Panel for tip clearance control

Abstract

The present invention relates to a panel for tip clearance control formed by: a first perforated sheet adapted for being seated on the turbine casing; a second sheet arranged on said first sheet and configured for being attached to the first sheet leaving a gap between both sheets; and a third sheet arranged between both first sheet and second sheet such that respective spaces in fluid connection by at least one hole are configured: a distribution chamber and an impingement chamber, both chambers extending from one end of the panel to the other. The panel further comprises a closure element together with a sealing element at one of its lateral ends for allowing the passage of fluid with another adjacent panel, whereas the sealing element is configured for allowing relative movement between both adjoining panels.

Claims

1. A panel for tip clearance control adapted for being placed on a compressor or turbine casing covering an arc portion thereof, wherein the panel is formed by: a first perforated sheet adapted for being arranged on said arc portion of the casing said first sheet defining two axes, a longitudinal axis and a circumferential axis, wherein said first perforated sheet further comprises a front end and a rear end, both substantially parallel to the circumferential axis; as well as two lateral ends substantially parallel to the longitudinal axis; a second sheet arranged on said first sheet and configured for being attached in a leak-tight manner at its front end and rear end, leaving a gap between the first perforated sheet and the second sheet; and a third sheet arranged between the first sheet and second sheet, configuring respective gaps with the first perforated sheet and the second sheet such that the third sheet forms together with the second sheet a distribution chamber, whereas it forms with the first sheet an impingement chamber, both chambers extending from one lateral end of the panel to the other; wherein said third sheet comprises at least one hole for the passage of fluid between both chambers; wherein the panel further comprises a closure element together with a sealing element at least at one of the lateral ends of the panel, said closure element being configured for allowing the passage of fluid with another adjacent panel, whereas the sealing element is configured for allowing relative movement between both adjoining panels.

2. The panel according to claim 1, wherein: the first perforated sheet further comprises at least one recess; and the second sheet further comprises at least one prominence; such that said at least one recess and at least one prominence of respective sheets coincide with one another so that when the recess is supported on the prominence a seating is formed.

3. The panel according to claim 2, wherein the seating is adapted for the passage of sensors to the casing.

4. The panel according to claim 1, wherein: the second sheet is divided according to the longitudinal direction into a front section and a rear section, each one of said front section and said rear section extending to its lateral ends; wherein said rear section is prominent with respect to the front section so as to form the distribution chamber together with the third sheet; and the third sheet has an extension configured to seal its perimeter with said rear section of the second sheet and thus prevent the passage of air to the impingement chamber through the attachment between the second sheet and third sheet.

5. The panel according to claim 1, wherein the second sheet further comprises an air inlet in fluid communication with the distribution chamber.

6. The panel according to claim 5, wherein said air inlet of the second sheet further comprises a distributing element configured for splitting an air inflow into branches.

7. The panel according to claim 6, wherein the branches into which the air inflow is split are two opposite branches.

8. A system for tip clearance control formed by a plurality of panels according to claim 5.

9. The system according to claim 8, wherein the system further comprises auxiliary sealing elements adapted for covering at least one portion of the periphery of the system for the purpose of containing the fluids exiting the impingement chambers of the panels to the casing.

10. An assembly comprising: a compressor or turbine casing, and a tip clearance control system for a compressor or turbine casing according to claim 8, wherein each panel is arranged consecutively on said casing by sandwiching between adjacent panels a sealing element of any of said panels; and wherein said panels are placed such that their respective distribution chambers form a distribution channel around the casing.

11. An assembly method for assembling a tip clearance control system for a compressor or turbine casing according to claim 8 on a compressor or turbine casing, wherein the method comprises the steps of: identifying a cooling air inlet intake and placing the panel with the air inlet in its second sheet close to said cooling air inlet intake; and consecutively placing the rest of the panels by sandwiching between adjacent panels a closure element together with a sealing element of any of said panels, assuring that their respective distribution chambers form a distribution channel around the casing.

12. The assembly method according to claim 11, wherein the method further comprises the step of: making the seatings formed by the at least one recess and by the at least one prominence of the first sheet and second sheet of each panel coincide with respective first sleeves arranged in the inlets of the casing for sensors; providing at least one spring element for each seating, said spring being configured for exerting a given force on the seating of the panel when it is supported on a second sleeve; providing a second sleeve for each of the first sleeves of the casing; and placing said spring element on said seating of the panel being retained between the second sleeve and the seating of the panel when the first sleeve and second sleeve are integrally attached to one another.

13. The assembly method according to claim 12, wherein the at least one spring element provided for each seating comprises a hole which coincides with the holes of the recess and the prominence of the first sheet and second sheet.

14. The panel according to claim 1, wherein the closure element is configured for closing an end of the impingement chamber between the first sheet and third sheet, while at the same time allowing the passage of air to or from the distribution chamber of an adjacent panel between the second sheet and third sheet, whereas the sealing element is configured for contacting the adjacent panel such that it seals against fluid leakages at the distribution chamber between the panel and the adjacent panel.

15. The panel according to claim 14, wherein the at least one closure element is integrally attached along the entire contour of a lateral end of the panel formed by the first sheet and second sheet, the closure element comprising: a sealing plate for the end of the impingement chamber, and a ridge which laterally extends the contour defined between the second sheet and third sheet such that the passage of air therethrough is allowed; wherein said ridge comprises means for retaining the sealing element.

16. The panel according to claim 15, wherein the sealing element is an O-ring type elastic gasket.

17. The panel according to claim 1, wherein the at least one closure element is integrally attached along the entire contour of a lateral end of the panel formed by the first sheet and second sheet, the closure element comprising: a sealing plate for the end of the impingement chamber, and a ridge on the contour defined between the second sheet and third sheet such that the passage of air therethrough is allowed; and this ridge being adapted for supporting a sealing element of an adjoining panel.

18. The panel according to claim 1, wherein the first sheet and/or the third sheet comprise a thermal insulation at least on one of their respective faces.

19. The panel according to claim 18, wherein the thermal insulation is applied by means of plasma spraying.

20. A securing system for securing a panel for tip clearance control on a compressor or turbine casing, wherein the panel comprises at least one seating, said securing system being formed by: a first sleeve adapted for being arranged in an inlet for sensors of the casing, wherein an end of said first sleeve is configured for serving as a support for a surface of the seating of the panel, a spring element configured for exerting a given force on the seating of the panel when it is supported on a second sleeve; said second sleeve comprising an end adapted for being seated on the spring element and configured for being integrally attached to the first sleeve by attachment means; such that a sliding of the panel in relation to the casing is allowed when the panel is subjected to a force that is greater than the friction exerted by the spring element.

21. The securing system according to claim 20, wherein the seating is adapted for the passage of sensors to the casing.

Description

DESCRIPTION OF THE DRAWINGS

(1) These and other features and advantages of the invention will become more apparent based on the following detailed description of a preferred embodiment given only by way of illustrative and non-limiting example in reference to the attached drawings.

(2) FIG. 1 shows a conventional TCC system.

(3) FIG. 2a shows a panel for tip clearance control according to the present invention.

(4) FIG. 2b shows an exploded view of the panel of FIG. 2a.

(5) FIG. 2c shows a detailed view of a section of the panel according to FIG. 2a, showing neither the closure element nor the sealing element.

(6) FIGS. 3a-3b show embodiments of the third sheet.

(7) FIGS. 4a-4b show an embodiment of the closure element together with the sealing element (FIG. 4a), in addition to an example of operation under thermal expansion of the casing (FIG. 4b).

(8) FIG. 5 shows an alternative embodiment in which the sealing element is a bellows-type sealing element.

(9) FIGS. 6a-6d show embodiments of the securing system according to the invention.

(10) FIG. 7 shows an example of an air inlet of the second sheet connecting with the distribution chamber.

(11) FIGS. 8a-8c show a system formed by a plurality of panels according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(12) One skilled in the art will recognize that the details described herein can be applied interchangeably to a panel (1) for tip clearance control, to a system (10) formed by a plurality of these panels (1), to an assembly method or even to a securing system for securing a panel on an engine or turbine casing (20).

(13) Notwithstanding what is shown herein, that is, a turbine casing (20), other embodiments with compressor casings (20) can likewise be considered.

(14) FIG. 1 illustrates a conventional TCC system. These conventional TCC systems are made up a series of impingement chambers (31) arranged on the turbine, or compressor, casing (20), as well as an air distribution duct (32) which receives the cooling air through a T-shaped inlet (33) and conveys it around the casing (20) to said chambers (31). The passage of this cooling air or feeding to the chambers is performed on an isolated basis by means of elbow fittings (34) provided for that purpose.

(15) The chambers (31) are secured to the casing (20) through stair-type securing elements (35) which in turn are secured to respective engine flanges (36), the front flange and rear flange of the casing (20).

(16) The bosses (37) which allow servicing the turbine can be furthermore observed, and their presence is what separates the chambers from one another and gives rise to extensive regions with an air leakage propensity, as well as shadow regions (38) (i.e., where there is no impingement in the casing) as those regions are not covered with chambers (31). Thus, this impingement air furthermore escapes around same.

(17) Finally, to absorb possible expansions, the sections of the distribution duct (32) are connected by means of “bellows”-type connections (39).

(18) The present invention as described hereinafter according to the first inventive aspect is a panel (1) for tip clearance control adapted for being placed on a compressor or turbine casing (20) covering an arc portion thereof.

(19) FIG. 2a illustrates an embodiment of a panel (1) according to the invention.

(20) It can clearly be observed that the system according to the invention is more compact, which results in lightness and, in this case, also in simplicity. It should be taken into account that in aviation, engines are usually exposed, hanging from the wings (pylon) in the most typical configuration. As a result, the entire additional space that is not intended for the operations of the engine per se may give rise to high aerodynamic loads (drag) having a secondary effect on fuel consumption.

(21) Furthermore, compared to the conventional TCC system explained in FIG. 1 that weights 30 kg, the system (10) made up of a plurality of these panels (1) as shown in FIG. 8 reduces this by one third, i.e., to 20 kg as nuts and bolts and additional elements are dispensed with and are now unnecessary as a result of its compact design.

(22) FIG. 2b illustrates an exploded view of the components of the embodiment of the panel (1) according to FIG. 2a.

(23) As can be seen in FIG. 2b, the panel (1) is formed in its most basic configuration by: a first perforated sheet (2) adapted for being arranged on said arc portion of the casing (20); a second sheet (3) arranged on said first sheet (2) and configured for being attached in a leak-tight manner by its front end (2.1) and rear end (2.2), leaving a gap between both sheets (2, 3); and a third sheet (4) arranged between the first sheet (2) and second sheet (3), configuring respective gaps with both sheets (2, 3) such that the third sheet (4) forms together with the second sheet (3) a distribution chamber (X), whereas it forms with the first sheet (2) an impingement chamber (Y), both chambers (X, Y) extending from one lateral end (1.1) of the panel (1) to the other (1.2); wherein said third sheet (4) comprises at least one hole (4.1) for the passage of fluid between both chambers (X, Y); wherein the panel (1) further comprises a closure element (5) together with a sealing element at least at one of the lateral ends (1.1,1.2) of the panel, said closure element (5) being configured for allowing the passage of fluid with another adjacent panel (1), whereas the sealing element is configured for allowing relative movement between both adjoining panels (1).

(24) The perforations (2.6) in the first perforated sheet (2) which enable the impingement process are shown. Furthermore, it can be seen how the first sheet (2) has a geometry suitable for being placed on the casing (20), optimizing the impingement on its upper cover.

(25) As already mentioned, the first sheet (2) defines two axes, a longitudinal axis (x-x′) and another circumferential axis (y-y′), which aid in referencing its front end (2.1) and rear end (2.2), both substantially parallel to the circumferential axis (y-y′); as well as its two lateral ends (2.3, 2.4), which are substantially parallel to the longitudinal axis (x-x′).

(26) As can be seen, the first perforated sheet (2) further comprises at least one recess (2.5) with a hole (2.5.1); and the second sheet (3) further comprises at least one prominence (3.1) the hole (3.1.1) of which is similar to the preceding hole (2.5.1). These at least one recess (2.5) and at least one prominence (3.1) of respective sheets (2, 3) coincide (see FIG. 2c) with one another so that when the recess (2.5) is supported on the prominence (3.1) a seating is formed, which is preferably adapted for the passage of sensors to the casing (20) by means of their respective holes (2.5.1, 3.1.1).

(27) Although it cannot be seen in this view, the panel further comprises at least one lug (6) at its rear end for stabilizing the seating of the panel (1) on the casing (20). See FIG. 7 for greater detail.

(28) Now referring to the second sheet (3), the sheet is divided, according to the longitudinal direction (x-x′), into a front section (3.2) and a rear section (3.3), each one extending to its lateral ends (3.5, 3.6). Both sections can be readily distinguished as a result of the rear section (3.3) being prominent with respect to the front section (3.2) so as to form the distribution chamber (X) together with the third sheet (4).

(29) As a result, the third sheet (4) comprises an extension similar to the perimeter of said rear section (3.3) of the second sheet (3) to favor the sealing of air along this perimeter. Furthermore, based on the number of seatings the panel has, the third sheet (4) is provided with a similar number of notches adapted to the shape of the respective recess and prominence that form it.

(30) Moreover, two closure elements (5) are also shown in FIG. 2a, one on each side of the panel (1). Nevertheless, in a panel system (10) such as the one shown in FIG. 8, it is necessary for a closure element (5) together with its sealing element to be placed between two panels (1), so each panel (1) will be provided with at least one closure element (5).

(31) Preferably, this panel (1) comprises a “male”-type closure element (5) at one of its ends and a “female”-type closure element (5) at the opposite end, thus only one of said closure elements (5) will comprise the retaining means for the sealing element. That is, the closure element (5) of its end (1.2) has the retaining means for the sealing element, whereas that of its other lateral end (1.1) will have a ridge adapted for supporting the sealing element of the adjoining panel.

(32) The sealing element can be seen in greater detail in FIGS. 4a to 5.

(33) Returning to the closure elements (5), each of them is configured for sealing or closing an end of the impingement chamber (Y) between the first sheet (2) and third sheet (4), while at the same time allowing the passage of air to or from the distribution chamber (X) of an adjacent panel between the second sheet (3) and third sheet (4).

(34) More specifically, as can be seen in detail in FIG. 4a, said closure element (5) is integrally attached along the entire contour of a lateral end (1.1, 1.2) of the panel (1) formed by the first sheet (2) and second sheet (3), the closure element (5) comprising: a sealing plate (5.1) for the end of the impingement chamber (Y), and a ridge (5.2) which laterally extends the contour defined between the second sheet (3) and third sheet (4) such that the passage of air therethrough is allowed.

(35) Moreover, as mentioned, the first sheet, second sheet, and third sheet can be formed from different sheets, giving rise to the three sheets according to the invention after their attachment. Namely, the attachment of a sheet comprising both the front section of the second sheet and the third sheet, together with another sheet in turn comprising the rear section of the second sheet would result in the second sheet and third sheet according to the present invention.

(36) FIG. 2c illustrate in greater detail the inside of the panel (1) shown in FIG. 2a as a result of a section view. For the sake of illustration, the section is in its intermediate region, and as a result neither the closure element (5) nor the sealing element has been shown.

(37) However, the third sheet (4) configuring respective gaps (X, Y) together with the first sheet (2) and second sheet (3) giving rise to the distribution chamber (X) and the impingement chamber (Y), respectively, can be seen. It can furthermore be observed that the third sheet ends at the height of the seating formed between the first sheet (2) and second sheet (3), or, in other words, it occupies an extension similar to the planar projection of the rear section (3.3) of the second sheet (3).

(38) It should be pointed out that in a preferred embodiment, the sheets are pressed sheets the attachment of which is produced by welding.

(39) Those surfaces susceptible to the application of thermal insulation, for example, by means of plasma spraying, are indicated with a discontinuous line. These candidate surfaces are either on the first sheet (2) on its face facing the casing (20), or the third sheet (4) on its face facing the impingement chamber (Y), as can be seen.

(40) FIGS. 3a and 3b illustrate detailed embodiments of the third sheet (4). Thus, FIG. 3a shows a third sheet (4) comprising two elongated holes (4.1) in the circumferential direction (y-y′) and spaced apart according to the longitudinal direction (x-x′), notwithstanding the fact that there could be a single elongated hole. Moreover, FIG. 3b shows a third sheet (4) with six holes (4.1′), separated in groups of two according to the circumferential direction (y-y′) and spaced apart according to the longitudinal direction (x-x′) in groups of three holes (4.1′).

(41) This arrangement of holes is for explanatory purposes and, accordingly, one skilled in the art will recognize other patterns, which may or may not be homogenous, of holes having the same or a different morphology with respect to those shown herein. As already mentioned, this allows the distribution of air into the chambers to be completely adaptable, being able to simply exchange the third sheet (4) with another more suitable one.

(42) As a result of these holes (4.1) of the third sheet (4), the operations of the panel in relation to the heat pick-up are improved compared to a conventional TCC system contemplated in the state of the art.

(43) Thus, since there was only one air feed (an intermediate hole) for feeding air into the impingement chamber (31) (as shown in FIG. 1) and it occurred through the elbow fitting (34), the long path of travel of the air from the feeding point (34) to the edges of the chamber (31) caused an increasing gain in temperature up to these edges.

(44) In turn, again referring to the panel according to the invention, as the third sheet (4) can comprise a larger number of holes (4.1) (see FIG. 3b), which is favored by the structural simplicity and adaptability of the panel (1), more feed points (4.1) distributed throughout the entire sheet are obtained, and the mean temperature of the cooling air to be injected is therefore reduced.

(45) FIG. 4a shows an embodiment of the closure element (5) together with the sealing element (5.2.1) cooperating with an adjacent panel. Particularly, the closure element is similar to the one illustrated in FIG. 2a, i.e., it is integrally attached to the contour of a lateral end (1.1) of the panel (1), plugging the impingement chamber (Y) by means of the sealing plate (5.1) and facilitating the passage of air to adjacent panels (1) by means of its ridge (5.2).

(46) Namely, this ridge (5.2), which laterally extends the contour defined between the second sheet (3) and third sheet (4) as if it were a projection, further comprises means for retaining the sealing element (5.2.1).

(47) In this particular example, the ridge (5.2) has an E-shape section, the sealing element, which in this case is an O-ring type elastic gasket (5.2.1), being retained between its two outermost tips.

(48) In turn, the closure element (5) of the adjoining panel (1) (the one on the right) is also integrally attached at a lateral end, plugging its impingement chamber by means of a sealing plate (5.1) and facilitating the passage of air to adjacent panels (1) by means of its ridge (5.3). Unlike the ridge (5.2) of the left panel (1) (the one retaining the sealing element (5.2.1)), this ridge (5.3) of the right panel (5.3) is adapted for supporting on its surface, in this specific case its internal surface, the sealing element (5.2.1).

(49) In a preferred embodiment, one and the same panel comprises two closure elements (5) as has been explained, but only one of them incorporates the means for retaining the sealing element (5.2.1) (male-female embodiment).

(50) Very briefly, the manner in which said closure element (5) works under thermal expansion of the casing (20) is shown below in FIG. 4b.

(51) With respect to FIG. 4b, the discontinuous line shows the original position of the closure and sealing elements, that is, when the turbine or compressor are not in operation and accordingly the casing (20) is cold.

(52) The solid line shows how the panel (1) moves upwards and is separated from the adjoining panel when the turbine or compressor is in operation and the casing (20) is hot. To that end, the sealing element (5.2.1) must allow said relative movement when the closure element (5) of the adjoining panel (1) slides thereon.

(53) In other words, the sealing element (5.2.1) is retained in a closure element (5) such that sliding of the closure element of the adjoining panel is enabled.

(54) A rotation allowed by this panel configuration could be in the order of an angular misalignment of 10° between adjoining panels. Thus, the sealing element (5.2.1) does not lose contact with the closure element (5) of the adjoining panel (1). In other words, it continues to exercise the function of the radial sealing of the distribution chamber.

(55) As a particular case, FIG. 5 illustrates another embodiment contemplated by the present invention where the sealing element, instead of being an elastic gasket (5.2.1) as defined in the preceding figures, is a bellows-type element (5.4).

(56) Accordingly, as a result of its flexibility, relative movement between adjoining panels during similar operations is likewise favored.

(57) FIGS. 6a to 6c show a securing system for securing a panel to a compressor or turbine casing (20) at the point where this panel comprises a seating.

(58) In FIG. 6a, where the securing system is depicted as a cross-section, it can be seen that this securing system is formed by: a first sleeve (7.1) adapted for being arranged in an inlet for sensors of the casing (20), the end of which is configured for serving as a support for a surface of the seating of the panel, a spring element (7.3, 7.4) configured for exerting a given force on the seating of the panel when it is supported on a second sleeve (7.2); a second sleeve (7.2) the end of which is adapted for being seated on the spring element (7.3, 7.4) and configured for being integrally attached to the first sleeve by attachment means (7.6); such that a sliding of the panel in relation to the casing is allowed when the securing system is subjected to a force that is greater than the friction exerted by the spring element (7.3, 7.4).

(59) The spring element is, preferably and in this figure, a plate (7.3) and at least one spring washer (7.4) such that: the plate (7.3) may comprise a surface similar to the upper end (“planar location”) of the first sleeve (7.1) and is configured for being arranged between the second sleeve (7.2) and the seating of the panel; at least one spring washer (7.4) configured for being arranged between the end of the second sleeve and the plate.

(60) Although it cannot be seen in these figures for the sake of illustration, the lower region of the first sleeve (7.1), the region that will contact the casing (20) and is now shown as a whole, would adopt the geometry of the latter so as to be supported thereon. In other words, this support base of the first sleeve (7.1) would adopt the inclination of the casing (20) at that point.

(61) In this particular case, this first sleeve (7.1) and second sleeve (7.2) furthermore guide the sensors into the casing. In their integral attachment, both sleeves (7.1, 7.2) form a conventional boss. It can also be observed that the screws (7.6) are arranged on respective sides of the hole, sensor guide, arranged on the seating of the panel, there being one spring washer (7.4) for each screw (7.6).

(62) When the attachment means (7.6) are based on nuts and bolts for integrally attaching the end of the first sleeve (7.1) and second sleeve (7.2) to one another, the seating must further comprise holes (7.5) for the passage of these screws (7.6). See FIG. 6c.

(63) The similar shape of the end of the first sleeve (7.1), of the end of the second sleeve (7.2), and the shape of the plate (7.3), all of them being rhomboid-shaped, can be seen in FIG. 6b.

(64) With a top view like that provided in FIG. 6c, the slot in the seating of the panel in which the plate (7.3), the spring washer (7.4), the first sleeve (7.1), and the screw (7.6) will be arranged in that order, can be seen.

(65) Furthermore, FIG. 6d shows another embodiment of the securing system for securing a panel to the casing (20) based on a floating plate and a wave washer (7.7) as the spring element.

(66) Namely, it shows a comparative image of a securing system according to the embodiment of FIG. 6a (based on the plate (7.3)-spring washer (7.4) assembly) and another one based on a plate (7.3′)-wave washer (7.7) assembly, with said wave washer being the spring element.

(67) In particular, a section of both configurations according to the longitudinal direction (x-x′) (i.e., from front to back of the axis of the engine) using the axis of symmetry of the bearing, is shown.

(68) Both securing systems use a first sleeve (7.1, 7.1′) and a second sleeve (7.2, 7.2′) integrally attached to one another by attachment means. In the left half, these attachment means are based on nuts and bolts (7.6), whereas in the right half an auxiliary internal thread (7.8) is used.

(69) Notwithstanding the foregoing, attachment means with a different typology can be used or those which are herein depicted could even be interchanged. Namely, in case of using nuts and bolts with the system on the right (plate (7.3′)-wave washer (7.7) assembly), the second sleeve could also comprise extensions exceeding the diameter of the wave washer (7.7) so as to be integrally attached with the first sleeve remotely so that it does not interfere with the spring element.

(70) Returning to FIG. 6d, it can be observed how the holes of the seating have a diameter that is slightly larger than the diameter occupied by the elements going through it, whether the second sleeve (7.2, 7.2′) or even the screws (7.6). This enables the sliding of the panel without being contained by the retention of these elements, or in other words, the holes of the panel are sized so as to allow the envisaged sliding (or relative movement) of the panel when accommodating the expansion of the casing (20).

(71) FIG. 7 illustrates an air inlet which is arranged in the second sheet (3) and connects with the distribution chamber (X). Furthermore, a distributing element (3.4.1) favoring the division of the air inflow into two opposite branches can be observed.

(72) FIG. 8a shows a system (10) for tip clearance control formed by a plurality of panels (1) according to the invention, wherein at least one of said panels (1) is as illustrated and described in relation to FIG. 7.

(73) Furthermore, in use, for the purpose of preventing post-impingement leakages, i.e., once the air exits the panel (1) through the first perforated sheet (2), the system (10) is provided with auxiliary sealing elements (11, 12). These auxiliary elements (11, 12) can be located, inter alia, close to the engine flange (36) and following its path, as shown in FIG. 8c.

(74) FIG. 8b shows a detail of the auxiliary longitudinal sealing element (11). This element (11) is integrally attached to the closure element (5), namely the one that does not comprise the O-ring type elastic gasket (5.2.1). It is a ridge or flap in the form of a continuous tab extending below the adjacent panel, hindering possible air leakages through the opening between panels.

(75) Its length is longer, i.e., overlapping the adjacent panel, so that in operation (hot state with the panels separated the maximum distance) it still has a part that overlaps the adjacent panel and can continue to perform its function.

(76) Moreover, FIG. 8c shows a detail of the auxiliary longitudinal sealing element (12). This element (12) is also in the form of a continuous ridge or tab arranged on the front end of the panels and being supported on a bend (36.1) of the engine flange (36).