HOLE FOR ROTATING COMPONENT COOLING SYSTEM
A rotor for a gas turbine engine comprises an annular body and a plurality of holes. The annular body is configured to rotate in a circumferential direction about an axis extending through a center of the annular body. The annular body comprises an outer diameter surface and an inner diameter surface. The plurality of holes extends through the annular body. Each of the holes comprises an elongate profile in the circumferential direction, and a side wall extending between the outer diameter surface and the inner diameter surface. The side wall is slanted in the circumferential direction.
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Gas turbine engines operate by passing a volume of high energy gases through a plurality of stages of vanes and blades, each having an airfoil, in order to drive turbines to produce rotational shaft power. The shaft power is used to drive a compressor to provide compressed air to a combustion process to generate the high energy gases. Additionally, the shaft power is used to drive a generator for producing electricity. In order to produce gases having sufficient energy to drive the compressor or generator, it is necessary to combust the air at elevated temperatures and to compress the air to elevated pressures, which again increases the temperature. Thus, the vanes and blades are subjected to extremely high temperatures, often times exceeding the melting point of the alloys comprising the airfoils.
In order to maintain the airfoils at temperatures below their melting point it is necessary to, among other things, cool the airfoils with a supply of relatively cooler air, typically bleed from the compressor. This siphoned compressor air must be routed from the compressor to the vanes and, as such, must pass through rotating components. For example, cooling air is often drawn from the radial outer ends of the high pressure compressor vanes and routed radially inward via plumbing to the high pressure shaft where the cooling air must pass through support struts and the high pressure turbine rotor to be directed radially outward for passing into roots of the turbine vanes in the rotor. Routing of the cooling air in such a manner incurs aerodynamic losses that reduce the cooling effectiveness of the air and overall gas turbine engine efficiency. There is, therefore, a continuing need to improve aerodynamic efficiencies in cooling systems involving rotating components.
SUMMARYThe present invention is directed toward a rotor for a gas turbine engine. The rotor comprises an annular body and a plurality of holes. The annular body is configured to rotate in a circumferential direction about an axis extending through a center of the annular body. The annular body comprises an outer diameter surface and an inner diameter surface. The plurality of holes extends through the annular body. Each of the holes comprises an elongate profile in the circumferential direction, and a side wall extending between the outer diameter surface and the inner diameter surface. The side wall is slanted in the circumferential direction.
Inlet air A enters engine 10 and it is divided into streams of primary air AP and bypass air AB after it passes through fan 12. Fan 12 is rotated by low pressure turbine 22 through shaft 24 (directly or via a transmission (not shown, also know as a gear box) to accelerate bypass air AB through exit guide vanes 26, thereby producing a major portion of the thrust output of engine 10. Shaft 24 is supported within engine 10 at ball bearing 25A, roller bearing 25B and roller bearing 25C. Primary air AP (also known as gas path air) is directed first into low pressure compressor (LPC) 14 and then into high pressure compressor (HPC) 16. LPC 14 and HPC 16 work together to incrementally step up the pressure of primary air A. HPC 16 is rotated by HPT 20 through shaft 28 to provide compressed air to combustor section 18. Shaft 28 is supported within engine 10 at ball bearing 25D and roller bearing 25E. The compressed air is delivered to combustors 18A and 18B, along with fuel through injectors 30A and 30B, such that a combustion process can be carried out to produce the high energy gases necessary to turn turbines 20 and 22. Primary air AP continues through gas turbine engine 10 whereby it is typically passed through an exhaust nozzle to further produce thrust.
HPT 20 and LPT 22 each include a circumferential array of blades extending radially from rotors 31A and 31B connected to shafts 28 and 24, respectively. Similarly, HPT 20 and LPT 22 each include a circumferential array of vanes extending radially from HPT case 23D and LPT case 23E, respectively. In this specific example, HPT 20 comprises a two-stage turbine having blades 32A and 32B extending from rotor disks 34A and 34B of rotor 31A. Vane 34A extends radially inward from case HPT case 23E between blades 34A and 34B. Blades 32A and 32B include internal passages into which compressed cooling air AC from, for example, HPC 16 is directed to provide cooling relative to the hot combustion gasses of primary air A. Rotor disks 34A and 34B include holes to permit cooling air AC (also known as secondary air) into roots of blades 32A and 32B. Specifically, as shown in
In conventional rotors, cooling air is delivered through straight circular holes. The cooling air thus needs to turn ninety degrees to pass through the straight holes, which produces pressure loss. Additionally, circular holes limit swirl ratio to unity. The swirl ratio comprises the swirl velocity of the cooling air divided by the speed of the rotor, which is a product of the rotational speed w of the rotor and the distance of the hole from the engine centerline. Holes 40 of the present invention reduce pressure loss, as compared to straight circular holes, by slanting the holes in a flow rotating direction to reduce the flow turning loss, and elongating the shape of the holes in the flow rotating direction to increase the swirl ratio.
In the depicted embodiment, holes 40 are racetrack shaped such that leading edge wall 62A and trailing edge wall 62B are semi-circular, and side walls 62C and 62C extend straight between walls 62A and 62B parallel to each other. However, in other embodiments leading edge wall 62A and 62B may have some other arcuate shape. In yet other embodiments, the leading and trailing edge walls may be straight or flat. In any embodiment, the distance between leading edge and trailing edge side walls 62A and 62B (width) is greater than the distance between side walls 62C and 62D (length) such that holes 40 are elongate in circumferential direction ω. In the disclosed embodiment, hole 40 is approximately twice as wide as it is long, with reference to
Walls 58, which include walls 62A-62D, are angled in circumferential direction w with respect to radial direction R. In the depicted embodiment, leading edge wall 62A and trailing edge wall 62B are angled in the circumferential direction ω by about thirty degrees to form angle α. In other embodiments, angle α can be anywhere from approximately fifteen degrees to approximately seventy-five degrees, with higher angles typically being used in rotors that rotate at higher speeds. As such, leading edge wall 62A angles toward the interior of hole 40, while trailing edge wall 62B angles away from hole 40. Side walls 62C and 62D extend straight between outer diameter surface 60B and inner diameter surface 62A. Angling of the walls of hole 40, particularly walls 62A and 62B, reduces pressure loss generated by rotor disk 34B. Specifically, as shown in
Some of the benefits of the present invention in rotating annular bodies include reduction in pressure loss through holes, and increase in the swirl ratio through holes. This is achieved by elongating the hole to a racetrack configuration and slanting the hole in a radial direction about thirty to about forty degrees, in one embodiment. These qualities increase flow area, reduce flow vector turning and overall pressure loss, as compared to straight circular holes. The swirl ratio of cooling air for the present invention is greater than one, whereas circular holes are limited to swirl ratios of unity. Thus, the swirl ratio can be increased to 1.2 or more, a 20% or more increase as compared to the straight circular holes.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A rotor for a gas turbine engine, the rotor comprising:
- an annular body configured to rotate in a circumferential direction about an axis extending through a center of the annular body, the annular body comprising: an outer diameter surface; and an inner diameter surface; and
- a plurality of holes extending through the annular body, each of the holes comprising: an elongate profile in the circumferential direction; and a side wall extending between the outer diameter surface and the inner diameter surface, the side wall being slanted in the circumferential direction.
2. The rotor of claim 1 wherein the elongate profile of each of the plurality of holes is racetrack shaped.
3. The rotor of claim 2 wherein the elongate profile of each of the plurality of holes includes a width in the circumferential direction that is approximately twice as large as a length in the axial direction.
4. The rotor of claim 1 wherein the side wall of each of the plurality of holes includes arcuate leading and trailing edge segments that are angled in the circumferential direction with respect to a radial direction.
5. The rotor of claim 4 wherein the side walls are angled between approximately fifteen degrees and approximately seventy-five degrees.
6. The rotor of claim 4 wherein the side walls are angled between approximately thirty degrees and approximately forty degrees.
7. The rotor of claim 1 wherein the elongate profile of each of the plurality of holes comprises:
- an arcuate leading edge;
- an arcuate trailing edge;
- a first side edge extending straight between the arcuate leading and trailing edges; and
- a second side edge extending straight between the arcuate leading and trailing edges.
8. The rotor of claim 7 wherein the first side edge and the second side edge are parallel to each other.
9. The rotor of claim 7 wherein the arcuate leading edge and the arcuate trailing edge are circular.
10. The rotor of claim 7 wherein the arcuate leading edge and the arcuate trailing edge extend straight between the inner diameter surface and the outer diameter surface.
11. The rotor of claim 7 wherein the arcuate leading edge and the arcuate trailing edge are extend arcuately between the inner diameter surface and the outer diameter surface.
12. The rotor of claim 7 wherein the arcuate leading edge and the arcuate trailing edge are angled in the circumferential direction with respect to a radial direction.
13. The rotor of claim 1 wherein the plurality of holes is arranged in a circumferential row spaced evenly about the outer diameter surface.
14. The rotor of claim 1 wherein the plurality of holes increases the swirl ratio across the annular body while decreasing pressure loss when the annular body is rotating.
15. The rotor of claim 1 wherein the rotor further comprises:
- a disk comprising: an outer diameter edge having slots for receiving airfoils; and an inner diameter bore surrounding the axis; and
- a hub extending from the inner diameter bore of the disk to form the annular body, the plurality of holes being positioned on the hub.
16. The rotor of claim 15 and further comprising a mini-disk disposed opposite the outer diameter surface to form a cooling channel, the mini-disk comprising:
- an axially extending portion extending opposite the hub; and
- a radially extending portion extending along the disk;
- wherein cooling air directed into the hole from the inner diameter surface flows along the hub and along the disk to the slots.
17. The rotor of claim 16 wherein the mini-disk further comprises:
- a lap joint coupling the axially extending portion to the hub; and
- a face seal adjoining the radially extending portion with the slots of the outer diameter edge of the disk.
18. A rotor for a gas turbine engine configured to rotate in a circumferential direction about an axis extending through a center of the rotor, the rotor comprising:
- a disk comprising: an outer diameter edge having slots for receiving airfoils; and an inner diameter bore surrounding the axis;
- a hub extending from the inner diameter bore of the disk to form an annular body;
- a plurality of holes extending through the hub, each of the plurality of holes comprising: an arcuate leading edge; an arcuate trailing edge; first and second elongate side edges extending between the arcuate leading and trailing edges; wherein the first and second elongate side edges are parallel; and wherein the arcuate leading edge and the arcuate trailing edge are angled with respect to a radial direction.
19. The rotor of claim 18 wherein:
- the arcuate leading edge and arcuate trailing edge define a width that is approximately twice as large as a distance between the first and second elongate side edges; and
- the arcuate leading edge and the arcuate trailing edge are angled approximately fifteen to approximately seventy-five degrees.
20. The rotor of claim 18 wherein the plurality of holes is arranged in a circumferential row spaced evenly about the hub.
21. The rotor of claim 18 wherein the plurality of holes increases the swirl ratio across the hub while decreasing pressure loss when the rotor is rotating about the axis.
22. The rotor of claim 18 and further comprising a mini-disk disposed opposite the rotor to form a cooling channel therebetween, the mini-disk comprising:
- an axially extending portion extending opposite the hub; and
- a radially extending portion extending along the disk;
- wherein cooling air directed into the hole from the inner diameter surface flows along the hub and along the disk to the slots.
23. The rotor of claim 18 wherein the arcuate leading edge and the arcuate trailing edge are contoured radially as they pass through the hub.
24. A method of passing flowing cooling air through a rotating annular body, the method comprising:
- rotating an annular body about an axis in a circumferential direction;
- passing cooling air through the annular body in an axial direction;
- turning the cooling air in a radial direction to pass through a plurality of holes in the annular body that are wider in the circumferential direction than in the axial direction; and
- bending the cooling air in a circumferential direction by passing over angled walls of the plurality of holes.
25. The method of claim 24 wherein:
- the holes are angled into the direction of rotation approximately thirty to approximately forty degrees; and
- each of the cooling holes has a racetrack shape profile.
26. The method of claim 25 wherein turning and bending of the cooling air with the plurality of holes increases the swirl ratio across the annular body and decreases pressure loss with respect to holes having circular profiles and un-angled walls.
Type: Application
Filed: Jul 15, 2011
Publication Date: Jan 17, 2013
Applicant: UNITED TECHNOLOGIES CORPORATION (Hartford, CT)
Inventors: Charles C. Wu (Glastonbury, CT), Kevin N. McCusker (West Hartford, CT), Mark S. Turner (Hartford, CT)
Application Number: 13/184,035
International Classification: F04D 29/38 (20060101);