AIRCRAFT TURBOMACHINE WITH A HEAT TRANSFER FLUID CIRCUIT

Abstract

A turbomachine comprising a heat transfer fluid circuit (2) which includes: a heat transfer fluid circulation loop (3) with a first volume of heat transfer fluid, a circulation line (4) of another fluid, a heat exchanger (5) between said heat transfer fluid of said loop and said other fluid of said line, and an expansion vessel (6), connected to said first loop, having a second volume of heat transfer fluid which is refillable, said second volume comprising a first sub-volume and a second sub-volume of heat transfer fluid, said first sub-volume being intended to compensate for a pressure variation in said loop, and said second sub-volume being intended to compensate for a loss of heat transfer fluid in said loop, such that a compensated volume corresponding to said loss in said loop is at least equal to the first volume. Figure for the abbreviation: Figure 2

Description

Title of the invention: AIRCRAFT TURBOMACHINE COMPRISING A HEAT TRANSFER FLUID CIRCUIT Technical field of the invention

[0001] The present invention relates to an aircraft turbomachine comprising a heat transfer fluid circuit equipped, in particular, with an expansion tank. The invention also relates to a method for maintaining the turbomachine comprising this heat transfer fluid circuit. Technological background

[0002] An aircraft turbomachine equipped with at least one heat transfer fluid circuit is well known in the prior art. Conventionally, the heat transfer fluid circulates in one or more loops in order to transfer or receive heat to various components of the turbomachine.

[0003] In any heat transfer fluid circuit or loop, fluid leaks can occur, primarily at the connections of the various components linked to the heat transfer fluid circulation loop. These leaks lead to a decrease in the volume of heat transfer fluid in the loop. This decrease in volume, in turn, results in a drop in pressure within the loop, causing the loop to deviate from its nominal operating point. This malfunction can lead to equipment damage if the heat transfer fluid level does not return to its initial level in the loop.

[0004] Conventionally, pressure variations in a fluid loop - which are linked to temperature variations - are compensated by the installation of an expansion vessel which allows the fluid to contract or expand in the loop so that the pressure in the loop remains substantially constant to maintain its performance level.

[0005] To prevent leaks, or failing that, to minimize them, high-sealing gaskets or gasket systems can be used. However, these gaskets or gasket systems may be expensive and / or poorly suited to the constraints of a heat transfer fluid circulation circuit in a turbomachine.

[0006] Also, an objective of the invention is to propose a turbomachine comprising a heat transfer fluid circulation circuit which does not present at least one of the aforementioned disadvantages.

[0007] Another objective of the invention is to avoid constraining the time between two maintenances to compensate for leaks by filling the loop.

[0008] Another objective of the invention is to optimize the performance of the heat transfer fluid circulation loop in the turbomachine. Summary of the invention

[0009] An aircraft turbomachine is therefore proposed comprising a heat transfer fluid circuit, this circuit comprising at least: - a heat transfer fluid circulation loop which has a given initial volume of heat transfer fluid, - a circulation line for another fluid, - a heat exchanger, known as a dual-fluid exchanger, configured to exchange heat between the heat transfer fluid of the circulation loop and the other fluid of the circulation line, and - an expansion vessel connected to the first loop, the expansion vessel containing a second volume of heat transfer fluid which is refillable, the second volume comprising a first sub-volume and a second sub-volume of heat transfer fluid, the first sub-volume of heat transfer fluid being intended to compensate for a pressure variation within the heat transfer fluid circulation loop, and the second sub-volume being intended to compensate for a loss of heat transfer fluid from the first given volume within the circulation loop, so that a compensated volume corresponding to the loss of heat transfer fluid by the first given volume of heat transfer fluid within the circulation loop is at least equal to the first given volume.

[0010] Thus, thanks to the invention, the performance of the heat transfer fluid circulation loop, and by extension that of the turbomachine, is optimized. Indeed, heat transfer fluid losses due to leaks are compensated by the second sub-volume of heat transfer fluid present in the expansion vessel, without the first sub-volume of heat transfer fluid, intended to compensate for pressure variations in the loop, being used. In this way, the initial volume of heat transfer fluid in the loop is kept to a minimum so that the turbomachine's circulation circuit maintains optimal operation.

[0011] The turbomachine according to the invention may comprise one or more of the characteristics below, taken individually or in combination with each other: - the heat transfer fluid circuit includes a second heat exchanger, called a nozzle exchanger, configured to recover heat at the level of an ejection of an airflow from the turbomachine; - the other fluid in the circulation line is hydrogen or a hydrogen-based mixture; - the turbomachine having a combustion chamber, the circulation line is connected to this combustion chamber; - the circulation line of the other fluid is a closed circulation loop.

[0012] The invention also relates to an aircraft comprising at least one turbomachine as described above.

[0013] The invention also relates to a method for maintaining a heat transfer fluid circuit of a turbomachine as described above, the method comprising the following steps: - fill the circulation loop with a first given volume of heat transfer fluid; - fill the expansion vessel, connected to the loop, with an initial sub-volume; and - fill said expansion vessel with a second sub-volume so that the second sub-volume compensates, in operation, for a loss of heat transfer fluid inside the circulation loop.

[0014] The turbomachine according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - the second sub-volume is equal to a nominal volume of heat transfer fluid lost by the circulation loop in a given time; - the second sub-volume is greater than a nominal volume of heat transfer fluid lost by the circulation loop in a given time; - the second sub-volume is less than a nominal volume of heat transfer fluid lost by the circulation loop in a given time; - the process includes a preliminary step of estimating the heat transfer fluid losses in the circulation loop in order to delay maintenance of the expansion vessel, this preliminary step comprising the following sub-steps: determining, in a given time, a volume of heat transfer fluid losses; and determining a second sub-volume greater than the volume of heat transfer fluid losses. Brief description of the figures

[0015] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0016] Figure [1] represents a schematic view of an aircraft turbomachine,

[0017] Figure 2 shows a schematic view of an example of a circuit implementation of heat transfer fluid for a turbomachine according to the invention,

[0018] Figure 3 represents a schematic view of a conventional expansion vessel as known,

[0019] Figure 4 represents a schematic view of the expansion vessel according to the invention, particularly in an initial state, before use.

[0020] Figure 5 shows a schematic view of the expansion vessel of Figure 4, particularly when, during operation, the circulation loop loses heat transfer fluid.

[0021] Figure 6 shows a schematic view of another embodiment of the expansion vessel according to the invention,

[0022] Figure 7 represents a schematic view of another embodiment of the expansion vessel according to the invention,

[0023] Fig. 8 represents a block diagram of a maintenance method for a heat transfer fluid circuit of a turbomachine according to the invention. Detailed description of the invention

[0024] Figure 1 shows an example of an aircraft turbomachine comprising a heat transfer fluid circuit. In this example, the turbomachine is a dual-flow, dual-spool type. The dual-flow turbomachine 1 comprises, successively in the direction of airflow, i.e., from upstream to downstream, an air inlet 10 and a fan 11, which delivers air on the one hand into a primary duct 12 and on the other hand into a secondary duct 13. By "duct" is meant the volume through which an airflow passes.

[0025] The airflow circulating in the primary vein 12 passes successively through a low pressure compressor 14a, a high pressure compressor 14b, a combustion chamber 15, a high pressure turbine 16a and a low pressure turbine 16b, before being ejected through a primary airflow nozzle 120.

[0026] Furthermore, the secondary airflow circulating in the secondary vein 13 is ejected separately through a secondary flow nozzle 130, after passing through a series of guide vanes 131.

[0027] Figure 2 shows the heat transfer fluid circuit 2 which is included in the turbomachine 1 as described above. It should be noted that the turbomachine 1 may be of another type, for example a single-shaft turbomachine or a turbomachine comprising only one compressor and one turbine.

[0028] In [Fig.2], the heat transfer fluid circuit 2 comprises at least a first loop 3 for circulating a heat transfer fluid, a line 4 for circulating another fluid, a heat exchanger 5 configured to exchange heat between the first loop 3 and line 4 and an expansion vessel connected 6 to the first loop 3.

[0029] The first loop 3 is closed. The first loop 3 is designed to receive a first given volume VI of heat transfer fluid. This first volume V1 is substantially equivalent to the intrinsic volume of the first loop 3. The first loop 3 may include at least one pump 8A to circulate the heat transfer fluid through the first loop 3.

[0030] . In the example of [Fig.2], the circulation line 4 of the other fluid is a closed circulation loop, called the second circulation loop. The second circulation loop for the other fluid may include at least one other 8B pump to drive the other fluid.

[0031] Alternatively, not shown, the circulation line 4 of the other fluid can be open. In such a case, the circulation line 4 connects one element of the turbomachine to another, for example a tank to an engine.

[0032] The heat exchanger 5 between loop 3 and line 4 is a so-called two-fluid exchanger. Preferably, the direction of flow of the fluid in line 4 is opposite to the direction of flow of the heat transfer fluid in loop 3.

[0033] It is known that the heat transfer fluid of the first loop 3, when subjected to temperature variations, will have its pressure modified and will tend to expand or contract.

[0034] To compensate for this pressure variation, an expansion vessel is connected to the first loop 3. A conventional expansion vessel EX is shown in [Fig. 3]. The expansion vessel EX has a second volume V'2 of heat transfer fluid. In practice, the second volume V'2 partially occupies the intrinsic volume of the expansion vessel EX, so that one part of the expansion vessel EX is occupied by the second volume V'2 and the other part is filled with air 9 (or a gas), which can be compressed. In operation, the heat transfer fluid from the second volume V'2 can fill the first loop 3 when the heat transfer fluid in the first loop 3 has a contracted volume VI. Conversely, when the heat transfer fluid in the first loop 3 expands and occupies an expanded volume VI', the difference in heat transfer fluid volume is absorbed by the expansion vessel EX.

[0035] With reference to Figures 4 to 7, according to the invention, the expansion vessel 6, which is connected to the first loop 3, is similar to a conventional expansion vessel EX. The expansion vessel 6 according to the invention has a second volume V2 of heat transfer fluid. This second volume V2 of heat transfer fluid is refillable. The second volume V2 comprises a first sub-volume V3 and a second sub-volume V4, V4', V4" of heat transfer fluid.

[0036] The first sub-volume V3 is configured to compensate for the pressure variation inside the first loop 3. In other words, the first fluid sub-volume V3 heat transfer fluid has an identical role to the second volume V'2 described previously for a classic expansion vessel EX.

[0037] The second sub-volume V4, V4', V4” of heat transfer fluid is intended to compensate for a loss of heat transfer fluid from the first volume V1 in the first loop 3. This loss of heat transfer fluid is generally due to leaks at the various connections between the different elements composing the first loop 3. These leaks are quantifiable and can be determined upstream during the design of the circuit 2. In other words, the second sub-volume V4, V4', V4” is a sacrificial volume at least equal to the maximum volume of heat transfer fluid losses. Figures 4 and 5 illustrate the drop in the heat transfer fluid level in the expansion vessel, and therefore the loss of heat transfer fluid in the first loop 3. [Fig. 4] shows a given initial second sub-volume V4 in an expansion vessel 6, for example before start-up. [Fig.[5] shows the same expansion vessel 6 during or after the operation of the circuit when the second sub-volume V4 has been used to compensate for leaks and only a residual second sub-volume V4f remains.

[0038] Thus, a so-called compensated volume Vc, which corresponds to the loss of heat transfer fluid from the first volume VI inside the first loop 3, is at least equal to the initial given volume VI. In other words, during operation, the first given volume V1 remains at least substantially constant because it is compensated by the first sub-volume V3 during a pressure variation and / or by the second sub-volumes V4, V4', V4" during heat transfer fluid losses due to leaks.

[0039] Advantageously, the circuit 2 includes a second heat exchanger 7 between the heat transfer fluid of the first loop 3 and the outlet airflow of the nozzle 120. This outlet airflow is conventionally exhaust gas taken from the outlet of the nozzle 120, i.e., the primary runner nozzle. In other words, the outlet airflow is a hot airflow. The heat exchanger 7 is connected to the nozzle 120 so that the hot air circulates inside the heat exchanger 7, counter-current to the heat transfer fluid circulating in the first loop 3. After supplying heat to the heat transfer fluid, the hot airflow is discharged into the atmosphere via the downstream part of the nozzle 120.

[0040] Circuit 2 may include one or more other heat exchangers, not shown, between the heat transfer fluid and other elements and / or loops of the turbomachine 1.

[0041] The other fluid in line 4 can be a fluid in the liquid state or in the gaseous state.

[0042] Advantageously, this other fluid is hydrogen or a hydrogen-based mixture. The hydrogen or the hydrogen-based mixture can be used as fuel for the turbomachine 1. In such a case, the line 4 can be connected to the combustion chamber 15 of the turbomachine 1. This is then referred to as an open loop.

[0043] It is also preferred, when the other fluid contains hydrogen, that the pressure inside the first loop 3 be greater than or equal to the pressure of line 4. This ensures the safety of the system.

[0044] The invention also relates to an aircraft which includes at least one turbomachine 1 as described above.

[0045] The invention further relates to a method 200 for maintaining a heat transfer fluid circuit 2 of the turbomachine 1 as described above. The method comprises the steps detailed below.

[0046] At a step 202, the first loop 3 is filled with a first given volume V1 of heat transfer fluid. Preferably, the first given volume V1 is substantially equal to, or at least equal to, the intrinsic volume of the first loop 3.

[0047] At a step 204, the expansion vessel is filled with a first sub-volume V3. The first sub-volume V3 is predetermined to correspond to the variations in volume of the heat transfer fluid as a function of pressure in the first loop 3.

[0048] At a step 206, the expansion vessel 6 is filled with a second sub-volume V4, V4', V4”.

[0049] As described previously, losses of heat transfer fluid may occur. These losses are mainly due to leaks between the various connections of the first loop 3. A nominal volume Vn of heat transfer fluid lost by the first loop 3 over a given time is defined. The given time is understood to be the time tl defined between two maintenance operations of the expansion vessel 6 to compensate for the losses.

[0050] Also, prior to step 206, the nominal volume Vn of the heat transfer fluid can be determined. It can be determined by numerical simulation or by direct measurements on a test bench, for example.

[0051] Thus in step 206, the second sub-volume V4 is predetermined to correspond to a loss of heat transfer fluid inside the first loop 3 during the operation of the circuit.

[0052] The process 200 may include a preliminary step of estimating the losses in heat transfer fluid in the first circulation loop 3 in order to delay maintenance of the expansion vessel 6, this preliminary step including the following substeps.

[0053] In a first sub-step, a volume of heat transfer fluid losses is determined in a given time.

[0054] In a second sub-step, a second sub-volume V4' is determined so as to be greater than the volume of heat transfer fluid losses determined in the first sub-step.

[0055] In practice, depending on the needs or the performance sought for the system, maintenance for elements other than the expansion vessel 6 may be planned. A time t2 is then defined, corresponding to the time between two maintenances for these other needs.

[0056] In one embodiment, at step 206, the second sub-volume V4 is at least equal to the nominal volume Vn. In such a case, maintenance of the expansion vessel 6 is the only maintenance required.

[0057] In one variant, at step 206, the second sub-volume V4' is greater than the nominal volume Vn. In such a case, the time t1 is greater than the time t2, i.e., maintenance for another need occurs before the maintenance of the expansion vessel 6. Thanks to the second sub-volume V4' being greater than the nominal volume Vn, an increase in the time between maintenance of the expansion vessel 6 is ensured, making it possible to ensure optimal operation of the circuit 2 for a longer period.

[0058] In another variant, at step 206, the second sub-volume V4” is less than the nominal volume Vn. In such a case, the time t1 is less than the time t2, i.e., maintenance for another need occurs after the maintenance of the expansion vessel 6. Thanks to the second sub-volume V4” being less than the nominal volume Vn, optimal operation of the circuit 2 is ensured, adjusted to the period considered.

[0059] Thus, it is understood that V4'' is less than V4 and that V4' is greater than V4.

[0060] In light of the foregoing, the invention offers the advantage of optimizing the performance of the heat transfer fluid circulation loop and, by extension, of the turbomachine. Indeed, heat transfer fluid losses due to leaks are compensated by the second sub-volume of heat transfer fluid present in the expansion vessel, without requiring the first sub-volume of heat transfer fluid, intended to compensate for pressure variations in the first loop, to be used. In this way, the initial volume of heat transfer fluid in the first loop is kept to a minimum so that the turbomachine circulation circuit maintains optimal operation.

[0061] Another advantage of the invention is to allow better integration of leak compensation in the heat transfer fluid loop without having to add new equipment.

[0062] Another advantage of the invention is that it allows the use of less complex and / or less high-tech seals. Since leaks are compensated, minimizing them as much as possible becomes secondary. In other words, the invention allows for a tolerance in the level of heat transfer fluid leaks. Thus, it is possible to use less expensive seals.

Claims

Demands

1. Aircraft turbomachine (1) comprising a heat transfer fluid circuit (2), said circuit comprising at least: - a heat transfer fluid circulation loop (3) having a first given volume (VI) of heat transfer fluid, - a circulation line (4) of another fluid, - a heat exchanger (5), said to be a two-fluid exchanger, configured to exchange heat between the heat transfer fluid of said loop and the other fluid of said line, and - an expansion vessel (6) connected to the first loop, said expansion vessel having a second volume (V2) of heat transfer fluid which is refillable, characterized in that said second volume comprises a first sub-volume (V3) and a second sub-volume (V4, V4', V4") of heat transfer fluid, said first sub-volume of heat transfer fluid being intended to compensate for a pressure variation within said heat transfer fluid circulation loop,and said second sub-volume being intended to compensate for a loss of heat transfer fluid from said first volume inside said loop (3), so that a compensated volume (Vc) corresponding to said loss of heat transfer fluid by the first volume of heat transfer fluid inside said loop (3) is at least equal to the first given volume (VI).

2. Turbomachine (1) according to claim 1, wherein said circuit includes a second heat exchanger (7), referred to as nozzle exchanger, configured to recover heat at the level of an ejection of an airflow (120) from the turbomachine.

3. Turbomachine (1) according to any one of claims 1 or 2, wherein said other fluid of the circulation line (4) is hydrogen or a hydrogen-based mixture.

4. Turbomachine (1) according to claim 3, comprising a combustion chamber (15), said circulation line (4) is connected to said combustion chamber (15).

5. Turbomachine (1) according to any one of claims 1 to 3, wherein said other fluid circulation line (4) is a closed circulation loop.

6. Aircraft comprising at least one turbomachine according to any one of claims 1 to 5.

7. Method (200) of maintaining a heat transfer fluid circuit of an aircraft turbomachine according to any one of claims 1 to 5, said method comprising the steps: - filling the circulation loop (3) with a given first volume (VI) of heat transfer fluid; - filling the expansion vessel (6), connected to said loop (3), with a first sub-volume (V3); and - filling said expansion vessel (6) with a second sub-volume (V4, V4', V4") such that the second sub-volume compensates, in operation, for a loss of heat transfer fluid inside said loop.

8. Method according to claim 7, wherein said second sub-volume (V4) is equal to a nominal volume (Vn) of heat transfer fluid lost by said circulation loop in a given time.

9. A method according to claim 7, wherein said second sub-volume (V4') is greater than a nominal volume (Vn) defined as a volume of heat transfer fluid lost by said circulation loop in a given time

10. Method according to claim 7, wherein said second sub-volume (V4”) is less than a nominal volume (Vn) defined as a volume of heat transfer fluid lost by said circulation loop (3) in a given time.

11. A method according to any one of claims 7 to 10, comprising a preliminary step of estimating the heat transfer fluid losses in the circulation loop (3) to delay maintenance of the expansion vessel, this preliminary step comprising the following substeps: - determining, in a given time, a volume of heat transfer fluid losses; and - determining a second subvolume greater than said volume of heat transfer fluid losses.

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