阅读说明：本技术 喷气发动机的风机 (Fan of jet engine ) 是由 劳伦特·雅布隆斯基 菲利普·杰拉德·埃德蒙·乔利 克里斯托弗·波德里根 达米恩·墨尔乐 哈维 于 2014-11-26 设计创作，主要内容包括：本发明提出一种风机,特别地用于小尺寸的涡轮机,诸如喷气发动机的风机,具有对应于风机叶片(10)前缘径向内端处的进气口气流(26)的内界限的直径除以风机叶片外端围绕通过的圆形的直径的比率的0.20和0.265之间数值的毂比率。(The invention proposes a fan, in particular for small-sized turbines, such as a fan of a jet engine, having a hub ratio corresponding to a value between 0.20 and 0.265 of the ratio of the diameter of the inner limit of the inlet airflow (26) at the radially inner end of the leading edge of the fan blade (10) divided by the diameter of the circle through which the outer end of the fan blade passes.)

1. A fan for a jet engine comprising fan blades (132), an annular casing, a hub rotating about an axis (130) of the turbine, and a fan disc (56) constructed in one piece with the fan blades (132), in an annular flow (144) delimited internally of the hub and externally of the annular casing (146), the fan blades (132) extending radially with respect to said axis, wherein said fan has an inlet diameter (a) of a value between 900mm and 1550mm, corresponding to the diameter of a circle containing the radially outer ends of the fan blades, and a hub ratio of a value between 0.20 and 0.265, corresponding to the ratio of the diameter of the inner limit of the flow at the radially inner ends of the leading edges of the fan blades divided by the inlet diameter.

2. The fan of claim 1, wherein: the inlet diameter is between 900mm and 1200 mm.

3. The fan of claim 1, wherein: the fan disc includes an annular row of axial splines (214) of the fan disc (56) that interact with an annular row of axial splines (216) of the drive shaft (208) centered on the axis (130) to ensure torque transfer between the fan disc and the drive shaft.

4. The fan of claim 3, wherein: splines (214) of a fan disc (56) are formed on an inner surface of a cylindrical wall (212) of the fan disc, wherein the cylindrical wall (212) surrounds a drive shaft (208).

5. The fan of claim 4, wherein: a cylindrical wall (212) is formed at the downstream end of the fan disk (56) and connects the remainder of the fan disk by a frusto-conical wall (210) that opens outwardly in the upstream direction.

6. The fan according to claim 3 or 4, wherein: at least one annular shoulder (218, 220) is formed on the surface of the drive shaft (208) and axially abuts downstream against a stop (212, 222) of the disc (56).

7. The fan of claim 6, wherein: the stop (212, 222) is formed by a downstream end of the cylindrical wall (212) and/or a radial annular edge (222) extending within the frustoconical wall (210).

8. The fan of claim 6, wherein: a nut (224) is disposed on the threads of the outer surface of the upstream end of the drive shaft (208) and forms an axial abutment on at least one of the fan disks (56) stop from the upstream direction to maintain the stop axially clamped between the nut and a shoulder (220) of the drive shaft (208).

9. The fan of claim 8, wherein: the nut (224) has a diameter of between 105mm and 135mm, and preferably between 115mm and 125 mm.

10. The fan of claim 1, wherein: a frusto-conical inner bore opening downstream forms a balancing profile for a fan disc (56), with the upstream end of the bore forming an inner limit for the fan disc.

11. The fan of claim 1, wherein: the fan disk has between 17 and 21 fan blades, preferably between 18 and 20 fan blades.

12. The fan of claim 1, wherein: the fan disks are made of titanium alloy, and more specifically of TA6V or TU7(TA5CD4) alloy.

13. A jet engine characterized by: comprising a fan according to any of the preceding claims 1-12; and a low pressure compressor disposed downstream of the fan disk and directly abutting against the downstream end of the fan disk.

Technical Field

The present invention relates to obtaining specific dimensions of a fan, in particular of a turbine, such as a fan of a jet engine.

Background

The present invention constitutes a real technical challenge and is particularly significant when it concerns turbines whose external dimensions have been designed to suit the field of commercial aviation. Typically, these turbines, being relatively small in size, have an air inlet diameter of between 900mm and 1550mm, defined by the upstream diameter of the turbine flow, so as to have dimensions closely related to the overall mass and suitable for installation on commercial jet engine type aircraft.

Since on any type of turbine the development regarding small size turbines of this type is mainly related to improved performance, reduced consumption and reduced weight. In this respect there are many development routes which may for example involve the selection of materials, the study of the shape of the blade, the optimization of the mechanical connection between the components, the prevention of leakage, etc.

One of the development routes generally sought involves reducing the hub ratio of the turbine fan. The hub ratio is the ratio between the outer diameter of the hub at the leading edge of the fan blades and the diameter of the circle around which the radial ends of the fan blades pass. A reduction in the hub ratio generally refers to a reduction in the radial dimension of the hub and therefore a reduction in weight, but also involves an increase in the air intake section of the turbine, resulting in an increase in the airflow propelling the turbine and therefore enhanced performance. However, considering the current technical secrets in the design and manufacture of small size turbines, such as those having the above defined inlet diameter, this type of turbine is considered to not allow reducing the outer diameter of the hub, in particular at the leading edge of the fan blades, to below the currently used diameter, which is typically between 570 and 585 mm. In fact, the current dimensions of the mechanical elements forming the hub are not considered reducible, mainly for obvious reasons of radial mechanical strength of the blades, torsional resistance, manufacturing tolerances and methods and accessibility of the tools.

Disclosure of Invention

In contradiction to these technical prejudices, the present invention proposes the selection of a specific size of the turbine fan, which offers a significant performance and weight improvement.

To this end, the invention proposes a fan, in particular for a turbine, such as a fan of a jet engine, wherein the fan comprises a fan blade at an air inlet, an annular housing, a hub rotating about an axis of the turbine and carrying the blade, in an annular flow delimited internally of the hub and externally of the annular housing, which extends radially with respect to said axis, wherein said fan has an air inlet diameter of a value between 900mm and 1550mm, corresponding to the diameter of a circle containing the radially outer end of the blade, and a hub ratio of a value between 0.20 and 0.265, corresponding to the ratio of the diameter of the inner limit of the flow at the radially inner end of the fan blade leading edge divided by the air inlet diameter.

According to a first embodiment, the hub comprises a fan disc constructed in a single piece with the blades.

According to a second embodiment, the hub comprises a fan disc comprising, on its outer circumference, substantially axial ribs alternating with grooves in which the roots of the blades engage.

More specifically, an air inlet diameter of between 900mm and 1200mm is recommended to obtain even more advantageous results in terms of weight. As will be explained later, this particular choice of outer diameter is still subject to technical prejudice.

Moreover, a specific mechanical arrangement of the fan rotor is proposed, which is particularly adapted to the dimensioning.

Typically, a turbomachine fan rotor comprises a disc constructed in a single piece with the blades or bearing against the blades of its outer circumference, the roots of the blades engaging in substantially axial grooves of the outer circumference of the disc.

With the blades engaged on the disc, the blades are radially retained on the disc by positive interlocking of their roots with the disc grooves, wherein the roots of the blades are of the dovetail type, for example. The inter-blade platform is mounted on the disc between the fan blades. The disks are typically equipped with a radially inwardly extending balancing system (known as "leeks").

In the current art, the blades are axially retained on the disc upstream and downstream of the blades by means mounted on the disc, which prevent the blade roots from moving axially in the grooves of the disc.

The retaining means downstream of the blades comprise, for example, at least one blade root hook which engages in a notch machined on the upstream end portion of the low-pressure compressor arranged downstream of the fan. To allow these hooks to be mounted in the slots of the low pressure compressor, it is necessary to expand the disk grooves radially with respect to the blade root. Thus, it is possible to move the blade axially in the bottom of the groove and to position the blade root hook radially aligned with respect to the slot. The blade may then be raised radially in the groove using a shim provided at the bottom of the groove that is thick enough to engage the blade root hook in the notch and hold the blade in the top position.

The upstream retaining means comprise, for example, an annular flange connected and fixed to the upstream end of the disc. The flange is coaxially mounted on the disc and includes a scalloped portion that interacts with a corresponding scalloped portion of the disc. The flange axially secures the ring to the disk and secures the flange against rotation relative to the disk. The outer circumference of the flange is axially supported on the blade root for their axial retention in the downstream direction, while its inner circumference is applied to and fixed to a corresponding annular flange of the disc. The outer circumference of the flange also includes a fastening pin for the upstream end of the platform between the blades.

Upstream of the blades, a substantially frustoconical housing mounted on the disk internally defines an annular inlet flow into the turbine. The casing comprises, near its downstream end, a radially inner annular flange applied axially to the above-mentioned flange and fixed by bolts to the flange of the disc together with the flange.

The frustoconical fairing is also mounted on the casing by means of further bolts which engage in holes in the flanges of the fairing and casing, the holes being radially internal, the bolts serving to fix the casing to the disc.

Whether it is a disc constructed as a single piece with the blades or a disc comprising a groove in which the blades are engaged, the disc is fixed to the downstream drive shaft via a radial annular flange of the disc fixed to the radial annular flange of the shaft, by means of a series of nuts circumferentially aligned and axially screwed through the flange.

In order to carry out the assembly and disassembly of the fan rotor, it is necessary to be able to obtain axial access to these nuts using tools. For this purpose, the operator must have sufficient space available around the central axis. The above-mentioned prior art structure does not allow to reach the above-mentioned nut if the fan diameter is small, and in particular if the hub ratio of the fan is the hub ratio mentioned in this patent application. In fact, in this case, the balancing system of the disc ("leek") is formed on the axial alignment of the nut and considerably reduces the space available around the central axis upstream of the drive shaft for reaching the nut.

Moreover, the loads transmitted by the shaft to the disks are carried entirely by the bolted aforementioned flanges, which are particularly sensitive elements to deformations and break in the torque transmission chain from the shaft to the fan disks. In the above case, since the radial and circumferential dimensions of these flanges are very small, there is a great risk of deformation and breakage of the flanges during operation.

The prior art does not allow the formation of a fan of the dimensions and hub ratio defined by the present invention, according to the technical prejudice mentioned, both in relation to a disc constructed in a single piece with the blades and a disc comprising grooves in which the blades engage.

Document EP 1357254 also discloses a fan rotor whose structure has a large radial and axial appearance casing.

Providing a simple, effective and economical solution to this problem is the object sought herein, and is itself an object, possibly independent of the above-mentioned and claimed limitations of air inlet diameter and hub ratio.

To this end, it is proposed and proposed that the torque transmission between the fan disc and the downstream conductive shaft, centred on the same axis, is obtained via an annular row of axial splines of the disc interacting with an annular row of axial splines of the shaft.

Preferably, the splines of the disc are formed on the inner surface of a cylindrical wall of the disc, wherein the cylindrical wall surrounds the drive shaft.

According to another feature, the cylindrical surface is formed at the downstream end of the disc and connects the remaining parts of the disc via a frustoconical wall opening out in the upstream direction.

Advantageously, at least one annular shoulder is formed on the surface of the drive shaft and abuts axially downstream against the stop of the disc.

The stop may be formed by the downstream end of the cylindrical wall and/or by a radial annular edge extending within the frustoconical wall.

Preferably, the nut is mounted on a thread on the outer surface of the upstream end of the shaft and forms an axial abutment on at least one stop of the disc from the upstream direction, to keep the stop axially clamped between said nut and the shoulder of the shaft.

The nut typically has a diameter of between 105mm and 135mm, and preferably between 115mm and 125 mm.

The above-defined structure provides a more durable method of torque transmission than a structure including bolted radial flanges. Indeed, when the flange connection involves the presence of a relatively weak radial wall during bending and the presence of bolts inserted into a limited number of holes concentrating the load along the circumference of the flange, the splined connection allows distributing the torque over the entire circumference of the splined cylindrical wall, enabling better resistance to high shear loads.

The construction defined above solves the problem of transmitting the mechanical strength between the shaft and the disc in the case of a fan of the dimensions and hub ratio defined in the present invention, both in relation to a disc constructed in a single piece with the blades and in relation to a disc comprising grooves in which the blades engage.

The above-mentioned fan rotors have further been developed in the technical context of the following, the proposed design of which directly relates to the choice of hub ratio in the case of implementing small-sized turbines. The environment proposed by the inventors allows in particular the creation of a specific arrangement of the fan rotor, which provides a solution for mounting the disks on the drive shaft to obtain the splined connection described in the present patent application.

The particular choice of hub ratio referred to in the present patent application actually involves an overall reduction in the size of the turbine fan disk relative to the prior art. The disc has an outer diameter, in which case its value is generally comprised between 245 and 275 mm. If the blades are engaged on a disc, it is necessary that the disc should meet the constraints regarding the retention of the fan blades in operation, the number and dimensions of which remain relatively the same with respect to the prior art. For this purpose, the number of blades is preferably between 17 and 21 blades, more particularly between 18 and 20 blades. And according to the knowledge of the current art, the height and width of the groove of the disc must not undergo any reduction in size, to allow, on the one hand, the engagement of the downstream hooks to axially retain the blade, as mentioned in the present application, and, on the other hand, to adapt to the size of the blade root, which has not been reduced yet, to carry the rotating blade.

While requiring the preservation of the dimensions of the grooves of the disc and the reduction of the overall diameter of the disc, in this case necessarily involves a reduction in the width, i.e. the circumferential dimensions of the ribs of the disc. The ribs of the fan disc, in this case thinner than the prior art, present a higher hub ratio and therefore show a greater weakness and a higher risk of breakage with respect to the torque maintained during operation than the prior art ribs.

To solve this problem, it is proposed to construct a inconel fan disk that is very strong. However, this alloy is very heavy, which impairs the overall performance of the turbomachine and therefore does not represent a satisfactory solution.

In the context of the above-described fan rotor, it is surprising to note that with such an assembly that the inventors have developed, the axial fixing of the blades, carried out by the specific arrangement of the disc, the retaining flange upstream of the disc, the ring and the fan cowling, is sufficiently effective and durable to distribute the axial fixing carried out by the downstream hooks of the root of the fan engaged in the low-pressure compressor, the dimensions of which have been detailed above with respect to the turbine.

This particular arrangement of the axial fixing of the blades comprises an annular fairing mounted on the disk upstream of the blades and an axial retention device of the blades on the disk, comprising a flange mounted in an annular recess of the disk and an axial abutment forming the root of the blades, wherein the flange comprises a scalloped radial annular edge interacting with a scalloped radial annular edge of the annular recess of the disk to ensure the annular fixing of the flange in the annular recess of the disk and of the device preventing the rotation of the flange, comprising a housing fitted with radially inwardly extending ears and a ring formed with the device when fixed on the upstream radial face of the disk, wherein the housing is fixed to the disk by being jointly fixed to a device which is a device fixing at least some of the ears of the ring to the disk, wherein the ring further comprises at least one radial projection interacting with a further stop of the flange, to prevent rotation of the flange relative to the ring.

The inventors have therefore advantageously eliminated the downstream hooks for the axial fixing of the blades and thus made it possible to reduce the radial height of the grooves of the fan disk, a portion of which was previously reserved for mounting the downstream hooks, at a height typically comprised between 18 and 22 mm.

The reduction in the radial dimension of the grooves directly relates to the radial reduction of the ribs, which allows the formation of the inner surface of the disc, by a balancing profile deriving from a frustoconical drilling coaxial with the axis of the fan, and the increase in the drilling radius from upstream to downstream. The balancing profile, apart from being sufficient to balance the fan disc, has a minimum diameter whose upstream value is generally comprised between 120 and 140mm, which is greater than the minimum diameter of the balancing profile with the "leek" for the higher grooves, for an equivalent outer diameter of the disc.

As described in this patent application, by utilizing the arrangement of the spline connection, the new disk balancing profile provides a larger annular space in the middle of the fan disk for axial passage through the tool that is required for mounting and clamping the fan disk on the drive shaft of the turbine.

Moreover, the reduction in radial dimension of the fan disk grooves gives the fan disk grooves a more compact proportion that better withstands shear torque during operation. With the solution shown here, the structure of the ribs of the fan disc thus creates a structure that is sufficiently strong to be formed of a titanium alloy that is lighter than inconel.

In the case of a fan rotor comprising blades engaged on a disk, it is therefore proposed that said fan rotor is free from axial retention means of the fan blades on the fan disk downstream of the blades. The fan rotor comprises only an upstream flange as described in the present patent application as axial retention means for the blades. This particular feature is particularly relevant in the context of wind turbines related to the present invention and small size turbines having the above dimensions and hub ratio. It is therefore proposed here that for such fans, the fan disks may be constructed from titanium alloys, more particularly from TA6V or TA17(TA5CD4) alloys.

Moreover, if the disk and vanes are implemented in a single piece, another further aspect of the present subject matter relates to shims that are typically used at the bottom of the grooves to hold the vanes upright against the ribs. These shims must in this case have the function of limiting the displacement of the blade root in the groove during operation, of protecting the bottom of the groove and of damping the blade in the event of breakage of the latter or during the intake of large objects by the turbine. In order to satisfy these constraints in the best possible way, in particular in the new circumstances mentioned above, and in particular in the circumstances of reducing the radial dimensions of the grooves mentioned in the present patent application, the present patent application proposes a gasket that is radially thinner than the previous solutions and has a radial thickness generally comprised between 1 and 3mm, more particularly equal to 2mm, it being stated that such a gasket can be provided even independently of the constraints of the above-mentioned claimed intake diameter and hub ratio. Each spacer is more particularly in the form of a two-sided sheet, lying along the axis of the fan and able to rest against the bottom of one of the grooves. Preferably, the spacer is axially, radially and circumferentially three-way symmetrical, which avoids any mounting errors. Each side face of the gasket advantageously has a lateral or circumferential edge, which are chamfered, wherein each chamfer forms an angle of 10 ° plus or minus 2 ° with one side face. According to another particular, each of the radially opposite side chamfers is connected at a lateral end of the gasket, forming two lateral edges of the gasket. The connection angle between the side faces of the gasket and the chamfer may be tapered to exhibit a radius of curvature of between 1.50mm and 1.80mm, and more particularly between 1.60mm and 1.70mm, and preferably equal to a radius of curvature of 1.65 mm. The connection angle between the chamfers forming the lateral edges of the gasket may be tapered to exhibit a radius of curvature of between 0.45mm and 0.75mm, and more particularly between 0.52mm and 0.68mm, and preferably equal to a radius of curvature of 0.6 mm. According to a particular embodiment, each shim has a lateral dimension of between 17.0mm and 18.2mm and more particularly a lateral dimension of 17.6 mm.

Drawings

Various aspects of the solution presented herein will be better understood and other details, features and advantages thereof will become more clearly apparent upon reading the following description, which is made by way of non-limiting example with reference to the accompanying drawings,

wherein:

FIG. 1 is a perspective view of a turbine with a portion removed, according to the prior art.

FIG. 2 is a view of a partial, cross-sectional axial schematic half of a turbomachine, according to the prior art.

Fig. 3 is a view of a true-scale part, cross-sectional axial schematic half of a turbomachine fan according to the invention, in this case with blades engaged in grooves of a disc.

Fig. 4 is a view of a true-scale part, axially schematic half of a section of a turbomachine fan according to the invention, in this case the blades being formed in one piece with the disc.

FIG. 5 is a perspective view of a renewed fan rotor with the fairing removed for the condition of FIG. 3.

Fig. 6 is a front view of the same assembly as shown in fig. 5.

Fig. 7, 8 and 9 are respective views of sections a-A, B-B and C-C of fig. 6.

Fig. 10 is a perspective view of a spacer for use in the blower according to the invention for the situation in fig. 3.

Fig. 11 is a cross-sectional view of the same gasket. First, reference is made to fig. 1 and 2, which thus illustrate a turbomachine fan according to the prior art of the invention.

Detailed Description

The fan comprises blades 10 carried by a disc 12, an outer annular casing 8 surrounding the disc 12, inter-blade platforms (not shown) being interposed between the blades, wherein the disc 12 is fixed to the upstream end of a turbine shaft 13.

Each fan blade 10 comprises a blade body 16 connected at its radially inner end to a root 18, the root 18 being engaged in a substantially axial groove 20 shaped to match the disc 12, the groove 20 being formed between two ribs 22 of the disc 12 and allowing to radially retain the blade 10 on the disc 12. Shims 24 are interposed between the root 18 of each blade 10 and the bottom of the respective groove 20 of the disk 12 to fix the blades 10 radially on the disk 12. A Leeks type 14 extending inwardly toward the fan is formed on the inner surface of the disc 12 to balance the disc 12.

Disc 12 includes a frustoconical wall 200, wall 200 being closed in the downstream direction and extending from a portion of disc 12 located radially between groove 20 and leek 14. The downstream end of the frustoconical wall 200 comprises a radial annular flange 202 featuring an axial aperture formed upstream of the drive shaft 13 for interacting with an axial aperture of a radial annular flange 204 for passing a bolt 206.

The inter-blade platforms form walls between the grooves 20 which internally delimit the air flow 26 entering the turbine and comprise means which interact with matching means provided on the disc 12 to secure the platforms to the disc.

The fan blade 10 is axially retained in the groove 20 of the blade 12 by suitable means mounted on the disc 12 upstream and downstream of the blade 10.

The upstream retaining means comprise an annular flange 28 coaxially connected and fixed to the upstream end of the disc 12.

The flange 28 comprises an inner annular edge 30, which edge 30 is scalloped or toothed and interacts with an outer annular edge 32 of the toothing or scalloping of the disc 12 to axially secure the flange 28 on the disc 12. The flange 28 is supported by an outer edge 34 on the shim 24 of the blade root 18.

The flange 28 also comprises an inner annular flange 36 interposed between a respective annular flange 38 of the disc 12 and an inner annular flange 40 of a casing 42 provided upstream of the fan disc 12. The flanges 36, 38, 40 include axial apertures (not visible) through which screws 44 or the like pass to clamp the flanges to one another.

The casing 42 has a substantially frustoconical shape opening out in the downstream direction, wherein the inter-vane platform extends in an axial extension of the casing 42. The housing includes radial bores 46 for mounting balance screws and a flange 48 at its upstream end. A conical fairing 50 is mounted to an upstream portion of the outer casing 42. More specifically, the downstream end of the cowl 50 includes a flange 52 that is secured to the upstream flange 48 of the casing 42 by screws 54.

Downstream of the blade 10, a hook 120 formed at the downstream end of the blade 10 allows axial retention and engagement in a notch 122 formed at the upstream end of a compressor 124 that extends the fan downstream airflow 26.

This structure has the above-mentioned disadvantages. In particular, it is not suitable for a relatively small-sized blower.

Fig. 3 and 4 illustrate an embodiment of a fan according to the solution developed in this patent application and comprise, with reference to fig. 3, a disc 56 with blades 132, the roots 138 of which engage in substantially axial grooves 58 of the outer circumference of the disc 56, and in the case of fig. 4 the disc 56 forms a single piece with the blades 132.

The disc 56 is disposed about the axis 130 of the turbine and is driven in rotation by a downstream drive shaft 208.

More specifically, the disc 56 connects to a frustoconical wall 210, which wall 210 extends and closes downstream of the disc 56. The downstream end of the frustoconical wall 210 joins a cylindrical wall 212, the inner surface of which includes axial splines 214 arranged circumferentially side by side. The splines 214 that directly connect the discs 56 engage by positively interlocking with mating splines 216 disposed on the outer surface of the drive shaft 208.

The shaft 208 has a first annular shoulder 218 formed on its outer surface downstream of the splines 214, 216, which shoulder 218 interacts by abutting axially against the downstream end of the cylindrical wall 212, which cylindrical wall 212 connects the disc 56 and bears against the splines 214. A second annular shoulder 220 formed upstream of the splines 214, 216 is in axial abutment against an annular rim 222, which annular rim 222 extends radially inwardly from the frustoconical wall 210.

The nut 224 interacts with the thread 226 formed on the outer surface of the upstream end of the shaft 208 and rests axially in the downstream direction against the radial annular edge 222, so that the latter and the downstream end of the cylindrical wall 212 cannot be separated from their abutment against the shoulders 218, 220 of the shaft 208. In this manner, the disc 56 is axially, radially and circumferentially constrained relative to the drive shaft 208.

This mounting between the disc 56 and the shaft 208 by means of splines has the advantages of mechanical strength described above, in particular for small-sized fans.

In the particular case of fig. 3, each fan blade 132 comprises a blade body 136 connected at its radially inner end to a root 138, the root 138 being engaged in a substantially axial groove 58 shaped to match the disc 56, the groove 58 being formed between two ribs 140 of the disc 56 and allowing the blade 132 to be radially retained on the disc 56.

With reference to fig. 5-9, and the devices 74, 86, 70, 96 described below disposed upstream of the fan blades 132, the fan blades 132 are axially retained in the grooves 58 of the disk 56.

Spacers 142 are interposed between the root 138 of each blade 132 and the bottom of the respective groove 58 of the disc 56 to fix the blade 132 radially on the disc 56.

The inter-blade platform 134 is circumferentially interposed between the blades 132. The inter-blade platforms 134 form walls between the grooves 58 which internally delimit the air flow 144 entering the turbine and comprise means which interact with matching means provided on the disc 56 to secure the platforms to the disc.

The vanes 132 are surrounded by an outer annular housing 146 which defines the inlet to the turbine. The outer casing 146 includes an inner annular wall 148 that externally bounds the air flow 144 entering the turbine, and the outer ends of the vanes 132 rotate circumferentially relative to the inner annular wall 148.

The hub ratio of the illustrated fan corresponds to the distance B between the axis 130 of the turbine and the inner limit of the air flow 144 at the leading edge of the blades 132 divided by the distance A between the axis 130 of the turbine and the outer ends of the blades 132. The fan of the example shown has been designed to obtain a hub ratio that can be between 0.25 and 0.27, while the distance a has a value between 450 and 600 mm. This choice of hub ratio involves the use of a disc, the outer limit of which at the top of the rib is a distance C from the axis 130 of between 115mm and 145 mm.

Finally, the means 74, 86, 70, 96 for axial retention of the blade 132, which will be described later, are sufficiently effective that, unlike the prior art fan illustrated in fig. 1 and 2, the fan according to the invention illustrated in fig. 3 does not have hooks for axial retention of the blade 132 arranged downstream of the blade 132. Instead, as can be seen, a low pressure compressor 150 disposed downstream of the fan disk 56 directly abuts against the downstream end of the root 138 of the blade and the squealer rib 140 of the disk. Thus, there is no longer any radial depth limitation of the rib associated with the downstream hook engagement.

Thus, the groove 58 is radially narrower than the groove adapted for hook mounting of axial retention of the blade, having a depth D of between 18mm and 22 mm. The shims 142 used to keep the blade root 138 radially abutted against the ribs 140 are also radially thinner. The ribs 140 are thus less elongated and in this case compact enough to resist deformation and breakage. This increased resistance of the ribs 140 allows the disk to be manufactured from a titanium alloy that is lighter than, for example, inconel.

Moreover, considering the new disc weight distribution due to the groove height changes, the inner wall of the disc 56 has been formed to have a balancing profile 152 of the disc 56 that is different from the balancing profile of the prior art disc having the "leek style". The profile 152 of the wall has a frustoconical shape opening out in the downstream direction and is formed by a reaming. In proportion to the disc, the equilibrium profile 152 extends less than "leek-style" towards the inside of the turbine, up to a minimum radius E comprised within the environment of the invention between 60mm and 70mm, which represents the inner limit of the disc. The balancing profile 152 is thus positioned radially outside of the nut 224, the nut 224 serving to clamp the disc 56 to the drive shaft 208. Thus, the profile 152 allows for a more voluminous tool to pass through the space for upstream axial access necessary to be located around the axis 130 of the disk 56 and to install a fan.

In the particular case of fig. 4, the disc 56 is formed in a single piece with the vanes 132, which extend from the outer surface 57 of the disc 56. Thus, no axial fixing means forming the blade are required. The specific mounting of the disc 56 on the drive shaft 208 may be performed using a nut 224, just as the balancing profile 152 in fig. 3 may be formed in the same way.

Reference is now made to fig. 5 to 9, which more particularly illustrate the axial retention means of the blade in the situation described with reference to fig. 3. The disk includes an annular rim 60 without the balance "leek" and an upstream elongated annular portion including an annular recess defined between an upstream face of the rim and an outwardly extending radial rim 64. The upstream end of the annular portion comprises a flange 66 extending radially inwards at a distance from the rim 64, and this flange 66 comprises axial holes 68 regularly distributed over its entire circumference, through which holes 68 screws 70, 72 pass. The edge 64 is scalloped or toothed and includes solid portions alternating with hollow portions.

The fan rotor is equipped with axial retention of the blades on the disk in the upstream direction. These means comprise a flange 74 mounted in the annular recess 62 of the disc 56 and forming an axial abutment for the vane rotor.

The flange 74 comprises a substantially frustoconical wall 76 opening out in the downstream direction, the thickness of the wall 76 increasing in the downstream direction. The flange 74 is bounded at its downstream end by a radial face 78 which abuts against the vane. The downstream end of the flange 74 comprises a scalloped or toothed inner annular edge 80 and comprises solid portions alternating with hollow portions, and has a shape substantially matching the shape of the edge 64 of the disc 56 to allow mounting and removal of the flange 74 in the annular recess 62 by axial translation, rotation relative to the flange 74 of the disc 56, and axial fixing of the flange 74 in the recess 62 of the disc by abutment of the solid portions of the edge 80 of the flange against the solid portions of the edge 64 of the disc.

The flange 74 finally comprises a bead 82 on its upstream edge or hollow sections alternating with solid sections 84.

The flange 74 is secured against rotation by a ring 86, which ring 86 includes a cylindrical portion 88 bounded by inner and outer cylindrical faces. The outer face includes a projection 90 which projection 90 extends radially outwardly and circumferentially along the outer surface of cylindrical portion 88 and is inserted in the rim ledge 82 of the upstream edge of flange 74, providing a solid portion 84 which abuts against the upstream edge of flange 74 to ensure locking against rotation. The upstream edge of the ring is connected to radially inwardly extending ears 92, which ears 92 are formed with holes 94 through which screws pass. The ears are located axially upstream against the flange 66 of the disc 56 such that the apertures 94 of the ears 92 are aligned with the apertures 68 of the flange 66 and the cylindrical portion 88 of the ring abuts axially against the flange 66 of the disc from the outside. The ring 86 is implemented in a high alloy steel to withstand breakage.

Thus, the flange 74 is secured against rotation by its solid portion 84 abutting against the ring's tab 90.

A conical fairing 96, for example made of aluminum, is fixed to the disc 12. To this end, the fairing 96 includes an inner annular rim 98 in a middle portion thereof, with axial holes 100 (through-holes) formed in the inner annular rim 98 (fig. 7) opposite the upper holes 94 on both of the rings 86, aligned with some of the holes 68 in the flange 66 of the disc 56. These holes 100 have screws 70 passing through them that interact with nuts 102 mounted against the downstream portion of the flange 66 of the disc 56 and allow the fairing 96, ring 86 and disc 56 to be connected together. The downstream portion of the fairing 96 covers the ring 86 and the flange 74 such that the inner flow 26 defined by the inter-blade platform extends in axial extension of the downstream portion of the fairing 96.

As can be seen in fig. 9, all but one of the other holes 94 of the ring, which are located opposite the other holes 68 in the flange 66 of the disc 56, also have a screw 72 passing through it, which screw 72 interacts with a nut 104 and serves only to fix the ring 86 to the disc 56. The heads of these screws are mounted in blind holes 106 formed in the inner edge 98 of the cowl 96.

The inner edge 98 of the fairing 96 also includes a cylindrical neck flange 108 extending in the downstream direction, the end of which bears against the inner end of the flange 66 of the disc.

The fairing 96 also includes radial threads 110 for mounting balance screws, as is known in the art. To ensure proper positioning of these screws, it is necessary to correct the positioning of the fairing 96 relative to the fan rotor. To this end, as illustrated in FIG. 8, a rotation pin 112 is mounted in the last hole 94 of the ring, aligned with the hole 68 in the flange 66 of the disc 56. The pin 112 includes a head 116 that fits within a blind hole 114 in the inner edge 98 of the cowl 96, wherein the head 116 of the pin 112 is sized in diameter so that it cannot be inserted into another blind hole 106, which blind hole 106 is provided to receive the head of the screw 72.

Referring now to fig. 10 and 11, a shim 142 is shown wherein the shim 142 has been adapted to reduce the depth of the groove 58. Each spacer is more specifically in the form of a two-sided sheet 154 that lies along the axis of the fan and against the bottom of one of the grooves 58. The spacer is symmetrical in three directions, axial, radial and circumferential, which avoids any mounting errors. Each side of the gasket has its lateral edges 156 or circumferential edges chamfered, wherein each chamfer 158 forms an angle of 10 ° with one side. The chamfers 158 of each of the radially opposite sides 154 join at the lateral ends of the gasket to form the two lateral edges 156 of the gasket. The connection angle between the side 154 of the shim and the chamfer 158 is tapered to exhibit a radius of curvature between 1.50mm and 1.80mm, and more particularly equal to a radius of curvature of 1.65 mm. The connection angle between the various chamfers 158 forming the lateral edges 156 of the gasket is tapered to exhibit a radius of curvature of between 0.45mm and 0.75mm, and more particularly equal to 0.6 mm. Each shim 142 has a radial thickness between 1mm and 3mm, more specifically equal to a radial thickness of 2mm, and a lateral dimension between 17.0mm and 18.2mm, and more specifically equal to a lateral dimension of 17.6 mm.