FR3101666A1 - Turbomachine oil circuit including a relief valve - Google Patents

Abstract

The invention relates to an oil circuit (38) for an aircraft turbomachine (10) comprising at least one oil circulation loop (40) successively comprising at least one oil reservoir (42), an oil pump. 'supply (44), an oil / fuel exchanger (46), at least one oil chamber (34, 36) defined by at least one rotor rotating in a housing and supplied with pressurized air, and at least one delivery pump (48) providing an oil return to the reservoir (42), characterized in that it comprises a discharge device (50) which is configured to open in response to the exceeding of a determined pressure threshold in said loop within a range of rated engine operating temperatures. Figure for the abstract: Figure 3.

Description

Turbomachine oil circuit comprising a relief valve

Technical field of the invention

The invention relates to a turbomachine equipped with an oil circuit. The field of application of the invention is that of turbomachines for aircraft engines, and in particular turbomachines comprising an accessory box or AGB (acronym for Accessory Gear Box).

Technical background

An aircraft turbomachine is generally a dual-flow turbomachine which comprises, from upstream to downstream in the direction of gas flow, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, and a low pressure turbine.

The high-pressure compressor and the high-pressure turbine are linked together by a high-pressure rotor and thus form a high-pressure body. The low pressure compressor and the low pressure turbine are linked together by a low pressure rotor and thus form a low pressure body. The low pressure spool rotor is mounted generally coaxially inside the high pressure spool rotor. The low pressure body drives, directly or via a reducer, a fan.

The high and low pressure rotors are mounted in a casing of the turbomachine which is delimited substantially, at the level of the upstream end of the high pressure body, by an upstream enclosure, and at the level of the downstream end of the high pressure body, by a downstream enclosure. These two enclosures contain bearing and gear type components intended to ensure the rotation of the high and low pressure rotors.

For their lubrication, oil is injected into the bearings and gears contained in these enclosures. The rotation of these bearings and gears expels the oil creating an atmosphere of suspended oil in the form of droplets. In addition, a flow of pressurized gas passes through these enclosures for pressurization purposes to prevent oil from being drawn out of these enclosures. The pressurization gases are evacuated via a degassing circuit containing an "oiler" intended to minimize oil losses in the turbomachine, and ejected through a degassing tube.

There are several configurations of oil separators, these being able on the one hand to be arranged internally and coaxially with the low pressure rotor, and/or on the other hand at the level of an accessory box of the turbomachine, which can be attached to an outer casing of the fan or one installed at the heart of the engine, and which comprises accessories allowing the operation of the turbomachine, such as a starter, alternators, etc.

The oil which supplies at least the upstream and downstream enclosures circulates in an oil circuit which comprises, essentially, at least one oil circulation loop successively comprising at least one oil tank, one supply, an oil/fuel exchanger, the upstream and downstream enclosures, and at least one delivery pump providing oil return to the tank.

The oil that circulates in the upstream and downstream enclosures not only has a lubricating function, but it also ensures the cooling of the enclosures by evacuating the calories found there. The calorie-laden oil must therefore be cooled. For this purpose, the oil circulation loop comprises at least one oil/fuel exchanger.

Indeed, the fuel is conventionally stored in tanks located in the wings of the aircraft, and it is therefore subjected to relatively low temperatures which are able to cool the oil through the oil / fuel exchanger.

Oil/fuel exchangers are exchangers with particularly thin walls. A breach may occur in their walls which then allow the passage of fuel into the oil, which has the effect of contaminating the oil.

This configuration should definitely be avoided, as the fuel is likely to vaporize quickly.

Indeed, vaporized fuel is extremely flammable and can cause, in the event of an overflow from one or more enclosures, fire outbreaks in hot areas near said enclosures with the consequent degradation of the components located there.

This configuration is all the more worrying in the case of an oil circuit for which the tank is formed in an accessory box comprising an oil separator, because a fuel leak in the oil has the effect of causing a filling the accessory box until the oil level reaches the degassing tube, which results in loss of pressurization of the upstream and downstream enclosures and leakage of highly flammable liquid and/or vapor to parts hot from the engine.

So far, no satisfactory solution has been proposed to counter such risks.

The document FR–2980238-A1 describes a turbomachine oil circuit comprising a tank provided with a means of measuring its oil level, and monitoring of this oil level allowing the triggering of an alert if the decrease in the level of oil, which is naturally consumed by the engine in operation, is less than a minimum setpoint decrease, a sign that the oil naturally consumed is replaced by fuel resulting from a leak. This document does not make it possible to detect a rise in pressure in the oil circuit. The disadvantage of this design is that it does not allow any action to be taken to maintain engine operation when the failure occurs, and only has a purely informative function.

The invention overcomes these drawbacks by proposing a new design of an oil circuit comprising a discharge device able to avoid any overpressure, and allowing in the case of a turbomachine comprising an accessory box provided with a device de-oiling, to avoid filling the box to a critical level where the degassing tube of the de-oiling device is clogged.

For this purpose, the invention proposes an oil circuit for an aircraft turbine engine comprising at least one oil circulation loop successively comprising at least one oil tank, a supply pump, an oil/fuel exchanger , at least one oil enclosure defined by at least one rotor rotating in a casing and supplied with pressurized air, and at least one delivery pump ensuring a return of oil to the reservoir, characterized in that it comprises a device for discharge which is configured to open in response to exceeding a determined pressure threshold in said loop within a range of rated engine operating temperatures.

According to other characteristics of the oil circuit:

- the discharge device comprises a valve means which is interposed in said circulation loop between the delivery pump and the oil tank,

- the valve means is a passive mechanical valve which is housed in a branch of said circulation loop which connects the delivery pump to the oil tank, and said passive mechanical valve comprises a seat receiving a movable closing element of said seat , said movable obturation element being subjected, on a side opposite said seat, to a fluid pressure coming from the oil circulation loop and being biased against said seat by a return force exerted by a calibrated elastic means at said determined pressure threshold,

- the oil circuit comprises a device for inhibiting the valve means which is configured to interrupt the circulation of fluid through said valve means below a determined temperature less than or equal to a minimum temperature of the temperature range rated operating hours of the motor,

- the passid mechanical damper inhibition device comprises a thermostatic element which is configured to lock the movable shutter element on its seat below the determined temperature,

- the passive mechanical valve comprises a tubular body, one end of which comprises a frustoconical seat supplied with fluid from the oil circulation loop, and receiving a shutter ball forming the movable shutter element, biased against said seat by a spring, forming the elastic means, which is calibrated at the determined pressure threshold, and a thermostatic element in the form of a washer arranged axially in line with a free end of the ball in said body, which is capable of expanding between a position when cold below the determined temperature, in which the washer is of a smaller diameter than that of the ball and locks the ball in its seat, and a position at normal operating temperature, within the range of rated operating temperatures of the motor, in which the washer is of a larger diameter than that of the ball and leaves the ball axially free,

- the valve means is a valve controlled by a control unit in response to pressure and temperature information provided by sensors arranged in the oil circulation loop, and which is controlled to open in response to the overflow of said determined pressure threshold in said loop only within the range of nominal operating temperatures of the engine by being inhibited below a determined temperature lower than a minimum temperature of said range of nominal operating temperatures of the engine.

The invention also relates to an aircraft turbine engine comprising an accessory box, characterized in that it comprises an oil circuit of the type described above, the oil tank of which is housed in a casing of said accessory box. , and a de-oiling device housed in said casing of said accessory box.

According to one characteristic of the turbomachine, the oil-removal device comprises a degassing tube.

The invention finally relates to a method for controlling a turbomachine oil circuit of the type described above, characterized in that it comprises at least one cold operation step during which the discharge device is inhibited below of a determined temperature below a minimum temperature of said rated engine operating temperature range, and a normal operation step in which, with the engine within the rated engine operating temperature range, the relief device remains closed below the determined pressure threshold during a first sub-step and opens in response to exceeding the determined pressure threshold in the oil circulation loop during a second sub-step.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

FIG. 1 is an axial sectional view of a turbomachine known from the state of the art;

FIG. 2 is a diagrammatic view in axial section of an oil circuit of a turbomachine according to the state of the art;

FIG. 3 is a diagrammatic view in axial section of an oil circuit of a turbomachine comprising a relief device according to the invention;

Figure 4 is a schematic view of a relief device comprising a valve means piloted according to a first embodiment of the invention;

Figure 5 is a schematic view of a relief device comprising a mechanical valve provided with a first embodiment of an inhibition device, shown closed with an inactive inhibition device;

Figure 6 is a schematic view of the discharge device of Figure 5 shown open with its inhibition device inactive;

Figure 7 is a schematic view of the discharge device of Figure 6 with its active inhibition device;

FIG. 8 is a block diagram illustrating the steps of a method for controlling a discharge device according to the invention.

Detailed description of the invention

There is shown in Figure 1 a turbomachine 10 with gas turbine 11 multi-body axis A, intended in particular to equip an aircraft.

In a known manner, as illustrated in FIG. 1, the turbomachine 10 comprises in a casing 13 at least one low-pressure rotating body 12 and one high-pressure rotating body 14. The low-pressure 12 and high-pressure 14 bodies are co-rotating.

The low pressure body (LP) 12 essentially comprises, in the direction of gas flow "G", a LP compressor rotor 16 connected by a LP shaft 18 to a LP turbine rotor 20.

The high pressure (HP) body 14 essentially comprises, depending on the direction of gas flow, an HP compressor rotor 22 connected by an HP shaft 24 to an HP turbine rotor 26. A combustion chamber 25 is mounted between the HP compressor 22 and the HP turbine 26 and delivers combustion gases to the HP turbine, in which the combustion gases expand to rotate the rotor of the HP turbine 26, which in turn drives the compressor rotor HP 22 through the HP 24 shaft.

The BP 18 and HP 24 shafts are coaxial. The tubular HP 24 shaft is crossed axially by the BP 18 shaft which is thus surrounded by the HP 24 shaft.

In this configuration, the LP compressor 16 supplies air to the HP compressor 22 which in turn supplies air to the combustion chamber 25. The HP turbine 26 supplies combustion gas to the LP turbine 20.

The LP shaft 18 for its part drives a fan 28 placed upstream of the low pressure 12 and high pressure 14 bodies. This fan drives the gas flow G which breaks down into a primary flow P which passes through the gas turbine engine 11 and a secondary flow S which circulates around the gas turbine engine 11. The primary P and secondary flows S meet at a nozzle (not shown) of the engine 10.

In known manner, the engine 10 comprises a drive unit 30 for accessory equipment of said engine, hereinafter called the accessory unit 30, which is mounted on a fan casing 32 or the HP compressor casing (not shown) of the engine and which carries at least one starter and a certain number of items of equipment or accessories capable of being connected in rotation to said turbomachine such as, in particular, an electric generator, an alternator, and hydraulic fuel and oil pumps (not represented ).

The motor 10 also comprises upstream 34 and downstream 36 enclosures which comprise internal bearings capable of ensuring the rotation of the low pressure 12 and high pressure 14 bodies.

As can be seen in Figure 2, the turbine engine 10 includes an oil circuit 38 intended to ensure the lubrication of the upstream 34 and downstream 36 enclosures.

Essentially, the oil circuit 38 comprises at least one oil circulation loop 40 in a closed circuit. The oil circulation loop 40 successively comprises at least one oil tank 42, a feed pump 44, an oil/fuel exchanger 46, the upstream 34 and downstream 36 oil enclosures which are supplied with pressurized air, and at least one delivery pump 48 providing oil return to reservoir 42.

In the configuration that has been shown in Figure 2, and in a non-limiting manner of the invention, the tank 42 is arranged in a housing of the accessories box 30. The housing of the accessories box 30 also comprises a tube degassing 31, shown schematically in Figure 3, intended to allow the evacuation of the air recovered with the oil inside the accessory box 30.

The accessory box 30 being of necessarily reduced size, the volume of the oil tank 42 is also reduced.

The oil which circulates through the circuit 40 passes through the oil/fuel exchanger 46 by which it is cooled.

However, this type of exchanger 46 has walls of reduced thickness, so that a rupture of its walls may occur, causing pollution of the oil by the fuel, which then tends to penetrate into the oil circuit 38 .

The fuel, in this case kerosene, is particularly volatile at high temperature and the introduction of the latter into the oil circuit 38 can cause the tank 42 to be overfilled to a level at which it is not expected and may lead to a spill of a relatively flammable oil/fuel mixture in the degassing tube 31 of the accessory box 30. This has the effect of causing a loss of the pressurization of the upstream 34 and downstream 36 enclosures, with the consequence a risk of fuel leaking out of the upstream 34 and downstream 36 enclosures and consequently a leak of highly flammable liquid towards hot parts of the engine.

The invention overcomes this drawback by proposing an oil circuit 38 equipped with a discharge device 50.

This configuration has been represented schematically in Figure 3.

In accordance with the invention, the relief device 50 is configured to open in response to the exceeding of a determined pressure threshold in the loop 40, and this, within a range of nominal operating temperatures of the motor 10. This threshold pressure P _min , will be described later in the following description with reference to Figure 8.

In the configuration that has been shown in Figures 2 and 3 for which the tank 42 is of limited capacity and arranged inside the accessory box 30, it is imperative that the oil contaminated by the fuel, which reaches the tank 42 and ends up overflowing, does not see its level increase too high in the accessory box 30 so as not to reach the degassing tube 31.

To this end, the relief device 50 comprises a valve means 52 which is interposed in a return branch 54 of the circulation loop 40 between the delivery pump 48 and the oil reservoir 42. Thus, any excess volume content in the circuit 38 resulting from the fuel leak through the exchanger is it discharged out of the circuit 38 by the relief device 50 and does not cause an increase in the level of the accessory box 30 beyond of the degassing tube 31.

It will be understood that other configurations are possible, depending in particular on the number of exchangers, enclosures, and oil recovery pumps, and their arrangement in the oil circuit 38. However, the location of the device discharge 50 will preferably be chosen in order to avoid overfilling of the accessory box 30.

According to a first embodiment of the invention which has been represented in FIG. 4, the valve means 50 is a valve 56 controlled by a control unit 58 in response to pressure P and temperature T information supplied respectively by sensors 60, 62 arranged in the oil circulation loop 40 previously described. The controlled valve 56 is arranged in the return branch 54 and it comprises an evacuation branch 64. The valve 56 is controlled to open in response to exceeding the pressure threshold P _min determined in the loop 40, shown in 8, only in the range of nominal operating temperatures of the engine 10, that is to say engine warm after starting, being consequently inhibited below a determined temperature T _min lower than a minimum temperature of a rated operating temperature range of motor 10, as will be seen with reference to Figure 8.

This design allows in particular a software adjustment of the pressure threshold P _min for which the valve means 50 is supposed to open, and of the permissible temperature range of the engine in which the valve means 50 can open.

However, as illustrated in Figures 5 to 7, in a preferred manner of the invention, the valve means 50 is a passive mechanical valve 66 which is housed in the return branch 54 of the circulation loop 40.

As illustrated in Figures 5 to 7, the passive mechanical valve 66 comprises, by way of example and in a non-limiting manner of the invention, a seat 68 receiving a movable closure element 70 of said seat 68. For example, in a non-limiting manner to the invention, the mobile shutter element 70 comprises a shutter ball 70 which is received on the frustoconical seat 68 .

The movable closure element 70 is subjected, on a side opposite the seat 68, to a pressure P of the fluid coming from the oil circulation loop and more particularly from the branch 54 and it is biased against the seat 68 by a return force exerted by an elastic means 72 which is calibrated at the determined pressure threshold P _min . The passive mechanical valve 66 comprises for example here a tubular body 74, one end of which comprises the frustoconical seat 68 supplied with fluid from the oil circulation loop, and receiving internally the closing ball 70 and a spring 72 forming the means elastic which recalls the shutter ball 70 against the seat 68.

Advantageously, the oil circuit 38 also comprises a device 76 for inhibiting the valve means 50, which is configured to prevent the circulation of fluid through the valve means 50 below the determined temperature T _min lower than the temperature of the rated operating temperature range of the motor. This device is integrated into the software-controlled valve or mechanically associated with the passive mechanical valve 66.

The device 76 for inhibiting the passive mechanical valve 66 is integrated into this valve, as shown in Figures 5 to 7.

More particularly, the device 76 for inhibiting the mechanical valve 66 comprises a thermostatic element 78 which is configured to lock the movable shutter element 70 on its seat 68 below the determined temperature T _min.

According to the previously described configuration, the thermostatic element has the form of a washer 78 arranged axially in line with a free end of the ball 70 in the body 74. This washer 78 is capable of expanding between a cold position in below the temperature T _min , as represented in FIG. 7, in which the washer 78 is of a smaller diameter than that of the ball 70 and locks the ball 70 on its seat 68, and a position comprised within the temperature range normal operation, shown in Figures 5 and 6, in which the washer 78 is of a diameter greater than that of the ball 70 and leaves the ball 70 axially free so that its movements are only conditioned by the pressure P.

In this configuration, the relief device 50 is capable of operating according to a method allowing the opening or closing of the relief device 50 according to the temperature and pressure conditions in the loop 40 of the circuit 38. This method is implemented works electronically when the relief device comprises a controlled valve, or purely mechanically when the relief device comprises a passive mechanical valve 66.

As illustrated in FIG. 8, the method comprises at least one cold operation step ET1 during which the valve means 50 is inhibited below the temperature T _min by the inhibition device 76, i.e. i.e. in any event below the rated operating temperature range of the engine. In the case of the passive mechanical valve 66, this configuration corresponds to FIG. 7. The temperature T _min is for example between 30° C. and 60° C.

The method comprises a step ET2 of normal operation during which, the circuit being in a range of nominal operating temperatures of the engine, that is to say at a temperature higher than the threshold temperature T _min determined, the device discharge 50 remains closed below the pressure threshold determined P _min during a first sub-step SET1 and opens in response to the exceeding of the pressure threshold P _min determined in the loop 40 of oil circulation during of a second sub-step SET2.

In the case of the passive mechanical valve 66, the first sub-step SET1, during which the inhibition device 76 releases the mechanical valve 76 and in which the pressure P in the circuit 38 is insufficient to open the passive mechanical valve 66 , is represented by FIG. 5. The second sub-step SET2, during which the inhibition device 76 releases the mechanical valve 76 but in which the pressure P in the circuit 38 is sufficient to open the passive mechanical valve 66, is shown in Figure 6.

The invention therefore makes it possible to automatically regulate in a simple and effective manner the level of the oil/fuel mixture in an oil circuit contaminated by fuel, in order to prevent the risks of degradation of this circuit and the outbreak of fire.

Claims (9)

Oil circuit (38) for an aircraft turbine engine (10) comprising at least one oil circulation loop (40) successively comprising at least one oil tank (42), a supply pump (44) , an oil/fuel exchanger (46), at least one oil enclosure (34, 36) defined by at least one rotor (16, 20 22, 26) rotating in a casing (13) and supplied with pressurized air, and at least one delivery pump (48) providing oil return to the tank (42), characterized in that it comprises a discharge device (50) which is configured to open in response to exceeding a threshold (Pmin) pressure determined in said loop in a range of nominal operating temperatures of the engine. Oil circuit (38) according to the preceding claim, characterized in that the relief device (50) comprises a valve means (52) which is interposed in the said circulation loop (40) between the delivery pump (48) and the oil reservoir (42). Oil circuit (38) according to the preceding claim, characterized in that the valve means (52) is a passive mechanical valve (66) which is housed in a return branch (54) of the said circulation loop (40) which connects the delivery pump (48) to the oil reservoir (42), and in that the said passive mechanical valve (66) comprises a seat (68) receiving a movable closing element (70) of the said seat, the said element movable shutter (70) being subjected, on a side opposite said seat (68), to a pressure (P) of a fluid coming from the loop (40) for circulating oil and being biased against said seat ( 68) by a return force exerted by an elastic means (72) calibrated to said determined pressure threshold (Pmin). Oil circuit (38) according to one of Claims 2 or 3, characterized in that it comprises a device (76) for inhibiting the valve means (50) which is configured to prevent the circulation of fluid through said valve means (50) below a determined temperature (T _min ) lower than a minimum temperature of the nominal operating temperature range of the engine. Oil circuit (38) according to Claim 4, characterized in that the device for inhibiting (76) the mechanical valve comprises a thermostatic element which is configured to lock the closing element (70) movable on its seat ( 68) below the set temperature (Tmin). Oil circuit (38) according to the preceding claim, characterized in that the passive mechanical valve (66) comprises a tubular body (74), one end of which comprises the seat (68), of generally frustoconical shape, supplied with fluid from the oil circulation loop (40), and receiving a shutter ball (70) forming the movable shutter element, biased against said seat by a spring (72), forming the elastic means, which is calibrated at the pressure threshold (Pmin) determined, and a thermostatic element (78) in the form of a washer arranged axially in line with a free end of the ball (68) in said body (74), which is capable of expanding between a position cold below the determined temperature (Tmin), in which the washer (78) is of a smaller diameter than that of the ball (68) and locks the ball (68) on its seat (70), and a position at normal operating temperature, within the rated operating temperature range of the engine, wherein the washer (78) is larger in diameter than the ball (68) and leaves the ball (68) axially free. Oil circuit (38) according to one of Claims 1 or 2, characterized in that the valve means (52) is a valve controlled by a control unit in response to pressure and temperature information provided by sensors arranged in the oil circulation loop, and which is controlled to open in response to the exceeding of said determined pressure threshold (Pmin) in said loop only within the nominal operating temperature range of the engine, being inhibited below a determined temperature (Tmin) lower than a minimum temperature of said nominal operating temperature range of the engine. Aircraft turbomachine (10) comprising an accessory box (30), characterized in that it comprises an oil circuit (38) according to one of Claims 1 to 7, the oil tank (42) of which is housed in a housing of said accessory box (30), and an oil separator housed in said housing of said accessory box (30). Method for controlling a turbomachine oil circuit according to one of Claims 1 to 7, characterized in that it comprises at least one step (ET1) of cold operation during which the discharge device (50 ) is inhibited below a determined temperature (Tmin) below a minimum temperature of said nominal operating temperature range of the motor, and a normal operating step (ET2) during which, the motor being in the range of nominal operating temperatures of the engine, the relief device (50) remains closed below the threshold (Pmin) of pressure determined during a first sub-step (SET1) and opens in response to exceeding the threshold (P _min ) of pressure determined in the oil circulation loop (40) during a second sub-step (SET2).