초록 ▼

A turbofan engine comprising an annular inner wall surrounding tips of the fan blades, a layer of insulating material surrounding the inner wall, and an outer casing including an annular outer wall surrounding the insulating material and concentric to the inner wall and at least two annular rub elem

A turbofan engine comprising an annular inner wall surrounding tips of the fan blades, a layer of insulating material surrounding the inner wall, and an outer casing including an annular outer wall surrounding the insulating material and concentric to the inner wall and at least two annular rub elements extending radially inwardly from the outer wall through only part of a radial thickness of the layer of insulating material, at least two of the rub elements being in axial alignment with the blade tips at every point around a circumference of the fan, each rub element having a radially inner end spaced apart from the inner wall and made of a material harder than that of the blades, and a containment fabric layer wrapped around a support structure of the outer wall.

대표청구항 ▼

1. A turbofan engine comprising: an axially extending annular inner wall surrounding tips of rotatable fan blades of the turbofan engine;a layer of insulating material surrounding the inner wall;an outer casing including an axially extending annular outer wall surrounding the insulating material and

1. A turbofan engine comprising: an axially extending annular inner wall surrounding tips of rotatable fan blades of the turbofan engine;a layer of insulating material surrounding the inner wall;an outer casing including an axially extending annular outer wall surrounding the insulating material and concentric to the inner wall, a plurality of intersecting outer ribs extending radially outwardly from the outer wall in an isogrid configuration and defining a support structure extending from a location forward of the blade tips to a location aft of the blade tips, and at least two annular rub elements extending radially inwardly from the outer wall through only a portion of a radial thickness of the layer of insulating material, at least two of the rub elements being in axial alignment with the blade tips at every point around a circumference of the fan, each rub element having a radially inner end spaced apart from the inner wall and composed of a material harder than that of the blades; anda containment fabric layer wrapped around the support structure. 2. The turbofan engine as defined in claim 1, wherein the at least two annular rub elements include two spaced apart circumferential rub elements oriented along a circumferential direction of the outer casing. 3. The turbofan engine as defined in claim 2, wherein the two spaced apart circumferential rub elements include a first rub element in an axial position located at least 5% and at most 30% of an axial chord length of the blade aft from a leading edge of the blade tips, and a second rub element in an axial position located at least 70% and at most 95% of the axial chord length aft from the leading edge. 4. The turbofan engine as defined in claim 1, wherein each rub element extends from an inner surface of the outer wall along a radial height, and has a thickness smaller than the radial height and defined perpendicularly thereto. 5. The turbofan engine as defined in claim 4, wherein the radial height of each rub element measured from the inner surface of the outer wall is at least twice and at most three times a radial thickness of the outer wall. 6. The turbofan engine as defined in claim 5, wherein the thickness of each rub element is at least equal and at most twice the radial thickness of the outer wall. 7. The turbofan engine as defined in claim 1, wherein each rub element includes an annular rib extending radially inwardly from the outer wall and an annular strip having at least an outer surface composed of the material harder than that of the blades and detachably connected to the rib to define the radially inner end. 8. The turbofan engine as defined in claim 7, wherein each strip has an L-shaped cross-section, including an axial leg defining the radially inner end of the rub element and a radial leg extending from the axial leg and disposed against a radial surface of the rib, the strip being detachably connected to the rib through the radial leg. 9. The turbofan engine as defined in claim 7, wherein each strip is a monolithic element composed of the material harder than that of the blades. 10. The turbofan engine as defined in claim 1, wherein each rub element includes an annular rib extending radially inwardly from the outer wall and an outer coating deposited directly on the rib to form the radially inner end thereof, the coating being composed of the material harder than that of the blades. 11. The turbofan engine as defined in claim 10, wherein the coating is a plasma spray coating, a hardcoat, a nano coating of Nickel or a nano coating of Cobalt. 12. The turbofan engine as defined in claim 1, wherein the material harder than that of the blades is harder than titanium. 13. The turbofan engine as defined in claim 1 wherein the material harder than that of the blades is also harder than that of the inner and outer walls. 14. A fan case for a turbofan engine comprising: an annular inner wall surrounding tips of a set of fan blades mounted for rotation about a central axis of the engine and extending axially from a first location fore of the fan blades to a second location aft of the fan blades;an annular outer wall concentric to the inner wall and interconnected thereto by front and aft circumferential flanges located respectively fore and aft of the fan blades, the interconnected inner and outer walls defining an annular enclosure therebetween bounded by the front and aft circumferential flanges;at least two annular inner ribs extending radially inwardly from the outer wall and configured such that at least two of the inner ribs are in axial alignment with the tips of the fan blades at every point around a circumference of the outer wall, the inner ribs extending from the outer wall across only part of a radial height of the enclosure, and a material harder than that of the fan blades at least covering the radially inner end of each inner rib;an acoustic material filling the enclosure; anda high-strength woven fibrous material wrapped around a plurality of intersecting outer ribs extending radially outwardly from the outer wall, the intersecting outer ribs forming a support structure supporting the fibrous material. 15. The fan case as defined in claim 14, wherein the at least two annular inner ribs include two spaced apart circumferential ribs oriented along a circumferential direction of the outer wall. 16. The fan case as defined in claim 15, wherein the two spaced apart circumferential ribs include a first rib in an axial position located at least 5% and at most 30% of an axial chord length of the blade aft from a leading edge of the blade tips, and a second rib in an axial position located at least 70% and at most 95% of the axial chord length aft from the leading edge. 17. The fan case as defined in claim 14, wherein each inner rib extends from an inner surface of the outer wall along a radial height of at least twice and at most three times a radial thickness of the outer wall, and has a thickness smaller than the radial height and defined perpendicularly thereto. 18. The fan case as defined in claim 14, wherein an annular strip is detachably connected to the radially inner end of each inner rib, the annular strip having at least an outer surface composed of the material harder than that of the blades. 19. The fan case as defined in claim 14, the material harder than that of the blades is in the form of an outer coating deposited directly on at least the radially inner end of each inner rib. 20. An outer casing for a fan case of a turbofan engine having a blade region in axial alignment with tips of rotating fan blades of the engine, the casing comprising an axially extending annular wall, a plurality of intersecting outer ribs extending radially outwardly from the wall in an isogrid configuration and defining a support structure extending from a location forward of the blade region to a location aft of the blade region, and at least two axially spaced apart circumferential annular rub elements extending radially inwardly from the wall within the blade region, each rub element extending from an inner surface of the wall along a radial height and having an axial thickness smaller than the radial height, each rub element having at least a radially inner end made of a material harder than that of the wall and that of the blades.