BE1027893B1 - Turbomachine maintenance test method and system - Google Patents

Abstract

Test method of a turbomachine (6) in maintenance for a test bench (1) in which the flight fan blades (19) are replaced by test fan blades (20), extension less radial, which makes it possible to reduce the air flow and therefore the dimensions of the test bench (1).

Description

* BE2019 / 5946 Method and system for testing turbomachine maintenance Technical field [00011 According to a first aspect, the invention relates to a test method for the maintenance of aircraft turbomachines. According to a second aspect, the invention relates to an aircraft turbomachine for a maintenance test and to a system for testing aircraft turbomachines during a maintenance operation. STATE OF THE ART 100021 Test benches are used to test turbomachines.

These make it possible to measure the performance of a turbomachine before delivery or during maintenance operations. The purpose of test benches is to recreate flight conditions for testing a turbomachine in order to reduce real-life test times and associated costs. The test benches are designed so that a self test is as similar as possible to a test of a turbomachine mounted on an aircraft in flight.

160031 When a turbomachine is about to be delivered, it undergoes complete tests intended to determine the correct functioning of all the components of the turbomachine but also its overall performance and in particular the thrust performance.

During the life of a turbomachine, it undergoes regular maintenances during which tests make it possible to ensure, among other things, the correct operation of the compressors and the combustion of the engine, for example by checking the lemperalures and responses to commands.

[00051] In order to respond to the development of the aeronautical sector, manufacturers of turbomachines are developing double-flow turbomachines with increasingly high dilution rates requiring blowers of increasingly large diameters. Such developments require increasingly larger maintenance test benches to provide adequate airflow conditions with large diameter blowers. This generally results in an increase in the size of the maintenance test benches, and in particular the sizing of the test chamber.

© BE2019 / 5946 as well as the section and height of the air inlet and gas outlet towers.

Summary of the invention 100061 According to a first aspect, one of the aims of the present invention is to reduce the air flow generated by a maintenance test of a turbomachine. [00071 To this end, the inventors propose a maintenance test method for an aircraft turbomachine, the test method comprising the following steps: a. supply the turbomachine comprising: - flight relief vanes; a motor shaft arranged to drive the flight fan blades; b. removing the voice fan blades from the turbomachine; vs. instead of the flight fan blades, positioning test fan blades, the test fan blades being shorter radially than the flight fan blades; d. start the turbomachine. 100081 In order to reduce the air flow generated by the turbomachine of a bypass aircraft during a maintenance test, the invention proposes to modify the length of the fan blades.

Thus, the invention proposes to test a bypass turbine engine by eliminating a large part of the air flow that it generates in operation.

The main advantage of this is to reduce the dimensions necessary for the test bench for a maintenance test.

In fact, the dimensions of the test bench depend above all on the quantity of air set in motion by the fan of the turbomachine.

In a turbomachine with double flow, it is the primary flow which makes the engine “turn” while the secondary flow serves only to generate the thrust.

However, since a maintenance test requires an engine test only, only the air in the primary flow is needed for this purpose.

Thus, the air of the primary flow is important for the proper functioning of the engine, and the air of the secondary flow, if it is essential in flight, does not have a significant impact on the results of a maintenance test.

Therefore, this secondary air flow can be suppressed during a maintenance test. The invention proposes, in order to suppress, OR at least reduce, the secondary alr flow, to replace the fan blades of the turbomachine with test fan blades, the test fan blades being shorter radially ( around the motor shaft) as the flight fan vanes. The air flow generated by the maintenance test is necessary for the maintenance test in order to have an air flow in the test bench (between an inlet and an outlet).

100091 One problem with shortening the fan blades is that the test would be flawed because the test fan blades brake less on the drive shaft than the blades of a normal (flight) fan. The invention solves this problem by compensating for the braking deficit by the presence of a braking means, which makes it possible to artificially reproduce the missing braking, The artificial reproduction of the missing braking can be simulated or emulated, the results of simulation or of emulation are then converted into instructions for the braking medium.

106161 Preferably, the method further comprises the following additional steps: e. provide a system for testing the turbomachine comprising: means for starting the turbomachine; - a braking means; - Means for coupling the braking means with the drive shaft of the turbomachine; mechanically coupling the braking means to the motor shaft with the coupling means.

[9911] Preferably, step e. of the method further comprises providing the system with a test chamber for a test of the turbomachine, and in that it further comprises the following additional step: f installing the turbomachine equipped with the test fan blades inside the system test chamber.

An advantage of the maintenance test method of the invention is to allow the use of a test bench (of a test chamber) significantly smaller than a test bench (d 'a test chamber) of the state of the art for testing a double-flow turbomachine The method of the invention is all the more advantageous for double-flow turbomachines having a high dilution falsehood, preferably greater to 5. In fact, the method of the invention makes it possible to test in maintenance a double-flow furbomachine with only the primary flow activated.

Thus the test bench (the test chamber) used requires dimensions much smaller than the dimensions necessary to test both the primary and secondary flows.

A test method for testing a bypass turbomachine having a dilution rate of 7 requires a test chamber of square section on the Cyan side.

Thus, for a test bench having a test chamber of square section, the sides of the square section can be reduced by a factor f, such that f = Tp where, Tp = PTE, where the primary flow and the secondary flow are mass flow rates, for example such flows are expressed in kg / s.

The test chamber of the invention then requires a square section on side C ,, such that: Jo f Thus, by reducing the air flow generated by the bypass turbomachine while maintaining the forces of the motor shaft (for example the low pressure compressor shaft) necessary for the rotation of the fan, it is possible to obtain a satisfactory maintenance test of a bypass turbomachine with a test bench (a test chamber) significantly more compact than the test benches (test chamber) offered by the state of the art for the same bypass turbomachine. 160131 For example, for a bypass turbomachine with a dilution ratio Tp of 10: 1 (ratio of the secondary flow rate to the primary flow rate - or BPR, acronym for Bypass Ratio), the primary flow test with braking means to simulate the forces necessary for the rotation of the fan blades requires a test bench (a test chamber) whose useful section for the air flow generated by the test is less than one factor f approximately equal to f = V1 - 3. The useful section of a test chamber in a test bench is for example its width multiplied by its height.

The length of a test bench being taken between the air inlet and the air outlet of a test bench.

> BE2019 / 5946 The same reasoning concerning the height and the section useful for the airflow of the towers of the test bench can be applied to the reasoning concerning the section useful for the airflow of the test chamber of the invention compared to the towers of a test bench of the state of the art.

Preferably, the test method of the invention is for a maintenance test of a turbomachine. A maintenance test of a turbomachine is simpler than a complete test of a turbomachine because it does not require carrying out thrust measurements of the turbomachine.

[9015] Preferably, the system for testing a turbomachine may be called a test bench for testing a turbomachine. A test chamber is a part of a building. Preferably, the braking means are positioned in the test chamber. 100161 Preferably. the turbomachine comprises an annular separator for separating a primary flow and a secondary flow. Preferably the motor shaft is a low pressure compressor motor shaft. Preferably, step f. is to mechanically couple in rotation the braking means to the motor shaft with the coupling means. Preferably, the fan blades are mounted on a disc, which disc is in direct engagement with the coupling means when the latter are mechanically coupled to the motor shaft. 100171 Preferably, the test fan blades define a test fan diameter Dr and the flight fan blades define a flight fan diameter Dr, so that there is a ratio Es: Rs = aL Rs being between 10% and 40%, more preferably between 15% and 35%. 100181 Preferably, the turbomachine has a dilution rate when the flight fan blades are installed between 2 and 40, more preferably between 5 and 20, and even more preferably between 8 and 15.

Preferably, the turbomachine comprises an annular separator for separating a primary flow and a secondary flow, and, a radial extension of said test fan blades extends beyond said annular separator (13) in a range included between 100% and 110% of the radius of the annular separator, more preferably in a range between 100% and 105%, even more preferably in a range between 100% and 102%. 100% means that the radial extension of the test vanes is equal to the diameter of the ring separator. 110% means that for an annular separator radius equal to 100, the radial extension of the test vanes is equal to 110. The radial extension of the test fan blades and the radius of the annular separator are measured around l axis of rotation of the motor axis. Preferably, the test fan comprises test vanes having radial ends. The radial ends of the test vanes define a radius or diameter of the test fan. A test fan diameter is the diameter of a circle passing through the radial ends of the test vanes. The radius is half the diameter of such a circle. The annular separator has an opening diameter, through which the air flow generated by the blower is directed. Preferably, the radial extension of the test fan blades is equal to the radius of the annular separator.

100201 Preferably, the turbomachine comprises a fan casing comprising an internal wall of the fan casing with a diameter of between 0.5 m and 4 m, more preferably between 1 m and 3.5 m. For example an internal blower housing wall with a diameter of 3.25 m. Preferably, there exists between the radial ends of the test fan blades and the internal wall of the fan casing, a distance d greater than 40 cm, more preferably greater than 70 cm, even more preferably greater than 1 m .

For example, the distance d is between 40 cm and 1 m. d can also be defined as a distance between a test fan diameter and an internal diameter of the fan housing.

[9021] Preferably, the system for implementing the method further comprises: a control unit for controlling the braking means during the test of the turbomachine.

[9022] Preferably, the method comprises the following additional step after step to. :

g. determining, preferably by simulation, a braking deficit between the test fan blades and the flight fan blades and artificially reproducing this braking deficit with the braking means.

Preferably, the method comprises the following additional steps: h. decouple the braking means from the motor shaft; i. remove the test fan blades; | reassemble the flight fan blades.

100241 According to a second aspect of the invention, the inventors propose a bypass aircraft turbomachine for a maintenance test, the turbomachine comprising: - test fan blades, - a drive shaft arranged to drive the blades of test blower, - a blower housing, - an annular separator for separating a primary flow and a secondary flow in the blower housing, in which the test fan blades have a radial extension such that they do not protrude radially the annular separator or such that they radially protrude the annular separator by a distance which is less than half of the radial distance between the annular separator and the fan housing.

[9025] The variants and advantages of the method according to the first aspect of the invention apply to the turbomachine according to the second aspect of the invention, mutatis mutandis.

100261 Preferably, the annular separator is configured to separate the primary flow and the secondary flow according to a BPR ratio given by the expression: BPR being between 2 and 40, more preferably between 5 and 20, and even more so preferred between 8 and 15.

100271 Preferably, the turbomachine further comprises a low pressure compressor positioned inside the annular separator, the blades of the rotational test fan are configured to essentially supply air to the low pressure compressor as well as the turbomachine elements in downstream thereof (high pressure compressor, combustion chamber, turbine), preferably, exclusively to supply air to the low pressure compressor as well as the turbomachine elements avai thereof. 10028! According to a third aspect of the invention, the inventors propose a system for testing a turbomachine in maintenance according to the second aspect of the invention, the system comprising: means for starting the turbomachine; - A means of braking; - Coupling means of the braking means with the drive shaft of the turbomachine. 100291 The variants and advantages of the method according to the first aspect and of the turbomachine according to the second aspect of the invention apply to the system according to the third aspect of the invention, mulatis mulandis. 106361 The system according to the third aspect of the invention can be called a test bench. For example, the braking means is an electromechanical braking means.

[9031] Preferably, the system further comprises a control unit for controlling the braking means during the testing of a turbomachine. A control unit for controlling the braking means during a test can comprise an arithmetic and logic unit, selected from: a central processing unit (CPU), a digital signal processor (DSP), an integrated circuit specific to a application (ASIC), a programmable logic circuit (FPGA) or a combination thereof and may also include digital or analog electronic elements or a combination thereof.

[9032] Preferably, the control unit is configured to take into account information coming from the speed sensor of the engine axis of the turbomachine. This allows better simulation of the braking deficit and therefore better artificial reproduction of the latter with the braking means.

[9033] Preferably, the system further comprises: a test chamber for a maintenance test of the turbomachine.

[9034] Preferably, the control unit is configured to implement a simulation of the forces of the blades of a flight fan and to control the braking means on the basis of the results of the simulation. 100351 Preferably, the system further comprises a ducted air duct comprising an air inlet and an air outlet to allow circulation of an air flow between the air inlet and outlet, the air chamber. 'test being located between the air inlet and the air outlet. 100361 Preferably, the braking means is an electric generator. Thus, it is possible to maximize the generation of electrical energy when testing a turbomachine while having a system to perform reliable maintenance testing. Such electrical energy recovery presents fewer losses than systems comprising energy recovery elements positioned in the air inlets and / or outlets of a test bench. Preferably, the braking means is a water brake.

Brief Description of Figures 100371 These and other aspects of the invention will be clarified in the detailed description of particular embodiments of the invention, with reference being made to the drawings of the figures, in which: - Figure 1 shows a schematic embodiment of the invention; - Figure 2a shows a schematic representation of a turbomachine to be tested; FIG. 2b shows a schematic representation of the replacement of the flight fan blades by test fan blades on the turbomachine to be tested; - Figures 2c, 3a, 3b show other schematic embodiments of the invention; - Figure 4 shows an exemplary schematic embodiment of the invention; - Figures 5 and 6 each show a flowchart representing an embodiment of the method of the invention.

The drawings of the figures are not to scale. Generally, like elements are denoted by like references in the figures. The presence of reference numbers in the drawings cannot be considered

+0 BE2019 / 5946 as limiting, including when these numbers are indicated in the claims.

Detailed Description of Certain Embodiments of the Invention 100381 Figure 1 shows an exemplary system embodiment | of the invention for testing a turbomachine 6. The turbomachine 6 to be tested comprises a drive shaft 16 arranged to drive fan blades 19; 20 of the turbomachine 6. The fan blades 19; 20 are mounted on and attached to a fan disk 15.

The fan disc 15 generally comprises grooves in which the roots of the fan blades 19; 20 are inserted and then fixed.

The system 1 comprises a test chamber 5 for a test of the turbomachine 6, means for starting the turbomachine 6 in order to be able to carry out its test, a braking means 7, coupling means 8 of the braking means 7 with the drive shaft 18 of the turbomachine 6. The coupling means 8 are generally mechanically coupled in rotation to the fan disk 15. To test the turbomachine 6, the latter is introduced into the test chamber 5 where it is positioned.

The braking means 7 are coupled to the motor shaft 16 in rotation so that a rotation of this motor shaft 16 can be influenced by the braking means 7. In particular, when a turbomachine 6 is tested by replacing the blades. of the flight fan 19 by test fan blades 20, it is necessary to compensate for the braking deficit of the drive shaft 16 normally generated by the flight fan blades 19. This compensation is achieved by the presence of a braking means 7, which makes it possible to artificially reproduce the missing braking.

The system 1 of the invention also provides all the connections necessary for the correct operation of the turbomachine 6 as well as for its testing, in a non-exhaustive manner: fluidic fuel supply connections, electrical connections for starting the turbomachine 6 , for its control and for the evaluation of the parameters of the turbomachine 6 during its test. 100391 FIG. 2a shows a turbomachine 6 to be tested.

The turbomachine 6 to be tested comprises a drive shaft 16 on which is fixed a fan disk 15. The flight fan blades 19 are mechanically coupled in rotation to the flight fan disk 19. The turbomachine 6 to be tested is a twin turbomachine. flux. A primary flow and a secondary flow are separated by an annular separator 13. The primary flow is directed inside the annular separator 13 and the secondary flow is directed around the annular separator 13, between the annular separator and the internal wall 26 of blower housing 25. For example, the motor shaft 16 is often an extension of a low-pressure compressor shaft. A low-pressure compressor being housed inside the annular separator 13. During the rotation of the flight fan 19 driven by the motor shaft 16, the flight fan 19 generates the primary flow and the secondary flow. 100401 FIG. 2b shows the turbomachine 6 to be tested and in particular the removal of the flight fan blades 19, in place of which the test fan blades 20 are positioned. FIG. 2b shows the steps c schematically. and D. of the method according to the first aspect of the invention. Arrow 520 illustrates the removal of the vanes from the flight fan 19. Arrow 530 illustrates the positioning of the vanes of the test fan 20. As shown, the test fan vanes 20 are smaller than the vanes. fan 19 and they have, when attached to the fan disc 15, radial extensions 209 substantially equal to the radius of the opening 18 of the annular separator 13. The vanes of the fan 19 have radial extensions 199 fitted to the inner wall 26 of the baffle casing

25. The fan disc 15 makes it possible to mechanically couple in rotation, the coupling means 8 (mechanically coupled to the braking means 7) to the motor shaft 16. [00411 FIG. 2c shows the system of the invention comprising a test chamber 5 in which the turbomachine 6 to be tested is installed. The turbomachine 6 to be tested is equipped with test fan blades 20. The test fan blades 20 are mounted and held on a fan disc 15, which makes it possible to mechanically couple the braking means 7 to the shaft. engine 16 thanks to the coupling means 8. The test fan blades 20 are delimited radially by radial ends 22 of test fan blades 20. There is a distance d between these radial ends 22 and the internal wall 26 of the fan housing 25. The annular separator 13 includes an annular separator opening 13 having an opening diameter 18. The annular separator opening has an annular cross section. Figure 2c shows the location of a low-pressure compressor 17 located directly after the fan blades (test 20 or flight 19). As illustrated in FIG. 20, during the test of the turbomachine 6, the test fan blades 20 make it possible to generate a primary flow similar or even identical to that generated by the voi fan blades 19, but by generating a negligible secondary flow see almost zero compared to the secondary flow generated by the flight fan blades 19. Thus, for a turbomachine 6 having a high dilution ratio To, for example close to 10, the air flow generated by the turbomachine 6 equipped with the test fan blades 20 is approximately 10 times less than the air flow generated by the same turbomachine 6 equipped with its flight fan blades 19. The sizing of the test chamber 5 and the inlets air 3 and air outlet 4 necessary being essentially based on the air flow generated by the turbomachine 6, it is possible to reduce these by a factor close to 10 for the implementation of the method according to the first aspect and for system 1 according to the third aspect of the invention for testing the same turbomachine 6 with test fan blades 20 rather than with flight fan blades 19. 100421 Figure 3a shows the embodiment of the system 1 of FIG. 2c and further comprising a control unit 40 for controlling the braking means 7 during the test of the turbomachine 6. The control unit 40 is connected to the braking means 7 so as to control it to artificially reproduce the missing braking due to the use of the test fan blades 20 instead of the flight fan blades 19. By controlling the braking means 7 by the control unit 40, it is possible to simulate the braking not generated by the test fan blades 20 and apply this braking not generated by the test fan blades 20 on the drive shaft

16. Thus, it is possible to ensure the correct operation of the compressors and the combustion of the engine, for example by controlling the temperatures and the responses to the commands by generating a very reduced or even zero secondary flow compared to the turbomachine 6. with its flight fan blades 19. 100431 Figure 3b shows the embodiment of Figure 3a which further comprises a sensor 31 of the speed of rotation of the motor shaft 16 connected to the control unit 40, so that the braking means 7 is controlled by taking into account the speed of rotation of the motor shaft 16. This is particularly advantageous because it is possible to apply a braking to the motor shaft 16 as a function of its speed of rotation.

Indeed, the missing force of the drive shaft 16 due to the presence of the test fan blades 20 rather than the flight fan blades 19 necessarily increases with an increase in the rotational speed of the drive shaft. 16. Thus, the taking into account of the speed of rotation of the motor shaft 16 by the control unit, in association or not with other operating parameters of the turbomachine 6 under test makes it possible to ensure correct operation. compressors and engine combustion by reproducing as closely as possible the forces generated by the flight fan blades 19. 10044! Figure 4 shows a preferred embodiment of the system 1 of the invention.

This further comprises a ducted air duct 2 comprising an air inlet 3 and an air outlet 4 to allow circulation of an air flow between the air inlet 3 and the air outlet 4. , the test chamber 5 being located between the air inlet 3 and the air outlet 4. The air flow passing through the ducted air duct 2 makes it possible to supply the turbomachine 6 with fresh air in the test chamber 5 through its air inlet 3 and extract the combustion gases and the air flow generated by the turbomachine 6 during its test.

This embodiment comprises means 23 for smoothing the air flow positioned in an inlet portion of the ducted air duct 2 so that the test of the turbomachine 6 is carried out under optimum laminar air flow conditions. .

According to an embodiment not shown, the ducted air duct 2 comprises an air flow duct portion positioned between the test chamber 5 and an outlet portion of the ducted air duct positioned downstream of the chamber. test 5. This portion of the air flow channel allows better management of the air flow at the outlet so that the air flow leaving the turbomachine 6 does not disturb the air flow entering the turbomachine. 6.

+4 BE2019 / 5946 Acoustic reduction means can be positioned at the level of the air outlet 4 so as to limit the noise pollution perceived outside the air duct 2. The arrows illustrated in figure 4 represent the directions preferred air flow in the air duct 2 at different locations. In particular, the four arrows close together in front of the turbomachine 6 represent a laminar air flow. 100451 FIG. 5 shows a flowchart showing the steps essential to the implementation of the method of the invention. Step 510 is to provide a turbomachine 6. Step 520 is to remove the flight fan vanes 19. Step 530 is to position the test fan vanes 20 in place of the flight fan vanes. on the fan disk 15. Step 540 consists in starting the turbomachine 6 in order to carry out a maintenance test of the turbomachine 6 with the test fan blades 20.

[00467 FIG. 6 shows a flowchart showing the essential steps described in FIG. 5 as well as optional steps. The order of the steps shown in FIG. 6 can be modified when this has no effect on the proper conduct of the maintenance test of the invention. Thus, step 500 consists in providing a system 1 (a test bench for maintenance} to test the turbomachine for maintenance. Step 505 consists in determining a braking deficit between the test fan blades 20 and the voi fan blades 19 and artificially reproduce this braking deficit with the braking means 7. For example, step 505 can be carried out during the maintenance test of the turbomachine 6 corresponding to step 540 or before. Step 531 consists of installing the turbomachine 6 equipped with the test fan blades 20 inside the test chamber 5 of the system 1. For example, step 531 can be performed at any time between step 500 and step 535. Step 535 consists in mechanically coupling the braking means 7 to the motor shaft 16 with the coupling means 8. Step 550 consists in decoupling the braking means 7 from the motor. motor shaft 16. Step 560 consists of removing the test fan blades 20. Step 570 consists in reassembling 570 the flight fan blades

19.

100471 The present invention has been described in relation to specific embodiments, which have a purely illustrative value and should not be considered as limiting.

In general, the present invention is not limited to the examples illustrated and or described above.

The use of the verbs “understand”, “inciure”, “comprise”, or any other variant, as well as their conjugations, cannot in any way exclude the presence of elements other than those mentioned.

The use of the indefinite article "un>," a ", or of the definite article" the "," the "or" l ", to introduce an element does not exclude the presence of a plurality of these elements.

Reference numbers in the claims do not limit their scope. 106481 In summary, the invention can also be described as follows.

Test method of a turbomachine 6 in maintenance for a test bench 1 in which the flight fan blades 19 are replaced by test fan blades 20, of less radial extension, which makes it possible to reduce the air flow and therefore the dimensions of the test bench 1.

Claims (1)

Claims 1. Maintenance test method for a turbomachine (6) of a by-pass aeronel, said test method comprising the following steps: a. providing (510) said turbomachine (6) comprising: - voice fan blades (19); - a drive shaft (16) arranged to drive said flight fan blades (19); b. removing (520) said flight fan blades (19) from said turbomachine (6); vs. positioning (530), in place of said flight fan blades (19), test fan blades (20), said test fan blades (20) being radially shorter than said flight fan blades see (19); d. start (540) said turbomachine (6). 2. Method according to the preceding claim, characterized in that it further comprises the following additional steps: e. providing (500) a system (1) for testing said turbomachine (6) comprising: - means for starting said turbomachine (6); - a braking means (7); - Coupling means (8) of said braking means (7) with said drive shaft (16) of said turbomachine (6): f. mechanically coupling (535) said braking means (7) to said motor shaft (16) with said coupling means (8). 3. Method according to the preceding claim, characterized in that step e. further comprises providing (500) to said system (1) a test chamber (5) for a test of said turbomachine (6), and in that it further comprises the following additional step: g. installing (531) said turbomachine (6) equipped with said test fan blades (20) inside said test chamber (5) of said system (1). Method according to any one of the preceding claims, characterized in that said test fan blades (20) define a test fan diameter Dr and said flight fan blades (19) define a fan diameter. of vol De, so that there is a ratio Rs Rs = 5 is between 10% and 40%, preferably between 15% and 35%. 5. Method according to any one of the preceding claims, characterized in that said turbomachine (6) has a dilution rate when said voice fan blades (19) are installed between 2 and 40, preferably between 5 and 20 , even more preferably between 8 and 15. 6. Method according to any one of the preceding claims, characterized in that said turbomachine (6) comprises an annular separator {13} for separating a primary flow and a secondary flow; and in that a radial extension of said test baffle vanes (20) extends beyond said annular separator (13) in a range between 100% and 110% of the radius of said annular separator (13), from preferably in a range between 100% and 105%, even more preferably in a range between 100% and 102%. 7. Method according to any one of the preceding claims, characterized in that it comprises the following additional step after step d. : h, determining (505), preferably by simulation, a braking deficit between said test fan vanes (20) and said flight fan vanes (19) and artificially reproducing this braking deficit with said braking means (7). 8. Method according to any one of the preceding claims, comprising the following additional steps: 1. decoupling (550) said braking means (7) from said motor shaft (16); | removing (560) said test fan vanes (20): k. reassembling (570) said flight fan blades (19). 9. Turbomachine (6) of a bypass aircraft for a maintenance test, said turbomachine (6) comprising: - test fan blades (20), - a drive shaft (16) arranged to drive said vanes. test blower (20), - A blower housing (25), - an annular separator (13) for separating a primary flow and a secondary flow in the fan housing (25), in which the fan vanes of test (20) have a radial extension (209) such that they do not radially exceed the annular separator (13) or such that they radially exceed the annular separator (13) by a distance which is less than half of the radial distance between the annular separator (13) and the fan housing (25). 10. Turbomachine (6) according to the preceding claim, characterized in that said annular separator (13) is configured to separate said primary flow and said secondary flow according to a BPR ratio given by the expression: BPR = FR BPR being between 2 and 40, preferably between 5 and 20, even more preferably between 8 and 15. 11. Turbomachine (6) according to the preceding claim, characterized in that said turbomachine (6) further comprises a low pressure compressor {17} positioned inside the annular separator (13), said blades (20) of the rotating test fan are configured to essentially supply air to said low pressure compressor (16), preferably to exclusively supply air to said low pressure compressor (16). 12. System (1) for maintenance testing of a turbomachine (6) according to any one of claims 9 to 11, said system (1) comprising: - means for starting said turbomachine (6); - a braking means (7); - Coupling means (8) of said braking means (7) with said drive shaft (16) of said turbomachine (6). 13. System (1) according to the preceding claim, characterized in that it further comprises: - a test chamber (5) for a maintenance test of said turbomachine (6). 14. System (1) according to any one of claims 12 to 13, characterized in that it further comprises a control unit (40) for controlling said braking means (7) during the maintenance test of said turbomachine (6), said control unit (40) is configured to implement a simulation of the forces of the blades of a void fan (19) and to control said braking means (7) on the basis of results of said simulation. 15. System (1) according to any one of claims 12 to 14, characterized in that said braking means (7) is an electric generator.