Permeability measurement of a turbomachinery injection system

Abstract

Permeability Measurement of a Turbomachinery Injection System. Permeability check of an injection system (8) comprising a fluid inlet (10) connected to a supply line: disconnect the supply line from the fluid inlet; connect the suction line (14) of a suction device (15) to the fluid inlet; draw air through the injection system using the suction device and measure the value p of a parameter P representative of the aspirated air flow rate; compare p to the nominal value pN of P previously measured when the injection system (8) was new; assess the actual permeability of the injection system (8). RD = (p - pN) / pN is then calculated and |RD| is compared to a determined threshold value S, the actual permeability of the injection system (8) being considered satisfactory if |RD| ≤ S, and unsatisfactory if |RD| Figure to be published with the abbreviation: Figure 2

Description

Title of the invention: Permeability measurement of a turbomachine injection system TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of injection systems mounted in an aircraft turbomachine and more particularly that of lubrication systems.

[0002] The present invention relates to a method for measuring the permeability of these injection systems and a device suitable for implementing this method. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In a known manner, with reference to [Fig.l], an aircraft turbomachine 1 comprises a gas generator 2 comprising a compression stage 3 and a turbine stage 4 connected to a propulsion shaft 5 to drive a propulsion member (not shown) in rotation around an axis X along which the turbomachine 1 extends longitudinally.

[0004] The propulsion shaft 5 is usually guided in rotation by bearings, in particular a rear bearing 6 equipped with bearings 7. In order to avoid heating of the rear bearing 6 during operation of the turbomachine 1, an injection system 8 of the lubrication circuit type injects oil onto the rear bearing 6 to lubricate it and drain calories. This injection is carried out by an injection member 9, such as a nozzle.

[0005] However, when the turbomachine 1 stops, the stored heat dissipates from the hottest parts to the coldest parts, which causes significant heating of the rear bearing 6 and the residual oil it contains. Such significant heating, which can exceed 300°C, can lead to premature aging of the oil and its thermal degradation, which causes the formation of solid particles according to a phenomenon commonly referred to as “coking”. The accumulation of solid deposits can obstruct the conduits of the lubrication circuit, and in particular the injection members, which can prevent the circulation of the oil.

[0006] An alteration of the circulation of oil in the lubrication circuit can lead to a deterioration in the cooling of the turbomachine, which can prematurely wear out the rear bearing and cause damage to the turbomachine.

[0007] Also, it is necessary to regularly check that the lubrication circuit is not obstructed. For this, it is known to monitor the flow rate of the oil circulating in the lubrication circuit, in particular, at the level of the oil injection members.

[0008] In this respect, a verification method is known in the prior art in which the oil is manually poured into the lubrication circuit during a maintenance operation. The oil flows by gravity into the lubrication circuit between an oil inlet and an oil outlet, via the injection members, according to a test duration, and is collected in a graduated cylinder. This test duration is compared to a reference duration, for example determined following a measurement carried out on a new turbomachine, in order to determine whether the flow rate is lower than initially, that is to say, whether the permeability of the injection members has decreased.

[0009] However, the duration of the flow depends directly on the exact volume of oil passing through the lubrication circuit, as well as its temperature. Since such an operation is not carried out in a controlled environment (such as a laboratory, for example), the results are imprecise and a source of error. Indeed, the fluidity and volume of the oil vary considerably with temperature. In addition, the introduction of unfiltered oil into the engine introduces a risk of introducing potentially harmful foreign bodies. Furthermore, since the turbomachine is mounted on the aircraft, the inlet of the lubrication circuit is difficult to access and requires an operator to be positioned on the aircraft while the cowling of the turbomachine is open, which is impractical and dangerous.

[0010] The invention thus aims to eliminate these drawbacks by proposing a system and a method for controlling the permeability of a lubrication circuit of an aircraft turbomachine which are simple, suitable and reliable, without being significantly altered by temperature variations. The system and the method aim in particular to detect in a simple and rapid manner an obstruction of the lubrication circuit, for example for the purpose of carrying out predictive maintenance.

[0011] It will be noted that the system and method according to the invention for controlling the permeability of a lubrication circuit can also be adapted to any injection system mounted in an aircraft turbomachine and likely to encounter clogging problems. Summary of the invention

[0012] The invention offers a solution to the problems mentioned above, by providing a new method for measuring the permeability of an injection system and a device suitable for implementing this method.

[0013] One aspect of the invention relates to a method for controlling the actual permeability of an injection system of an aircraft turbomachine, the injection system comprising an injection member having a fluid inlet connected to a fluid supply via a fluid supply pipe and a fluid outlet located in the turbomachine, the method comprising the following successive steps: • supply of an air suction device comprising a suction pipe; • disconnection of the fluid supply line from the fluid inlet; • connection of the suction line to the fluid inlet; • suction of air through the injection system by means of the air suction device via the suction line and measurement of the value p of a parameter P representative of the flow rate of suctioned air; • comparison of p with the nominal value pN of P previously measured when the injection system was new; • assessment of the actual permeability state of the injection system.

[0014] This method is advantageous in that it is simple and reliable, and easy and quick to implement.

[0015] Based on suction, it does not have all the disadvantages of injection, in particular the risks of soiling or introduction of a foreign body or a substance harmful to the proper functioning of a turbomachine.

[0016] Using air rather than a liquid, the method of the invention is inexpensive and does not present any risk to the environment or the operator. Furthermore, unlike when a liquid is used, the measurements taken are practically invariable depending on the temperature, particularly in the temperature ranges in which the permeability measurements are likely to be taken.

[0017] The air suction device comprising a suction pipe which may in particular have a length of several meters, said air suction device can be offset and positioned at a distance from the turbomachine, which in particular allows the operator to be on the ground, several meters away from the turbomachine, rather than being at height, leaning inside the turbomachine.

[0018] According to one aspect of the invention, after having compared p to pn, the ratio RD = (p - pN) / pN is calculated and its absolute value IRDI is compared to a determined threshold value S in order to assess the actual permeability state of the injection system, the permeability being considered satisfactory if IRDI < S, and unsatisfactory if IRDI > S, with S preferably being such that 0.2 < S < 0.4, more preferably 0.25 < S < 0.35, and even more preferably S = 0.3.

[0019] This is a simple and reliable comparison method for evaluating the changes in permeability of the injection system compared to the nominal value p N. According to the studies carried out by the applicant, the value S chosen for the threshold makes it possible to validate or not that the injection system is indeed capable of providing a fluid flow rate in accordance with the minimum certification flow rate.

[0020] According to another aspect of the invention, the parameter P is a value of duration of flow of a determined quantity of liquid, said flow generating a vacuum in the suction line.

[0021] According to a further aspect of the invention, the parameter P is a suction pressure value generated in the suction line by the air suction device.

[0022] According to one aspect of the invention, the parameter P is a value of the duration of movement of a piston to move a determined distance, said movement generating a vacuum in the suction pipe.

[0023] Another aspect of the invention relates to an air suction device for implementing the method, which comprises a sealed container equipped with a tap in the lower part and connected to the suction pipe in the upper part, which container being transparent and graduated or being equipped with a means for indicating the quantity of liquid present in the container, preferably a transparent graduated gauge.

[0024] This type of air suction device has the particular advantage of being very easy and very simple to use, and of not requiring electricity for its operation.

[0025] According to one aspect of the invention, the container is a tube of height H and internal diameter D, in which 0.5 m < H < 2 m, preferably 0.8 m < H < 1.5 m and more preferably H = 1 m, and in which 2 cm < D < 20 cm, preferably 5 cm < D < 10 cm and more preferably D = 8 cm.

[0026] According to the studies carried out by the applicant, these dimensions make it possible to provide an air suction device which is sufficiently small and light to be transportable and which also makes it possible to have a sufficient liquid height to be able to carry out sufficiently reliable and precise measurements to validate or not the fact that the injection system is capable of providing a fluid flow rate conforming to the minimum certification flow rate.

[0027] According to another aspect of the invention, the tap has an outlet orifice equipped with an evacuation tube of length L and internal diameter d, in which 5 cm < L < 50 cm, preferably 15 cm < L < 25 cm and more preferably L = 20 cm, and in which 2 mm < d < 30 mm, preferably 5 mm < d < 15 mm and more preferably d = 10 mm.

[0028] Such a tube advantageously makes it possible to prevent air from entering the air suction device through the tap.

[0029] A further aspect of the invention relates to an air suction device for carrying out the method, which comprises a vacuum pump connected to the suction line and a pressure measuring device measuring the pressure in said suction line.

[0030] This type of air suction device is advantageously small and easily trans- portable, while being reliable and accurate at a lower cost.

[0031] Another aspect of the invention relates to an air suction device for implementing the method, which comprises a cylinder inside which the piston is housed sliding in a sealed manner, a first end of the cylinder being connected to the suction pipe, and the piston being connected to a weight of determined mass which causes by gravity the displacement of the piston towards a second end of the cylinder.

[0032] This type of air suction device has the particular advantage of being very easy and very simple to use, and of not requiring electricity for its operation.

[0033] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0034] The figures are presented for information purposes only and in no way limit the invention.

[0035] [Fig.l] is a schematic representation of an engine system comprising an aircraft turbomachine and a lubrication circuit.

[0036] [Fig.2] is a detail view of the part framed in [Fig.l], in which the fluid inlet of the injection member is connected to an air suction device according to a first variant of the invention.

[0037] [Fig.3] is a detail view of the part framed in [Fig.l], in which the fluid inlet of the injection member is connected to an air suction device according to a second variant of the invention.

[0038] [Fig.4] is a detail view of the part framed in [Fig.l], in which the fluid inlet of the injection member is connected to an air suction device according to a third variant of the invention.

[0039] [Fig.5] illustrates an alternative of the air suction device according to the third variant of the invention.

[0040] [Fig.6] is a graph representing the evolution of the value p of the parameter P for different regimes R of the turbomachine over time. DETAILED DESCRIPTION

[0041] In a turbomachine 1, injection system 8 comprises an injection member 9 usually comprising a fluid inlet 10 connected to a fluid supply (not shown) via a fluid supply pipe 11. The injection member 9 also comprises a fluid outlet pipe 12 ending in a fluid outlet 13, located in the turbomachine 1 and provided to supply fluid into said turbomachine 1.

[0042] The injection member 9 may be a nozzle connected to a lubricant supply, in order to provide lubricant in the turbomachine 1, in particular to lubricate a rear bearing 6.

[0043] The invention is concerned with determining whether the injection system 8 is not clogged and has satisfactory permeability so as to be able to provide a fluid flow rate in accordance with the minimum certification flow rate.

[0044] The method for controlling the permeability of an injection system of an aircraft turbomachine according to the invention comprises several successive steps. For its implementation, it requires the use of an air suction device 15 equipped with a suction pipe 14.

[0045] This method makes it possible to measure the actual permeability of an injection system, i.e. its current permeability, for example after a certain number of usage cycles.

[0046] First, the operator must disconnect the fluid supply line 11 from the fluid inlet 10 to connect the suction line 14 of the air suction device 15 to it.

[0047] Then, air is sucked in by the air suction device 15 through the injection system 8. During this step, air is therefore sucked into the injection system 8, through the suction pipe 14, along a path which is reversed compared to that usually taken by the fluid which normally circulates in the injection system 8.

[0048] During this step, a value p of a parameter P representative of the flow rate of sucked air is measured.

[0049] The value p is then compared to the nominal value pN of P. This nominal value pN represents the parameter P for an injection system 8 in which the permeability is optimal, that is to say that the fluid intended to circulate in the injection system 8 can circulate freely therein. Thus, the nominal value pN is usually measured by sucking air by the air suction device 15 through a new injection system 8.

[0050] This comparison makes it possible in particular to see whether the permeability has changed or not.

[0051] In order to determine whether the injection system 8 is capable of providing a flow rate of fluid conforming to the minimum certification flow rate or if it must be subject to maintenance, several methods are possible.

[0052] For example, we can calculate the difference ratio RD defined by the formula: RD = (p - pN) / pN and compare the absolute value IRDI of this difference ratio with a given threshold value S. Since we are using the absolute value IRDI, we can just as easily use RD = (pN - p) / pN for the calculation of RD.

[0053] The value S is preferably determined experimentally so that when IRDI is less than or equal to S, this means that the injection system is capable of provide a fluid flow rate that meets the minimum certification flow rate.

[0054] Thus, if IRDI < S, then the permeability of the injection system 8 is considered satisfactory, while if IRDI > S, then the permeability of the injection system 8 is not considered satisfactory.

[0055] For example, in particular when the injection system 8 is a lubrication system, S is such that 0.2 < S < 0.4, preferably 0.25 < S < 0.35, and more preferably S = 0.3. This value can of course be different depending on the types and models of injection systems.

[0056] Tests were carried out by artificially reducing the injection flow rate while recording the value p of the parameter P for different RA, RB, RC, etc. regimes of the turbomachine. The results of these tests are summarized in [Fig.6]. A first threshold pO corresponds to the minimum injection flow rate certified on the machine. The threshold S is defined to alert before reaching this certification threshold pO while giving a variation of p sufficient to be detectable.

[0057] It is possible to envisage several types of injection system, so there are several possible embodiments for the invention. By way of example, we will describe three here, although the person skilled in the art can easily envisage others.

[0058] According to a first embodiment shown in [Fig.2], the air suction is generated by emptying a container previously filled with liquid, the volume and viscosity of which are not very variable at room temperature, preferably water. Thus, the parameter P is a value of the duration necessary for the flow of a determined quantity of liquid. This time can be timed manually, for example by means of a watch or a stopwatch, or be measured by a suitable automated device.

[0059] According to this first embodiment, the air suction device 15 comprises a sealed container 16, for example tubular, equipped with a tap 17, for example in its lower part, and a suction pipe 14, for example in its upper part. In order to be able to measure the flow of liquid, the container 16 comprises a means for indicating the quantity of liquid present in the container 16. Thus, the container 16 can for example be transparent and graduated, or be equipped with a transparent graduated gauge 18.

[0060] The gauge 18 shown as an example in [Fig.2] has four successive graduations numbered from 0 to 3 and regularly spaced. The visible flow between graduations 0 to 1 allows the outgoing liquid flow to stabilize. A first measurement of flow duration can then be carried out during the flow between graduations 1 to 2, and a second measurement can be carried out between graduations 2 to 3. This double measurement makes it possible to obtain several measurements, in particular for more reliability. More graduations can be considered, but graduations that are too close together reduce the accuracy of the measurements, while graduations that are too far apart increase the size and bulk of the air suction device 15.

[0061] For example, the sealed container 16 is a tube of height H and internal diameter D, in which 0.5 m < H < 2 m, preferably 0.8 m < H < 1.5 m and more preferably H = 1 m, and in which 2 cm < D < 20 cm, preferably 5 cm < D < 10 cm and more preferably D = 8 cm.

[0062] According to a preferred variant, the tap 17 is equipped with an evacuation tube 19 at its outlet orifice 20.

[0063] This discharge tube 19 is sized to prevent air from entering through the tap 17, while allowing a satisfactory outlet flow rate for the liquid. Thus, the discharge tube 19 has a length L such that 5 cm < L < 50 cm, preferably 15 cm < L < 25 cm and more preferably L = 20 cm, and an internal diameter d such that 2 mm < d < 30 mm, preferably 5 mm < d < 15 mm and more preferably d = 10 mm.

[0064] The container 16 may also be equipped with an air intake 28, for example in its upper part, making it possible to check the tightness of the system. This air intake 28 is closed when the container 16 is used for permeability measurements.

[0065] According to a second embodiment shown in [Fig. 3], the air suction is generated by a suction pump. Thus, in this case, the parameter P is a suction pressure value generated in the suction line 14 by the air suction device 15.

[0066] According to this second embodiment, the air suction device 15 comprises a vacuum pump 21 connected to a suction line 14, and a pressure measuring device 22, for example a pressure gauge, connected to said suction line 14.

[0067] In order to avoid overheating of the pump, in particular in the event of significant clogging of the injection system 8, the pressure measuring device 22 can for example be connected to an alarm which is activated and / or which automatically switches off the pump when the measured suction value is too low.

[0068] According to a third embodiment shown in [Fig.4] and [Fig.5], the air suction is generated by the movement of a piston in a cylinder connected to the suction pipe 14. Thus, according to this embodiment, the parameter P is a value of the duration necessary for said piston to move a determined distance in a cylinder.

[0069] According to a preferred variant, the air suction device 15 comprises a cylinder 23 equipped with a piston 24 housed sliding in a sealed manner inside said cylinder 23. Said piston 24 is preferably ballasted, for example by being connected to a weight 25 of determined mass, in order to move by gravity.

[0070] Thus, the cylinder 23 is divided into two chambers by the piston 24, namely into a suction chamber 26 connected to the suction pipe 14 and in which the vacuum is created, and into a displacement chamber 27 in which the piston 24 moves.

[0071] The weight 25 preferably moves vertically, but the piston 24 can move vertically (see [Fig.4]), horizontally (see [Fig.5]) or inclined.

[0072] Vertical displacement is however preferred because it facilitates taking into account the friction generated by the piston 24 inside the cylinder 23.

[0073] The displacement distance of the piston 24 is for example determined by the internal length of the cylinder 23.

[0074] According to the embodiments envisaged, the air suction device 15 can also be equipped with a frame, a tripod or any other support to position it in a stable manner close to the turbomachine 1.

[0075] Experimental tests were notably carried out by the applicant with an air suction device 15 according to the first embodiment on turbomachine lubrication circuits.

[0076] The table below shows flow times for water through a tubular container 1 m high and 8 cm internal diameter, the tap of which is equipped with a discharge tube 20 cm long and with an internal diameter of 1 cm. The suction line 14 was a flexible tube 10 m long with an internal diameter of 1 cm. In this table, the flow time through a new injector in a new engine, through a new injector in a used engine and through an injector which was intentionally clogged at 60% but which is representative of an injector clogged at 60% following use in a real situation have been compared. [Tables 1] New injector - new engine New injector - engine under review Injector artificially clogged at 60% Flow time 25 seconds 26 seconds 45 seconds

[0077] From these results, it is noted that the flow times are significantly higher in the case of a partially clogged injection system, which is not capable of providing a fluid flow rate conforming to the minimum certification flow rate.

[0078] It is also noted that the different duration values ​​measured for an injection system in the same state are significantly close, which proves the reliability of the method and the equipment used for the permeability measurements.

[0079] Consequently, these experimental tests make it possible to validate both the permeability measurement method of the invention, and an example of a suction device. air 15 capable of implementing this process.

Claims

Claims

1. Method for controlling the actual permeability of an injection system (8) of an aircraft turbomachine (1), the injection system (8) comprising an injection member (9) having a fluid inlet (10) connected to a fluid supply via a fluid supply line (11) and a fluid outlet (13) located in the turbomachine (1), characterized in that the method comprises the following successive steps: - providing an air suction device (15) having a suction line (14); - disconnecting the fluid supply line (11) from the fluid inlet (10); - connecting the suction line (14) to the fluid inlet (10); - suction of air through the injection system (8) by means of the air suction device (15) via the suction line (14) and measurement of the value p of a parameter P representative of the flow rate of suctioned air;- comparison of p with the nominal value pN of P previously measured when the injection system (8) was new; - assessment of the actual permeability state of the injection system (8).;

2. Method according to claim 1, characterized in that after having compared p to pn, the ratio RD = (p - pN) / pN is calculated and its absolute value IRDI is compared to a determined threshold value S in order to assess the actual permeability state of the injection system (8), the permeability being considered satisfactory if IRDI < S, and unsatisfactory if IRDI > S, with S preferably being such that 0.2 < S < 0.4, more preferably 0.25 < S < 0.35, and even more preferably S = 0.

3.

3. Method according to claim 1 or 2, characterized in that the parameter P is a value of duration of flow of a determined quantity of liquid, said flow generating a vacuum in the suction pipe (14).

4. Method according to claim 1 or 2, characterized in that the parameter P is a suction pressure value generated in the suction line (14) by the air suction device (15).

5. Method according to claim 1 or 2, characterized in that the parameter P is a value of duration of movement of a piston (24) to move a determined distance, said movement generating a vacuum in the suction pipe (14).

6. Air suction device (15) for implementing the method according to claim 3, characterized in that it comprises a sealed container (16) equipped with a tap (17) in the lower part and connected to the suction pipe (14) in the upper part, which container (16) is transparent and graduated or is equipped with a means for indicating the quantity of liquid present in the container (16), preferably a transparent graduated gauge (18).

7. Device according to the preceding claim, characterized in that the container (16) is a tube of height H and internal diameter D, in which 0.5 m < H < 2 m, preferably 0.8 m < H < 1.5 m and more preferably H = 1 m, and in which 2 cm < D < 20 cm, preferably 5 cm < D < 10 cm and more preferably D = 8 cm.

8. Device according to claim 6 or 7, characterized in that the tap (17) has an outlet orifice (20) equipped with an evacuation tube (19) of length L and internal diameter d, in which 5 cm < L < 50 cm, preferably 15 cm < L < 25 cm and more preferably L = 20 cm, and in which 2 mm < d < 30 mm, preferably 5 mm < d < 15 mm and more preferably d = 10 mm.

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