FLUID COOLING DEVICE FOR A TURBOMACHINE

Abstract

Device (70) for cooling a fluid for a turbomachine (10), the device comprising a heat exchanger (72) which comprises at least one internal conduit (78) for circulating the fluid, the heat exchanger (72) having at least one first wall (76) which is configured to carry out a heat exchange between the fluid and an air flow flowing at least partly around the first wall (76) of the heat exchanger (72), the cooling device (10) further comprising a heating element (80) thermally coupled to an external face of at least one second wall (74) of the heat exchanger (72). Abstract figure: Figure 1

Description

Title of the invention: DEVICE FOR COOLING A FLUID FOR A TURBOMACHINE Technical field

[0001] The present description relates to a device for cooling a fluid for a turbomachine. The present description also relates to a dual-flow turbomachine comprising such a cooling device and to an aircraft comprising such a dual-flow turbomachine. Prior art

[0002] Like all internal combustion engines, turbomachines, whether turbojets or turboprops, include moving parts that rub against other moving parts or against fixed parts.

[0003] To prevent them from breaking due to heating caused by friction, the parts are sprayed with oil which, on the one hand, limits (or contains) their heating and, on the other hand, lubricates them to facilitate the sliding of the parts over each other.

[0004] The oil is injected into a conduit (or conduits) of a heat exchanger arranged in a flow of cold air to be cooled before being re-injected onto said parts.

[0005] When starting a turbomachine in cold conditions (for example with a temperature below 0°C), the oil in the duct (or ducts where applicable) of the heat exchanger may have a high viscosity, or even be frozen, making heat exchange between the oil and the air difficult or even impossible since the oil cannot circulate in the duct of the heat exchanger. It is then necessary to preheat the oil in the duct of the air / oil heat exchanger.

[0006] For this, solutions, known as passive solutions, are known, consisting of increasing the passage section of the heat exchanger duct and / or providing the air / oil heat exchanger with a bypass duct serving as a defrosting channel and which surrounds the duct (or ducts where appropriate) of the heat exchanger so as to heat the frozen oil.

[0007] However, these solutions have the disadvantage of increasing the size and mass of the heat exchanger, leading to a reduction in the performance of the turbomachine. Furthermore, these passive solutions cannot be activated as needed.

[0008] Document US 2016 / 0090863 A1 describes a solution, called active, consisting of provide the exchanger with a pipe containing a supersaturated solution which is in a metastable state and which is adapted to produce an exothermic reaction following an increase in pressure initiated by a piston. The heat resulting from this reaction is transferred to the heat exchanger so as to heat the oil. However, this solution also has the disadvantage of increasing the mass and size of the heat exchanger. In addition, the exothermic reaction of the supersaturated solution can be initiated unintentionally due to external conditions (temperature, pressure) favorable to an increase in pressure of the supersaturated solution.

[0009] The purpose of the present description is to provide a solution for preventing the freezing of oil in a heat exchanger duct or for defrosting oil in a heat exchanger duct while making it possible to further reduce the mass and size of the heat exchanger. Summary

[0010] A device for cooling a fluid for a turbomachine is proposed, the device comprising a heat exchanger which comprises at least one internal fluid circulation conduit, the heat exchanger having at least a first wall which is configured to carry out a heat exchange between the fluid and an air flow flowing at least partly around the first wall of the exchanger, the cooling device further comprising a heating element thermally coupled to an external face of at least a second wall of the exchanger.

[0011] Such a heating element makes it possible to transfer heat to the fluid circulating in the internal duct by thermal conduction through the walls of the exchanger to allow either the fluid in the internal duct to be thawed, in particular before starting the turbomachine, or to prevent the fluid from freezing in the internal duct, in particular when the turbomachine is operating in an environment that is cold.

[0012] Such a heating element has the advantage of being adaptable to any type of heat exchanger. Also, with such a heating element, it is not necessary to modify the geometry of the heat exchanger (increasing the cross-section of the internal duct, adding a bypass duct or a duct containing a super-saturated solution in a metastable state) to avoid or prevent the freezing of the fluid. Thus, the cooling device can advantageously have a reduced mass and a small overall volume. The pressure losses of the air flow around the exchanger are also reduced, which is advantageous when it is an air flow from a turbomachine vein because this makes it possible to increase the performance of the turbomachine.

[0013] The fluid may be a turbomachine lubricating fluid, such as oil. The second wall of the heat exchanger may be opposite the first wall. The second wall may comprise several faces of the exchanger.

[0014] The heating element may be adapted to generate a heat input over a relatively long period, this heat input being able to be substantially constant. This thus makes it possible to maintain a low viscosity of the fluid circulating in the internal conduit, in particular when the turbomachine operates, or is parked, in an environment which is cold for a long period.

[0015] The heating element may be selectively controlled. Unlike passive heating solutions that are only activated when the temperature of the fluid in the internal conduit drops below a threshold temperature at which the cooling device exhibits reduced performance, the selectively controlled heating element may be activated at any time as required. In this sense, the selectively controlled heating element is an active heating solution. Thus, the heating element may, for example, be activated preventively, before the temperature of the fluid in the internal conduit of the heat exchanger drops to a point where the performance of the cooling device is reduced.

[0016] The activation of the heating element is thus independent of the operation of the cooling device. The heating element can also be activated while the fluid is in a state at rest in the internal conduit, i.e. in a state where it is not circulating. The heating element can thus be activated while the turbomachine is stopped, for example in anticipation of a programmed start.

[0017] The heating element may be servo-controlled to maintain a constant temperature or viscosity of the fluid within the internal conduit of the heat exchanger.

[0018] The heating element may comprise a heating wall arranged opposite or in support of, all or part of, the second wall of the heat exchanger. This improves the heat supply to the second wall of the heat exchanger.

[0019] The heating element may comprise at least one electrical resistor.

[0020] The heating element may comprise a pneumatic air circulation circuit hot.

[0021] The heat exchanger may extend annularly around a first axis extending in a first direction. Thus, the heat exchanger may be mounted on a turbomachine revolution part. In other words, the heat exchanger may have an arcuate shape around the first axis extending in a first direction. The heat exchanger may have an inlet and an outlet of said at least one internal conduit, the inlet and the outlet being, preferably, each located at a first end of the heat exchanger. Such an arrangement makes it possible to bring the inlet and the outlet of the internal conduit of the exchanger, thus allowing the installation of a safety bypass conduit which is space-saving. The heat exchanger may comprise a plurality of internal conduits.

[0022] The heat exchanger may comprise a plurality of fins extending from the first wall, in a radial direction if applicable. The fins may be regularly distributed around the first axis.

[0023] The cooling device may comprise a plurality of heat exchangers. The heat exchangers may be circumferentially arranged end to end about the first axis. More particularly, the cooling device may comprise two heat exchangers.

[0024] According to another aspect, a longitudinal axis dual flow turbomachine is proposed, the turbomachine comprising a primary annular air flow vein and a secondary annular air flow vein, the secondary annular vein being located coaxially around the primary annular vein, the turbomachine comprising a cooling device as described above, the heat exchanger being arranged, in whole or in part, in the secondary annular vein to carry out a heat exchange between the fluid circulating in the internal duct and the air flow of the secondary annular vein.

[0025] The heat exchanger of the cooling device may be attached to an inner annular wall radially inwardly delimiting the secondary annular vein, the heating element being arranged radially between the inner annular wall and the heat exchanger.

[0026] The annular air flow surface may radially delimit the secondary annular vein on the inside. The heating element may be arranged radially between the annular air flow surface and a radially inner face of the heat exchanger.

[0027] The annular air flow surface may radially delimit the secondary annular vein on the outside. The heating element may be arranged radially between the annular air flow surface and a radially outer face of the heat exchanger.

[0028] According to another aspect, there is provided an aircraft comprising a turbomachine as described above, in which the heating element of the cooling device is electrically connected to an auxiliary power unit of the aircraft or to an installation for electrically connecting the aircraft to an airport network. Brief description of the drawings

[0029] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0030] [Fig.l] is a partial schematic sectional view of a turbomachine comprising a device for cooling a fluid;

[0031] [Fig.2] is a schematic perspective view of a heat exchanger of the cooling device of [Fig.l];

[0032] [Fig.3] is a partial schematic sectional view of a first embodiment of the cooling device of [Fig.l];

[0033] [Fig.4] is a partial schematic sectional view of a second embodiment of the cooling device of [Fig.l]. Description of the embodiments

[0034] Reference is now made to [Fig.l]. [Fig.l] represents a turbomachine 10 of the double-flow turbojet type which comprises, from upstream to downstream in the direction of circulation of the gases inside the turbomachine 10, a fan 16, a low-pressure compressor 34, a high-pressure compressor 36, a combustion chamber 38, a high-pressure turbine 42, a low-pressure turbine 40 and an exhaust nozzle 44. An intermediate casing 18 comprises two cylindrical and coaxial shells, respectively an inner shell 20 and an outer shell 24, which are connected to each other by structural arms or radial blades 22 of a flow straightener.

[0035] Each of the fan 16, the low-pressure compressor 34, the high-pressure compressor 36, the high-pressure turbine 42 and the low-pressure turbine 40 comprises a rotor rotatable about a longitudinal axis X of the turbomachine 10. In the following, the orientation qualifiers, such as “longitudinal”, “radial” or “circumferential”, are defined with reference to the longitudinal axis X. The fan 16, the low-pressure compressor 34 and the low-pressure turbine 40 are capable of being rotated together by a first shaft 46 extending in the direction of the longitudinal axis X of the turbomachine 10. Similarly, the high-pressure compressor 36 and the high-pressure turbine 42 are capable of being rotated together by a second shaft 48 extending in the direction of the longitudinal axis X of the turbomachine 10.

[0036] The fan 16 comprises a plurality of fan blades 16 which are fixed at their radially internal ends on the periphery of a fan disc of the turbomachine 10, which is itself fixed at the upstream end of the first shaft 46. The fan blades 16 are surrounded externally by a casing 14 of the fan 16 mounted at the upstream end of a nacelle 12 which is substantially cylindrical.

[0037] This casing 14 of the fan 16 makes it possible to channel the incoming air flow F into the turbomachine 10. A part of this air flow, forming the primary flow Fp or hot flow, engages in a primary annular air flow vein 52. The primary flow Fp successively enters the low pressure compressor 34, the high pressure compressor 36, then is mixed with fuel and burned in the combustion chamber 38. The gases resulting from the combustion are then injected into the high pressure turbine 42 and the low pressure turbine 40 in order to provide energy to the rotor blades of the turbines and drive the first and second shafts 48 in rotation. A radially internal annular face of the internal shell 20 of the intermediate casing 18 delimits the primary annular vein 52 radially on the outside. The radially internal annular face of the intermediate casing 18 defines an annular air flow surface of the primary annular vein 52.

[0038] The other part of the air flow entering the turbomachine 10 forms the secondary flow Fs or cold flow. The secondary flow Fs engages in a secondary annular air flow vein 54. The secondary annular vein 54 is located coaxially around the primary annular vein 52. The secondary annular vein 54 is delimited, radially on the inside upstream, by a radially external annular face of the internal shell 20 of the intermediate casing 18. The secondary annular vein 54 is also delimited, radially on the inside downstream, by a radially external annular face of an internal annular wall 28 of an external annular fan duct 26. The internal annular wall 28 is formed by a cowling of an inter-vein compartment located between the primary vein and the secondary vein of the turbomachine. This cowling 28 is sometimes called IFD for “Inner Fan Duct” in English.The radially outer annular face of the inner shell 20 of the intermediate casing 18 and the radially outer annular face of the inner annular wall 28 of the outer fan duct 26 each define an annular air flow surface of the secondary annular vein 54, in this case radially inside.

[0039] The outer fan duct 26 is delimited radially on the outside by an outer annular wall 30 (sometimes called OFD for “Outer Fan Duct” in English) which is fixed at its upstream end to the downstream end of the outer shell 24 of the intermediate casing 18. The secondary annular vein 54 is delimited, radially on the outside, by a radially internal face of the outer shell 24 upstream and, downstream, by a radially internal face of the outer annular wall 30 of the outer fan duct 26. The radially internal face of the outer shell 24 and the radially internal face of the outer annular wall 30 of the outer fan duct 26 each define an annular air flow surface of the secondary annular vein 54, in this case radially on the outside. The secondary airflow provides additional thrust in addition to that provided by the combustion gases ejected from the turbines.Cold air from the secondary flow Fs can also be used. for cooling, for example, fluid circuits, such as lubricating fluids (such as oil for example), fuel or hot air, generally using a cooling device 70 as will be described in more detail below.

[0040] The turbomachine 10 comprises a fluid cooling device 70. The cooling device 70 firstly comprises a heat exchanger 72. An example of a heat exchanger 72 is shown in [Fig. 2]. The heat exchanger 72 extends annularly around the longitudinal axis X. It is understood here that the heat exchanger 72 has an arcuate shape around the longitudinal axis X. According to the example shown, the heat exchanger 72 extends over an angular sector of less than 180°. Alternatively, the heat exchanger 72 may extend over an angular sector of greater than 180°. According to the example shown, the heat exchanger 72 is fixed to the inner annular wall 28 of the outer fan duct 26.

[0041] Optionally, the cooling device 70 may comprise a plurality of heat exchangers. The heat exchangers may be arranged circumferentially end to end around the longitudinal axis X. More particularly, the cooling device 70 may comprise two heat exchangers.

[0042] The heat exchanger 72 comprises at least one internal conduit 78 for circulating the fluid. According to the example shown, the heat exchanger 72 here comprises an internal conduit 78. The heat exchanger 72 has an inlet orifice 79a and an outlet orifice 79b of the internal conduit 78. The inlet orifice 79a and the outlet orifice 79b are each located at a first circumferential end of the heat exchanger 72. Such an arrangement makes it possible to bring the inlet and outlet of the internal conduit 78 closer to the exchanger, thus allowing the installation of a safety bypass conduit (not shown) between the inlet orifice 79a and the outlet orifice 79b which has the advantage of being space-saving. Here, the internal conduit 78 forms a loop. Alternatively, it may be provided that the inlet orifice 79a and the outlet orifice 79b are each disposed at a respective circumferential end of the heat exchanger 72.

[0043] Optionally, the exchanger may comprise a plurality of internal conduits, preferably parallel to each other. A heat exchanger 72 comprising a plurality of internal conduits is shown in Figures 3 and 4.

[0044] In the example illustrated in [Fig. 1], the heat exchanger 72 is fixed to an annular air flow surface which radially delimits the secondary annular vein 54 on the inside. In particular, the heat exchanger 72 of the cooling device 70 is here fixed to the inner annular wall 28 of the outer blower duct 26, the latter defining an annular air flow surface of the secondary annular vein 54 as described previously. According to the example re shown, the heat exchanger 72 is attached to the inner annular wall 28 of the outer blower duct 26 at a radially inner wall 74.

[0045] The heat exchanger 72 furthermore has at least one first wall which is configured to carry out a heat exchange between the fluid and the air flow of the secondary annular vein 54 which flows around the first wall of the exchanger. The first wall is here a radially external wall 76 of the heat exchanger 72.

[0046] As shown in Figures 3 and 4, the cooling device 70 further comprises a heating element 80 thermally coupled to an outer face of the radially inner wall 74 of the exchanger. The heating element 80 is thus arranged radially between the inner annular wall 28 of the outer blower duct 26 and the heat exchanger 72. The heating element 80 may be attached to the heat exchanger and / or to the inner annular wall 28 of the outer blower duct 26.

[0047] Such a heating element 80 makes it possible to transfer heat to the fluid in the internal duct 78 by thermal conduction through the walls of the exchanger to allow either the fluid in the internal duct 78 to be thawed, in particular before the turbomachine 10 is started, or to prevent the fluid from freezing in the internal duct 78, in particular when the turbomachine 10 is operating in an environment that is cold.

[0048] In particular, the element is thermally coupled to an external face of the heat element. The term "external face" is used in opposition to an internal face of the exchanger which delimits the internal conduit 78. Thus, such a heating element 80 has the advantage of being adaptable to any type of heat exchanger 72. Also, with such a heating element 80, it is not necessary to modify the geometry of the heat exchanger 72 (increasing the cross-section of the internal conduit 78, adding a bypass conduit or a conduit containing a super-saturated solution in a metastable state, for example) to avoid or prevent the freezing of the fluid. Thus, the cooling device 70 can advantageously have a reduced mass and a small overall volume. The pressure losses of the air flow around the heat exchanger 72 are also reduced, which is advantageous because it makes it possible to increase the performance of the turbomachine 10.

[0049] The heating element 80 comprises a heating wall 82 arranged to bear on the radially internal wall 74 of the heat exchanger 72. This increases the heat supply to the heat exchanger 72. The heat transfer by thermal conduction between the heating element 80 and the fluid circulating in the internal conduit 78 of the heat exchanger 72 is, overall, carried out through the radially internal wall 74 of the heat exchanger 72.

[0050] According to a first embodiment shown in [Fig.3], the heating element 80 comprises an electrical resistance 86 which is here embedded in the heating wall 82.

[0051] According to a second embodiment shown in [Fig. 4], the heating element 80 comprises a pneumatic hot air circulation circuit 90 internal to the heating wall 82. For this purpose, the heating element 80 may comprise a heating resistor associated with a means for driving the hot air, such as a fan 88 for example. Alternatively, the hot air may be taken from the high-pressure turbine 42 or the low-pressure turbine 40 and be conveyed to the pneumatic circuit of the heating element 80. In the case of an aircraft comprising two turbomachines, the hot air may be taken from a first turbomachine in operation, for example from a compressor stage, to be conveyed to the heating element 80 of the heat exchanger 72 of the second turbomachine, the latter possibly being stopped for example.Alternatively, the hot air may be supplied by an airport compressed air network, particularly when the aircraft on which the turbomachine is mounted is on the ground. The heating element may be a combination of the first embodiment and the second embodiment.

[0052] As shown in Figures 3 and 4, the heating element 80 of the cooling device 70 is, in each of the first and second embodiments, electrically connected to an auxiliary power unit 84 (APU) of the aircraft on which the turbomachine 10 is installed. Alternatively, the heating element 80 of the cooling device 70 may be electrically connected to an installation for electrically connecting the aircraft to an airport electrical network. Alternatively again, in the case of the second embodiment, the hot air may be supplied by an auxiliary power unit which is adapted to supply pneumatic power. Such an auxiliary power unit is known and will not be detailed here.

[0053] According to both embodiments, the heating element 80 is adapted to generate a continuous supply of heat. In other words, the heating element is adapted to generate a supply of heat over a relatively long period, this supply of heat being able to be substantially constant. This thus makes it possible to maintain a low viscosity of the fluid in the internal conduit 78, in particular when the turbomachine 10 operates, or is parked, in a usage environment which is cold for a long period.

[0054] According to both embodiments, the heating element 80 is selectively controlled. Unlike passive heating solutions which are only activated when the turbomachine is started and when the temperature of the fluid in the internal conduit 78 is below a threshold temperature in which the cooling device 70 has reduced performance, the heating element 80 is selectively controlled. selective control can be activated at any time as required, and in particular before the turbomachine is started. The heating element 80 can thus be activated while the turbomachine 10 is stopped, while the fluid is at rest in the circulation duct, for example in anticipation of a scheduled start in cold weather. In this sense, the selectively controlled heating element 80 is an active heating solution. Thus, the heating element 80 can, for example, be activated preventively before the temperature of the fluid in the internal duct 78 of the heat exchanger 72 drops to a point where the performance of the cooling device 70 is reduced. The activation of the heating element 80 is thus independent of the operation of the cooling device 70.The heat output delivered by the heating element 80 can be controlled to maintain a constant temperature or viscosity of the fluid inside the internal conduit 78 of the heat exchanger 72.

[0055] Furthermore, it is possible to activate the heating element 80 even after the turbomachine has started so as to heat the oil more quickly, and also the fuel thanks to the heat exchanges with the oil. The operational advantages in cold weather are then twofold. On the one hand, the minimum oil temperature required to allow acceleration of the engine at full throttle, for example between 15°C and 20°C, is reached more quickly. On the other hand, the maneuvers of the aircraft during taxiing can be carried out with the heating element 80 activated, thus making it possible to limit or even prevent icing of the water contained in the fuel during takeoff.

[0056] The heating element 80 can be activated either before or after the start of the aircraft's turbomachine(s). In both cases, this allows the aircraft to take off after a shorter turbomachine warm-up time. Current aircraft comprising two turbomachines generally use only one of the turbomachines for taxiing; the heating element of the other turbomachine that is stopped can be activated to allow the oil of this stopped turbomachine to be heated during taxiing before takeoff, thus reducing the waiting time before takeoff due to preheating of the turbomachines.

[0057] The invention is not limited to the examples described above and is susceptible to numerous variants.

[0058] According to a variant not shown, the heat exchanger 72 can be arranged in the secondary annular vein 54 by being fixed to the internal shell 20 of the intermediate casing 18. In this configuration, the heating element 80 is arranged radially between the internal shell 20 of the intermediate casing 18 and the heat exchanger 72.

[0059] According to a variant not shown, the heat exchanger 72 can be fixed to a annular air flow surface radially delimiting the secondary annular vein 54 on the outside. In particular, the heat exchanger 72 can be arranged in the secondary annular vein 54 by being fixed to the outer shell 24 of the intermediate casing 18 or to the outer annular wall of the external blower duct 26. The heat exchange then takes place at a radially internal wall of the heat exchanger 72. In these configurations, the heating element 80 is arranged radially respectively between the outer shell 24 of the intermediate casing 18 and the heat exchanger 72 and between the outer annular wall of the external blower duct 26 and the heat exchanger 72.

[0060] According to a variant not shown, the heat exchanger 72 may comprise a plurality of fins extending from the first wall configured to carry out a heat exchange between the fluid and the air. The fins may each extend radially. The fins may be regularly distributed around the longitudinal axis.

[0061] According to a variant not shown, the heating element 80 can be thermally coupled to a plurality of walls of the heat exchanger 72. In other words, the heating element 80 can partially cover the heat exchanger 72. According to the configuration of the example shown in [Fig. 1], it can be provided that the heating element 80 is, in addition, in support or facing the upstream wall and / or the downstream wall of the heat exchanger 72.

Claims

Claims

1. A device (70) for cooling a fluid for a turbomachine (10), the device comprising a heat exchanger (72) which comprises at least one internal conduit (78) for circulating the fluid, the heat exchanger (72) having at least one first wall (76) which is configured to carry out a heat exchange between the fluid and an air flow flowing at least partly around the first wall (76) of the heat exchanger (72), the cooling device (10) further comprising a heating element (80) thermally coupled to an external face of at least one second wall (74) of the heat exchanger (72), the second wall of the heat exchanger being opposite the first wall, and in which the heating element is configured to be activated independently of the circulation of the fluid in the internal conduit of the exchanger,the heating element being adapted to transfer heat to the fluid circulating in the internal conduit by thermal conduction through the walls of the exchanger.,

2. A cooling device (70) according to claim 1, wherein the fluid is a turbomachine lubricating fluid.

3. A cooling device (70) according to claim 1 or 2, wherein the heating element (80) is selectively controllable.

4. Cooling device (70) according to any one of the preceding claims, in which the heating element (80) comprises a heating wall (82) arranged opposite or in abutment with, all or part of, the second wall (74) of the heat exchanger (72).

5. Cooling device (70) according to any one of the preceding claims, wherein the heating element (80) comprises at least one electrical resistor (86).

6. A cooling device (70) according to any preceding claim, wherein the heating element (80) comprises a pneumatic hot air circulation circuit (90).

7. A cooling device (70) according to any preceding claim, wherein the heat exchanger (72) extends annularly about a first axis extending in a first direction.

8. Turbomachine (10) with double flow of longitudinal axis (X), the turbomachine (10) comprising a primary annular vein (52) air flow and a secondary annular air flow vein (54), the secondary annular air flow vein (54) being located coaxially around the primary annular air flow vein (52), the turbomachine (10) comprising a cooling device (70) according to any one of the preceding claims, the heat exchanger (72) being arranged, in whole or in part, in the secondary annular air flow vein (54) to carry out a heat exchange between the fluid circulating in the internal duct (78) and the air flow of the secondary annular air flow vein (54).

9. Turbomachine according to claim 8, claim 7 applying, the heat exchanger (72) of the cooling device (70) being fixed to an internal annular wall (28) delimiting radially inwards the secondary annular vein (54), the heating element (80) being arranged radially between the internal annular wall (28) and the heat exchanger (72).

10. Aircraft comprising a turbomachine according to claim 8 or 9, wherein the heating element (80) of the cooling device (70) is electrically connected to an auxiliary power unit (84) of the aircraft or to an installation for electrically connecting the aircraft to an airport network.

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