Patent Grant
10156244
The present disclosure relates generally to gas turbine engines, and more specifically to fan assemblies used in gas turbine engines.
Gas turbine engines used to power aircraft often include a relatively-large diameter fan assembly that is driven by an engine core. The fan assembly blows air to provide thrust for moving the aircraft. Such fans typically include a fan wheel mounted to the engine core to be rotated by the engine core and a plurality of blades mounted to the fan wheel to rotate with the fan wheel to push air.
During operation, the blades may experience an undesirable dynamic instability called flutter. Flutter may occur when energy associated with the airflow through the fan assembly is transferred to the blades in the form of vibrations. Flutter in the fan assembly may cause high-cycle fatigue blade failure.
The present disclosure may comprise one or more of the following features and combinations thereof.
According to an aspect of the present disclosure, a fan assembly may include a fan wheel, a plurality of blades, and an annular mistuning band. The plurality of blades may extend radially from the fan wheel away from a central axis. Each of the blades may include a root coupled with the fan wheel and an airfoil extending radially outwardly from the root. The annular mistuning band may be positioned adjacent to the fan wheel along the central axis and engaged with the roots of a predetermined number of more than one but less than all of the plurality of blades.
In some embodiments, the plurality of blades may be spaced circumferentially from one another about the fan wheel. The annular mistuning band may engage every other root of the plurality of blades. In some embodiments, the annular mistuning band may engage the roots of less than half of the plurality of blades.
In some embodiments, the fan assembly may have a fore end and an aft end. The fan assembly may further include a fore retainer located toward the fore end. The annular mistuning band may be located toward the aft end and may be spaced apart from the fore retainer to locate the plurality of blades therebetween.
In some embodiments, the fan assembly may have a fore end and an aft end. The fan assembly may further include an aft retainer located toward the aft end. The annular mistuning band may be located toward the fore end and may be spaced apart from the aft retainer to locate the plurality of blades therebetween.
In some embodiments, the fan wheel may be formed to include a plurality of axially extending slots. The root of each blade may be received in a corresponding slot. The root of each of the predetermined number of blades may extend axially out of the slots. The annular mistuning band may engage a portion of the roots extending axially out of the slots.
In some embodiments, the annular mistuning band may include an annular body and a plurality of engagement flanges extending radially outward away from the annular body and may be spaced circumferentially apart from one another. In some embodiments, the annular mistuning band may be castellated.
According to another aspect of the present disclosure, a fan assembly may include a fan, a fore retainer, an aft retainer, and an annular mistuning band. The fan may include a fan wheel and a plurality of blades extending radially outward from the fan wheel relative to a central axis. Each of the blades may include a root coupled with the fan wheel and an airfoil extending radially outward from the root. The fore retainer may be coupled to the fan wheel and adapted to limit axial movement of the plurality of blades along the central axis. The aft retainer may be spaced apart axially from the fore retainer to locate the plurality of blades therebetween. The aft retainer may be coupled to the fan wheel and adapted to limit axial movement of the plurality of blades. The annular mistuning band may extend around the central axis. The annular mistuning band may be positioned axially between the fore retainer and the aft retainer and may engage the root of a predetermined number of more than one but less than all of the plurality of blades.
In some embodiments, the annular mistuning band may include an annular body and a plurality of engagement flanges. The engagement flanges may extend radially outward from the annular body and may be spaced apart circumferentially from one another.
In some embodiments, the annular body may be spaced apart from the roots of the blades and the plurality of engagement flanges may engage the predetermined number of blades. In some embodiments, the annular mistuning band may be castellated.
In some embodiments, the fan wheel may be formed to include a plurality of axially extending slots. The root of each blade may be received in a corresponding slot. The root of each of the predetermined number of blades may extend axially beyond the slots. The engagement flanges may engage a portion of the roots extending axially beyond the slots.
In some embodiments, the annular mistuning band may further include a lip extending axially away from the annular body. The lip may be located radially between the central axis and the portion of the roots extending axially beyond the slots to center the annular mistuning band relative to the central axis. In some embodiments, the annular mistuning band may engage the roots of less than half of the plurality of blades.
According another aspect of the present disclosure, a method of assembling a fan assembly may include a number of steps. The method may include coupling roots of a plurality of blades to a fan wheel so that the blades extend radially from the fan wheel away from a central axis to provide a fan, and positioning an annular mistuning band that extends around the central axis adjacent to the fan along the central axis such that the annular mistuning band contacts the root of a predetermined subset of more than one but less than all of the plurality of blades.
In some embodiments, the method may further include clamping the annular mistuning band and the predetermined subset of blades between a fore retainer and an aft retainer of the fan assembly. In some embodiments, the method may further include clamping the predetermined subset of blades between a fore retainer of the fan assembly and the annular mistuning band.
In some embodiments, the plurality of blades may be spaced circumferentially from one another about the fan wheel. The annular mistuning band may engage every other root of the plurality of blades. In some embodiments, the annular mistuning band may engage the roots of less than half of the plurality of blades.
These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.
An illustrative aerospace gas turbine engine 10 for use in an aircraft is cut-away to show that the engine 10 includes a fan assembly 12 and an engine core 13 adapted to drive the fan assembly 12 as shown in
The illustratively fan assembly 12 includes a plurality of fan blades 36 for pushing air and a mistuning band 28 which engages a predetermined number of the fan blades 36 to mistune the fan assembly 12 as shown in
The illustrative fan assembly 12 includes a fan 22, a fore retainer 24, an aft retainer 26, and the mistuning band 28 as shown in
The fan 22 includes a fan wheel 34 and a plurality of blades 36 extending radially from the fan wheel 34 away from the central axis 20 as shown in
The illustrative fan wheel 34 is formed to include a plurality of radially inwardly extending slots 40 shown in phantom in
Each blade illustratively includes a root 42, a platform 44, and an airfoil 46 as shown in
The fore retainer 24 extends radially outward to limit forward axial movement of the blades 36 and block the blades 36 from escaping from the slots 40 at the fore end 30 as shown in
The aft retainer 26 extends radially outward to limit rearward axial movement of the blades 36 and block the blades 36 from escaping from the slots 40 at the aft end 32 as shown in
The mistuning band 28 is positioned adjacent to the fan 22 along the central axis 20. The mistuning band 28 contacts the root 42 of a predetermined number of the plurality of blades 36 to mistune the fan assembly 12 and reduce flutter. In the illustrative embodiment, the mistuning band contacts more than one but less than all of the plurality of blades 36. The life of the blades 36 may be increased by reducing the flutter as the high cycle fatigue of the blades 36 may be reduced. In the illustrative embodiment, the mistuning band 28 is an annular mistuning band 28 that extends around the central axis 20.
In the illustrative embodiment, the roots 42 have an axial length that is longer than the slots 40. As such, each root 42 extends axially out of and beyond the slot 40 as shown in
The plurality of blades 36 and the mistuning band 28 are positioned axially between the fore retainer 24 and the aft retainer 26 as shown in
In the illustrative embodiment, the mistuning band 28 includes an annular body 48, a plurality of engagement flanges 50 that extend radially outward away from the annular body 48, and an lip 54 that extends axially away from the annular body 48 as shown in
The engagement flanges 50 engage the predetermined number of blades 36 as shown in
The lip 54 extends axially from the annular body 48 as shown in
In some embodiments, the mistuning band 28 engages every other root 42 of the plurality of blades 36. In the illustrative embodiment, the mistuning band 28 engages the roots 42 of less than half of the plurality of blades 36. In other embodiments, the mistuning band 28 engages the roots 42 of more than half of the plurality of blades 36. In other embodiments, the mistuning band 28 is adapted to engage every third, fourth, or nth blade 36. In yet other embodiments, the mistuning band 28 may engage two or more adjacent blades 36.
In some embodiments, the mistuning band 28 is integrally formed with one or both of the fore retainer 24 and the aft retainer 26. In some embodiments, the mistuning band 28 is monolithically formed with one or both of the fore retainer 24 and the aft retainer 26. In some embodiments, the mistuning band 28 comprises a fret-resistant material. In some embodiments, an anti-fret coating is applied to one or more surfaces of the mistuning band. In the illustrative embodiment, the mistuning band 28 is consumable and disposable. In the illustrative embodiment, the mistuning band 28 comprises steel.
The mistuning band 28 may have a relatively large or relatively small thickness to vary the mistuning of the fan assembly 12. In some embodiments, the mistuning band 28 may have a thickness of between about three thousandths of an inch and about fifteen-thousandths of an inch.
According to at least one method of assembling the fan assembly 112, a sheet of material is stamped in a manufacturing process to form the mistuning band 28. The root 42 of each blade 36 is aligned with a corresponding slot 40 and translated into the slot 40 until a blade 36 is received in each slot 40. The aft retainer 26 is aligned with the fan wheel 34 relative to the central axis 20 and coupled with the fan wheel 34 at the aft end 32 of the fan assembly 12. The aft retainer 26 engages the blades 36 to cause a portion of the blades 36 to extend beyond the slots 40 at the fore end 30 of the fan assembly 12.
The mistuning band 28 is aligned with the fan wheel 34 relative to the central axis 20 and translated axially. The lip 54 of the mistuning band 28 is located radially between the central axis 20 and the portion of the roots 42 that extend beyond the slots 40. The engagement flanges 50 are engaged with the predetermined number of blades 36. The fore retainer 24 is aligned with the fan wheel 34 relative to the central axis 20 and coupled with the fan wheel 34 at the fore end 30 of the fan assembly 12. The fore retainer 24 and aft retainer 26 are tightened to apply a desired clamp force to the predetermined number of blades 36 and the mistuning band 28 to mistune the fan assembly 12.
Another illustrative fan assembly 112 is shown in
The fan assembly 112 includes a fan 122, a fore retainer 124, and a mistuning band 128 as shown in
The fore retainer 124 extends radially outward to limit forward axial movement of the blades 136 and block the blades 136 from escaping from the slots 140 at the fore end 130 as shown in
The mistuning band 128 extends radially outward to limit rearward axial movement of the blades 136 and block the blades 136 from escaping from the slots 140 at the aft end 132 as shown in
The mistuning band 128 contacts the root 142 of a predetermined number of the plurality of blades 136 to mistune the fan assembly 112. In the illustrative embodiment, the mistuning band 128 contacts the root 142 of more than one but less than all of the plurality of blades 136. In the illustrative embodiment, the mistuning band 128 is an annular mistuning band 28 that extends around the central axis 20.
In the illustrative embodiment, the roots 142 of the blades 36 have an axial length that is longer than the slots 140. As such, each root 142 extends axially in the aft direction out of and beyond the slot 140 as shown in
The predetermined number of blades 136 are clamped between the fore retainer 124 and the mistuning band 128 to cause the mistuning band 128 to engage the roots 142 of the predetermined number of blades 136 and stiffen the predetermined number of blades 136 to mistune the fan assembly 112. In the illustrative embodiment, the mistuning band 128 is located toward the aft end 32. In other embodiments, the fan assembly 112 may include a mistuning band 128 located toward the fore end 130 and an aft retainer 126 located toward the aft end 132 to clamp the blades 136 between the mistuning band 128 and the aft retainer 126.
In the illustrative embodiment, the mistuning band 128 includes an annular body 148 formed to include a plurality of apertures 152 spaced circumferentially apart from one another and a lip 154 as shown in
In the illustrative embodiment, the remaining blades 136 extend out of the aft end 32 of the slots 140 and into the apertures 152 so that they are spaced apart from the mistuning band 128. In the illustrative embodiment, the mistuning band 128 is castellated. The annular body 148 illustratively extends radially outward toward the platform 144 to seal the fan assembly 112.
In some embodiments, the mistuning band 128 engages every other root 142 of the plurality of blades 136. In the illustrative embodiment, the mistuning band 128 engages the roots 142 of less than half of the plurality of blades 136. In other embodiments, the mistuning band 128 engages the roots 142 of more than half of the plurality of blades 136. In other embodiments, the mistuning band 128 is adapted to engage every third, fourth, or nth blade 136. In yet other embodiments, the mistuning band 128 may engage two or more adjacent blades 36.
While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/117,230, filed 17 Feb. 2015, the disclosure of which is now expressly incorporated herein by reference.
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