 41. The two portions are in radial contact, via radial bearing faces 45, to complete the sealing of the second annular portion 25. In this configuration, the second portion 42 includes the second annular face 35. The second annular face 35 is cylindrical and extends along the longitudinal axis L23. The first annular portion 24 also includes a first annular face 34. In this configuration, as in the example described above, the first annular face 34 is cylindrical of revolution and extends along the longitudinal axis L23. Furthermore, in relation to the longitudinal axis L23, the second annular face 35 is arranged radially outside with respect to the first annular face 34.

[0052] Identical to the example in [Fig.5], the elastomer annular piece 301 is arranged radially between, and in contact with, the first annular face 34 and the second annular face 35. In addition, the longitudinal dimension E301 of the elastomer annular piece 301 is, for example, at least 5 times greater than the radial dimension R301 of said elastomer annular piece 301.

[0053] In the example of [Fig.6], the vibration damping means thus mainly provides radial damping along the longitudinal axis L23.

[0054] Furthermore, in this configuration, the second annular portion, divided into two parts, facilitates the overall mounting of the spark plug on the crankcase. Indeed, in order to adjust the depth of insertion of the spark plug 22 into the mounting device, it is often necessary, after the spark plug has been initially inserted into the mounting device, to machine the face of the first annular portion that contacts the contact face 26 of the spark plug. This requires disassembling the entire mounting device, which is already fixed to the crankcase 11, in order to perform the machining, and then reassembling the device on the crankcase. In the configuration detailed here, it is only necessary to unscrew the second portion 42, which is integral with the first annular portion 24. The first portion 41 thus remains fixed to the crankcase, awaiting the rest of the mounting device, which has been machined to the correct height.

Claims

Demands

1. Combustion chamber assembly (10) of an aircraft turbomachine comprising a housing (11), and a tubular mounting device (23) for a spark plug (22) on the housing (11), the tubular mounting device (23) comprising: - a first annular portion (24) in which the spark plug (22) is able to be sealed, - and a second annular portion (25) sealed to the housing (H), the tubular mounting device (23) further comprising a vibration damping means (30) connecting the first annular portion (24) to the second annular portion (25), the vibration damping means (30) comprising an elastomeric annular piece (301), the first annular portion (24) comprising a first annular face (34) and the second annular portion (25) comprising a second annular face (35), the elastomeric annular piece (301) being arranged between, and in contact with,the first annular face (34) and the second annular face (35).

2. Assembly according to claim 1, wherein the first annular part (24) comprises a first radial annular rim (36) having the first annular face (34), extending radially, the second annular part (25) comprises a second radial annular rim (37) which comprises an annular portion (38) radially curved inwards, and having the second annular face (35), oriented radially, the second radial annular face (35) being arranged longitudinally opposite the first radial annular face (34).

3. Assembly according to claim 2, wherein the vibration damping means (30) further comprises a longitudinal gap (302) arranged between the second radial annular rim (37) and the first radial annular rim (36).

4. Assembly according to any one of claims 1 to 3, wherein the elastomeric annular piece (301) comprises a longitudinal dimension (E301) and a radial dimension (R301) defined between an inner diameter (D1) and an outer diameter (D2) of the elastomeric annular piece, the longitudinal dimension (E301) being at least 1.5 times smaller than the radial dimension (R301).

5. Assembly according to claim 1, wherein the elastomeric annular piece (301) is arranged radially between, and in contact with, the first annular face (34) and the second annular face (35), the second annular face (35) being arranged radially outside with respect to the first annular face (34).

6. Assembly according to claim 1, wherein the second annular part (25) comprises a first portion (41) and a second portion (42), the first portion (41) having a threaded portion (43) which cooperates with a threaded portion (44) of the second portion (42), the elastomeric annular piece (301) being arranged radially between the first annular part (24) and the second portion (42), the first annular part (24) being arranged radially inside with respect to the second portion (42), and the second portion (42) being arranged radially inside with respect to the first portion (41).

7. Assembly according to any one of claims 1, 4 or 5, wherein the elastomeric annular piece comprises a longitudinal dimension (E301) and a radial dimension (R301) defined between an inner diameter (D1) and an outer diameter (D2) of the elastomeric annular piece, the longitudinal dimension (E301) being at least three times greater than the radial dimension (R301).

8. Assembly according to any one of the preceding claims, the housing (11) further comprising an opening (12), and the assembly further comprising the spark plug (22) extending along a longitudinal axis (L22) and passing through the opening (12) of the housing (11).

9. Aircraft turbomachine, such as for example a turbojet or a turboprop, characterized in that it comprises an assembly according to any one of claims 1 to 8.

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