FR3066783B1 - SHIRT FOR OPTIMIZED COOLING TURBINE BLADE - Google Patents

Abstract

Cooling jacket (30) for cooling a hollow part in which it is intended to be inserted, comprising a longitudinal hollow body (32) surmounted by a flange (34) intended to be secured at its periphery in a sealed manner with this hollow part, the flange comprising a plurality of perforations (34A, 34B, 34C) for separating a main flow of cooling air Ft feeding the cooling jacket into two separate secondary flows, a first secondary cooling air flow Fc passing through the longitudinal hollow body at a central cavity (32A) to be discharged to the outside and a second secondary flow of cooling air F1, F2, F3 passing through the perforations and circulating around the longitudinal hollow body.

Description

Field of the invention

The present invention relates to the general field of turbomachine turbine blades, and more particularly to turbine blades provided with cooling jackets.

Prior art

In a manner known per se, a turbomachine comprises a combustion chamber in which air and fuel are mixed before being burned. The gases from this combustion flow downstream of the combustion chamber and then feed a high pressure turbine and a low pressure turbine. Each turbine has one or more rows of stationary vanes (called stator distributors) alternating with one or more rows of moving blades (called moving wheels) circumferentially spaced around the rotor of the turbine. The turbine blades are subjected to the very high temperatures of the combustion gases, which reach values much higher than those which can withstand without damage the vanes which are in direct contact with these gases, which has the consequence of limiting their duration. life.

Also, in order to reduce the temperature, it is known to provide these vanes with perforated cooling jackets.

FIGS. 2 and 3 represent a conventional distributor sector 10 of aeronautical engines comprising a plurality of fixed vanes 12 forming a grid that straighten the flow of air F passing through the engine gas stream delimited by a ferrule or external platform 14 and a ferrule or inner platform 16 supporting the fixed blades 12. The hollow blade 12 comprises a cooling jacket 18 which defines an annular peripheral cavity 20 between the inner wall of the blade and the outside of the jacket (On the Figure 2 and for the sake of better understanding, the leftmost liner 18 has been shown partially extracted from the cavity 20). At its top 18A in the form of a flange, the liner is sealingly attached to the outer platform of the blade by welding or brazing and its lower end portion 18B is embedded in the internal platform of the dawn at a guide zone 16A, leaving a determined clearance necessary for mounting and sliding of the jacket under the effects of thermal expansion. According to the configuration envisaged, studs 22 secured to the inner wall or formed by bosses of the liner maintain a constant spacing between the liner and this inner wall.

The jacket 18 is of the multi-perforated type so that the cooling air flow delivered by a source of pressurized air, generally the compressor of the turbomachine, enters the external platform 14 through a port of FIG. 24, arrives inside the liner 18 and escapes in part by the multi-perforation of the liner forming in the peripheral cavity 20 air jets which cool by impact (or via fins 26 forming disrupters ) the internal wall of the blade 12, and are evacuated by calibrated holes made on the trailing edge or on the underside of this blade to form a protective air film (unrepresented bridges can be provided to the inside the dawn to accommodate the circulation of this cooling air). The remaining air flow exits the liner through the inner platform 16 which it passes through cooling it to escape through an outlet port 28 on the outside of the blade to other parts of the engine. cool and including turbine disks (high or low pressure purges).

This configuration, however, has disadvantages related to the fact that this impact cooling (or percussion) in very specific areas of the blade, its trailing edge and its leading edge in particular, creates very large thermal gradients between the cold flow and the hot zone impacted which has the effect of loading other areas and causing premature wear. In addition, it is difficult to ensure a transfer of the cooling air to the turbine disks at the right pressure and at the right temperature.

Object and summary of the invention

The present invention therefore aims to overcome the disadvantages associated with this inappropriate creation of thermal gradients by providing a cooling jacket which avoids this premature wear of the blade. The invention also aims to achieve a blade whose geometry and therefore the manufacturing process is very little modified compared to the traditional manufacturing process foundry, so as to avoid any degradation in the general mechanical strength of the blade. Finally, it aims at any turbomachine turbine equipped with such blades with improved cooling jacket. For this purpose, there is provided a cooling jacket for cooling a hollow part in which it is intended to be inserted, comprising a longitudinal hollow body terminated by a free end and surmounted by a flange intended to be secured to its periphery. in leaktight manner with said hollow part, characterized in that said flange comprises a plurality of perforations for separating a main flow of cooling air Ft feeding said cooling jacket into two separate secondary flows, a first secondary cooling air flow Fc passing through said longitudinal hollow body at a main cavity to be discharged through said free end and a second secondary flow of cooling air F1, F2, F3 passing through said perforations and circulating around said longitudinal hollow body.

In this way, it is provided by simple convection good ventilation of the hollow part in which the jacket is inserted and by the passage of air in the central cavity is fulfilled the conditions of temperature, pressure and flow desired for the cooling of elements external to this hollow part, for example turbine discs in the case where this hollow part is a turbine engine valve blade. The structure of the folder is simplified by removing its multi-perforation without changing the manufacturing process of the hollow part in which the folder is inserted.

Preferably, said main cavity is a central cavity of substantially oblong shape and disposed in a centered position.

According to the embodiment envisaged, said flange comprises two perforations disposed at two ends of said central cavity and preferably at least one lateral perforation disposed on a sidewall of said central cavity.

Advantageously, said first cooling air secondary stream Fc represents 55 to 65% of said main cooling air flow Ft and preferably 60%. The invention also relates to a hollow part comprising a cooling jacket as mentioned above defining an annular cavity between an outer wall of said cooling jacket and an inner wall of said hollow part, said main flow of cooling air Ft being introduced into said hollow part for one hand, through said perforations, to ensure its internal cooling and for the other part, through said main cavity, to evacuate a portion of this cooling air outside said hollow part.

Said hollow part advantageously forms a fixed blade of a turbomachine distributor, the cooling air passing through said main cavity being intended to cool a disk carrying said fixed blade. Finally, the invention relates to any turbomachine turbine provided with a plurality of blades fixed as above.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an embodiment of this embodiment devoid of any limiting character and in which: FIG. FIG. 1 is a sectional view of a blade provided with the jacket of FIG. 1, FIG. perspective of a prior art turbine distributor part, and - Figure 3 is a sectional view of the distributor of Figure 2.

Detailed description of an embodiment

It will be noted first of all that if the invention as described is applied to the fixed vanes of low pressure distributors, it can of course easily be adapted to any other part requiring internal cooling (more generally any hollow part to be vented).

According to the invention, it is proposed to change the way of distributing the cooling air in this hollow room by promoting convection to cool the hot walls of the room while keeping a central cavity naturally remote from these hot walls to direct cooler air towards areas external to this part, in this case, the low pressure turbine discs when the hollow part is a fixed blade of turbomachine distributor.

Thus, considering the total available cooling flow, the present invention makes it possible, by the innovative configuration of the cooling jacket, to separate this main flow into two secondary streams: one passing through the cooling jacket, and going directly to the cooling jacket. the outside towards the turbine discs and the other circulating inside the blade, around the cooling jacket, before being expelled by the trailing edge and / or the leading edge for the or cool them by forming a protective air film. This configuration makes it possible to respect the criteria for purging, cooling the discs and cooling the leading edge and / or the trailing edge, while avoiding favoring a particular type of thermal degradation as in the devices of the prior art. .

It was recalled in the preamble of the present application that a fixed blade of turbine distributor is mounted between an external platform and an internal platform, the external platform defining an outer wall for the flow of gas flow. combustion through the turbine and the inner platform an inner wall for the same flow vein. Such a fixed blade of hollow structure is subjected to very high temperatures of the combustion gases and therefore needs to be cooled. For this purpose and as illustrated in FIGS. 1 and 1A, the blade 12 comprises a cooling jacket 30 comprising on the one hand a longitudinal hollow body 32 terminated by a free end 33, supplied with cooling air by a first flow of secondary air Fc entering at a first end into a main cavity 32A of this body and out through this free end, and which defines an annular peripheral cavity 20 between the inner wall of the blade and the outer wall of the jacket and other share a perforated flange 34 overlying the hollow body and arranged to fix this liner sealingly on the outer platform 14 of the blade by welding or brazing and supplied with cooling air by a second secondary air flow Fl, F2, F3 through its perforations 34A, 34B, 34C, all of these secondary air flows forming the main air flow Ft. The first secondary air flow Fc represents 55 to 65% of the main air flow F t and preferably 60%. The main cavity is preferably substantially oblong in shape and disposed in a centered position.

The flange is preferably obtained by forming the sheet constituting the liner but it could also be attached to the body of this liner and it comprises the various perforations allowing the passage of the second secondary air flow. More particularly, a first perforation 34A made in the extension of a first end of the main cavity 32A forming the inner portion of the liner allows the passage of a first flow Fl of cooling air proportional to the section of this opening. Similarly, a second perforation 34B made in the extension of another end of the main cavity allows the passage of a second flow of cooling air F2 proportional to the section of this opening and optionally a third perforation 34C (shown in FIG. dotted in the figure) made on one of the two sides of the main cavity allows the passage of a third cooling air flow F3 also proportional to the section of this opening. More generally, these perforations, the number of which is not limited, are practiced in the available spaces of the flange around the main cavity 32A, with the exception, of course, of the periphery 34D of the flange necessary for its fixing in a watertight manner. external platform. The cooling air introduced into the main cavity 32A of the jacket is in turn directly at its lower part to purge the turbine discs.

Thus, by separating the cooling of the blade from that of the turbine discs, it can be taken into account the specific needs in temperature, pressure and flow of both the blade and the discs then allowing optimized cooling.

With the invention, it can be noted that the dawn manufacturing process does not have to be modified, only the configuration of the liner being changed in a minor way, its manufacturing process by stamping and brewing being not more modified. In addition, this allows to feed the turbine discs with a temperature and a flow rate to extend their life compared to a blade without a jacket without changing the cooling air flow (no variation of the purge) . It also increases the life of the dawn by reducing cracks and burns. The invention thus makes it possible to cumulate the benefits of the two solutions (with and without jacket) usually used for such ventilated hollow parts without adding manufacturing complexity and without changing the design of parts having high industrial impact and remaining interchangeable with the parts. already implemented (this "retrofit" may for example be performed during a maintenance operation). In addition, in the case of turbine engine dispensers, the manufacturing cycle of the shirt is reduced because of the lack of multi-perforation on this shirt.

Claims (9)

Cooling jacket (30) for cooling a hollow part (12) in which it is intended to be inserted, comprising a longitudinal hollow body (32) terminated by a free end (33) and surmounted by a collar ( 34) intended to be secured to its periphery in a sealed manner with said hollow part, characterized in that said flange comprises a plurality of perforations (34A, 34B, 34C) for separating a main flow of cooling air Ft feeding said jacket cooling in two separate secondary flows, a first secondary flow of cooling air Fc passing through said longitudinal hollow body at a main cavity (32A) to be discharged through said free end and a second secondary air flow of cooling Fl, F2, F3 passing through said perforations and circulating around said longitudinal hollow body. 2. Cooling jacket according to claim 1, characterized in that said main cavity is a central cavity of substantially oblong shape and disposed in a centered position. 3. Cooling jacket according to claim 2, characterized in that said flange comprises two perforations (34A, 34B) disposed at two ends of said central cavity. 4. Cooling jacket according to claim 2, characterized in that said collar further comprises at least one lateral perforation (34C) disposed on a sidewall of said central cavity. 5. Cooling jacket according to any one of claims 1 to 4, characterized in that said first cooling air secondary stream Fc represents 55 to 65% of said main cooling air flow Ft and preferably 60%. 6. hollow part (12) comprising a cooling jacket according to any one of claims 1 to 5 defining an annular cavity (20) between an outer wall of said cooling jacket and an inner wall of said hollow part, said main flow cooling air Ft being introduced into said hollow part for firstly, through said perforations, ensure its internal cooling and for the other part, through said main cavity, evacuate a portion of this cooling air to the outside said hollow piece. 7. hollow part according to claim 6 forming a fixed blade of turbomachine distributor, the cooling air passing through said main cavity being intended to cool a disk carrying said fixed blade. 8. A turbomachine distributor comprising a plurality of blades according to claim 7. 9. Turbomachine comprising a turbomachine distributor according to claim 8.