Patent ID: 12253000

FIG.1illustrates a gas turbine engine10having a main axis of rotation9. The engine10comprises an air inlet12and a thrust fan23that generates two air flows: a core air flow A and a bypass air flow B. The gas turbine engine10comprises a core11which receives the core air flow A. In the sequence of axial flow, the engine core11comprises a low-pressure compressor14, a high-pressure compressor15, a combustion device16, a high-pressure turbine17, a low-pressure turbine19, and a core thrust nozzle20. An engine nacelle21surrounds the gas turbine engine10and defines a bypass duct22and a bypass thrust nozzle18. The bypass air flow B flows through the bypass duct22. The fan23is attached to and driven by the low-pressure turbine19by way of a shaft26and an epicyclic transmission30. The shaft26herein is also referred to as the core shaft.

During use, the core air flow A is accelerated and compressed by the low-pressure compressor14and directed into the high-pressure compressor15, where further compression takes place. The compressed air expelled from the high-pressure compressor15is directed into the combustion device16, where it is mixed with fuel and the mixture is combusted. The resulting hot combustion products then propagate through the high-pressure and the low-pressure turbines17,19and thereby drive said turbines, before being expelled through the nozzle20to provide a certain propulsive thrust. The high-pressure turbine17drives the high-pressure compressor15by way of a suitable connecting shaft27, which is also referred to as the core shaft. The fan23generally provides the majority of the propulsion force. The epicyclic transmission30is a reduction transmission.

An exemplary arrangement for a geared-fan gas turbine engine10is shown inFIG.2. The low-pressure turbine19(seeFIG.1) drives the shaft26, which is coupled to a sun gear28of the epicyclic transmission arrangement30. Multiple planet gears32, which are coupled to one another by means of a planet carrier34, are situated radially outside the sun gear28and mesh with the latter, and are in each case arranged so as to be rotatable on carrier elements29which are connected in a rotationally fixed manner to the planet carrier34. The planet carrier34limits the planet gears32to orbiting around the sun gear28in a synchronous manner while enabling each planet gear32to rotate about its own axis on the carrier elements29. The planet carrier34is coupled by way of linkages36to the fan23so as to drive the rotation of the latter about the engine axis9. Radially to the outside of the planet gears32and meshing therewith is an annulus or ring gear38that is coupled, via linkages40, to a stationary support structure24.

It is noted that the terms “low-pressure turbine” and “low-pressure compressor” as used herein can be taken to mean the lowest pressure turbine stage and the lowest pressure compressor stage (that is to say not including the fan23) respectively and/or the turbine and compressor stages that are connected to one another by the connecting shaft26with the lowest rotational speed in the engine (that is to say not including the gear box output shaft that drives the fan23). In some documents, the “low-pressure turbine” and the “low-pressure compressor” referred to herein may alternatively be known as the “intermediate-pressure turbine” and “intermediate-pressure compressor”. Where such alternative nomenclature is used, the fan23can be referred to as a first compression stage or lowest-pressure compression stage.

The epicyclic transmission30is shown in greater detail by way of example inFIG.3. Each of the sun gear28, the planet gears32and the ring gear38comprise teeth about their periphery to mesh with the other gears. However, for clarity, only exemplary portions of the teeth are illustrated inFIG.3. Although four planet gears32are illustrated, it will be apparent to the person skilled in the art that more or fewer planet gears32may be provided within the scope of protection of the claimed invention. Practical applications of an epicyclic transmission30generally comprise at least three planet gears32.

The epicyclic transmission30illustrated by way of example inFIGS.2and3is of the planetary type, in which the planet carrier34is coupled to an output shaft via linkages36, wherein the ring gear38is fixed. However, any other suitable type of epicyclic transmission30can be used. By way of further example, the epicyclic transmission30can be a star arrangement, in which the planet carrier34is held so as to be fixed, wherein the ring gear (or annulus)38is allowed to rotate. In the case of such an arrangement, the fan23is driven by the ring gear38. As a further alternative example, the transmission30can be a differential transmission in which both the ring gear38and the planet carrier34are allowed to rotate.

It will be appreciated that the arrangement shown inFIGS.2and3is merely exemplary, and various alternatives fall within the scope of protection of the present disclosure. Purely as an example, any suitable arrangement may be used for positioning the transmission30in the engine10, and/or for connecting the transmission30to the engine10. By way of a further example, the connections (such as the linkages36,40in the example ofFIG.2) between the transmission30and other parts of the engine10(such as the input shaft26, the output shaft and the fixed structure24) may have a certain degree of stiffness or flexibility. By way of a further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts of the transmission and the fixed structures, such as the transmission casing) may be used, and the disclosure is not limited to the exemplary arrangement ofFIG.2. For example, where the transmission30has a star arrangement (described above), a person skilled in the art will readily understand that the arrangement of output and support linkages and bearing positions would usually be different than that shown by way of example inFIG.2.

Accordingly, the present disclosure extends to a gas turbine engine having an arbitrary arrangement of transmission types (for example star-shaped or planetary), support structures, input and output shaft arrangement, and bearing positions.

Optionally, the transmission may drive additional and/or alternative components (e.g. the intermediate-pressure compressor and/or a booster compressor).

Other gas turbine engines in which the present disclosure can be used may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of connecting shafts. By way of a further example, the gas turbine engine shown inFIG.1has a split flow nozzle20,22, meaning that the flow through the bypass duct22has a dedicated nozzle that is separate from and radially outside the engine core nozzle20. However, this is not restrictive, and any aspect of the present disclosure can also apply to engines in which the flow through the bypass duct22and the flow through the core11are mixed or combined before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) can have a fixed or variable region. Although the example described relates to a turbofan engine, the disclosure can be applied, for example, to any type of gas turbine engine, such as, for example, an open rotor engine (in which the fan stage is not surrounded by an engine nacelle) or a turboprop engine.

The geometry of the gas turbine engine10, and components thereof, is or are defined using a conventional axis system which comprises an axial direction (which is aligned with the axis of rotation9), a radial direction (in the direction from bottom to top inFIG.1), and a circumferential direction (perpendicular to the view inFIG.1). The axial, radial and circumferential directions are mutually perpendicular.

FIG.4andFIG.5each show a part of a first exemplary embodiment of an oil system42of the gas turbine engine10in various operating states. The oil system42comprises a first oil circuit43and a second oil circuit45. The first oil circuit43and the second oil circuit45are operatively connected to a return50of the transmission30. Furthermore, the first oil circuit43and the second oil circuit45are connected to separate inlets48and49of the transmission30. Oil from the oil circuits43and45can be introduced into the transmission30via the inlets48and49to the extent described in more detail below. A hydraulic consumer62of the transmission30which comprises bearing units, for example plain bearings of the planet gears32, can be charged with oil via the second oil circuit45. Oil introduced into the transmission30from the first oil circuit43via the inlet48is fed to the hydraulic consumer62and additionally also to other hydraulic consumers66of the transmission30, such as toothings between the sun gear28and the planet gears32and between the planet gears32and the ring gear38.

A return pump57is provided downstream of the return50of the transmission30and upstream of an oil tank53, via which oil can be guided from the return50of the transmission30in the direction of the oil tank53. The oil is introduced into the oil tank53by the return pump57via an inlet51of the oil tank53. A feed pump59is provided downstream of an outlet54of the oil tank53and, like the return pump57, is driven by an auxiliary equipment transmission31of the gas turbine engine10. The auxiliary equipment transmission31is operatively connected to the shaft26or to the connecting shaft27and is rotationally driven in each case by the shaft.

In addition, downstream of the feed pump59a heat exchanger44is provided, in the region of which the oil guided through the transmission30and the oil tank53is cooled or temperature-controlled in a manner known per se. Downstream of the heat exchanger44, the second oil circuit45branches off in the direction of the inlet49and the first oil circuit43continues in the direction of the inlet48of the transmission30.

In addition, the second oil circuit45downstream of the heat exchanger44and upstream of the inlet49comprises an oil accumulator70which is connected to the inlet49via a line L2B and to the heat exchanger44via a line L2A. The oil accumulator70is designed as a spring accumulator. In this case, the oil accumulator70has a piston72of a piston-cylinder unit73, which piston is arranged in a cylinder71of the piston-cylinder unit73in a longitudinally displaceable manner. The piston72is cushioned against a supply pressure p45acting in the second oil circuit45upstream of the inlet49. The piston72and the cylinder71delimit an oil storage chamber74. The volume of the oil storage chamber74varies depending on an axial position of the piston72in the cylinder71.

The line L2A of the second oil circuit45opens into the oil storage chamber74downstream of the return50or downstream of the heat exchanger44. The oil storage chamber74is connected to the inlet49via the further line L2B. On that side of the piston72which faces away from the oil storage chamber74, the piston72and the cylinder71delimit a piston chamber75. In the piston chamber75there is a spring unit76, the spring force of which counteracts a compressive force Fp45acting on the piston72. The compressive force Fp45corresponds to the product of the supply pressure p45of the second oil circuit45acting in the oil storage chamber74and an effective surface77of the piston72, to which the supply pressure p45is applied.

In the present case, the piston chamber75or the spring chamber is in operative connection via a line L1to the two oil circuits43and45in the region between the return50of the transmission30and the return pump57. Since this region of the two oil circuits43and45is substantially pressure-free, the piston chamber75is correspondingly vented via the line L1. This ensures that no pressure builds up in the piston chamber75due to leakage oil volume flows from the oil storage chamber74in the direction of the piston chamber75that counteracts an axial adjustment movement of the piston72, during which the volume of the oil storage chamber74increases and the oil volume stored in the oil accumulator70increases.

The second oil circuit45has a nonreturn valve78between the heat exchanger44and the oil accumulator70. The nonreturn valve78releases the connection between the heat exchanger44and the oil accumulator70, and therefore between the return50and the oil accumulator70, when there is a positive pressure drop between the pressure in the region of the second oil circuit45upstream of the nonreturn valve78and the pressure in the region of the second oil circuit45downstream of the nonreturn valve78.

This is the case when the feed pressure of the feed pump59is of such a magnitude that the supply pressure p45holds the piston72in the position shown inFIG.4or transfers same in the direction of this position and oil stored in the oil accumulator70from the spring unit76via the line L2B is not pushed out of the oil accumulator70in the direction of the inlet49.

If the feed pressure of the feed pump59drops, for example because a filling level of the oil tank53is too low, and the spring force of the spring unit76exceeds the compressive force Fp45acting on the piston72, the spring unit76increasingly pushes the piston72in the direction of the position shown inFIG.5. The volume of the oil storage chamber74is continuously reduced and the oil volume stored in the oil accumulator70is guided in the direction of the inlet49via the line L2B. During such an operating state of the oil system42, the supply pressure p45downstream of the nonreturn valve78is greater than the feed pressure of the feed pump59. The nonreturn valve78then blocks the operative connection between the heat exchanger44and the oil accumulator70. The hydraulic consumer62of the transmission30is then acted upon by the volume of oil stored in the oil accumulator70and an undersupply of lubricant and cooling oil that impairs the functioning of bearing units of the hydraulic consumer62is avoided to the desired extent.

In the oil system42according toFIG.4andFIG.5, the oil is guided through the oil storage chamber74between the heat exchanger44and the inlet49of the second oil circuit45. As a result, a flushing oil volume flow flows through the oil storage chamber74in the normal operating state, during which there is a sufficient supply of oil to the transmission30via the second oil circuit45and during which no volume of oil is pushed out of the oil storage chamber74in the direction of the inlet49of the second oil circuit45by the spring force of the spring unit76. This is a simple way of avoiding the oil stored in the oil storage chamber74having too long a dwell time in the oil storage chamber74and its temperature rising to an undesirable extent. The resulting limitation of the oil temperature in the oil accumulator70prevents, in a simple manner, the oil stored in the oil accumulator70from igniting due to operating temperatures that are too high.

There is also the possibility that oil is guided from the oil storage chamber74in the direction of the piston chamber75if the supply pressure p45is greater than the pressure in the piston chamber75. The oil storage chamber74is then additionally flushed through with oil and an undesired increase in the operating temperature of the oil stored in the oil storage chamber74is avoided.

The opening regions of the lines L2A and L2B can be offset from one another in the circumferential direction and/or in the axial direction of the cylinder71in such a manner that the flow path of the oil volume flow guided through the oil storage chamber74is as long as possible and a greatest possible amount of heat is carried away from the oil accumulator70via the flushing oil volume flow.

The oil can be guided from the oil storage chamber74into the piston chamber75, for example in the region of one or more bores in the piston72and/or via one or more recesses, such as a groove or the like, provided in the contact region between an outer side of the piston72and an inner side of the cylinder71. Furthermore, there is also the possibility of releasing or blocking the connection between the oil storage chamber74and the piston chamber75depending on the pressure drop between the pressure in the oil storage chamber74and the pressure in the piston chamber75. In any case, the flow cross section, which is available for the flushing oil flow, of the bores and/or recesses is dimensioned in such a way that the functioning of the oil accumulator70is not impaired by the flushing oil volume flow.

FIG.6andFIG.7respectively show an illustration corresponding toFIG.4of a second and a third exemplary embodiment of the oil system42of the gas turbine engine10, which are also designed with the oil accumulator70and with the nonreturn valve78and have a similar structure to the oil system42according toFIG.4. For this reason, essentially only the differences between the oil system42according toFIG.6or according toFIG.7and the oil system42according toFIG.4or between the oil systems42according toFIG.6andFIG.7are explained in more detail in the following description. With regard to the further functioning of the oil system42according toFIG.6and according toFIG.7, reference is otherwise made to the above description ofFIG.4andFIG.5.

The oil systems42according toFIG.6andFIG.7each comprise a first oil circuit43with a heat exchanger44, a second oil circuit45with a heat exchanger46, and a third oil circuit47. The first oil circuit43and the second oil circuit45are connected to inlets48,49of the transmission30and to the return50of the transmission30. Furthermore, oil can be guided from the oil tank53to the turbomachine68of the gas turbine engine10via the second oil circuit45. The hydraulic consumers66and the hydraulic consumer62of the transmission30can be charged with oil via the inlet48. In contrast to this, oil from the second oil circuit45can only be guided to the hydraulic consumer62of the transmission30via the inlet49.

In addition, the first oil circuit43downstream of the return50of the transmission30is connected to the inlet51of the oil tank53and the second oil circuit45downstream of the return50is connected to a further inlet52of the oil tank53. The third oil circuit57is in operative connection with an inlet56of the transmission30and with the return50of the transmission30.

In addition, the first oil circuit43and the second oil circuit45each comprise a return pump57,58and a feed pump59,60, which can be driven by the shaft26and thus by the auxiliary equipment transmission31of the gas turbine engine10. In addition, the third oil circuit47is designed with a feed pump61that can be driven by the fan23.

Oil can be introduced from the oil tank53into the transmission30via the first oil circuit43and the second oil circuit45. In contrast to this, oil from the return50of the transmission30is guided directly to the inlet56of the transmission30via the third oil circuit47, with the oil being forwarded from the inlet56in the direction of the hydraulic consumer62.

The heat exchanger44of the first oil circuit43is arranged between the feed pump59and the inlet48of the transmission30. The heat exchanger46of the second oil circuit45is arranged between the feed pump60and an optional throttle67which can be provided between the inlet49of the transmission30and the feed pump60of the second oil circuit45.

The return50of the transmission30comprises a device63. Oil is conducted from the transmission30into the first oil circuit43, into the second oil circuit45and into the third oil circuit47via the device63when the transmission30is subjected to an oil volume flow greater than a predefined value or an operating value differs from a defined operating value of the gas turbine engine10corresponding to this oil flow rate. Additionally, the device63is configured to conduct the oil from the transmission30into the third oil circuit47when the supply to the transmission is less than or equal to the predefined flow rate, or less than or equal to at least one corresponding operating value, or greater than or equal to at least one other corresponding operating value.

For this purpose, the device63includes an oil reservoir64from which oil taken up by the transmission30can be returned directly to the transmission30via the third oil circuit47and to the oil tank53via the first oil circuit43and the second oil circuit45. From the oil reservoir64, the oil is conducted directly to the inlet56of the transmission30only via the third oil circuit47as long as the filling level of the oil reservoir64is below the defined filling level65of the oil reservoir64. In addition, oil is conducted via the first oil circuit43and via the second oil circuit45into the oil tank53and via the third oil circuit47to the inlet56as soon as the defined filling level65of the oil reservoir64is reached.

In the oil system42according toFIG.6, the oil accumulator70is arranged downstream of the throttle67and upstream of the inlet49in the second oil circuit45. The oil storage chamber74is connected via the line L2A to the nonreturn valve78which is arranged upstream of the oil accumulator70in the second oil circuit45. In addition, the oil storage chamber74is directly connected to the inlet49via the line L2B. The nonreturn valve78is arranged between the oil accumulator70and the throttle67. The line L1connects the piston chamber75of the oil accumulator70, in the exemplary embodiment of the oil system42shown inFIG.6, to the second oil circuit45in the region between the return50of the transmission30and the return pump58. The piston chamber75is vented via the line L1in order to avoid a pressure increase in the piston chamber75and a resulting impairment of the functioning of the oil accumulator70.

In contrast to the oil system42according toFIG.6, the oil accumulator70is integrated in the third oil circuit47in the oil system42according toFIG.7. The oil accumulator70or its oil storage chamber74and the nonreturn valve78are arranged between the feed pump61and the inlet56of the transmission30in order to supply the hydraulic consumer62with oil stored in the oil storage chamber74in the event of a correspondingly low supply pressure p47and a correspondingly low compressive force Fp47upstream of the inlet56, in the manner described forFIG.4andFIG.5. The oil storage chamber74is connected directly to the inlet56via the line L2B and to the nonreturn valve78via the line L2A. The nonreturn valve78is arranged upstream of the oil accumulator70and between the feed pump61and the oil storage chamber74in the third oil circuit47. The piston chamber75is connected to the oil reservoir64of the return50of the transmission30via the line L1for venting purposes.

FIG.8shows an individual illustration of a region VIII of further embodiments of the oil system42, which is identified in more detail inFIG.4,FIG.6andFIG.7. The region VIII comprises the oil accumulator70and the nonreturn valve78. In the embodiments of the oil system42according toFIG.8, the oil storage chamber74of the oil accumulator70is connected via a so-called stub line L3by a line L2running between the nonreturn valve78and the inlet49of the second oil circuit45according toFIG.4or according toFIG.6, or the inlet56of the third oil circuit47, to the second oil circuit45and to the third oil circuit47, respectively.

In order to avoid an undesired rise in temperature of the oil stored in the oil storage chamber74, in these embodiments of the oil system42, during operation of the gas turbine engine10, oil can in each case be conducted out of the oil storage chamber74into the piston chamber75and from there in the direction of the region of the oil system42downstream of the return50of the transmission30or into the oil reservoir64from the piston chamber75. The oil storage chamber74is thus flushed through with oil starting from the line L2in the direction of the piston chamber75, and a flushing oil volume flow through the oil storage chamber74that limits the temperature of the oil in the oil storage chamber74is produced.

It will be understood that the invention is not limited to the above-described embodiments and various modifications and improvements can be made without departing from the concepts described herein. Any of the features may be used separately or in combination with any other features, unless they are mutually exclusive, and the disclosure extends to and includes all combinations and subcombinations of one or more features that are described herein.

LIST OF REFERENCE SIGNS

9Main axis of rotation10Gas turbine engine11Core12Air inlet14Low-pressure compressor15High-pressure compressor16Combustion device17High-pressure turbine18Bypass thrust nozzle19Low-pressure turbine20Core thrust nozzle21Engine nacelle22Bypass duct23Thrust fan24Support structure26Shaft, connecting shaft27Connecting shaft28Sun gear30Transmission, planetary transmission31Auxiliary equipment transmission32Planet gear34Planet carrier36Linkage38Ring gear40Linkage42Oil system43First oil circuit44Heat exchanger45Second oil circuit46Heat exchanger47Third oil circuit48,49Inlet of the transmission50Return of the transmission51,52Inlet of the oil tank53Oil tank54,55Outlet of the oil tank56Inlet of the transmission57,58Return pump59,60Feed pump61Feed pump62Hydraulic consumers63Device64Oil reservoir65Level66Further hydraulic consumers of the transmission67Throttle68Further regions of the gas turbine engine, turbomachine70Oil accumulator71Cylinder72Piston73Piston-cylinder unit74Oil storage chamber75Piston chamber76Spring unit77Effective area of the piston78Nonreturn valveFp45, Fp47Compressive forceL1, L2, L2A, L2B LineL3Stub linep45, p47Supply pressure