Cooling device for a turbomachine casing

Abstract

A turbine for a turbomachine has a first rotor and a second rotor configured to pivot about an axis in two opposite directions of rotation. The first rotor includes a radially outer drum from which blades extend radially inwards. The turbine has cooling means attached relative to the outer drum. The cooling means include a support plate with at least one first orifice and a calibration plate that is attached to the support plate and located radially inside the support plate. The calibration plate has at least one second calibration orifice facing the outer drum to allow the passage of cooling air radially from the outside to the inside through the first and second orifices.

Claims

1. A turbine for a turbomachine comprising a first rotor and a second rotor configured to pivot about an axis (X) in two opposite directions of rotation, the first rotor comprising a radially outer drum from which blades extend radially inwards, the turbine comprising cooling means attached with respect to the outer drum, said cooling means comprising a support plate comprising at least one first orifice, the cooling means further comprising at least one calibration plate attached to the support plate and located radially inside the support plate, the at least one calibration plate comprising at least one second calibration orifice turned towards the outer drum to allow passage of cooling air radially from the outside to the inside through the at least one first orifice and the at least one second orifice.

2. The turbine according to claim 1, wherein a total cross-sectional area of the at least one first orifice is greater than a total cross-sectional area of the at least one second orifice.

3. The turbine according to claim 1, wherein at least one of the at least one calibration plate delimits with the support plate at least one intermediate chamber into which the at least one first orifice and the at least one second orifice open.

4. The turbine according to claim 3, wherein at least one of the at least one intermediate chamber has a trapezoidal cross-section.

5. The turbine according to claim 4, wherein each of the at least one calibration plate has a central area and fixing areas attached to the support plate on either side of the central area, the central area being spaced radially inwards from the support plate.

6. The turbine according to claim 1, the at least one calibration plate comprising a plurality of calibration plates axially offset from each other and attached to the support plate.

7. The turbine according to claim 1, wherein the outer drum comprises through orifices opening out opposite the blades of the first rotor.

8. The turbine according to claim 1, wherein at least one of a downstream end and an upstream end of the support plate is attached by screwing or riveting to the outer drum.

9. The turbine according to claim 1, wherein at least one of an upstream end and a downstream end of the support plate is held radially with respect to the outer drum, the at least one of an upstream end and a downstream end being configured to translate axially with respect to the outer drum.

10. A turbomachine comprising the turbine according to claim 1.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view in axial section of a turbomachine of the prior art,

(2) FIG. 2 is a half-view in axial section of a turbine of the prior art,

(3) FIG. 3 is a perspective view of a cooling device of the prior art,

(4) FIG. 4 is a schematic half-view of a counter-rotating low-pressure turbine,

(5) FIG. 5 is a view in axial section of part of a turbine according to a first embodiment of the disclosure,

(6) FIG. 6 is a detailed view of part of FIG. 5,

(7) FIG. 7 is a view corresponding to FIG. 5, illustrating a second embodiment of the disclosure,

(8) FIG. 8 is a view corresponding to FIG. 5, illustrating a third embodiment of the disclosure.

DETAILED DESCRIPTION

(9) FIGS. 4 to 6 illustrate a low-pressure turbine 7 of a turbomachine according to a first embodiment of the disclosure.

(10) The turbine 7 is of the counter-rotating type and comprises a first rotor 25 comprising one or more stages formed by bladed wheels 26, rotating about the X axis of the turbine 7 in a first direction of rotation, and a second rotor 27 with one or more stages 28 formed by bladed wheels, rotating about the X axis in a second direction of rotation, opposite to the first direction of rotation.

(11) The first rotor 25 has a radially outer drum 29, from which blades 26 extend radially inwards. The second rotor 27 has a radially inner drum 30, from which blades 28 extend radially outwards.

(12) The rotors 25, 27 are housed in a stationary casing 31, the casing 31 comprising in particular a radially outer annular wall 32.

(13) As mentioned above, the rotors 25, 27, in particular the radially outer drum 29 of the first rotor 25, must be cooled.

(14) To this end, the turbine 7 comprises cooling means 33 stationary with respect to the outer drum 29, the cooling means 33 comprising an annular support plate 34.

(15) The support plate 34 is annular and has, from upstream to downstream, a radial rim 35, a frustoconical part 36 flaring downstream, a cylindrical part 37 and a radial rim 38.

(16) The flanges 35, 38 form the upstream and downstream ends of the support plate 34 and extend radially outwards from the frustoconical part 36 and from the cylindrical part 37.

(17) Each flange 35, 38 is attached to a radial rim 39 of the outer drum 29 or a part connected to the first rotor 25.

(18) The support plate 34 has first orifices 40 distributed in rows axially offset from each other. The first orifices 40 in a row are evenly distributed around the circumference of the support plate 34. The first orifices 40 each have a circular cross-section. The axes of the first orifices 40 are perpendicular to their implantation zone in the frustoconical part 36 or in the cylindrical part 37 of the support plate 34.

(19) The cooling means 33 also comprise calibration plates 41 attached to the support plate 34. The calibration plates 41 are annular and are axially offset from each other. Each calibration plate 41 has two axial ends 42 which are sealingly attached, for example by welding or soldering, to the support plate 34, and at least one middle part 43 which is spaced radially inwards from the support plate 34. The middle part 43 is frustoconical or cylindrical, and coaxial with the frustoconical 36 or cylindrical part 37 of the support plate 34 to which it is attached. The calibration plate 41 can have one or more separate middle sections 43, spaced axially apart from each other, and spaced from the support plate 34. In this case, two middle parts are separated by an attachment part 44 which is welded or soldered to the support plate 34. Each middle area 43 is connected to the ends 42 or to the attachment part 44 by connecting areas 45 (FIG. 6). The distance between the middle area 43 and the radially outer face of the outer drum 29 can be between 1 and 10 mm.

(20) Each calibration plate 41 is annular and thus defines one or more annular intermediate or stilling spaces 46 with the support plate 34, the intermediate spaces 46 having a generally trapezoidal cross-section. Each intermediate space is delimited by the support plate 34, the middle part 43 and the corresponding connecting parts 45.

(21) Second orifices 47 are provided in each middle area 43 of each calibration plate 41. The second orifices 47 are arranged in at least one row. The second orifices 47 within a row are evenly distributed around the circumference of the calibration plate 41. The second orifices 47 each have a circular cross-section.

(22) The diameter of the second orifices 47 is smaller than the diameter of the first orifices 40. The diameter of the first orifices 40 is for example between 0.1 and 10 mm. The diameter of the second orifices 47 is for example between 0.1 and 10 mm.

(23) The axes of the second orifices 47 are perpendicular to the area where they are located in the frustoconical or cylindrical central part 43 of the corresponding calibration plate 41. The second orifices 47 can be located opposite the corresponding first orifices 40. Each second orifice 47 can be coaxial with a first orifice 40.

(24) The outer drum 29 also has third through-orifices 48, which connect the annular space 48 between firstly, the casing 31 and the support plate 34, on the one hand, and secondly, the space radially inside the outer drum 29 forming the primary vein 10. The third orifices 48 are located opposite the radially outer platforms of the blades 26 of the first rotor 25, the blades 26 not being shown in FIGS. 5 to 8.

(25) In operation, cooling air is taken from the high-pressure compressor 4 of the turbomachine 1 and fed into the annular space 48 between the casing 31 and the support plate 34. This cooling air is at a higher pressure than the gas pressure within the primary vein 10 of the turbine 7.

(26) As illustrated by the arrows in FIG. 5, this air then passes through the first orifices 40, the intermediate chambers 46 and the second orifices 47 in succession before impacting the radially outer surface of the outer drum 29, thereby cooling it. This cooling air then passes through the third orifices 48 to cool the blades 26, before being discharged into the turbine 7 vein 10.

(27) FIG. 7 illustrates a second embodiment of the disclosure, which differs from that set out with reference to FIGS. 4 to 6 in that the radial rim 35 of the upstream end of the support plate 34 extends radially inwardly from the frustoconical part 36 and is threadedly attached to a radial rim 49 of the outer drum 29.

(28) FIG. 8 illustrates a third embodiment of the disclosure, which differs from that set out with reference to FIG. 7 in that the upstream end 50 of the support plate 34 extends axially and is engaged in an axially extending annular space 51 provided between a holding member 52 and the upstream end of the outer drum 29.

(29) The holding member 52 is annular. It has an L-shaped cross-section and comprises a radial attachment part 53 and an axial holding part 54. The annular space 51 is defined between the holding part 54 and the outer drum 29.

(30) The upstream end 50 of the support plate 34 is thus held radially with little or no radial clearance in the aforementioned annular space 51, an axial displacement being possible between the upstream end 50 of the support plate 34 and the outer drum 29, so as to compensate in particular for any phenomena of differential expansion during operation. The axial movement is guided by a plane-on-plane contact between the outer surface of the upstream end 50 and the inner surface of the holding part 54.

(31) A seal or elastic member 55 can be mounted axially between the attachment part 53 of the holding member 52 and the upstream axial end 50 of the support plate 34. This seal or elastic member is for example formed by a corrugated sheet.