FR3095836A1 - Fluid separator of a two-phase mixture that can circulate in an aircraft engine fluid circuit, in particular for overflow in a lubrication circuit - Google Patents

Abstract

The fluid separator of a two-phase mixture comprises a reservoir (25) occupied by a float (26). A phase-separated circulation is created by an advantageous construction, such as promoting centrifugation or other flow irregularities, inside the tank, and the liquid accumulating at the bottom ends up lifting the float, which opens. then an evacuation connector (15). One envisaged application is on overflow conduits (2) of lubricant reservoirs, normally traversed by oiled air directed to an enclosure to be lubricated, then to a vent for pressurized lubricant circuits. Figure for the abstract: Fig. 2

Description

Fluid separator for a two-phase mixture that can circulate in a fluidic circuit of an aircraft engine, in particular for overflow in a lubrication circuit

The subject of the present invention is a fluid separator for a two-phase mixture that can circulate in a fluid circuit of an aircraft engine, in particular for overflow in a lubrication circuit.

Dynamic lubrication circuits exist in aircraft engines to ensure oil circulation through enclosures and equipment, with the advantage that continuous lubrication prevents excessive heating of certain equipment contained in these enclosures, such as machine shaft bearings. These circuits include a reservoir where the lubricating oil stays between passing cycles through the equipment of the turbomachine. The tank has an overflow pipe that connects to its upper part and avoids excessive pressure in the tank, which is typically occupied by a mixture of air and oil. Lubrication ducts transport either oil in its pure state at the equipment inlet, or oiled air at the equipment outlet. It is a flow of oiled air which normally travels through the overflow duct, which typically rejects it into one of the enclosures comprising components to be lubricated, for example a gear box provided with a grounding duct. free air which allows excess air to escape from the lubrication circuit, after having dried it with an oil separator. A pressurization valve is installed on the overflow pipe to prevent it from opening when an overpressure threshold is not reached in the tank.

An excess of liquid can appear in certain circumstances in the reservoir, and also in the overflow pipe: a typical (but not exclusive) case is that of a perforation in a heat exchanger between the lubrication circuit and the circuit fuel supply to the engine, since it is conceivable to use the latter to absorb part of the heating received by the lubricant during its service. As the fuel is most often pumped at a higher pressure than the lubricant, such a perforation produces a fuel leak in the lubrication circuit, which mixes with the oil. The liquid content in the lubrication circuit and the reservoir becomes increasingly important, and the overflow pipe can end up rejecting liquid in the equipment preceding the vent, which can disturb this last, whether the excess liquid is pure lubricant or a mixture of lubricant and fuel, for example. The vent duct itself may become clogged, making pressure rise in the lubricant circuit unavoidable.

Another circumstance in which the overflow conduit may temporarily carry near or pure liquid is that of a reversal of gravity, which throws the liquid contents of the reservoir to its top and to the entrance of the conduit. overflow.

A fluid separator has been designed here allowing excess liquid to be evacuated from the overflow pipe before it reaches the equipment preceding the venting and allowing the drainage of this excess liquid towards a recovery enclosure, or possibly towards the combustion chamber (if it is expected that the excess fluid will contain fuel), or even reject it outside the engine. This separator is designed to allow a gaseous mixture to pass, for example oily air formed by a mixture of air and oil vapours, coming from an overpressure discharge from a pressurized liquid tank such as for example a oil tank. If, on the other hand, the mixture arriving via the inlet duct becomes gaseous-liquid two-phase, the separator is also designed to extract the liquid from this mixture by drainage. The drainage obtained thus prevents a significant quantity of liquid from escaping through the outlet duct towards the equipment preceding the venting, for example a gearbox. The invention applies above all to pressurized lubrication circuits, for which simple drainage devices would be inappropriate.

A general aspect of the invention is a fluid separator for a two-phase gas-liquid mixture that can circulate in a fluid circuit of an aircraft engine, comprising a reservoir, an inlet connector and an outlet connector connectable to conduits for entering and exiting the mixture and passing through upper portions of a wall of the tank, a connection for discharging the liquid separated from the mixture, passing through the wall at a lower portion thereof, and a movable float in the tank between a lower position, where it rests on the drain connection and seals it, and raised positions caused by a rise in the level of liquid in the tank, where it is moved away from the drain connection, the float leaving the inlet fitting open at any position.

When the separator tank fills with a certain height of liquid which accumulates at the bottom of the tank, the float is lifted by opening the discharge connection, which therefore allows at least partial emptying of the liquid content of the tank. As the inlet and outlet ducts open into the upper part of the tank which always remains occupied by gas and whose layout can be chosen with great freedom, it is easy to promote there flows which favor the separation between the air and suspended liquid, possibly in excess, to trickle it over the wall of the tank and let it flow away, while drier air leaves the separator.

Thus the inlet connector and the outlet connector are advantageously misaligned with each other, for example at different levels, to produce a flow irregularity which promotes separation.

An advantageous construction comprises the wall of the tank having a shape of revolution and the inlet connection directed in a direction tangential to an internal face of the wall, to promote a circumferential or cyclonic movement, favorable to the centrifugation of its liquid content, of the air in the tank.

An advantageous way of arranging the float in the tank is to place it in the center and to allow it a vertical translational movement. It is then advantageous for the float to be guided in the vertical direction in the tank by a centering device. It should however be emphasized that the invention is practicable with other possible movements of the float, in particular pivoting movements.

In another advantageous design, the float comprises a rod projecting out of the reservoir through an orifice in the wall of the reservoir and arranged as an indicator of the raised state or position of the float.

In another particularly interesting design, the float is separated from the tank wall by an annular space and the outlet connection is placed at a higher level than the inlet connection. This construction makes it easy to establish the circumferential or cyclonic movement mentioned above between the float and the wall; it also makes it easy to obtain that the float includes a part which closes off the outlet connection at certain of the raised positions, with the advantage of then safely avoiding the irruption of an excess of liquid in the enclosure downstream of the separator; this last improvement can also be obtained with other constructions of the tank.

The float can include a float block - hollow or lighter than the liquid - alone or integral with other parts, which then make up a float assembly with it: the functions, in particular shutter, of the float can be performed either by the block , or by other parts of the assembly; examples will be given later.

It is also possible to have the tank with an upper pocket, above the inlet and outlet connectors, to conserve the liquid in the event of the separator overturning, or of reversal of gravity as a result of a flight attitude in zero or negative gravity of the aircraft, one engine of which includes the separator.

Another aspect of the invention is a lubrication circuit for an aircraft engine comprising the separator according to the foregoing on a conduit normally carrying oiled air; a particularly contemplated application, already mentioned, is that the inlet connection leads to a top of an oil recovery tank via said conduit, which is an overflow drain, and the outlet connection leads to an enclosure to be lubricated; and the oily air duct can be fitted with an opening pressure threshold valve, which is arranged in series with the separator.

In general, the equipment mentioned in this description and connected to each other by ducts can be directly or indirectly, intermediate equipment (mentioned or not) can be interposed on the ducts.

The various aspects, characteristics and advantages of the invention will now be described in connection with the following figures, which describe certain embodiments given by way of illustration thereof:

illustrates the separator on a portion of a lubrication circuit,

illustrates a first embodiment of the invention, in vertical section,

the same, in horizontal section along line III of figure 2,

the same, in horizontal section along line IV of figure 2,

the same, to another state,

illustrates a second embodiment of the invention,

the same, to another state,

illustrates yet another third embodiment of the invention,

the same, to another state,

illustrates a fourth embodiment of the invention, in a vertical section,

the same, in horizontal section along line XI.

FIG. 1 represents a typical location of a separator 1 in accordance with the invention, placed on an overpressure evacuation conduit 2, provided to evacuate the excess pressure from a pressurized oil tank 3 towards an enclosure 4 containing components to be lubricated, such as a gearbox. The overpressure evacuation conduit 2 is provided with a pressurization valve 5 of the oil reservoir 3, allowing the conduit to open only at a determined pressure threshold which corresponds to the desired pressure in the oil reservoir 3 The pressurization valve 5 is shown here downstream of the separator 1, but it could be upstream of it. The gearbox 4 is fitted with a vent pipe 6 which allows the excess gas to be evacuated from the lubrication circuit; this vent duct 6 is normally fitted with an oil separator, not shown. Oil tank 3 is fitted with a level probe 7; the overpressure evacuation conduit 2 comprises, upstream of the separator 1, an inlet conduit connected to the oil reservoir 3 at the level of its top wall 8 (the connection may in practice be indirect, if for example the conduit of inlet opens into a deaerator mounted on the top wall 8); other ducts 9 are connected to the oil tank 3 and pour their contents into it, which in normal times is deaerated oil as well as possibly oily air. The rest of the lubrication circuit of this particularly envisaged application is conventional for aircraft engines and will not be represented here. As has been pointed out, the fluid flowing through the overpressure discharge pipe 2 is generally oily air, but it may contain excess liquid such as lubricant or even a mixture of lubricant or of a other liquid, such as fuel that accidentally entered the lubrication circuit. The inlet duct of the overpressure evacuation duct 2 can therefore be used to evacuate an overflow of liquid coming from the tank. The overpressure evacuation conduit 2 is also referred to as the overflow conduit 2 in what follows.

Separator 1 can be used in other applications without departing from the scope of the invention.

The embodiment of FIGS. 2 to 5 is a separator 10 which basically comprises a wall 11 encompassing a cavity 12 and through which inlet 13, outlet 14 and evacuation 15 connectors pass. The inlet 13 and outlet 14 connectors are connected to two separate parts of the overflow conduit 2, and the discharge connector 15 leads to a drainage conduit 16 which itself leads, for example, to a recovery enclosure 17 of liquid. Advantageously, the pressure in the recovery enclosure 17 is kept lower than the pressure prevailing in the cavity 12, for example by venting the enclosure 17 which could also serve as an overflow outlet for this recovery enclosure. In this way, a passage of liquid from the cavity 12 to the enclosure 17, when the cavity 12 fills with liquid and the discharge connection 15 is no longer blocked, takes place not only under the effect of the weight gravity of the liquid but also under the effect of the thrust created on the liquid by the pressure difference between the cavity 12 and the enclosure 17.

The wall 11 has a shape of revolution essentially, and more precisely cylindrical, with the axis of the vertical cylinder in the normal position of the lubrication circuit. The evacuation connector 15 extends through a flat bottom 18 of the wall 11, while the inlet 13 and outlet 14 connectors connect to the peripheral face of the wall 11, at an upper part thereof. here, and moreover at different levels, the outlet connection 14 being higher than the inlet connection 13. The regularity of shape of the wall 11 is thwarted by a boss 19 of vertical groove projecting outwards , through which the inlet connector 13 joins the cavity 12; and again by an accumulation pocket 20 established on a projection 21 of a cover 22 which closes a top opening of the wall 11. The cover 22 is provided with a central orifice 23 delimited by a guide sleeve 24 vertical. The wall 11 and the cover 22 form a reservoir 25.

The cavity 12 contains a float 26 comprising a main part 27, a collar 28 and a guide rod 29 which can serve as a position indicator for the float 26. The collar 28 surmounts the main part 27, the rod 29 stands above the above the flange 28, and it passes through the guide sleeve 24. All parts of the float 26 are cylindrical with a vertical axis. A seal 30 is placed at the bottom of the main part 27. Advantageously, the section of the guide rod 29 is less than or equal to the passage section of the evacuation connector 15. In this way, if the pressure in the recovery chamber 17 is substantially equal to the pressure outside the reservoir 25, which is lower than the pressure prevailing in the cavity 12, the resultant of the antinomic pressure difference forces acting on the float 26 at the level of the rod 29 and the seal 30 does not raise the float 26, but on the contrary tends to create on the float 26 a support directed towards the evacuation connection 15. It is understood that if the section of the guide rod 29 is equal to the passage section of the evacuation connection 15, these contradictory pressure difference forces compensate each other and their resultant is therefore zero, in other words these forces do not create support on the float 26. usual state, represented in the Figure 2, where the cavity 12 is essentially occupied by gas, the float 26 rests at the bottom 18 of the tank 25 and the seal 30 closes the evacuation connection 15, and the stem 29 has a top which is flush with the upper surface of the lid 22. The inlet connector 13 then extends at the height of the upper part of the main part 27, just below the flange 28, and the outlet connector 14 extends immediately above of the collar 28. The collar 28 has a diameter slightly less than that of the inner face of the wall 11, as shown in FIG. 3, which clearly illustrates the vertical groove 31. FIG. 4 clearly illustrates that an annular space 32 remains between the main part 27 of the float 26 and the internal face of the wall 11. As the inlet connector 13 arrives obliquely on the wall 11, it projects the fluid which travels through it tangentially to the annular space 32, which imparts to it a circumferential or cyclonic movement, represented nted in Figures 2 and 4, with a descending component, until the fluid rises through the vertical groove 31, to an upper space 33 of the cavity 12, above the collar 28 and at the height of the connection outlet 14, then leaves separator 10 by entering this one.

The circumferential or cyclonic movement promotes separation of the liquid content of the two-phase mixture which most often travels through the separator 10, and the liquid descends to the bottom of the cavity 12 by streaming along the wall 11.

When the liquid level rises in the cavity 12, it ends up raising the float 26: Figure 5 shows the state obtained, in which the discharge connection 15 is open and the reservoir 25 is emptied. It will be noted that the flange 28 of the float 26 then at least partially closes the outlet connector 14, thus necessarily preventing a significant evacuation of liquid towards the enclosure 4, and that the end of the rod 29 protrudes above the cover 21, which makes it possible to detect, visually or otherwise, the state reached. In a case where the flow of liquid arriving in the separator 10 would exceed the flow of this same liquid evacuated via the evacuation connection 15, which may correspond to a case of a major fuel leak in the oil circuit and/or at a relatively limited passage section of the discharge connection 15, the level of liquid would rise in the cavity 12 to a sufficient height for the collar 28 of the float to almost completely close the outlet connection 14. Complete sealing is not necessary for this closure of the outlet connection, some leaks due to the operating clearance between the collar 28 and the outlet connection 14 are therefore acceptable. Closing of the outlet connector 14 can generate a relative increase in the pressure of the liquid in the cavity 12, which will increase the flow rate of the liquid evacuated via the evacuation connector 15 until the pressure stabilizes at a new level. oil tank 3 pressurization value which remains acceptable.

Another situation is that of an inversion of gravity, following a strong vertical acceleration of the aircraft in which the lubrication circuit may be located, or a reversal of the latter. The contents of the tank 25 tilt, that is to say that the collar 28 still closes the outlet connector 14, while the liquid present occupies the pocket 20.

The invention can be implemented in many ways. The embodiment of Figures 6 and 7 shows a simplified embodiment 34 which differs from the previous one in that the float 35 is composed of a single cylindrical part, guided by a cylindrical centering partition 36 welded to the bottom 37 of a tank 38 here perfectly cylindrical.

As before, the inlet and outlet fittings 13 and 14 pass through the top of the tank wall 38, and the discharge fitting 15 pass through the bottom 37. The float 35 rests on the discharge fitting 15 by a seal seal 39 as before. The centering partition 36 is provided with a lower opening 40 to allow pressure to enter below the periphery of the float 35 and allow it to rise surely when a sufficient level of liquid extends into the tank 38, which is the FIG. 7: emptying via the evacuation connection 15 then takes place via the opening 40. The centering partition 36 holds the float 35, allowing it only a vertical translation. A vertical stop, not shown, can be provided so that the float 35 does not come out of the centering partition 36 when the level of liquid rises in the tank 38.

A third embodiment 41 of separator is described in Figures 8 and 9 and comprises a float 42 arranged differently in the tank 43, since it consists of a pivoting mechanism, comprising a float block 68 (float in the strict sense) mounted by a lever 44 on a hinge 45 assembled on the side wall 46 of the tank 43. Other levers 47 and 48 are hinged to the hinge 45 by forming angles with the lever 44, and they carry valves 49 and 50 able to shut off in turn the outlet connector 14 and the discharge connector 15 respectively. The general operation is the same as before: when liquid accumulates at the bottom of the tank 43, the float block 68 is raised and drives the levers 44, 47 and 48 connected to each other to detach the valve 50 from the evacuation connector 15 and then possibly close the outlet connector 14 by the valve 49. The inlet connector 13 and the outlet connector 14 are as previously placed at the upper part of the tank 43, but the discharge connector 15 can without inconvenience be placed through the side wall 46 of the tank 43, while remaining below the previous ones. The float block 68 can be of any shape and here it is a cubic block. It will be noted a deflecting partition 51 which compartmentalizes the cavity of the tank 43 by separating the outlet connector 14 from the inlet connector 13, bends the flow of the incoming fluid downwards to impose a vortex flow on it in a first compartment 52 of the cavity, occupied by the float block 68, before it passes under the deflecting partition 51, joins the other compartment 53 occupied by the valve 49, and then leaves the reservoir 43. This vortex flow further promotes the separation of fluids diphasic mixing, even if the swirling movement takes place above all around a horizontal axis, instead of the vertical axis of the tank, cylindrical, of the other embodiments.

Yet another embodiment of the invention is described by means of FIGS. 10 and 11. The separator bears the reference 54. There is found a cylindrical float 55 sliding vertically along its axis in a tank 56, the wall of which is also cylindrical of vertical axis. The inlet connector 13 crosses the peripheral wall of the tank 56, the outlet connector 55 the bottom of the tank 56, but the outlet connector 14 is reduced here to a simple drilling of a flat top face 57 of the tank 56 A non-return valve 58 providing the function of the pressurization valve 5 of FIG. 1 is mounted on this flat top face 57. Here it comprises two valve elements 59 and 60 able to open successively at two pressure thresholds different to first open a reduced passage section, then a larger passage section tolerating an increased leakage rate to the enclosure 4 through the mixture outlet duct. This outlet duct forms part of the overpressure evacuation duct 2, located downstream of the separator. The outlet connector 14, which is located at the top of the tank 56, is connectable to the mixture outlet pipe via the non-return valve 58. This non-return valve 58 does not form part of the invention, being the subject of document FR 3068102 A1. It is mentioned here for illustrative purposes only, being able to be replaced by an ordinary non-return valve.

Note some construction features: the outlet 14 and evacuation 15 connections are opposed, and can be alternately closed off by a lower seal 61 and an upper seal 62 at the bottom and at the top of the float 55; the float 55 is guided by ribs 63 assembled on the inner face of the tank 55, these ribs 63 being vertical and provided with orifices 64 for the passage of a flow of fluid through an annular space 65 around the float 55, as in a previous embodiment; the inlet connector 13 is also tangent to this annular space 65; and the float 55 is provided with a rod 66 for indicating the position of the float which extends it downwards, through the bottom of the tank 56, to allow a change in state of the float 55 to be recorded if necessary by a visual observation or an eddy current or other position sensor 67, which measures the displacements of the rod 66. The rod 66 can pass through a wall of the bottom of the tank 56 with sealing, as shown in FIG. 10. Alternatively, it is possible for the rod to extend along a central vertical axis of the float 55 and pass through the center of the lower seal 61 to cross the bottom of the tank 56 passing through the inside of the discharge connection 15. rod can then pass through, if necessary with sealing, a wall of a drainage conduit leading to a liquid recovery enclosure or to the outside of the aircraft engine. In all embodiments comprising a float position indicating rod, such as rod 29 in FIG. 2 or rod 66 in FIG. rod, at least when the aircraft engine is stopped, in order to move the float. This makes it possible in particular to check that there is no abnormal resistance to the displacement of the float, which could be caused for example by a sticking effect of the material of the lower seal 30 or 61.

Claims (10)

Fluid separator for a two-phase gas-liquid mixture capable of circulating in a fluid circuit of an aircraft engine, comprising a reservoir (25, 38, 43, 56), an inlet fitting (13) and a pressure fitting. outlet (14) connectable to inlet and outlet conduits (2) for the mixture and passing through upper portions of a wall (19, 46) of the tank, an outlet connection (15) for the liquid separated from the mixture, passing through the wall of the tank to a lower portion (18) thereof, and a float (26, 35, 42, 55) movable in the tank between a lower position, where it rests on the discharge fitting (15) and the clogging, and raised positions caused by a rise in liquid level in the tank, where it is moved away from the drain fitting, the float leaving the inlet fitting (13) open to any position, characterized in that that the outlet connection (14) is formed by a bore in a top face (57) of the reservoir (56), and a non-return valve (58) is mounted on the top face (57). A fluid separator according to claim 1, characterized in that the wall of the reservoir has a shape of revolution, and the inlet connection is directed in a direction tangential to an internal face of the wall. Fluid separator according to any one of claims 1 or 2, characterized in that the float is guided in the vertical direction in the tank by a centering device (24, 36, 63). Fluid separator according to any one of claims 1 to 3, characterized in that the float (26, 55) comprises a rod (29, 66) projecting out of the reservoir through an orifice (23) in the wall of the reservoir and arranged as float position indicator. Fluid separator according to claims 2 and 3, characterized in that the float is separated from the wall of the tank by an annular space (32, 65). Fluid separator according to any one of claims 1 to 5, characterized in that the float has a part which closes the outlet fitting (14) at some of the raised positions. Fluid separator according to any one of claims 1 to 6, characterized in that it comprises an upper pocket (20), above the inlet connections (13) and of
outlet (14), for preservation of the liquid in the event of overturning of the separator or negative gravity undergone by the separator. Lubrication system of an aircraft engine, characterized in that it comprises the fluid separator (1) according to any one of the preceding claims on a duct (2) normally carrying oiled air. Lubrication circuit according to claim 8, characterized in that said duct (2) is an overpressure discharge duct connected upstream to a pressurized oil recovery tank (3) and connected downstream to an enclosure (4) containing parts to be lubricated. Lubrication circuit according to any one of claims 8 or 9, characterized in that the non-return valve (58) is arranged on the oiled air duct (2).