Patent Application
20130183157
This application relates to a surface treatment method for treating a dovetail in a blade.
Gas turbine engines are known, and typically have a fan delivering air to a compressor. From the compressor, the air passes downstream into a combustion section where it is mixed with fuel and burned. Products of that combustion pass downstream over turbine rotors which in turn drive the fan to rotate.
The fan may include a plurality of separate blades mounted into a rotor. The blades have an airfoil which moves the air, and a radially inner portion, known as a dovetail, which is received within a slot in the rotor.
The dovetail is subject to high stress during operation of the gas turbine engine. Thus, it presents challenges to a designer of a fan blade.
One method that has been proposed to address the stresses applied into the dovetail is to utilize a burnishing operation on the dovetail. A burnishing operation will induce stresses within the part. These induced stresses are residual compressive stresses that can be induced into the part to a desired depth. The induced stresses counter applied stresses during operation to result in an overall lower stress level.
The burnishing operation does provide good control over the level of induced stresses and the depth into the material. However, burnishing typically requires a somewhat flat surface, and thus, complex surfaces may not be candidates for burnishing.
Once a burnishing operation has been applied to a part, surfaces that have not been burnished may have increased stresses or other changes which may be undesirable.
A method of surface treating a dovetail in a blade includes the steps of providing a burnishing operation along circumferential sides of the dovetail. Next, shot peening is provided at axial ends of the dovetail. A blade made by the method is also claimed.
These and other features of this application will be better understood from the following specification and drawings, the following of which is a brief description:
In order to surface treat the fan blade dovetail to withstand such forces, a first surface treatment step, burnishing, is shown in
A burnishing operation with a burnishing tool, shown rather schematically at 50, has surfaces 104 brought into contact with the side surfaces 100. The burnishing tool 50 may provide low plasticity burnishing. One known low plasticity technique is disclosed in U.S. Pat. No. 6,415,486. Other burnishing operations can be used however.
As shown in
While burnishing works very well on the circumferential side surfaces 100, it is not as effective for the ends 102 and 104. Since the ends 102 and 104 have complex surfaces, they are not as easily treated with the burnishing technique. In addition, the burnishing of the sides 100 does result in undesirable stress distribution at the ends 102 and 104.
Thus,
After the two-step method is complete, the fan blade 20 has been surface treated at both of its ends 102/104, and the sides 100 of the dovetail such that it will provide effective operation in the challenging environment of the gas turbine engine.
In addition, as an initial optional step prior to the
The blade as disclosed above is for use as a fan blade. It is believed the teachings of this application would have most success when utilized on blades that will exist in lower temperature portions of a gas turbine engine. However, it is possible that blades in higher temperature regions may also benefit from the methods. In addition, the methods may have application in blades having air foils and dovetails for use in applications other than gas turbine engines. Thus, while the invention might have most application in fan blades and lower pressure compressor sections, it may also have application in other locations.
Although an embodiment has been disclosed, a worker of ordinary skill in the art would recognize that certain modification would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
