System and method for supplying lubrication fluid to at least one member of an aircraft propulsion assembly

Abstract

A feed system for feeding lubricating oil to members of a turbine engine including a reduction gearbox, the feed system including a nonpositive-displacement pump device for connecting upstream to an oil tank and driven in rotation at a speed that is not correlated with an operating speed of the turbine engine; a separator node connected to the outlet of the nonpositive-displacement pump device; a first delivery branch for lubricating the RGB connected to the nonpositive-displacement pump device via the separator node; a second delivery branch for lubricating other members connected to the nonpositive-displacement pump device via the separator node, the second delivery branch including a positive-displacement pump; and at least one fluid metering device having a metering slot fed by the nonpositive-displacement pump device via the separator node for the purpose of feeding the RGB.

Claims

1. A feed system for feeding lubricating oil to members of a turbine engine including a reduction gearbox (RGB), the feed system comprising: a nonpositive-displacement pump device for having an inlet connected to an oil tank and driven in rotation at a speed that is not correlated with an operating speed of the turbine engine, and comprising a nonpositive-displacement pump or at least two nonpositive-displacement pumps connected in a series fluid-flow connection; a separator node connected to the outlet of the nonpositive-displacement pump device; a first delivery branch for lubricating at least the RGB, which branch is connected to said nonpositive-displacement pump device via the separator node; a second delivery branch for lubricating other members, which branch is connected to said nonpositive-displacement pump device via the separator node and includes a positive-displacement pump; and at least one fluid metering device having a metering slot and fed by the nonpositive-displacement pump device via the separator node for the purpose of feeding the RGB.

2. The feed system according to claim 1, further comprising a drive device for driving the positive-displacement pump device in rotation at constant speed.

3. The feed system according to claim 2, wherein the device for driving the nonpositive-displacement pump device in rotation comprises a pneumatic actuator.

4. The feed system according to claim 2, wherein the device for driving the nonpositive-displacement pump device in rotation comprises an electric motor.

5. The feed system according to claim 1, further comprising a drive device for driving the positive-displacement pump device at a speed of rotation that can vary between a minimum speed and a maximum speed, said maximum speed being not less than 1.2 times the minimum speed and not greater than twice the minimum speed.

6. The feed system according to claim 5, wherein the device for driving the nonpositive-displacement pump device in rotation comprises a drive shaft coupled to a turbine shaft of the turbine engine via an automatic gearbox having a plurality of transmission ratios.

7. The feed system according to claim 1, further comprising a monitor device for monitoring the fluid flow rate delivered at the outlet from the fluid metering device.

8. The feed system according to claim 7, wherein the monitor device for monitoring the fluid flow rate comprises a measurement sensor for measuring the pressure difference between the upstream and downstream sides of the fluid metering device, said measurement sensor being coupled to a sensor for sensing the position of a movable member for controlling the flow section of the metering slot of the fluid metering device.

9. The feed system according to claim 1, wherein said nonpositive-displacement pump device comprises at least one centrifugal pump.

10. The feed system according to claim 1, wherein the first delivery branch between the separator node and the RGB does not have a fluid recirculation loop.

11. A method of using the feed system according to claim 1, the method comprising a step of regulating the flow rate of the lubricating oil by controlling the position of the movable member for controlling the flow section of the fluid metering device.

12. An aircraft propulsion assembly including a feed system according to claim 1, for feeding lubricating oil to a reduction gearbox of a turbine engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention can be better understood on reading the following description given by way of non-limiting indication and with reference to the accompanying drawing, in which:

(2) FIG. 1 is a diagram of a fluid feed system in a first embodiment;

(3) FIG. 2 is a diagram of a fluid feed system in a second embodiment; and

(4) FIG. 3 is a diagram of a fluid feed system in a third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) FIG. 1 is a diagram of a first embodiment of an oil feed system 1 for a reduction gearbox (RGB) of an aeroengine that comprises a turbine engine.

(6) In the embodiment shown in FIG. 1, the feed system 1 comprises a centrifugal pump 2 having its inlet connected to a fuel tank 3 via a feed branch 4 of the centrifugal pump 2, and two delivery branches 5 and 6 connected to the outlet of the centrifugal pump 2 via a separator node 7.

(7) The first delivery branch 5 includes fluid metering device 8 with a metering slot connected to an RGB 9 via a flow meter 10.

(8) The oil metering device 8 with a metering slot is itself known. By way of example, it may be in the form of a slide and a sheath typically used for metering fuel, as mentioned in Document FR 2 950 864. The controlled movement of the slide in the sheath or bushing masks the slot to a greater or lesser extent. The uncovered section of the slot through which the fluid passes is thus controlled depending on the desired flow rate. Movement of the slide in the metering device is driven by a servo-valve type member, for example.

(9) In this example, the flow meter 10 is used to provide proper metering at the outlet from the oil metering device 8.

(10) In the example shown, the second delivery branch 6 includes a positive-displacement pump 11 connected at its outlet to other members of the turbine engine (not shown).

(11) The feed system 1 thus delivers oil to various members of the propulsion assembly of the aircraft. Upstream from the centrifugal pump 2, the oil comes from the oil tank 3. The centrifugal pump 2 then serves to raise the pressure of the oil and it adapts to the flow rate needed.

(12) Because the positive-displacement pump is boosted by the nonpositive-displacement pump, there is no need to pressurize the oil tank. The oil pressure at the inlet to the nonpositive-displacement pump may specifically equal or close to atmospheric pressure. In certain configurations, it can nevertheless be useful to pressurize the tank.

(13) The centrifugal pump 2 is driven in rotation at a speed that is not correlated with the operating speed of the turbine engine.

(14) In the example shown in FIG. 1, the centrifugal pump 2 is driven at a constant speed by an electric motor 12 that is independent of the speed of the turbine engine.

(15) By setting a target pressure increase, e.g. 10 bars, and by setting a speed of rotation, e.g. 10,000 revolutions per minute (rpm), it is possible to deduce the radius that the centrifugal pump needs to have. Thus, during all stages of flight, and knowing the temperature of the oil, the pressure downstream from the centrifugal pump is known.

(16) With the centrifugal pump 2 delivering oil at a given pressure, oil is available under pressure upstream from the oil metering device 8 having a metering slot, and its flow rate is still not imposed at this moment.

(17) It is the metering slot of the oil metering device 8 that regulates the flow rate.

(18) As mentioned above, the relationship for hydraulic flow through a section is written as follows:
Q=K.sub.SP
The pressure upstream from the slot of the oil metering device 8 is imposed by the centrifugal pump 2, and the pressure downstream is imposed by the pressure in the inside of the RGB 9 and by the head loss through injector nozzles (not shown).

(19) The pressure difference P across the terminals of the slot in the oil metering device 8 is thus variable and depends on the flow rate into the inside of the RGB 9, and can therefore be modeled in order to manage transient stages.

(20) The pressure downstream from the slot of the oil metering device 8 is the sum of the pressure inside of the RGB 9, which depends on the operating point in the flight envelope, and on the head losses through the nozzles, which depends on the flow rate delivered to the inside of the RGB 9. The sum of these two pressures serves to model the pressure downstream at any operating point in the flight envelope and during all stages of operation, which is very useful for transient stages.

(21) From the resulting model for the pressure difference P, it is possible to control the movement of the slot via an open loop in order to increase or decrease the flow rate. The information delivered by the flow meter 10 serves both to reset the model during a transient stage, and also, and above all, to provide regulation during a stabilized stage of flight or during stages that are only slightly transient. If the model is sufficiently accurate, it is possible to use it during stabilized flight while omitting the flow meter.

(22) FIG. 2 is a diagram of a second embodiment of an oil feed system 100 for an RGB of an aeroengine comprising a turbine engine.

(23) Elements that are identical to the feed system 1 of FIG. 1 are given the same numerical references.

(24) The feed system 100 of the second embodiment differs from the first embodiment in that the centrifugal pump 2 is driven at a variable speed by a pneumatic drive 13 operating on air taken from a compressor of the engine.

(25) The pneumatic drive 13 is configured so that the drive speed range of the centrifugal pump 2 lies within a range defined relative to a minimum speed. The operating range is defined so that the operating speed lies in the range 1.2 times the minimum speed and twice the minimum speed.

(26) The feed system 100 of the second embodiment also differs from the first embodiment in that the flow meter is replaced by a pressure sensor 14 connected between the inlet and the outlet of the oil metering device 8. Such a configuration is independent of the type of drive of the centrifugal pump 2 and is therefore equally applicable to the feed system 1 of the first embodiment.

(27) FIG. 3 is a diagram showing a third embodiment of a system 110 for feeding oil to an RGB of an aeroengine comprising a turbine engine.

(28) Elements that are identical with the feed system 1 of FIG. 1 are given the same numerical references.

(29) This third embodiment differs from the first embodiment in that it does not have a separator node at the outlet from the centrifugal pump 2 since there is only the first branch 5 connected to the outlet of the centrifugal pump 2, with the second branch 6 having the positive-displacement pump 11 being connected directly to the tank via a separator node 15 provided in the feed branch 4. The oil tank 3 generally needs to be pressurized so as to ensure there is sufficient oil pressure at the inlet to the positive-displacement pump 11, in particular in order to avoid any risk of cavitation in the pump 11.

(30) In a utilization of an oil feed system of the invention, that can be applied to any embodiment of the feed system, provision may be made in the event of the feed system being used in a low temperature environment for the oil metering device 8 to be opened in such a manner as to force a large flow rate to flow through the feed system in order to heat the oil. For this purpose, the oil metering device is caused to open excessively so as to increase the pump flow rate above the normal flow rate setpoint as calculated for higher temperatures. This leads to recirculation or churning of the oil in the RGB 9, thus serving to heat the oil.

(31) Furthermore, the above description relates to a nonpositive-displacement pump device having only a single nonpositive-displacement pump 2 feeding the fluid metering device having a metering slot. In another alternative, instead of a single pump, there may be provided two nonpositive-displacement pumps that are connected in a series fluid-flow connection in order to constitute the nonpositive-displacement pump device. These nonpositive-displacement pumps in series may be driven in rotation by a common drive device, or by independent drive devices.

(32) The feed system thus provides a solution that adapts to a flow rate requirement that varies during a flight of an aircraft. In particular, compared with prior art systems, the system serves to minimize energy losses and to manage feed at very low speeds without being overdimensioned at high speeds. Furthermore, the relative simplicity of the system makes it possible to achieve savings in size and weight.