System and method for cooling a hover-capable aircraft transmission

1. A system ( 7 ) for cooling a transmission ( 6 ) of a hover-capable aircraft ( 1 ), the system comprising:

a stator ( 3 );

a heat exchanger ( 8 ) connectable thermally to said transmission ( 6 );

a fan ( 9 ) for creating a first current (P) of a first heat-carrying fluid from said heat exchanger ( 8 ) to the fan ( 9 ) itself, to remove heat from said heat exchanger ( 8 );

a rotary member ( 10 ), which rotates about an axis (A) to rotate an impeller ( 20 a ) of said fan ( 9 ) about said axis (A); and

a bearing ( 16 ) supporting said rotary member ( 10 ) for rotation about said axis (A) and with respect to said stator ( 3 );

the system being characterized by comprising cooling means for cooling said bearing ( 16 ); said cooling means comprising conducting means ( 40 ; 42 , 41 , 30 , 29 ) for conducting a second current (Q) of a second heat-carrying fluid along a path from an outside environment ( 50 ), external to said bearing ( 16 ), to said bearing ( 16 ), so as to cool the bearing ( 16 );

said conducting means ( 40 ; 42 , 41 , 30 , 29 ) comprising:

a first cavity ( 41 ) defined by said rotary member ( 10 ) and connectable fluidically to said outside environment ( 50 ); and

a second cavity ( 29 ) into which said bearing ( 16 ) faces, and which, when said impeller ( 20 a ) is operated, is at a lower pressure than said outside environment ( 50 ) external to said bearing ( 16 );

said second cavity ( 29 ) being defined by said impeller ( 20 a ).

2. A system as claimed in claim 1 , characterized in that said rotary member ( 10 ) comprises an open first axial end ( 44 ) connecting said first and second cavity ( 41 , 29 ).

3. A system as claimed in claim 2 , characterized in that said rotary member ( 10 ) comprises:

a lateral surface ( 43 ) defining said holes ( 42 ); and

a closed second axial end ( 47 ) opposite said first axial end ( 44 ).

4. A system as claimed in claim 1 , characterized in that said conducting means ( 40 ; 42 , 41 , 30 , 29 ) also comprise a number of inlet openings for said second current (Q) of said second heat-carrying fluid; said inlet openings being defined by respective through holes ( 42 ) in said rotary member ( 10 ); and said holes ( 42 ) being open on the side facing said outside environment ( 50 ), and on the opposite side facing said first cavity ( 41 ).

5. A system as claimed in claim 1 , characterized in that said fan ( 9 ) comprises a diffuser ( 20 b ) fixed angularly with respect to said axis (A);

said conducting means ( 40 ; 42 , 41 , 30 , 29 ) comprising a third cavity ( 30 ), which is defined by said diffuser ( 20 b ), is traversed by said second heat-carrying fluid, and is connected fluidically to said first cavity ( 41 ) and said second cavity ( 29 ).

6. A system as claimed in claim 5 , characterized in that said third cavity ( 30 ) is connected fluidically to said first cavity ( 41 ) at said first axial end ( 44 ) of said rotary member ( 10 ); and in that said third cavity ( 30 ) is connected fluidically to said second cavity ( 29 ) at a section of the third cavity radially outwards of said first axial end ( 44 ) of said rotary member ( 10 ) with respect to said axis (A).

7. A system as claimed in claim 5 , characterized in that said diffuser ( 20 b ) comprises an inlet section ( 24 ) and an opposite outlet section ( 25 ) in the flow direction of said first current (P) of said first heat-carrying fluid;

said diffuser ( 20 b ) and said fan ( 9 ) together defining an annular passage ( 45 ) for said second current (Q) of said second heat-carrying fluid;

and said annular passage ( 45 ) being connected fluidically to said inlet section ( 24 ) of said diffuser ( 20 b ) and to said second cavity ( 29 ), to permit flow of said second current (Q) of said second heat-carrying fluid to said outlet section ( 25 ) of said diffuser ( 20 b ).

8. A system as claimed in claim 5 , characterized in that said bearing ( 16 ) is located radially outwards of said rotary member ( 10 ); and in that said third cavity ( 30 ) tapers radially from said second cavity ( 29 ), on the opposite side to said heat exchanger ( 8 ); the maximum radial size of said third cavity ( 30 ) being greater than the radial distance between said bearing ( 16 ) and said axis (A), so as to first conduct said second current (Q) of said second heat-carrying fluid along a spinning path inside said third cavity ( 30 ), and then into said second cavity ( 29 ) adjacent to said bearing ( 16 ).

9. A method of cooling a transmission ( 6 ) of a hover-capable aircraft ( 1 ), the method comprising the steps of:

operating the impeller ( 20 a ) of a fan ( 9 ) of a cooling system ( 7 ) by means of a rotary member ( 10 ), which rotates about an axis (A) and is supported by a bearing ( 16 ) with respect to a stator ( 3 ) of said system ( 7 ); and

creating a first current (P) of a first heat-carrying fluid from a heat exchanger ( 8 ), connectable thermally to said transmission ( 6 ), to said fan ( 9 ), so as to draw heat from said heat exchanger ( 8 );

said method being characterized by comprising the step of cooling said bearing ( 16 );

said cooling step comprising the step of conducting a second current (Q) of a second heat-carrying fluid along a path from an outside environment ( 50 ), external to said bearing ( 16 ), to the bearing ( 16 ).

10. A method as claimed in claim 9 , characterized in that said step of operating said impeller ( 20 a ) comprises the step of bringing the environment of said bearing ( 16 ) to a lower pressure than that of said outside environment ( 50 ) external to said cooling system ( 7 ).

11. A method as claimed in claim 10 , characterized in that said conducting step comprises the step of conducting said second current (Q) from said first cavity ( 41 ) into a second cavity ( 30 ) defined by a diffuser ( 20 b ) of said fan ( 9 ), which is angularly fixed with respect to said axis (A);

said step of conducting said second current (Q) from said first cavity ( 41 ) into said second cavity ( 30 ) comprising the step of conducting said second current (Q) along a spinning path with respect to said axis (A).

12. A method as claimed in claim 11 , characterized in that said step of conducting said second current (Q) comprises the further step of conducting said second current (Q), by virtue of a pressure gradient, to an inlet section ( 24 ) of said diffuser ( 20 b ) traversed by said first current (P).

13. A method as claimed in claim 9 , characterized in that said conducting step comprises the step of conducting said second current (Q) into a first cavity ( 41 ) defined by said rotary member ( 10 ).

14. A method as claimed in claim 13 , characterized in that said conducting step also comprises the step of conducting said second current (Q) from said second cavity ( 30 ) into a third cavity ( 29 ) defined by said impeller ( 20 a ) and housing said bearing ( 16 );

said step of conducting said second current (Q) from said second cavity ( 30 ) into a third cavity ( 29 ) comprising the step of creating a vortex inside said third cavity ( 29 ).