FR2938013A1 - Turbomachine e.g. turbojet engine, for aircraft, has set of roller bearings placed within lubricated sealed chamber and arranged in upstream of combustion chamber along direction of main flow of gases through turbomachine - Google Patents

Abstract

The present invention relates to a turbomachine (1), preferably for an aircraft, comprising a compressor part (2), a combustion chamber (4), a turbine part (6), at least one shaft (10a, 10b) carrying the rotating elements of the compressor part and the turbine part, as well as a plurality of bearings supporting the shaft. According to the invention, the plurality of bearings comprises one or more aerodynamic bearings (12) and one or more rolling bearings (14), each of the rolling bearings (14) being arranged upstream of the combustion chamber (4). ), according to a main flow direction of the gases (5) through the turbomachine.

Description

TECHNICAL FIELD The present invention relates generally to the field of turbomachines, preferably for aircraft, for example of the turbojet, turboprop, turbine engine, auxiliary power unit (English Auxiliary) type. Power Unit). STATE OF THE PRIOR ART A turbomachine conventionally comprises one or more shafts carrying the rotating elements of the compressor and turbine parts of this turbomachine. Usually, these shafts are guided by rolling bearings axially spaced from one another, the bearings being of the ball or roller type. They need to be lubricated, generally by an oil jet, permanently during operation of the turbomachine. To do this, each rolling bearing is arranged in a lubricated chamber of the turbomachine, the sealing is provided by a system of labyrinth seals pressurized by a sample of air, generally performed on the compressor. To this end, so-called double rotary joints, of complex design, are employed. As mentioned above, these lubricated rolling bearings are axially spaced from each other, generally involving the presence of one or more of them in a hot zone of the turbomachine, namely to the right of the chamber. combustion or downstream of this chamber, for example in the turbine part.

This arrangement generates a high exposure of the lubricant to heat. This results in several disadvantages, including that of the need, in some cases, to implement a heat exchanger system to cool the lubricant, likely to heat up considerably in contact with the hot elements. In addition, the heated lubricant degrades rapidly, which has the effect of multiplying the maintenance operations to change the lubricant present in the cavities housing the rolling bearings. In addition, the separation of the pressurizing air / hot lubricant mixture from the drainage of the cavities is difficult to manage, and lubricant vapors are necessarily emitted, involving a risk of pollution of the pressurizing air circuit of the aircraft. From the prior art, it is also known, in particular from US Pat. No. 7,251,942 B2, the use of aerodynamic bearings for rotating the rotating shafts of an auxiliary power unit. While this technology makes it possible to overcome the constraints of lubrication, it nevertheless has the disadvantage of supporting only low axial loads, and therefore can not be applied to high power turbomachines.

DISCLOSURE OF THE INVENTION The object of the invention is therefore to remedy at least partially the disadvantages mentioned above, relating to the embodiments of the prior art.

For this purpose, the subject of the invention is an aircraft turbomachine comprising a compressor part, a combustion chamber, a turbine part, at least one shaft carrying the rotating elements of the compressor part and of the turbine part, as well as a plurality of bearings supporting said shaft. According to the invention, said plurality of bearings comprises one or more aerodynamic bearings and one or more rolling bearings, each of said one or more rolling bearings being disposed upstream of the combustion chamber, in a main direction of flow. gases through the turbomachine. In other words, the entire hot part of the turbomachine is free of rolling bearings, since this or these bearings are now exclusively upstream of the combustion chamber, and even more preferably upstream of the compressor part where the temperature is significantly lower. As a result, the lubrication associated with these rolling bearings is no longer penalized by a surrounding hot environment. This allows in particular to eliminate or reduce the size of the heat exchanger system for cooling the lubricant, to limit the degradation of the latter under the effect of heat, and therefore to reduce the maintenance operations to change 3 the lubricant passing through the cavities housing the rolling bearings. In addition, the separator of the pressurizing air / hot lubricant mixture from the drainage of the cavities can also be removed or reduced. Furthermore, the toxic vapors of lubricant emitted are greatly reduced, advantageously involving a decrease in the pollution of the pressurizing air circuit of the aircraft.

Therefore, the invention provides, due to the location of the bearings or bearings in the cold zone of the turbomachine, a reduction in overall weight, a reduction in production and maintenance costs, a reduction in steam discharges. lubricant, a reduction in lubricant consumption, a better reliability of these bearings, and a decrease in the power dissipated in the lubricant circulation. In addition, the one or more aerodynamic bearings, replacing the traditional rolling bearings of the hot zone of the turbomachine, do not need to be lubricated, and therefore require no equipment relating to such lubrication. As a result, compared to a solution where only rolling bearings are employed, a reduction in the number of parts and the overall mass, a reduction in production and maintenance costs, a decrease in lubricant vapor discharges. , a reduction in lubricant consumption, and a decrease in the power dissipated in the lubricant circulation. In addition, even though the aerodynamic bearings are intended to be placed in cavities whose sealing is provided by a system of dynamic seals, for example of the type joined labyrinths, this system being pressurized by a sample of air, this sampling does not need to be as important as that operated to ensure the sealing of a lubricated cavity incorporating a rolling bearing, so that another advantage lies in the reduction of air losses, and therefore in the increase overall performance of the turbomachine. In addition, the dynamic seals required to seal these cavities containing aerodynamic bearings, are significantly less complex and less cumbersome than those used to seal against lubricated enclosures. With the mix offered by the present invention in bearings supporting the rotating shaft (s) of the turbomachine, the aerodynamic bearings essentially take up the radial loads, while the rolling bearings essentially take up the axial loads. This solution is thus quite suitable for high power turbomachines, unlike prior art embodiments incorporating only aerodynamic bearings. Preferably, said plurality of bearings comprises at least one rolling bearing housed within a lubricated sealed enclosure incorporating a gearbox of the turbomachine.

Thus, this makes it possible to share the management of the lubrication with another element of the turbomachine, namely the gearbox, known to those skilled in the art and having specific functions depending on the nature of the turbomachine concerned. By grouping this gearbox with one or more rolling bearings in the same lubricated sealed enclosure, this results in a reduction in the number of parts and the overall mass, a reduction in production and maintenance costs, a reduction in reduction of the quantity of lubricant required, and a reduction of the power dissipated in the circulation of the lubricant. In addition, it is preferably made so that said plurality of bearings comprises at least two rolling bearings housed in the same lubricated sealed enclosure, for example that incorporating the aforementioned gearbox, or any other enclosure of the turbomachine. Here again, it is possible to benefit from all the advantages that have just been described, since the lubrication management of several rolling bearings can be ensured by the same system of equipment dedicated to the enclosure integrating these bearings. Preferably, the turbomachine comprises one or more shafts carrying the rotating elements of the compressor part and the turbine part, for example two. As an indication, the turbomachine is a turbojet engine, a turboprop, a turbine engine, or an auxiliary power unit (English Auxiliary Power Unit).

Other advantages and features of the invention will become apparent in the detailed non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS This description will be made with reference to the appended drawings among which; - Figures 1 to 6 show longitudinal sectional views of aircraft turbomachines according to preferred embodiments of the present invention; and FIG. 7 represents a view in longitudinal section schematizing an exemplary embodiment of a pressurized enclosure housing an aerodynamic bearing.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to FIG. 1, part of a turbomachine 1 can be seen according to a first preferred embodiment of the present invention.

From upstream to downstream in a main flow direction of the gases within the turbomachine, represented by the arrow 5, the turbomachine 1 comprises, a compressor part 2, a combustion chamber 4, and a turbine part 6 all these elements being centered on the longitudinal axis 8 of this turbomachine. In this preferred embodiment, the turbine portion 6 comprises a high-pressure turbine 6a and a low-pressure turbine 6b offset from the first in the axial direction.

In addition, the turbomachine comprises a shaft system 10 carrying the rotating elements of the compressor 2 and turbine 6 parts. More specifically, a first shaft 10a carries the rotating elements of the high-pressure turbine 6a, and the rotating elements of the compressor part. 2, which is here a single high pressure compressor. The front end of the shaft 10a can be connected to any receiver of the turbomachine. In addition, a second shaft 10b, concentric with the first, carries the rotating elements of the low pressure turbine 6b. The front end of the shaft 10b can be connected to any receiver of the turbomachine. In a known manner, the expansion of the gases through the turbines 6a, 6b ensures the rotation of the shafts 10a, 10b, which are connected to the casing of the turbomachine by a plurality of bearings ensuring their support in rotation along the axis 8. One of the particularities of the present invention is the simultaneous use of rolling bearings and aerodynamic bearings, each having a design known to those skilled in the art. Rolling bearings, of the ball-bearing or roller type, are preferably arranged upstream of the high-pressure compressor 2, namely in the coldest part of the turbomachine, while the aerodynamic bearings are preferably arranged in line with the combustion chamber, or downstream thereof.

In the first preferred embodiment, two aerodynamic bearings 12 are arranged in line with the turbine part 6, preferably in the inter-turbine space delimited between the turbine 6a and the turbine 6b, each supporting one of the shafts 10a, 10b. As will be described with reference to FIG. 7, each of these bearings 12 can be arranged in an enclosure sealed with the aid of an air bleed from the high-pressure compressor 2. The sealing is then sought to avoid the ingestion of hot gas in the aerodynamic bearings. As an indication, one and the same sealed enclosure can combine the two bearings 12. In addition, there are two rolling bearings 14 upstream of the high pressure compressor 2, each supporting one of the shafts 10a, 10b, implying that each of these is carried by a rolling bearing at its front end ensuring the bulk of the recovery of the axial load, and an aerodynamic bearing at its rear end ensuring part of the recovery of the radial load.

For better optimization, the two bearings 14 are grouped together in the same lubricated sealed enclosure 16, generally with oil. Thus, they can advantageously share the same lubrication circuit (not shown), integrating, for example, a separator of the air / lubricant mixture, a pump system for recovering this mixture, and / or an air / lubricant heat exchange system. or fuel / lubricant. For an even better optimization, this chamber 16 is chosen to be one already incorporating a gearbox (not shown), dedicated to the operation of the turbomachine and having specific functions depending on the nature of the turbomachine concerned. It may for example be the reducer of a turbojet engine or a turboprop, the relay box of an auxiliary power unit, or the tapered bevel gear of a turbojet engine. In particular, one or more components can be mechanically connected to the output of this gearbox, itself driven by the shaft system 10. As component, it can for example be a starter, one or more generators, a main transmission shaft in the case of a turbine engine, fuel and lubrication pumps, an air / lubricant separator, or a low pressure compressor in the case of a turbofan engine. Naturally, it is envisaged the case where the gearbox drives one or more of these components by being placed in a chamber other than that housing the rolling bearings 14, and the case where one or more of these components are driven directly by the shaft system 10. In the second embodiment shown in Figure 2, the aerodynamic bearing 12 associated with the first shaft 10a has been moved to the right of the combustion chamber 4, that is to say said to be radially covered by it, while the aerodynamic bearing 12 associated with the second shaft 10b has been moved downstream of the low pressure turbine 6b.

In the third embodiment shown in FIG. 3, the aerodynamic bearing 12 associated with the first shaft 10a is arranged in line with the combustion chamber 4, while the aerodynamic bearing 12 associated with the second shaft 10b is arranged in the interstitial space. -turbines. In the fourth embodiment shown in FIG. 4, the aerodynamic bearing 12 associated with the first shaft 10a is arranged in the inter-turbine space, while the aerodynamic bearing 12 associated with the second shaft 10b is arranged downstream of the low turbine. pressure 6b. In the embodiments of FIGS. 5 and 6, the tree system actually comprises only one shaft 10, just as the turbine part has only one turbine 6, connected to the compressor 2 by the same shaft. 10. Therefore, only an aerodynamic bearing 12 and a rolling bearing 14 are provided to support the shaft 10 in rotation, respectively at its rear and front ends. More precisely, in the fifth embodiment shown in FIG. 5, the aerodynamic bearing 12 is arranged downstream of the turbine 6, whereas in the sixth embodiment shown in FIG. 6, the aerodynamic bearing 12 is arranged at the right 4. With reference to FIG. 7, an exemplary embodiment of a pressurized enclosure 20 housing one or more aerodynamic bearings 12 can be seen. To pressurize this non-lubricated enclosure, air is drawn at the compressor 2, through a pipe 22 which opens into the same chamber 20. The latter is delimited by one or more rotating joints 24, preferably of the labyrinth type. In the example of Figure 7, a first seal 24 is arranged upstream of the enclosure, while a second seal 24 is arranged downstream of this enclosure. An air flow then passes through the pipe 22 to enter the chamber 20. Next, a leakage flow through the dynamic seals 24, to escape to the outside of the enclosure 20. For s' ensure that the leakage rate is exerted well from the inside to the outside of the enclosure, and therefore to avoid ingestion of hot gas in the aerodynamic bearing 12, the air pressure in this chamber 20 is rendered greater than the pressure of the surrounding cavities upstream 28 and downstream 30, thanks to the pressure of the air from the pipe 22. Of course, various modifications may be made by those skilled in the art to the invention which has just been described, by way of non-limiting examples only.

Claims (7)

REVENDICATIONS1. Turbomachine (1) comprising a compressor part (2), a combustion chamber (4), a turbine part (6), at least one shaft (10, 10a, 10b) carrying the rotating elements of the compressor part and of the part turbine, as well as a plurality of bearings supporting said shaft, characterized in that said plurality of bearings comprises one or more aerodynamic bearings (12) and one or more rolling bearings (14), each of said one or more bearings with bearings (14) being arranged upstream of the combustion chamber (4), in a main flow direction of the gases (5) through the turbomachine. 2. A turbomachine (1) according to claim 1, characterized in that each of said one or more rolling bearings (14) is disposed upstream of the compressor part (2), in said main flow direction of the gases (5). ) through the turbomachine. 3. The turbomachine (1) according to claim 25 1 or claim 2, characterized in that said plurality of bearings comprises at least one rolling bearing (14) housed within a lubricated sealed enclosure (16) incorporating a box of gears of the turbomachine. 30 4. Turbomachine (1) according to any one of the preceding claims, characterized in that said plurality of bearings comprises at least two rolling bearings (14) housed in the same lubricated sealed enclosure (16). 5. Turbomachine (1) according to any one of the preceding claims, characterized in that it comprises one or two shafts (10, 10a, 10b) carrying the rotating elements of the compressor part and the turbine part. 6. Turbomachine (1) according to any one of the preceding claims, characterized in that it is a turbojet engine, a turboprop, a turbine engine, or an auxiliary power unit. 7. Turbomachine (1) according to any one of the preceding claims, characterized in that at least one aerodynamic bearing is placed in line with the combustion chamber, or in an inter-turbine space of the turbine part, or downstream this turbine part.