AIRFOIL WITH COOLING HOLE HAVING A FLARED SECTION
An airfoil is provided for a gas turbine engine. The airfoil may comprise a main body comprising a leading edge having a leading edge outer surface, a trailing edge having a trailing edge outer surface, a suction side having a suction side outer surface and a pressure side having a pressure side outer surface. The main body may further comprise at least one interior cooling passage and a plurality of cooling holes extending from the cooling passage to at least one of the leading edge outer surface, the trailing edge outer surface, the suction side outer surface and the pressure side outer surface. Preferably, at least one of the cooling holes includes a proximal metering section having a first dimension extending transverse to an axis extending in a flow direction of a cooling fluid passing through the one cooling hole, a flared section and an exit opening having a second dimension transverse to the axis which is larger than the first dimension. The flared section is preferably curvilinear as it extends from the proximal metering section towards the exit opening.
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This application claims priority from U.S. Provisional Application Ser. No. 60/973,573, which was filed on Sep. 19, 2007, the disclosure of which is incorporated by reference in its entirety herein.
FIELD OF THE INVENTIONThe present invention relates to an airfoil for a gas turbine engine having at least one cooling hole extending from an interior cooling passage to an outer surface of the airfoil and wherein the cooling hole has a flared section.
BACKGROUND OF THE INVENTIONA conventional combustion gas turbine engine includes a compressor, a combustor, and a turbine. The compressor compresses ambient air. The combustor combines the compressed air with a fuel and ignites the mixture creating combustion products defining a working gas. The working gases travel to the turbine. Within the turbine are a series of rows of stationary vanes and rotating blades. Each pair of rows of vanes and blades is called a stage. Typically, there are four stages in a turbine. The rotating blades are coupled to a shaft and disc assembly. As the working gases expand through the turbine, the working gases cause the blades, and therefore the shaft and disc assembly, to rotate.
Combustors often operate at very high temperatures. Typical combustor configurations expose turbine vanes and blades to these high temperatures. As a result, turbine vanes and blades must be made of materials capable of withstanding such high temperatures. In addition, turbine vanes and blades often contain cooling systems for prolonging the life of the vanes and blades and reducing the likelihood of failure as a result of excessive temperatures.
Conventional turbine blades and vanes have many different designs of internal cooling systems. For example, a plurality of cooling holes may extend from an interior cooling passage to an outer surface of an airfoil of a turbine vane or blade. It is preferred that the wall of the vane or blade be as thin as possible. It is also preferred that the cooling openings be shaped and sized such that the cooling fluid moving through each cooling opening does not separate from a wall defining the cooling opening.
SUMMARY OF THE INVENTIONIn accordance with an aspect of the present invention, an airfoil is provided for a gas turbine engine. The airfoil may comprise a main body comprising a leading edge having a leading edge outer surface, a trailing edge having a trailing edge outer surface, a suction side having a suction side outer surface and a pressure side having a pressure side outer surface. The main body may further comprise at least one interior cooling passage and a plurality of cooling holes extending from the cooling passage to at least one of the leading edge outer surface, the trailing edge outer surface, the suction side outer surface and the pressure side outer surface. Preferably, at least one of the cooling holes includes a proximal metering section having a first dimension extending transverse to an axis extending in a flow direction of a cooling fluid passing through the one cooling hole, a flared section and an exit opening having a second dimension transverse to the axis which is larger than the first dimension. The flared section is preferably curvilinear as it extends from the proximal metering section towards the exit opening.
The one cooling hole may further comprise a distal section extending from at least a portion of the flared section to at least a portion of the exit opening.
In accordance with a first embodiment of the present invention, the one cooling hole may further comprise a concave interface section located between the flared section and the distal section. In accordance with a second embodiment of the present invention, the flared section meets directly with the distal section.
The proximal metering section may have a diameter D and a length between about 1.0D and about 5.0D. The diameter D of the proximal metering section may be from about 0.5 mm to about 5.0 mm.
The one cooling hole may extend at an angle θ of from about 20 degrees to about 90 degrees to the one outer surface.
The one outer surface may have a thickness T and the one cooling hole may have an overall length L determined from the following equation:
length L=thickness T/Sin θ
The exit opening may be substantially square or substantially circular in shape as viewed along the axis of the one cooling hole. With the exit opening square or circular in shape, the shape of the flared section may be defined by the following equation:
wherein:
-
- y1=an exit radius or dimension for a largest portion of the flared section;
y0=a radius of the proximal metering section;
Id=a length of a longest portion of the flared section;
x=independent coordinate extending along the axis with an origin at a beginning point of the flared section; and
y=dependent coordinate perpendicular to the axis with an origin at a central axis of the one cooling hole.
Alternatively, the shape of the flared section may be defined by the following equation:
wherein:
-
- y1=an exit radius or dimension for a largest portion of a curvilinear portion of the flared section;
- y0=a radius of the proximal metering section;
- Id=a length of a longest portion of the flared section;
- x=independent coordinate extending along the axis with an origin at a beginning of the flared section; and
- y=dependent coordinate perpendicular to the axis with an origin at a center axis of the one cooling hole.
Referring now to
The blades are coupled to a shaft and disc assembly. Hot working gases from a combustor (not shown) in the gas turbine engine travel to the rows of blades. As the working gases expand through the turbine, the working gases cause the blades, and therefore the shaft and disc assembly, to rotate.
The blade 10 comprises an attachment portion or a root 12, a platform 14 integral with the root 12 and an airfoil 20 formed integral with the platform 14, see
A conventional thermal barrier coating (not shown) is provided on an outer surface 102 of the main body 100. The outer surface 102 of the main body 100 is defined by the leading edge outer surface 122, the trailing edge outer surface 132, the pressure side outer surface 142 and the suction side outer surface 152.
In the illustrated embodiment, the airfoil main body 100 further comprises an interior cooling passage 160 and a plurality of cooling holes 170 extending from the cooling passage 160 to at least one of the leading edge outer surface 122, the trailing edge outer surface 132, the pressure side outer surface 142 and the suction side outer surface 152, see
A cooling fluid, such as air or steam, is supplied under pressure in the direction of arrow A in
The cooling fluid moves through the cooling fluid entrance, through the platform 14 and into the interior cooling passage 160 of the airfoil main body 100. From the airfoil cooling passage 160, the cooling fluid passes through the cooling holes 170 and, after exiting the cooling holes 170, provides film cooling for a downstream portion, i.e., in a direction away from the leading edge 120 toward the trailing edge 130, of the outer surface 102 of the main body 100.
Each of the cooling holes 170 may be formed so as to have substantially the same shape and size. Hence, only a single cooling hole, for each embodiment of cooling holes, will be discussed herein.
Referring now to
In the embodiment illustrated in
wherein:
-
- y1=an exit radius for the largest portion, i.e., the first portion 174A, of the flared section 174;
- y0=a radius of the proximal metering section 172;
- Id=a length of the longest portion, i.e., the first portion 174A, of the flared section 174;
- x=independent coordinate extending along the central axis A170 of the cooling hole 170 with an origin at a beginning point PB174 of the flared section 174; and
- y=dependent coordinate perpendicular to the central axis A170 of the cooling hole 170 with an origin at the central axis A170.
The radius y0 (also referred to herein as “a first dimension”) of the proximal metering section 172 is less than a largest dimension (also referred to herein as “a second dimension”) of the exit opening 178.
The shape and size of the cooling hole 170 may be designed as follows. Typically, the thickness T of the airfoil main body 100 is predefined. Also, the diameter D172 of the proximal metering section 172 is predefined and typically selected to be as small as possible, e.g., 1 mm, so as to minimize the risk that the cooling hole 170 may be blocked by dirt and the like. With the diameter D172 of the proximal metering section 172 equal to about 1 mm, the main body thickness T may equal 3.8D172 or 3.8 mm. The angle θ, the angle at which the cooling hole 170 is positioned relative to the outer surface 102 of the main body 100, is also predefined and is typically selected to be as small as possible so as to be within manufacturing capabilities.
With the angle θ and the thickness T of the airfoil main body 100 predefined, the overall length L170 of the cooling hole 170 may be determined via the following equation:
length L170=thickness T/Sin θ (Equation 2)
With the angle θ and the thickness T of the airfoil main body 100 predefined and the overall length L170 of the cooling hole 170 predetermined, different values of y1/y0 and Id from Equation 1, above, are selected and tested to determine the values for y1/y0 and Id which provide a desired film cooling effectiveness for the outer surface 102 of the airfoil main body 100. The length L172 of the proximal metering section 172 is equal to the overall length L170 of the cooling hole 170 minus the length Id of the longest portion, i.e., the first portion 174A, of the flared section 174. Equation 1, above, is then used to determine values for x and y, i.e., the shape, of the flared section 174.
In prior art cooling holes, a transition section extending away from the proximal metering section towards an exit opening had a straight or linear shape as the transition section expanded away from the metering section. If the metering section had a length less than about 5.0D (where D=the diameter of the metering section), there was risk that the cooling fluid would separate from the wall defining the transition section, causing a reduction in film cooling for a downstream portion of the outer surface of the airfoil main body. Because the flared section 174 of the cooling hole 170 of the present invention has a curvilinear shape as it extends away from the proximal metering section 172 towards the distal section 176 and exit opening 178 in a X direction, see
In the embodiment illustrated in
In
In the embodiment illustrated in
y1=an exit radius or dimension for the largest portion, i.e., the first portion 274A, of the flared section 274;
y0=a radius of the proximal metering section 272;
Id=a length of the longest portion, i.e., the first portion 274A, of the flared section 274;
x=independent coordinate extending along the central axis A270 Of the cooling hole 270 with an origin at a beginning point PB274 of the flared section 274; and
y=dependent coordinate perpendicular to the central axis A270 of the cooling hole 270 with an origin at the central axis A270. In this embodiment, values for z substantially equal values for y, when both z and y have the same corresponding x value.
The shape and size of the cooling hole 270 may be designed using generally the same steps set out above for designing the cooling hole 170 of the first embodiment.
In the embodiment illustrated in
In
In the embodiment illustrated in
wherein:
-
- y1=an exit radius or dimension for a largest portion of a curvilinear portion of the flared section 374;
- y0=a radius of the proximal metering section 372;
- Id=a length of the longest portion of the flared section 374;
- x=independent coordinate extending along the central axis A370 of the cooling hole 370 with an origin at a beginning point PB374 of the flared section 374; and
- y=dependent coordinate perpendicular to the central axis A370 of the cooling hole 370 with an origin at the central axis A370.
The shape and size of the cooling hole 370 may be designed using generally the same steps set out above for designing the cooling hole 170 of the first embodiment.
While a particular embodiment of the present invention has been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
Claims
1. An airfoil for a gas turbine engine comprising:
- a main body comprising a leading edge having a leading edge outer surface, a trailing edge having a trailing edge outer surface, a suction side having a suction side outer surface and a pressure side having a pressure side outer surface, said main body further comprising at least one interior cooling passage and a plurality of cooling holes extending from said cooling passage to at least one of said leading edge outer surface, said trailing edge outer surface, said suction side outer surface and said pressure side outer surface; at least one of said cooling holes including a proximal metering section having a first dimension extending transverse to an axis extending in a flow direction of a cooling fluid passing through said one cooling hole, a flared section and an exit opening having a second dimension transverse to the axis which is larger than said first dimension, wherein said flared section is curvilinear as it extends from said proximal metering section towards said exit opening.
2. An airfoil as set out in claim 1, wherein said one cooling hole further comprises a distal section extending from at least a portion of said flared section to at least a portion of said exit opening.
3. An airfoil as set out in claim 2, wherein said one cooling hole further comprises a concave interface section located between said flared section and said distal section.
4. An airfoil as set out in claim 2, wherein said flared section meets directly with said distal section.
5. An airfoil as set out in claim 1, wherein said proximal metering section has a diameter D and a length between about 1.0D and about 5.0D.
6. An airfoil as set out in claim 5, wherein said one cooling hole extends at an angle θ of from about 20 degrees to about 90 degrees to said one outer surface.
7. An airfoil as set out in claim 6, wherein said one outer surface has a thickness T and said one cooling hole has an overall length L determined from the following equation:
- length L=thickness T/Sin θ
8. An airfoil as set out in claim 5, wherein said diameter D of said proximal metering section is from about 0.5 mm to about 5.0 mm.
9. An airfoil as set out in claim 1, wherein the shape of said flared section is defined by the following equation: y = y 1 4 × 1 + [ ( y 1 / y 0 ) 4 - 1 ] · [ 1 - x 1 d ]
- wherein: y1=an exit radius or dimension for a largest portion of said flared section; y0=a radius of said proximal metering section; Id=a length of a longest portion of said flared section; x=independent coordinate extending along the axis with an origin at a beginning of said flared section; and y=dependent coordinate perpendicular to the axis with an origin at a central axis of said one cooling hole.
10. An airfoil as set out in claim 9, wherein said exit opening is square or circular in shape as viewed along the axis of said one cooling hole.
11. An airfoil as set out in claim 1, wherein the shape of said flared section is defined by the following equation: y = y 1 1 + [ ( y 1 / y 0 ) 2 - 1 ] · [ 1 - x 1 d ]
- wherein: y1=an exit radius or dimension for a curvilinear portion of said flared section; y0=a radius of said proximal metering section; Id=a length of a longest portion of said flared section; x=independent coordinate extending along the axis with an origin at a beginning of said flared section; and y=dependent coordinate perpendicular to the axis with an origin at a central axis of said one cooling hole.
Type: Application
Filed: Jan 24, 2008
Publication Date: Mar 19, 2009
Applicant: SIEMENS POWER GENERATION, INC. (Orlando, FL)
Inventor: Robert K. Scott (Geneva, FL)
Application Number: 12/018,994
International Classification: F01D 5/18 (20060101); F01D 5/08 (20060101);