Assembly for a jet engine of an aircraft

The present invention proposes a structural unit for an aircraft engine having at least one fuel pump of a fuel circuit and at least one hydraulic fluid pump of a hydraulic fluid circuit, where the structural unit can be coupled to an accessory gearbox shaft of an accessory gearbox of the engine.

This application claims priority to German Patent Application

DE 102011112253.6 filed Sep. 2, 2011, the entirety of which is incorporated by reference herein.

This invention relates to a structural unit for an aircraft engine in accordance with the type defined in greater detail herein.

Known engines for aircraft have a fuel circuit that passes fuel by means of fuel pumps from a fuel tank to combustion chambers, and a separate lubrication oil system with an oil tank and an oil filter by which oil is conveyed by oil pumps for lubrication and cooling of the main engine bearings and of the bearings and other moving parts of the accessory gearbox including the auxiliary units. A fuel pump, a bleed unit, a generator or the like can, for example, be employed as auxiliary units. The fuel circuit and the oil circuit are both routed to a heat exchanger, in order to heat the fuel regardless of the operating state, and at the same time to cool the oil of the oil circuit.

Conventionally, the fuel pumps and the oil pumps are coupled to an accessory gearbox driven by an engine shaft. The fuel pumps and the oil pumps interact here with separate accessory gearbox shafts which can be provided to drive further auxiliary units too, for example a bleed unit, a generator, a pneumatic starter or the like.

Accessory gearbox shafts of this type are arranged substantially parallel to the axis of one another and are adapted to the available installation space inside the engine. They are here positioned substantially adjacent to one another and spread in the circumferential direction of the engine, and they are driven via spur gear stages by an accessory gearbox drive shaft operatively connected to the engine shaft.

The auxiliary units are each arranged on a separate accessory gearbox shaft of the accessory gearbox and are for example connectable by bolt connections to a casing of the accessory gearboxes, where the accessory gearbox disadvantageously requires a large installation space and is characterized by a high overall weight due to the large number of accessory gearbox shafts needed.

The object underlying the present invention is to provide a structural unit for an engine in which the arrangement of auxiliary units on an accessory gearbox is improved such that an engine favourable in terms of installation space and having a low overall weight can be provided.

It is a particular object of the present invention to provide solution to the above issues by a structural unit for an aircraft engine in accordance with features described herein.

A structural unit is proposed for an aircraft engine, in particular a jet engine, having at least one fuel pump of a fuel circuit and at least one hydraulic fluid pump of a hydraulic fluid circuit, where the structural unit can be coupled to an accessory gearbox shaft of an accessory gearbox of the engine.

The solution in accordance with the invention has the advantage that due to the structural unit several pumps that can in conventional engines each be coupled to a separate accessory gearbox shaft can be coupled to a single common accessory gearbox shaft. Compared with known accessory gearboxes, in which fuel pumps and hydraulic fluid pumps are arranged on separate accessory gearbox shafts, it is possible with a structural unit in accordance with the invention to reduce the number of accessory gearbox shafts. By leaving out at least one accessory gearbox shaft and the corresponding gears, installation space and weight are advantageously saved, so that the costs of an entire engine too can be reduced with the solution in accordance with the invention.

Furthermore, the length of an accessory gearbox interacting with the structural unit in accordance with the invention can be advantageously reduced by dispensing with at least one accessory gearbox shaft in the circumferential direction of the engine, so that the complexity of supply lines inside the now shortenable accessory gearbox is reduced in turn.

The working time needed for assembly of the engine is also shortened by the solution in accordance with the invention, as fewer parts have to be installed.

In an advantageous embodiment of a structural unit in accordance with the invention, the at least one fuel pump and the at least one hydraulic fluid pump are arranged inside a common casing. This measure in turn allows weight and cost savings.

If a high-pressure fuel pump and a low-pressure fuel pump are provided which are arranged on a common shaft of the structural unit, an installation space required by said structural unit in the radial direction can be very small.

An alternative or additional possibility for reducing the structural unit installation space facing in the radial direction is that a hydraulic fluid delivery pump and at least one hydraulic fluid return pump are provided which are arranged on a common shaft of the structural unit. This shaft then runs in particular parallel to the shaft on which the fuel pumps are arranged.

In an alternative embodiment of the invention to the above, an oil delivery pump and at least one hydraulic fluid return pump can be provided which are arranged on separate shafts of the structural unit which in particular run parallel to one another. With this arrangement, the hydraulic fluid delivery pump and the at least one hydraulic fluid return pump can be driven at different speeds by an appropriate coupling.

A coupling of the shafts of the structural unit is, in a simple embodiment of the invention, achieved by a gearbox of the structural unit in particular with at least one gear stage. The shafts can as a result be driven with a required gear transmission ratio to one another.

To couple the structural unit in a simple manner to an accessory gearbox shaft of the accessory gearbox, the gearbox has in an advantageous embodiment a shaft area that can be coupled to an accessory gearbox shaft and is designed in particular with external teeth. The shaft area can in particular interact with a hollow shaft of the accessory gearbox which has internal teeth corresponding to the external teeth.

In a preferred embodiment of the invention, a heat exchanger forms part of the structural unit and is in particular integrated into the casing of the structural unit. Due to the proximity of the heat exchanger to the pumps, a length of the lines connecting the heat exchanger to the pumps is greatly reduced in comparison with known solutions where pumps and heat exchangers are arranged separately from one another, and the lines connecting the pumps to the heat exchanger can be integrated into the structural unit, thereby keeping an installation space required by the structural unit very small. In addition, an embodiment of this type of the structural unit in accordance with the invention has the advantage that the entire structural unit with the pumps and the heat exchanger can be removed from the accessory gearbox shaft in its entirety, for example to carry out maintenance and repair work, and also arranged thereon, hence requiring fewer individual parts to be installed or deinstalled. In addition, this creates a structural unit which handles both conveying and temperature control of the hydraulic fluid and of the fuel.

Temperature control of the fuel with simultaneous cooling of the hydraulic fluid, in particular oil, is achieved in an advantageous embodiment of the invention in that the heat exchanger for temperature control of coolant/lubricant conveyed by the hydraulic fluid pump and/or at least one hydraulic fluid return pump operates with a fuel conveyed by the low-pressure fuel pump and/or the high-pressure fuel pump, where the heat exchanger in particular is designed as a fuel-cooled oil cooler.

The heat exchanger can be designed in simple manner as a lamellar cooling device, a rib plate heat exchanger or the like. A heat exchanger of this type, designed for example with plates welded to one another, can be adjusted very easily to an outer contour of the pumps, so that an installation space required by the entire structural unit is very small and heat exchange is very efficient due to the adapted contours.

To achieve an efficient heat exchange in the area of the heat exchanger, the latter can be arranged substantially vertical to the shafts of the structural unit in a lateral rim area of the pumps and/or in an area on the circumferential side of at least one of the pumps and in particular enclose all pumps of the structural unit.

It is particularly advantageous when the heat exchanger is arranged in tubular or annular form around at least one pump. This permits an improved heat transfer and a further weight reduction, since an outer wall of the pumps can be used as an inner wall of the heat exchanger. In addition, the pumps can be shielded by a heat exchanger of this type from heat input from the outside.

If the heat exchanger is arranged at least partially in an area between one of the fuel pumps and one of the hydraulic fluid pumps, the fuel pumps and the hydraulic fluid pumps can be spatially separated from one another, so that a fuel circuit is safely separated from a hydraulic fluid circuit.

The pumps of the structural unit can be designed, depending on their application, as gear, spindle, rotary vane pumps or the like.

The features stated in the following exemplary embodiments of the structural unit in accordance with the invention are each suitable, singly or in any combination with one another, to develop the subject matter of the invention. The respective feature combinations do not represent any restriction with regard to the development of the subject matter in accordance with the invention, but have substantially only exemplary character.

FIG. 1andFIG. 2each show a jet engine1of an aircraft with substantially identical design. The jet engine1is provided with a bypass duct2and an intake area3. A fan4adjoins downstream the intake area3in a manner known per se.

Downstream of the fan4, the fluid flow in the jet engine1splits into a bypass flow and a core flow, with the bypass flow flowing through the bypass duct2and the core flow into an engine core5. The engine core5is designed in a manner known per se with a compressor device6, a burner7, a low-pressure turbine8intended for powering the fan4and a high-pressure turbine8.1intended for powering the compressor device6.

FIG. 1furthermore shows a schematically represented accessory gearbox9, which is substantially arranged in the area of an intermediate casing10of the jet engine1. The intermediate casing10is provided in the radial direction of the jet engine1in an area between engine core5and bypass duct2.

The accessory gearbox9is driven by a drive shaft12interacting with an engine shaft11and which is arranged substantially parallel to said engine shaft11and can be put into operative connection with this engine shaft11in this case via an auxiliary shaft13. The auxiliary shaft13is connected via a bevel gearing14to the engine shaft11, where it interacts with a high-pressure shaft which in the operating state of the jet engine1rotates at a higher speed than a low-pressure shaft arranged coaxially thereto and linked to the fan4.

Starting from the engine shaft11, the auxiliary shaft13runs substantially in the radial direction of the jet engine1through a so-called inner strut15, i.e. a strut designed with a hollow section outwards through the engine core5to the intermediate casing10. In the area of the intermediate casing10, the auxiliary shaft13interacts via a bevel gearing16with the drive shaft12.

The drive shaft12is connected to accessory gearbox shafts of the accessory gearbox9, not shown in greater detail and arranged substantially downstream of the intermediate casing10, by gear pairings17of a gearbox19that are designed in particular as spur gear stages. The accessory gearbox shafts of the accessory gearbox9are arranged substantially parallel to the axis of the engine shaft11and positioned substantially adjacent to one another and spread in the circumferential direction of engine1in the area of the intermediate casing10, i.e. in the radial direction between the bypass duct2and the engine core5.

The accessory gearbox shafts are designed for interaction with auxiliary/secondary units18, which can be designed for example as bleed unit, pneumatic starter, generator or the like and are driveable by the drive shaft12via the gear pairings17of the accessory gearbox9.

In the embodiment of the jet engine1shown inFIG. 2, an alternatively designed accessory gearbox20is shown which is arranged substantially inside an area of a casing21arranged outside the bypass duct2. A drive shaft22of the accessory gearbox20interacts here directly with the engine shaft11and extends, starting from the engine shaft11, in the radial direction first through the inner strut15, then through the intermediate casing10and finally through an outer strut23.

One structural unit each can be coupled to the accessory gearbox shafts, and its various designs are described in greater detail in the following.

FIG. 3shows a structural unit25which in this case is designed with a low-pressure fuel pump26, a high-pressure fuel pump27, an oil delivery pump28and three oil return pumps29,30,31, where all pumps26to31in the exemplary embodiment are designed as rotary vane pumps.

The fuel pumps26,27form part of a fuel circuit, where fuel is conveyed via the low-pressure fuel pump26to a heat exchanger arranged in this case outside the structural unit25and is cooled there before the fuel is raised by the high-pressure fuel pump27to a required supply pressure level. The oil pumps28to31form part of an oil circuit. The main delivery pump28provides a delivery pressure necessary for lubrication and cooling of various consumers inside the engine. The oil return pumps29to31return an oil volume collected in the area of the consumers, for example the gearbox19, to a main tank of the oil circuit.

The structural unit25has two shafts32,33, where the fuel pumps26,27are arranged together on a first shaft32and the oil pumps28to31together on a second shaft33. The shafts32,33are in turn coupled to one another via a gearbox38having a gear pairing34with a first gear35connected to the first shaft32and with a second gear36connected to the second shaft33, so that the shafts32have a required gear transmission ratio to one another.

For connection of the structural unit25to an accessory gearbox shaft39of the accessory gearbox9shown only schematically inFIG. 3, a shaft area37arranged coaxially to the first shaft32and having external teeth is provided. The accessory gearbox shaft39is designed as a hollow shaft with internal teeth corresponding to the external teeth of the shaft area37, so that the structural unit25shown inFIG. 3at a distance from the accessory gearbox9can be brought into engagement with the accessory gearbox9by a movement in the direction of the arrow P. A gear80of the gearbox19that in turn engages with a gear81of the gearbox19that is in operative connection to the drive shaft12is arranged on the accessory gearbox shaft39. The structural unit25can in this manner be easily and quickly connected to the hollow shaft39of the accessory gearbox9or detached therefrom.

The entire structural unit25is arranged inside a casing not shown in greater detail and attachable to/detachable from the accessory gearbox9as a complete unit.

FIG. 4shows an alternatively designed structural unit40, which unlike the structural unit25has four shafts41,42,43,44. On a first shaft41of the structural unit40the low-pressure fuel pump26is arranged, on a second shaft42the high-pressure fuel pump27, on a third shaft43the oil delivery pump28, and on a fourth shaft44the three oil delivery pumps29to31are arranged.

The shafts41to44are in turn operatively connected to one another by gears45to48assigned to the shafts41to44respectively and can be coupled to the accessory gearbox9,20by the shaft area37assigned in this case to the second shaft42.

A further embodiment of a structural unit50is shown inFIG. 5. In the highly schematized representation, the fuel pumps26,27and the oil pumps28to31are arranged on separate shafts51,52in analogous manner to the structural unit25inFIG. 3. In addition,FIG. 5shows a heat exchanger53which is likewise arranged inside a casing of the structural unit50not shown in greater detail. The heat exchanger53is in this case designed as a lamellar cooling device and arranged substantially vertically to the shafts51,52of the structural unit50in a lateral rim area of the pumps26to31. The lamellar cooling device53emulates a shape of the substantially circular pumps26to31and has a shape substantially similar to two connected circles.

FIG. 6shows a further embodiment of a structural unit55designed with two shafts56,57, where the fuel pumps26,27are arranged on a first shaft56and the oil pumps28to31on a second shaft57. There is a space58between the fuel pumps26,27and the oil pumps28to31transversely to the direction of extent of the shafts56,57. The structural unit55has a plate-like rib plate heat exchanger59which passes through the space58between the pumps26to31substantially vertically in the sectional view and almost complete fills this space. The area60of the heat exchanger59filling the space58is adjacent at one end to an area61which in this case contacts approximately over a quarter-circle an outer wall of the fuel pumps26,27. At the other end, the area60is adjacent to a further area62which in this case contacts approximately over a quarter-circle an outer wall of the oil pumps28to31. The heat exchanger59thus has an S-shaped cross-section. The heat exchanger59and the pumps26to31arranged on the shafts56,57are arranged overall inside a casing63of the structural unit55.

FIG. 7shows a structural unit65similar to the structural unit40inFIG. 4with pumps26to31arranged on four shafts66to69, where a rib plate heat exchanger70is provided which has an S-shaped cross-section and, in analogous manner to the heat exchanger59of the structural unit55, passes between a shaft67having the high-pressure fuel pump27and a shaft68having the oil delivery pump28, thereby separating the fuel pumps26,27from the oil pumps28to31. The heat exchanger70has in the sectional view two legs72,73, where a first leg72interacts with an outer wall of the fuel pumps26,27and a second leg73with an outer wall of the oil pumps28to31each. The legs72,73are designed substantially straight and are connected to one another by an area74passing between the high-pressure fuel pump27and the oil delivery pump28. The heat exchanger70, which is also designed plate-like, the shafts66to69and the pumps26to31are in turn arranged inside a common casing71.

The above embodiments are described only as examples for a number of possible combinations. For example, the structural unit can have only one fuel pump26or27. Similarly, the structural unit can have only the oil delivery pump28or one or more oil return pumps29to31. All elements of the structural units25,40,50,55and65described in the above can be combined with one another as required.

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