Patent Application
20130149163
The present disclosure relates to a blade tip having a chamfered configuration for reducing bending stress at the tip.
Many turbine engines have fans formed by a plurality of blades. In order to obtain better fan performance, an outer air seal is provided in the form of a rub strip. Occasionally, the fan blade will rub against the outer air seal rub strip. Blade tip treatments may be needed to provide an abrasive or hardened layer for rub resistance to the seal material to protect the fan blade. These treatments may cause a fatigue debit to the fan blade.
In accordance with the present disclosure, there is provided a turbine engine component which broadly comprises an airfoil portion with at least one chamfered edge on at least one side.
Further in accordance with the present disclosure, there is provided a method for creating a turbine engine component, which method broadly comprises forming a turbine engine component having an airfoil portion with a pressure side and a suction side and with at least one chamfered edge on one of the pressure side and the suction side.
Other details of the method for reducing stress on a fan blade tip are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.
Referring now to the drawings,
The fan 102 consists of a plurality of fan blades 120 which are mounted to a disk 122. Each of the fan blades 120 has an airfoil portion 123 with a leading edge 124, a trailing edge 126, a root portion 128, and a tip portion 129. Each fan blade 120 is attached to the disk 122 at the root portion 128. The fan blades 120 may be formed from any suitable material known in the art. For example, the fan blades 120 may be formed from an aluminum alloy. If desired, the fan blades 120 may be hollow.
If desired, as shown in
Referring now to
In a useful embodiment, the tip portion 129 is provided with two chamfered edges 140 and 142. The chamfered edges 140 and 142 are cut so as to leave a flat portion 144 therebetween.
The tip treatment or coating 132 is applied to the flat portion 144 of the modified blade tip portion 129. Each chamfered edge 140 and 142 may be as large as possible because larger chamfers lead to more stress reduction. The size is limited however by the need to maintain a minimum amount of flat portion 144 at the tip in order to have a surface capable of an effective tip gap and/or rub,
As can be seen from
In order to ensure a smooth flow of air over the pressure and suction sides 146 and 144 respectively, a sheath 160 may be placed over the leading edge 124 of the fan blade 120. The sheath 160 may be formed from a metal selected from the group consisting of titanium, nickel, steel, alloys of the foregoing, and any material more erosion-resistant than the material forming the fan blade 120.
Each chamfered edge 140 or 142 may be cut to have a radius or may be cut straight to create a setback of the corner and reduce the peak bending stress at the tip portion 129 where the tip treatment or coating 132 may be applied. The radius of each chamfered edge 140 and 142 or the straight cut of each chamfered edge 140 and 142 should be such as to create the flat tip portion 129. The provision of the chamfered edges 140 and 142 reduces the peak bending stress by moving the stress points away from the tip edge. This effectively restores the fatigue strength back to the original substrate. The radius, when sued, also provides a surface that will enable treatments such as a hardcoat which has a propensity for cracking if a break edge is not provided. The value of the radius and the size of the flat tip portion 129 may be determined by which treatment is selected and overall blade requirements.
The fan blade 120 of the present disclosure may be manufactured using any desired technique. For example, the fan blade 120 with the chamfered edges 140 and 142 may be manufactured using an investment casting technique in which the chamfered edge 140 and/or 142 are integrally formed with the remainder of the fan blade 120. Alternatively, the fan blade 120 without the chamfered edges 140 and/or 142 may be manufactured using any suitable casting technique known in the art. After the fan blade 120 is cast, the chamfered edges 140 and/or 142 may be formed using any suitable cutting technique known in the art to form the edges 140 and/or 142 with a straight cut or a radius and to form the flattened tip portion 129.
After the tip portion 129 is formed, the tip treatment or coating 132 may be applied using any suitable technique known in the art.
While the present disclosure has focused on fan blades, it should be recognized that the chamfered edges described herein may be applied to other types of blades and to vanes.
There has been described in accordance with the instant disclosure a method for reducing stress on a blade tip. While the method set forth herein has been described in the context of a particular embodiment, other unforeseeable alternatives, modifications, and variations may become apparent to those skilled in the art. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.
