HOLLOW FAN BLADE RIB GEOMETRY
A fan blade has a main body extending between a leading edge and a trailing edge. Channels are formed into the main body from at least one open side. A plurality of ribs extend across the main body intermediate the channels. The fan blade has a dovetail and an airfoil extending radially outwardly from the dovetail. The ribs have a thickness defined as measured generally from the leading edge toward the trailing edge. A thickness of at least one of the ribs is generally thicker adjacent radially inner ends and becomes thinner moving in a radially outward direction.
This application relates to a hollow fan blade for a gas turbine engine, wherein a unique rib geometry is utilized.
Gas turbine engines may be provided with a fan for delivering air to a compressor section. From the compressor section, the air is compressed and delivered into a combustion section. The combustion section mixes fuel with the air and combusts the combination. Products of the combustion pass downstream over turbine rotors, which in turn are driven to rotate and rotate the compressor and fan.
The fan may include a rotor having a plurality of blades.
One type of fan blade is a hollow fan blade having a plurality of channels defined by intermediate ribs in a main fan blade body. An outer skin is attached over the main fan blade body to close off the cavities. The blades are subject to a number of challenges, including internal stresses that vary along a length of the fan blade.
SUMMARYA fan blade has a main body extending between a leading edge and a trailing edge. Channels are formed into the main body from at least one open side. A plurality of ribs extend across the main body intermediate the channels. The fan blade has a dovetail and an airfoil extending radially outwardly from the dovetail. The ribs have a thickness defined as measured generally from the leading edge toward the trailing edge. A thickness of at least one of the ribs is generally thicker adjacent radially inner ends and becomes thinner moving in a radially outward direction.
The invention will be described with regard to the specific and drawings, the following of which is a brief description.
A fan blade 20 is illustrated in
As shown in
As shown, a plurality of ribs 26 separate channels 30 in the cross-section illustrated in
In addition, the channels may be filled with lighter weight filler material to provide stiffness, as known.
A contact area 132 at the forward face of the ribs 26 serves as a mount point for the skin 32, and receives an adhesive. Chamfers 38 are formed at the break-edges, or the edges of the ribs 26, and will be described in more detail below. As shown, the channels 30 have a side extent formed by a compound radius 34 and 36, again to be described in greater detail below.
To reduce the weight, it is desirable to maximize the amount of channels and minimize the amount of rib. However, there is also a need for additional stiffness adjacent the radially inner edge 42, to provide greater durability, and minimize blade pull. Thus, the ribs 26 may be formed such that they tend to be thicker adjacent a radially inner edge 42, and become thinner when moving toward the radially outer portions 44.
It is also desirable to form a blade which avoids certain operational modes across the engine operational range. Additional mass toward the tip or outer end of the blade raises challenges against tuning away from fundamental modes.
As shown schematically in
As shown in
By modifying these several variables, a designer is able to tune or optimize the operation of the fan blade for its use in a gas turbine engine.
Notably, as will be explained below, it is desirable that the upper end 48/52/58 actually has a more complex surface at its break-edges.
As shown in
A ratio of c to t3 may be between 0.02-0.15. The use of the chamfer at the break-edge location reduces the stress. There would otherwise be stress concentrations at that area. On the other hand, by utilizing a chamfer within the disclosed range, the amount of surface area available to provide a good adhesion to the cover is still adequate.
The features of the break-edges are disclosed in co-pending U.S. patent application Ser. No. ______, filed on even date herewith and entitled “FAN BLADE HAVING INTERNAL RIB BREAK-EDGE.”
An Application directed to the features of
Finally
An Application directed to the features of
The compound fillets as disclosed in
The fan blade as described above reduces stresses that are raised during operations, when mounted in a gas turbine engine.
Although embodiments have been disclosed, a worker of ordinary skill in the art would recognize the modifications which come within the scope of this Application. Thus, the following claims should be studied to determine the true scope and content.
Claims
1. A fan blade comprising:
- a main body extending between a leading edge and a trailing edge, and having channels formed into said main body from at least one open side with a plurality of ribs extending across the main body intermediate the channels, the fan blade having a dovetail, and an airfoil extending radially outwardly from said dovetail; and
- said ribs having a thickness defined as measured generally from said leading edge toward said trailing edge, with a thickness of at least one said ribs being formed to be generally thicker adjacent a radially inner end, and becoming thinner moving in a radially outward direction.
2. The fan blade as set forth in claim 1, wherein a ratio of a thickness of said at least one rib selected near the radially inner end compared to a thickness selected near a radially outer end is between 1.1 and 8.
3. The fan blade as set forth in claim 1, wherein a cross-section through at least one said rib from the open side, and toward the closed side is trapezoidal.
4. The fan blade as set forth in claim 3, wherein an end of said trapezoidal rib spaced toward said open side is smaller than an end at said closed side.
5. The fan blade as set forth in claim 1, wherein a cross-section taken through at least one rib moving from the open side and, toward said closed side is rectangular.
6. A fan blade as set forth in claim 1, wherein a cross-section through at least one rib from the open side edge toward the closed side has generally curved sides, and is smaller at said open side than it is at said inner side.
7. The fan blade as set forth in claim 1, wherein an outer skin closes off the channels at the at least one open side.
8. The fan blade as set forth in claim 7, wherein said outer skin and said main body are both formed of aluminum or aluminum alloy.
9. The fan blade as set forth in claim 7, wherein said outer skin and said main body are both formed of titanium or a titanium alloy.
10. The fan blade as set forth in claim 7, wherein said channels extend from said open side to a closed side within said main body.
Type: Application
Filed: Sep 23, 2011
Publication Date: Mar 28, 2013
Inventors: Christopher S. McKaveney (East Hartford, CT), Letian Wang (Amston, CT)
Application Number: 13/241,756
International Classification: F01D 5/30 (20060101);