WO2010021573A1

WO2010021573A1 - A gas turbine engine structure

Info

Publication number: WO2010021573A1
Application number: PCT/SE2008/000477
Authority: WO
Inventors: Niklas Boman; Nicklas Holmberg
Original assignee: Volvo Aero Corporation
Priority date: 2008-08-22
Filing date: 2008-08-22
Publication date: 2010-02-25

Abstract

The invention relates to gas turbine engine structure, e.g. a bearing support structure (17, 18, 19) such as a Fan Hub Frame (17), comprising at least one casted part. The casted part extends at least partly around an axial opening (33) in the structure (17, 18, 19) for receiving a gas turbine engine shaft (15, 16). The structure comprises a conduit (29) for transport of a liquid phase fluid, e.g. oil or lubricant. The conduit (29) extends through a section of the casted part and a wall defining the conduit (29) forms a casted portion. One purpose of the invention is to provide a gas turbine engine structure which is adapted for an improved fluid distributing system, e.g. lubricant distribution during operation. By integrating the conduit (29) in the structure (17, 18, 19) may the conduit be designed such that a loss of pressure can be reduced during operation. More particularly, the invention creates conditions for achieving a desired performance concerning flow properties for the fluid within the system since it may be easier to allow larger cross sectional dimensions of the conduit (29) and thus less friction and pressure losses for the fluid flowing in the conduit (29). In addition, less work in fitting a conduit (29) into the structural unit is needed since it is already integrated at manufacturing.

Description

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¹ 2 2 -08- 2008

A GAS TURBINE ENGINE STRUCTURE

TECHNICAL FIELD

The present invention relates to gas turbine engine structure according to the preamble of claim 1. The invention further relates to a gas turbine engine such as a jet engine for an aircraft comprising the gas turbine engine structure.

BACKGROUND ART

For gas turbine engines, as for essentially all engines, it is important to provide the engine with lubricating media, e.g. oil, in order to avoid wear of the engine and engine parts. In particular it is important to lubricate such parts which are subjected to frequent friction wear, e.g. transmissions and gear box assemblies. Hence, it is essential for the performance of the engine from a life time view perspective, as well as for the overall efficiency of the engine, to provide a well conditioned and dimensioned lubrication system for gas turbine engines.

The fluid delivery or distributing system may be used in stationary gas turbine engines but is particularly developed for aircraft jet engines. By jet engine is meant to include various types of engines, which admit air at relatively low velocity, heat it by combustion and shoot it out at a much higher velocity. Accommodated within the term jet engine are, for example, turbojet engines and turbo-fan engines. The invention will below be described for a turbo-fan engine, but may of course also be used for other engine types.

An aircraft gas turbine engine of the turbofan type generally comprises a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. The core engine comprises a high pressure compressor, a combustor and a high pressure turbine in a serial relationship. The high pressure compressor and high pressure turbine of the core engine are interconnected by a high pressure shaft. The high- pressure compressor, turbine and shaft essentially form a high pressure rotor. The high-pressure compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. The gas stream flows aft and passes through the high-pressure turbine, rotatably driving it and the high pressure shaft which, in turn, rotatably drives the high pressure compressor.

The gas stream leaving the high pressure turbine is expanded through a second or low pressure turbine. The low pressure turbine rotatably drives the fan and booster compressor via a low pressure shaft, all of which form the low pressure rotor. The low pressure shaft extends through the high pressure rotor. Most of the thrust produced is generated by the fan. Engine frames, e.g. Fan Hub Frames (FHF), are used to support and carry the bearings, which in turn, rotatably support the rotors. Conventional turbo fan engines have a fan frame, a mid-frame and an aft turbine frame. This kind of structures serve normally two purposes in the engine, a first issue of being a load carrying structure in the engine and a second issue of being a flow director for guiding flows of fluids. In addition, it is of course desired to minimize the weight of the structural unit. Hence, this kind of machine parts are specified to have a rigid, strong structure provided with channels for guiding flows of fluids to desired locations. In order to be able to produce such machine components, having the desired load carrying properties while at the same time minimising the weight of the components, are these parts generally casted in light weight material such as titan alloys.

Even though the frames, e.g. Fan Hub Frames (FHF), Compressor Rear Frames (CRF), Intermediate Compressor Casings (ICC) and the like structures, are casted so as to include a multitude of the desired features and details necessary for the functioning of the unit, it is usually necessary to modify the frames before, or at, the time of mounting of the frames. Such _j

modifications are made afterwards in order to facilitate the casting procedure and ensure a desired quality of the casted product. These features may for example be fine structures or complex and complicated 3-dimensional structures which are difficult or impossible to reproduce in the cast, e.g. due to flow properties of the casting material, and are thus not integrated in the casting process. By adding items or features which not are a part of the casted FHF or ICC, e.g. additional piping or tubes for guiding of fluids or otherwise shaping the casted product, the FHF or ICC will be ready to be mounted into the engine.

The load carrying structures described above may also need to be modified in further ways due to additional equipment in the engine. The engines of an aircraft is usually adapted to, in addition to use the power from the jet engine for thrust of the aircraft, supply power to one or several Power Take Offs (PTOs) connected to the high pressure and/or the low pressure shafts. The PTOs are used for such purposes as generation of electricity, powering of hydraulic and/or pneumatic control units or any device or feature having a power demand. The PTOs are usually connecting the low pressure or high pressure shafts to a generator for generating electricity for the power consuming devices via a gear box which for example is mounted in the engine close to the powering shafts. Furthermore, the same gear box assembly, or another gear box assembly, is used as a reduction gear assembly for controlling the input power to the bladed rotors, e.g. control of the forward fan rotors of a turbofan gas turbine engine. In order to provide lubrication of the machinery and reducing friction losses, oil or some kind of lubricant is supplied to the bearings of the rotating shafts and the gear box assembly or assemblies. In the case of an engine for an aircraft, there is a desire for all components and parts to minimize the weight.

A light weight lubrication system for a gas turbine engine is for example described in WO 2006/059995 where an oil pump is connected to a piping system. The oil system includes a lubricating media which is delivered to a gearbox assembly through a multitude of passages in a circular plenum which surrounds the gear box assembly. The oil returns to a sump tank via a multitude of drain passages. Still other systems describing the lubrication of a jet engine are described in US 3,907,386 and GB 2 234 035.

The above described systems seem to work satisfactorily but require a rather complex and complicated piping system. Furthermore, it may be desired to be able to circulate a rather large volume of oil, and in order to avoid friction losses when pumping the lubricating oil, a rather large pipe cross sectional dimension is desired. However, it is also desired to provide a piping system having as low weight as possible as discussed in WO 2006/059995 since weight reduction is a generally desired feature for aircraft components. To reduce the weight while providing a large flow volume oil distributing system seems to be a contradictory desire since a larger cross sectional area of the pipes generally implies the use of more material and, hence, a heavier weight of the pipes. There is also a problem today in fitting an oil distributing system into the jet engine due to lack of space in the jet engine and mounting of the system into the engine may sometimes be difficult.

DISCLOSURE OF INVENTION

One purpose of the invention is to provide a gas turbine engine structure which is adapted for an improved fluid distributing system, e.g. lubricant distribution during operation.

This purpose is achieved by a gas turbine engine structure according to claim 1. Thus, it is achieved by a gas turbine engine structure, comprising at least one casted part, which casted part extends at least partly around an axial opening in the structure for receiving a gas turbine engine shaft, and wherein the structure comprises a conduit for transport of a fluid in liquid phase, e.g. oil or lubricant, which conduit extends through a section of the casted part wherein a wall defining the conduit forms a casted portion. In this way, the conduit can be designed such that a loss of pressure can be reduced during operation. More particularly, the invention creates conditions for achieving a desired performance concerning flow properties for the fluid within the system since it may be easier to allow larger cross sectional dimensions of the conduit and thus less friction and pressure losses for the fluid flowing in the conduit. In certain cases, depending on the position of the aircraft, will the pressure losses in the prior art solutions be so severe that the supply of oil not will be enough for the need of the engine. This may for example occur when the aircraft is taking off or landing and/or when the aircraft is turning such that the aircraft has a roll angle. In these cases is the position of the aircraft, and thus the engine, deviating from its normal position and there may be needed a more efficient oil supply system in order to overcome an enhanced flow resistance and provide the desired lubrication of the engine. The pressure losses are a function of the capacity of the oil supply conduit system which is influenced by the cross sectional diameter of the conduit and the geometry of the conduit, e.g. bends. Hence, a conduit having less bends, or less sharp bends, and a larger cross sectional area will improve the capacity of the conduit and reduce the pressure losses.

According to one embodiment, the casted conduit wall is formed integral with the casted part, e.g. a gas turbine engine structure or, commonly referred to herein, the structural unit. Thus, the conduit is incorporated into the structural unit in the casting step of the unit or part thereof and thus the need of inserting or adding a separate tube to the engine structural unit afterwards is avoided. Hence, there will be no problems by fitting such a conduit into the engine structure since it already forms a part of the casted structure when the unit is ready to be put in place in the engine and no after mounting of a pipe is needed.

This way of producing the structural unit and the conduit as an integral entity may also have such benefits as time saving, weight reduction of the complete structural unit comprising the conduit due to less material needed and better performance of the fluid in the conduit since it will be possible to use larger dimensions of the conduit in an easy way. In addition, to use a conduit which is manufactured as an integral part of the structural unit will make the conduit more reliable and less probable to be leaking due to less seems and less damages at mounting. Thus, the invention reduces the total need of material and total time of construction and mounting such that economical benefits at manufacturing, due to less production time and less material needed, and in use, due to lees weight and less fuel consumption for an aircraft, will be achieved.

According to one embodiment of the invention forms the casted part a structural unit which is a continuous member around the axial opening

The gas turbine engine structure, or structural unit, may for example be a bearing support structure, e.g. a Fan Hub Frame (FHF), a Compressor Rear Frame (CRF), an Intermediate Compressor Frame (ICF) or the like structural unit intended to be mounted in a gas turbine engine. Such a bearing support structure is usually intended to be mounted between radially inner bearings, for supporting at least one bearing for rotatably mounting at least one shaft connected to a rotor in the engine, and a radially outer engine frame or casing. Hence, the support structure is generally mounted circumferentially around a central axis along the extension of the engine in the length direction in general is the support structure formed from one or several casted parts to form a structural unit which is a continuous member around the axial opening. In the centre of the support structure are usually two shafts, a high pressure shaft connected to a high pressure compressor and a low pressure shaft connected to a low pressure compressor, which are rotatably supported by the bearing of a bearing support structure. However, the engine may comprise only a single shaft or may as well comprise an additional shaft such that three shafts are used. It is not essential for the invention the number of compressor or rotor shafts comprised in the engine and supported by the frames. A bearing support structure such as a FHF normally comprises a plurality of struts so as to form a frame work. The struts and other interconnecting rods or bars are generally forming a load bearing network having an outer shape essentially corresponding to an annularly shaped contour, i.e. a segment of a cylinder provided with a hole in its centre, or a truncated cone, likewise provided with a hole in its centre for shafts from the rotors of the engine. The struts are distributed around the annularly shaped inner contour, e.g. a centre hole being a bearing for the shafts, and reaching towards the outer surface of the contour, i.e. the envelope surface of the cylindrical or conical shaped structural unit. The struts, and interconnecting bars and other structural elements may be evenly distributed circumferentially around the bearing support structure to form a generally symmetrical shape of the framework around the centre axis of the structural unit. However, there are sometimes an urge to make the framework unsymmetrical due to certain desires or practical features such as allowing pipes or shafts to be mounted to the unit, e.g. the mounting of Power Take Off (PTO) shafts connected to the engine shafts for generation of electricity or pumps for hydraulic/pneumatic power, and to fit these components into the structure. It is also possible that an asymmetric framework, and thus asymmetric load bearing properties, is desired due to different loads in different directions. However, said framework comprising the struts, and optionally other elements, will form a load carrying part of the bearing support structure. The framework comprising said struts will be formed by casting. A common way of making a load bearing structure, e.g. a Fan Hub Frame, is to cast it as one single piece, i.e. the framework forming the load bearing structure is casted in its entirety. However, it is also possible to cast the structural unit in subparts which are joined together to form said framework of the bearing support structure, e.g. by assembling different casted subunits or essentially similar parts ("cake pieces"). The bearing support structure further comprises a tube/conduit for transport of a fluid, e.g. oil or lubricant, for lubrication of the engine in general and gearboxes within the engine in particular. These tubes may be used for the guidance of return oil for the lubrication system from an oil sump. In the case of a Fan Hub Frame, oil or oil mist from gear boxes and other devices in the FHF are collected and guided to the oil return conduit which guide the flow in a direction backwards in the engine (i.e. in the same direction as the air flows through the engine) to an oil pump located in the high pressure zone close to the low pressure zone.

The present invention creates conditions for integrating a part of a fluid delivery system, e.g. a conduit which for example is used for a return flow of oil or oil mist, used to lubricate engine parts and collected in an oil sump, to an oil pump in a gas turbine engine structure. The conduit is preferably formed as an integrated part of the engine structure, e.g. a bearing support structure, when the engine structure is casted. If the framework of the engine structure is casted as one single unity, the conduit is casted as an integrated part of the structure. However, the engine structure may also comprise a framework which is assembled from casted subparts which are casted such that the conduit is formed when these parts are assembled. It may of course also be possible that the conduit is casted and formed in one single subpart if engine structure is formed by assembling several subparts. Thus, it is not necessary to mount a separate tube for guiding the flow through the bearing support structure.

According to one embodiment is the integrated conduit designed such that a first end point of the conduit is located within the engine structure, e.g. such that the conduit guides a fluid, which is collected and/or stored in the structural, unit^', from this location or the fluid is guided from outside the structural unit to a functional unit, e.g. gear box, which is built in the engine structure and need to be supplied by a fluid. As an example, the end point located within the structure may be connected to an oil sump. The oil sump may in this case also be an integral casted part of the gas turbine engine structure.

In one embodiment is the first end point of the conduit which is located within the structure, located closer to the axial opening in the structure than a 9

second end point of the conduit which is an opening located at or close to the limiting surface of the structure. Hence, an end point of the integrated tube located within the engine structure is located radially inwards of a second end point of the conduit located at or near a limiting surface of the engine structure. In one practical embodiment of the invention may the conduit be adapted to direct a liquid phase fluid, e.g. oil or lubricant, from a first endpoint in an oil sump in an outwards radial direction towards a second endpoint at or close to the limiting surface of the structure.

The above described strategy is in particular successful when rather large dimensions of the tube is desired since large structures are generally considered to be easier to be casted and it is also in general harder to fit a large dimensional tube than a small into an existing gas turbine engine structure such as a load bearing structure. In addition to be able to avoid an after-mounting of a tube into the gas turbine engine structure, which is achieved by making the tube as an integral unit of the engine structure, it may also be easier to provide a desired performance concerning flow properties for the fluid within the system with an integrated conduit. It may be easier to allow larger cross sectional dimensions of an integrated conduit than of a separate tube and thus less friction and pressure losses for the fluid flowing in a conduit formed as an integral part of the engine structure.

A preferred fluid for the present invention is oil for lubrication of the engine system. An intended use for the conduit is to return oil which has been used for lubrication of the engine. In this case, it is desired to use a conduit having a rather large cross sectional area allowing a large flow through the tube. To fit in a tube with large diameter in for example a Fan Hub Frame may be hard due to the structure of the FHF and the tube may either be smaller than desired or having to be shaped to include several bends and be longer and comprising undesired bends. In both these cases there will be undesired friction and pressure losses in the tube while guiding the oil back to the pump. If a conduit structure is to be an integrated part in the FHF it will be possible to shape a rather large dimensioned tube which not needs to bend that much if the desired tube properties are considered while designing and performing calculations of the load carrying properties of the load carrying unit at the same time.

Hence, to incorporate the tube as an integrated part in the casted structure will provide the possibility to manufacture a tube having the desired dimensions to allow a flow with small pressure losses while at the same time avoiding the need of adding a separate tube to the bearing support structure. The feature of including the tube in the casted structure makes it possible to save weight and money by using less material for the overall construction and also avoiding a time consuming step of mounting the tube to the structure. In addition, there will be a very small risk of leakage in a tube casted to be integrated with the engine structure.

As a general rule, it is an advantage to include pipes of a rather large dimension in the casting procedure since it is easier to cast large dimensions. In addition, it is harder to fit tubes having a large cross sectional area into the bearing support structure afterwards and it is usually considered to consume less extra material when adding tubes of small dimensions. Hence, when there is a need to provide a certain capacity or performance concerning flow properties for the fluid within the system, it is usually essential to provide a sufficiently large cross sectional area of the tubes or pipes and when there is needed a large capacity tube it would be a benefit to be able to cast the pipe or conduit as an integrated part of the casted structural unit.

According to a further embodiment of the invention, the casted part forms a continuous member around the axial opening. Thus, the casted part with the integrated conduit forms an annular structure. In addition, the casted part preferably comprises a main channel for gas flow to or from the gas turbine engine combustor. Especially, the casted part may comprise a plurality of circumferentially spaced struts, which extend in a radial direction of the /

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structure. The main flow channel extend in an axial direction of the structure between the struts.

According to a further embodiment of the invention, the bearing support structure is a Fan Hub Frame which is located in the front part of the engine and is used to support the low pressure compressor or booster

The bearing support structure, e.g. the FHF, may be a part of a gas turbine engine, e.g. a jet engine, and in particular a turbo fan engine, for an aircraft.

According to one example, the integrated conduit is forming part of the lubrication system of the engine and is used for a return flow of oil after lubricating the engine and engine parts to an oil pump. In for example a FHF there are usually located certain components, e.g. a gear box and gearwheels, which need to be lubricated and droplets and oil mist may be collected in a collector in the FHF and guided via an oil return pipe to an oil pump which once again distributes the oil to different parts of the engine, e.g. the gear box assembly in the FHF. Hence, in this embodiment may the conduit form a part of a piping system extending between an oil sump and an oil pump in a gas turbine engine.

In general, the oil return conduit, in particular near the collector, is usually of a rather large cross sectional diameter compared to other pipes or conduit, e.g. oil delivery pipes, and is therefore in particular suitable for the present invention which is most advantageous for pipes and tubes having a rather large cross sectional flow area.

According to one embodiment, the cross sectional area of the tube, integrated with the bearing support structure, is in average at least 3 or 5 square centimetres, more preferably at least 10 square centimetres and in many cases from 15 square centimetres and above. In the case of an oil return conduit a suitable dimension of the cross sectional area of the pipe may be around 10 to 20 square centimetres. There is no specific upper limit concerning the flow performance. However, for practical reasons when rCl / SE 2008 / 00 0 477

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casting the structure, a diameter of a round conduit above 20 centimetres, e.g. about 60 - 65 square centimetres cross sectional area, is not likely to be used even though it would be possible. In general, diameters above 15 centimetres is neither commonly used and in most cases is the diameter below 10 centimetres. If the conduit is shaped otherwise but round, they have a similar effective diameter or cross sectional area.

The integrated casted structure intended to replace the conduit or pipe may in addition to the pipe itself also comprise a collection and storage unit, e.g. an oil sump in the case of an oil return flow, which may be even more difficult to place in the structural unit due to its size if it is not integrally casted in the structure.

In the above description of the invention it has been exemplified by an oil pipe or conduit which has been integrated in the structural unit. The invention may however be suitable for pipes for other purposes. However, a reason why an oil return conduit is used as an example is because the fluid (oil) is suitable for the material in which the structure is made since it is adapted to resist and last in an oily environment and oil mist is to be found around many of the structural units in the engine. In addition, it is desired that the oil return conduit has a large cross sectional dimension, e.g. around 20 square centimetres, which renders the pipe to be integrally casted with the structure in an easy way. However, it is also possible to use the invention for conduits intended for other fluids. Even though it is preferred to use the integrated pipe for fluids which may be in contact with the material used for casting of the structural without causing any harm, the integrated pipe may be surface treated to be suitable for more aggressive fluids.

The invention further relates to a gas turbine engine, e.g. a jet engine, comprising a bearing support structure as described above.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 A schematic overview of a jet engine Fig. 2 A piping arrangement for guiding of fluid from a Fan Hub Frame to a an oil pump according to prior art

Fig. 3 A Fan Hub Frame comprising a tube according to a first embodiment of the invention as seen from the side facing the outlet of a jet engine when mounted in the engine

Fig. 4 A detailed view of the tube arrangement in figure 3 as seen from below according to prior art (fig. 4a) and according to the first embodiment of the invention (fig. 4b)

Fig. 5 A detailed view of the tube arrangement in figure 3 as seen from the left side according to prior art (fig. 5a) and according to the first embodiment invention (fig. 5b)

EMBODIMENT(S) OF THE INVENTION

Hereinafter, when referred to relative locations by using "upstream of, it refers to an item located closer to the air inlet side of the engine and "downstream of refers to a location closer to the outlet side.

The invention will below be described for a turbofan gas turbine aircraft engine 1, which in figure 1 is circumscribed about an engine longitudinal central axis 2. The engine 1 comprises an outer casing or nacelle 3, an inner casing 4 (rotor) and an intermediate casing 5 which is concentric to the first two casings and divides the gap between them into an inner primary gas channel 6 for the compression of air and a secondary channel 7 in which the engine bypass air flows. Thus, each of the gas channels 6, 7 is annular in a cross section perpendicular to the engine longitudinal central axis 2.

The engine 1 comprises a fan 8 which receives ambient air 9, a booster or low pressure compressor (LPC) 10 and a high pressure compressor (HPC) 11 arranged in the primary gas channel 6, a combustor 12 which mixes fuel with the air pressurized by the HPC 11 for generating combustion gases which flow downstream through a high pressure turbine (HPT) 13 and a low pressure turbine (LPT) 14 from which the combustion gases are discharged from the engine. The engine 1 is further provided with a first or high pressure shaft 15 which joins the HPT 13 with the HPC 11 to form a first or high pressure rotor. A second or low pressure shaft 16 joins the LPT 14 to the LPC 10 to substantially form a second or low pressure rotor. The low pressure shaft 16 is rotatably disposed coaxially with and radially inwardly of the first or high pressure shaft 15. The engine further comprises a Fan Hub Frame (FHF) 17, Intermediate Compressor Frame (ICF) 18 and a Rear Turbine Frame (RTF) 19 which all function as bearing support structures. The FHF 17 comprises a first bearing 20 for the inner, low pressure shaft 16 and a second bearing 21 , located downstream of the first bearing 20, for the outer, high pressure shaft 15. Further downstream is a third bearing 22 attached to the ICF 18 and supporting the high pressure shaft 15 and near the downstream end of the engine 1 is a fourth bearing 23 for the inner low pressure shaft 16 supported by the RTF 19.

In figure 2 is described a piping arrangement for return oil from a Fan Hub Frame 117 according to background art. The return flow of oil to an oil pump 131 is guided from the FHF 117 to the oil pump via the piping arrangement comprising a part of the pipe 129 outside the FHF 117 and also a part of the pipe 129, marked with dashed lines, which is inserted into the structural unit of the FHF 117 through an opening 132. The FHF further comprises an axial opening 133, also referred to as centre hole or shaft hole, for receiving power shafts (15, 16 in fig 1). Further, the FHF comprises a main channel 134 for gas flow to the gas turbine engine combustor. The FHF further comprises a plurality of circumferentially spaced struts, which extend in a radial direction of the structure. The main flow channel 134 extend in an axial direction of the structure between the struts.

According to the invention the part of the tube 129 which is introduced into the FHF 117 is replaced by a conduit 29 which is casted as an integrated part of the FHF 17. At least a part of the pipe 129 located in the FHF is / 8 / 0 0 0 477

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substituted for the integrated conduit 29. However, a part of the pipe 129 may for example be partly introduced into the FHF structure in order to connect with the integrated conduit 29, e.g. in order to provide a leak tight and secure connection between the separate pipe 129 outside the FHF and the conduit 29 integrated in the FHF may a part of the separate pipe may penetrate into the FHF structure.

To be noted, even though the present invention is exemplified for and suitable for the FHF 17 and the conduit 29 serving as an oil return flow conduit, the invention may very well be used for other engine structures or load bearing structures than the FHF as well as for conduits serving other purposes. However, the present use exemplified herein is considered particularly suitable concerning the desired dimensions of the return oil pipe, which cross sectional area preferably is in the range of 20 square centimetres, i.e. around 6 centimetres in diameter for a round shaped pipe. In the case of an integrated, casted conduit in the load bearing structure, it is in general easier to manage to cast an integrated conduit structure having a large cross sectional area than a conduit having a small one due to the casting procedure. In addition, it is in general harder to fit a conduit having a large cross sectional area into a load bearing structure and it is thus also with respect to this problem an advantage to cast such a conduit as an integrated part.

In figure 3, the Fan Hub Frame 17 is described in detail and will serve as an example for the invention. The FHF 17 has an outer shape generally corresponding to a truncated cone, or a cylinder segment having a diameter slightly smaller at one side than at the other, having its side with the largest diameter 25 facing the inlet side of the engine and having its side with the smallest diameter 24 facing the outlet side of the engine and being concentrically located around the longitudinal axis of the engine 1 between the LPC 10 and the HPC 11 (see fig. 1). The FHF 17 is also provided with a hole 26 for a Power Take Off shaft (not shown) connected to the high pressure shaft 15 or the low pressure shaft 16 (see fig 1). The FHF 17 is also provided with a sump 27 for collection of oil which for example have been used to lubricate a gear box assembly 28 in the FHF 17. The FHF 17 also comprises the oil conduit 29 which guides the oil from the sump 27 through the FHF 17 and out through an opening 32 in order to guide the oil back to the oil pump. Hence, according to the invention, the oil pipe 29 which is added to the FHF 17 as a separate unit in prior art as described in figure 2 is replaced by a conduit 29 which is casted as a part of the FHF 17 at the casting procedure. The FHF 17 further comprises a number of struts 30 in order to reinforce the structural unit and an axial opening 33, also referred to as centre hole or shaft hole, for receiving power shafts (15, 16 in fig 1). The main flow channel 34 extend in an axial direction of the structure between the struts. More specifically, the holes 34 circumferentially spaced around the peripheral part of the FHF 17 are allowing a main air flow to pass when the FHF 17 is mounted in an engine (fig. 1).

In figure 4a is shown in detail a view of the FHF provided with the traditional arrangement having the separate pipe 129 which is placed in the FHF 117 and guides oil from a sump 127 (see figure 5a) through the FHF structure to the outlet opening 132, located close to the hole 126 for the PTO, where the oil may be further guided via a piping system outside the FHF structure to the oil pump 131 (see fig. 2). In figure 4b is shown how the pipe 129 described in figure 4a have been replaced from a separate part to an integrated, conduit structure 29 which is casted together with the FHF 17 and is used to channel the oil to the outlet 32. The FHF is also provided with a hole 26 for a Power Take Off shaft (not shown).

In figure 5a is shown another view of the traditional mounting of the pipe 129 in a FHF 117 as disclosed in figure 4a indicating also the outlet hole 132 in the FHF, the sump 127 and the hole 126 for the PTO. Figure 5b is showing the same view as fig. 5a when the separate pipe has been replaced with the conduit 29 integrated in the structure. The engine 1 described in figure 1 is an explanatory example of an engine suitable for the invention comprising a number of bearing support structures 17, 18, 19 which may be constructed according to the invention. However, it is obvious for the skilled person in the art that the invention may be used for other engines than the one described in figure 1. Furthermore, the invention is not restricted to a FHF as described in figures 2-5 but may be used for other kinds of engine structures, in particular bearing support structures.

Claims

1. A gas turbine engine structure (17, 18, 19), comprising at least one casted part, which casted part extends at least partly around an axial opening (33) in the structure for receiving a gas turbine engine shaft

(15, 16), and wherein the structure comprises a conduit (29) for transport of a liquid phase fluid, e.g. oil or lubricant, which conduit (29) extends through a section of the casted part characterized i n that a wall defining the conduit (29) forms a casted portion.

2. A structure (17, 18, 19) according to claim 1 characterized i n that the casted conduit wall is formed integral with the casted part.

3. A structure (17, 18, 19) according to claim 1 or 2 characte rized in that the casted part forms a continuous member around the axial opening (33).

4. A structure (17, 18, 19) according to any previous claim characterized in that a first end point of the conduit (29) is located within the structure (17, 18, 19).

5. A structure (17, 18, 19) according to claim 4 characterized in that the end point located within the structure is connected to an oil sump (27).

6. A structure (17, 18, 19) according to claim 5 characterized in that the oil sump (27) also is an integral casted part of the gas turbine engine structure (17, 18, 19).

7. A structure (17, 18, 19) according to any of claims 4 to 6 characterized in that the first point of the conduit (29) within the structure (17,18,19) is located closer to the axial opening (33) in the structure than a second end point of the conduit (29) which is an opening (32) located at or close to the limiting surface of the structure (17, 18, 19).

8. A structure (17, 18, 19) according to any previous claim ch aracterized i n that the conduit (29) is adapted to direct the liquid phase fluid from a first endpoint in an oil sump (27) in an outwards radial direction towards a second endpoint (32) at or close to the limiting surface of the structure (17, 18, 19).

9. A structure (17, 18, 19) according to any previous claim characte rized in that the conduit forms part of a piping system (129, 29) extending between an oil sump (27) and an oil pump

(131) in a gas turbine engine (2).

10. A structure (17, 18, 19) according to any previous claim characterized in that the structure (17, 18, 19) is a bearing support structure.

11. A gas turbine engine structure (17, 18, 19) according to claim 8 characterized in that said bearing support structure (17, 18, 19) is a Fan Hub Frame (17).

12. A structure (17, 18, 19) according to any previous claim characterized in that said conduit (29) has a cross sectional area above 5 square centimetres, more preferably above 10 square centimetres and most preferably above 15 square centimetres.

13.A gas turbine engine (1) characterized in that it comprises a gas turbine engine structure (17, 18, 19) according to anyone of claims 1-12.