Patent Publication Number: US-2022235670-A1

Title: Inlet cone for an aircraft turbine engine and associated aircraft turbine engine

Description:
TECHNICAL FIELD OF THE INVENTION 
     The field of the present invention is that of turbine engines, in particular that of gas turbine engines, for example and not restrictively a turbojet engine or an aircraft turboprop. 
     The present invention relates more particularly to an air inlet cone for a turbine engine. 
     TECHNICAL BACKGROUND 
     The prior art comprises, in particular, the documents GB-A-1 557 856, FR-A1-2 943 726, FR-A1-3 027 878, FR-A1-2 943 725 and FR-A1-2 898 939. 
     It is known from the prior art that turbine engines extend along a longitudinal axis and comprise, from upstream to downstream, in the direction of gas flow, a fan, one or more compressor stages (e.g., a low-pressure compressor and a high-pressure compressor), a combustion chamber, one or more turbine stages (e.g., a high-pressure turbine and a low-pressure turbine), and a gas exhaust nozzle. 
     Conventionally, such turbine engines further comprise an upstream air inlet cone which is mounted on the fan, for example by means of a generally annular upstream shell which is itself connected to a low-pressure compressor shaft of the turbine engine. The connection between the inlet cone and the upstream shell is usually made by means of bolted joints. The downstream end of the shell is flush with the platforms of the fan blades, being in the front aerodynamic continuity of the latter. 
     Such an inlet cone comprises an upstream end in the form of a cone tip centred on an axis of rotation of the inlet cone, also corresponding to the longitudinal axis of the fan and the entire of the turbine engine. 
     This tip is known to be a point in the turbine engine that promotes ice accretion, since its centering on the axis of rotation does not allow the application of significant centrifugal forces. As a result, the ice forming on the inlet cone tip could grow to a large size before breaking off, with the risk, when it eventually disengages from the tip, of damaging the fan blades it strikes or the engine of the aircraft that ingests it. The ice pack can also accumulate unevenly on the tip of the inlet cone, resulting in undesirable vibrations of the turbine engine. 
     In order to overcome this problem, it has been proposed to so implement a de-icing system, the aim of which is to ensure that the ice accreted on the cone tip is ejected before it reaches a critical size. However, this type of system is expensive in terms of mass and size, and above all particularly difficult to implement due to the rotating nature of the inlet cone that is equipped with it. 
     It has also been proposed that the inlet cone  10 , as shown in  FIG. 2 , be made with an upstream tip  11  of flexible material and a downstream body  12  of rigid material. In operation, the layer of ice accreted in particular at the level of the connection between the tip and the body is weakened to promote the detachment of the ice and thus reduce the size of the pieces of ice potentially ingested by the turbine engine. However, this way of detaching the ice layer, by embrittling it and allowing cracks to propagate along it, may be slower than expected in the case of in-flight operation of the turbine engine. Indeed, the larger the size of the ice layer, the slower and more difficult it is to form cracks in this layer. Such a solution is therefore not sufficient to quickly and completely detach the ice layer forming on the tip of the inlet cone. 
     In this context, it is interesting to propose a solution to overcome the disadvantages of the prior art, in particular by implementing a geometry of an air inlet cone that is more conducive to the rapid break-up of the ice in operation. 
     SUMMARY OF THE INVENTION 
     The present invention thus proposes an inlet cone for an aircraft turbine engine, comprising a frustoconical body and a tip made from elastically deformable material fixed to an end of smaller diameter of said body, the tip comprising a top configured to be situated on an axis of rotation of the cone and a fastening base for attachment on said end of said body. Said base extends in a connecting plane P. Said connecting plane P is inclined relative to said axis of rotation. Said base has a generally circular or oval shape. Preferably, said connecting plane P is inclined relative to a transverse plane T perpendicular to said axis of rotation. 
     Such an oval may be regular by being symmetrical or asymmetrical as an egg which would be considered in section. 
     The inclination of the connecting plane P between the tip and the frustoconical body of the cone allows to design a tip made from elastically deformable material which is not axisymmetrical. This design has the advantage of amplifying the phenomenon of de-accretion of the ice forming on the air inlet cone of the turbine engine during operation. 
     Indeed, the tip of the inlet cone is made from an elastically deformable material, such as an elastomer, so as to allow the tip to deform as it rotates and also to withstand temperature variations. This therefore promotes the release of ice accretions forming on the surface of the inlet cone, as described above. Furthermore, in operation, when ice is accreted onto the upstream end of the inlet cone, the eccentric (or non-axisymmetric) shape of the inlet cone tip advantageously implies that the ice is subject to significant centrifugal forces. These forces promote its ejection, and allow it to separate from the inlet cone before it reaches a critical size with respect to the risk of damage to the fan blades situated downstream. 
     Thus, the eccentric shape of the tip made from elastically deformable material allows the displacements under the action of the centrifugal force to be de-symmetrized. This creates an unbalance at its end which promotes deformation of the elastically deformable material of the tip to create more cracks in the ice and eject it evenly before its volume becomes too large and dangerous in the event of ingestion into the turbine engine. Therefore, under the combined effect of centrifugal force and the radial pull of the ice (itself driven by this centrifugal force), the tip deforms more rapidly. This amplification of the deformation of the tip of the inlet cone therefore leads to an increase in the stresses applied to the ice, so as to increase the frequency of ice detachment. This ultimately leads to a reduction in the size of the ice fragments, and a reduction in the impact energies undergone by the turbine engine during ice detachment. 
     The invention therefore has the advantage of being based on a simple design, offering very high reliability, with little cost and space penalty. 
     The inlet cone for the aircraft turbine engine according to the invention may comprise one or more of the following features, taken in isolation from each other or in combination with each other:
         said connecting plane P is inclined at an angle of between 10° and 35° relative to the transverse plane perpendicular to said axis of rotation;   the tip is single part;   the tip is bound to the body;   one of the elements chosen from the tip and the body comprises at least one lug engaged in a recess of the other of the elements, in order to block the tip in rotation on the body and/or facilitate the centering of the tip on the body;   the body is made of composite or metallic material;   the tip is made of elastomer.       

     The invention also relates to an aircraft turbine engine comprising an inlet cone according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention will be better understood and other details, characteristics and advantages of the invention will become clearer on reading the following description made by way of non-limiting example and with reference to the attached drawings in which: 
         FIG. 1  is a schematic half-view in axial section of an aircraft turbine engine, according to one of the embodiments of the invention, 
         FIG. 2  is a schematic front perspective view of an inlet cone, according to the prior art, 
         FIG. 3  is a schematic view in axial section of an inlet cone, according to one embodiment of the invention, 
         FIG. 4  is a schematic view in axial section of an inlet cone, according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     By convention in the present application, the terms “interior” and “exterior”, and “inner” and “outer” are defined radially with respect to a longitudinal axis X of the aircraft engine of the turbine engine. Thus, a cylinder extending along the axis X of the engine comprises an interior surface facing the axle of the engine and an exterior surface opposite its interior surface. “Axial” or “axially” means any direction parallel to the axis X and “transversely” or “transverse” means any direction perpendicular to the axis X. Similarly, the terms “upstream” and “downstream” are defined with respect to the direction of airflow in the turbine engine. 
       FIG. 1  shows a turbine engine  1  with dual flow. However, this is not limiting and the turbine engine may be of another type, such as for example a turboprop engine. 
     The turbine engine  1  extends along a longitudinal axis X and comprises from upstream to downstream, in the direction of the gas flow, a fan  2 , one or more compressor stages (e.g. a low-pressure compressor  3  and a high-pressure compressor  4 ), a combustion chamber  5 , one or more turbine stages (e.g. a high-pressure turbine  6  and a low-pressure turbine  7 ), and a gas exhaust nozzle  8 . The fan  2 , the low-pressure compressor  3  and the low-pressure turbine  7  are connected to a low-pressure shaft extending along the longitudinal axis. The high-pressure compressor  4  and the high-pressure turbine  6  are connected to a high-pressure shaft arranged around the low-pressure shaft. The low-pressure turbine  7  drives the low-pressure shaft in rotation, while the high-pressure turbine  6  drives the high-pressure shaft in rotation. 
     The turbine engine  1  further comprises, upstream of the fan  2 , an air inlet cone  10  which is mounted on the fan  2  by means of a shell (not shown), preferably by bolt-type attachment. The shell is arranged downstream of the inlet cone  10  and this shell is also connected to the low-pressure shaft. 
     The inlet cone  10  together with the shell are connected to the rotor, i.e. to the rotating parts of the turbine engine  1 . The inlet cone  10  therefore rotates around the longitudinal axis X. 
     The air inlet cone is shown in more detail in  FIGS. 2 to 4 . 
       FIG. 2  shows the inlet cone  10  of the prior art, as previously described, in the technical background of the present application. 
       FIG. 3  shows the inlet cone  10  according to the invention, which comprises a tip  11  disposed upstream and a frustoconical body  12  disposed downstream. In operation, the inlet cone  10  rotates about the longitudinal axis X. 
     The tip  11  of the cone  10  is made from elastically deformable material. For example, this tip  11  may comprise an elastomer or silicone material. The frustoconical body  12  of the inlet cone is made of a material which is more rigid than the tip  11 . For example, this frustoconical body  12  may be made of a metallic or composite material. 
     The tip  11  comprises a top through which the axis of rotation X of the inlet cone  10  passes, which is therefore coincident with the longitudinal axis X of the turbine engine. On the side opposite the top, the tip  11  also comprises a fastening base  11  p for attachment to an upstream end  12   p  of the frustoconical body  12  in order to be aerodynamically continuous. The frustoconical body  12 , in turn, comprises the upstream end  12   p  and a downstream end which is configured to assemble with the front shell on the fan  2  of the turbine engine. The upstream end  12   p  attaches to the fastening base  11   p  of the tip  11 , and has a diameter smaller than the diameter of the downstream end of the frustoconical body  12 . 
     The fastening base  11   p  and the upstream end  12   p  of the frustoconical body  12  have a generally circular or oval shape, preferably complementary to each other, and extend in a connecting plane P. 
     One of the particularities of the invention lies in the fact that this connecting plane P is inclined with respect to the axis X of rotation of the inlet cone, preferably with respect to a transverse plane T perpendicular to the axis X. This gives the tip  11  its eccentric shape. The connecting plane P may be inclined at an angle α to the transverse plane T perpendicular to the axis X. The angle α may be between 10° and 35° relative to the axis X. Preferably, the angle α is between 15° and 25°. The angle α of the connecting plane P is, for example, chosen as a function of the size of the inlet cone, the speed of rotation of the cone and/or the type of turbine engine. 
     The connecting plane P is positioned so as to define a centre of gravity of the inlet cone offset from its geometrical axis. This causes an imbalance or unbalance in the tip during operation, and advantageously favours the stalling of the ice that forms on the tip during operation. 
     According to the invention illustrated in  FIG. 3 , the fastening base  11   p  of the tip  11  is glued to the upstream end  12   p,  so as to assemble the tip to the frustoconical body in an efficient and simple manner, while limiting the size of the air inlet cone. 
     According to the invention illustrated in  FIG. 4 , the frustoconical body  12  may comprise one or more lugs  14  engaging in a recess  13  of the tip  11 , so as to lock the tip to the frustoconical body in rotation and/or to facilitate the centering of the tip on the body. The lugs  14  are distributed around the circumferential periphery of the upstream end  12   p  of the frustoconical body  12 . The recesses  13  are also distributed around the circumferential periphery of the fastening base  11   p  of the tip  11 . 
     The tip  11  of the inlet cone  10  may be monobloc. For example, an elastomer tip  11  can be made by moulding, while optimising the draft angles and thicknesses to respect the constraints linked to the moulding and demoulding technique. 
     The tip  11  can be applied to any type of air inlet cone of a turbine engine, while adapting the angles and lengths of the tip to the dimensions of the inlet cone. Furthermore, the hardness of the tip, made from elastically deformable material, is a parameter that can be varied according to the speed of rotation, the angle of attack and the dimensions of the inlet cone. 
     The design of the air inlet cone according to the invention brings several advantages, which are, in particular:
         weakening a significant size of the ice layer accreted to the air inlet cone, and increasing the frequency of ice detachment;   amplifying effectively and rapidly the break-up of the ice sheet forming on the inlet cone;   reducing the impact on the turbine engine during the break-up of the ice;   simplify and unclutter the assembly and the operation of the inlet cone on the turbine engine;   easily adaptable to current turbine engine.       

     Overall, this proposed solution is simple, effective and economical to build and assemble on a turbine engine, while ensuring ice de-accretion and an optimum service life of the air inlet cone.