WO2017003457A1

WO2017003457A1 - Turbine blade with integrated multiple pass cooling circuits

Info

Publication number: WO2017003457A1
Application number: PCT/US2015/038566
Authority: WO
Inventors: Ching-Pang Lee
Original assignee: Siemens Aktiengesellschaft; Siemens Energy, Inc.
Priority date: 2015-06-30
Filing date: 2015-06-30
Publication date: 2017-01-05

Abstract

A turbine blade (10) and method of cooling. The turbine blade (10) having multiple aft flowing cooling circuits formed within the blade (10) including at least a leading edge circuit (12) and a trailing edge circuit (14). Each cooling circuit includes a first pass channel (16) flowing aft with two substantially 180-degree turns at a tip end (44) and a root end (42) of the blade (10) providing a second pass channel (18), and a third pass channel (20). The leading edge circuit (12) starts along a leading edge (24) of the blade (10) and the trailing edge circuit (14) starts along a mid-chord area (46) of the blade (10) with the third pass channel (20) located along a trailing edge (26) of the blade (10). A tip axial cooling passage (22) comprising a first opening (48) and a second opening (50) connects the leading edge circuit (12) to the trailing edge circuit (14), integrating the at least two multiple pass serpentine flow cooling circuits.

Description

TURBINE BLADE WITH INTEGRATED MULTIPLE PASS COOLING

CIRCUITS

BACKGROUND 1. Field [0001] The present invention relates to gas turbine engines, and more specifically to a turbine blade with multiple internal cooling air circuits.

2. Description of the Related Art

[0002] In an industrial gas turbine engine, hot compressed gas is produced. The hot gas flow is passed through a turbine and expands to produce mechanical work used to drive an electric generator for power production. The turbine generally includes multiple stages of stator vanes and rotor blades to convert the energy from the hot gas flow into mechanical energy that drives the rotor shaft of the engine. Turbine inlet temperature is limited to the material properties and cooling capabilities of the turbine parts. This is especially important for first stage turbine vanes and blades since these airfoils are exposed to the hottest gas flow in the system.

[0003] A combustion system receives air from a compressor and raises it to a high energy level by mixing in fuel and burning the mixture, after which products of the combustor are expanded through the turbine.

[0004] Since the turbine blades are exposed to the hot gas flow discharged from combustors within the combustion system, cooling methods are used to obtain a useful design life cycle for the turbine blade. Blade cooling is accomplished by extracting a portion of the cooler compressed air from the compressor and directing it to the turbine section, thereby bypassing the combustors. After introduction into the turbine section, this cooling air flows through passages or channels formed in the airfoil portions of the blades.

[0005] In order to allow for higher temperatures, turbine blade designers have proposed several complex internal blade cooling circuits to maximize the blade cooling through the use of convection cooling, impingement cooling and film cooling of the blades. FIGS. 1 through 3 show a prior art turbine blade with two aft flowing triple pass cooling circuit designs. Each blade cooling circuit includes a first pass cooling channel, a second pass cooling channel, and a third pass cooling channel. The cooling circuits flow from a leading edge aft ward towards a trailing edge of the blade.

[0006] FIG. 1 shows a turbine blade with two aft flowing triple pass serpentine cooling circuits. The leading edge circuit enters from the leading edge and flowing aft with two 180 degree turns at the tip and the root and exits the blade through the tip in the mid portion of a squealer tip cavity. The trailing edge circuit enters from the mid- chord and flowing aft with two 180 degree turns at the tip and the root and exits through trailing edge pin banks and trailing edge exit holes. The third leg or pass cooling channel of the trailing edge circuit may include pin fins extending across the walls of the blade to promote heat transfer, and may include a row of exit cooling holes or slots to discharge the cooling air from the serpentine flow circuits axially out from the blade.

[0007] While this design provides good cooling to the majority of the airfoil, the blade tip section is much hotter than the other portions of the airfoil, as is shown in Fig. 2.

SUMMARY [0008] In one aspect of the present invention, a turbine rotor blade comprises: at least two integrated multiple pass serpentine flow cooling circuits formed within the blade to provide cooling for the blade comprising; a leading edge circuit comprising a first pass channel located along a leading edge of the blade and flowing aft with two substantially 180-degree turns at a tip end and a root end of the blade providing a second pass channel and a third pass channel; a trailing edge circuit comprising a first pass channel located in a mid-chord area of the blade and flowing aft with two substantially 180-degree turns at the tip end and the root end of the blade providing a second pass channel and a third pass channel, wherein the third pass channel is located along a trailing edge area of the blade; and a tip axial cooling passage comprising a first opening and a second opening, wherein the tip axial cooling passage connects the leading edge circuit to the trailing edge circuit, integrating the at least two multiple pass serpentine flow cooling circuits.

[0009] In another aspect of the present invention, a method for increasing cooling to a tip section of a turbine blade, comprises: providing a tip axial cooling passage comprising a first opening and a second opening; connecting the first opening of the tip axial cooling passage to an end of a third pass channel of a leading edge circuit, wherein the leading edge circuit comprises a first pass channel located along a leading edge of the blade and flowing aft with two substantially 180-degree turns at a tip end and a root end of the blade providing a second pass channel and the third pass channel; connecting the second opening of the tip axial cooling passage to a trailing edge circuit, wherein the trailing edge circuit comprises a first pass channel located in a mid-chord area of the blade and flowing aft with two substantially 180-degree turns at the tip end and the root end of the blade providing a second pass channel and a third pass channel, wherein the third pass channel is located along a trailing edge area of the blade; sending cooling air through the leading edge circuit and the trailing edge circuit, wherein the cooling air flowing through the leading edge circuit then flows through the tip axial cooling passage and into the trailing edge circuit, merging with the cooling air in the trailing edge circuit.

[0010] These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention is shown in more detail by help of figures. The figures show preferred configurations and do not limit the scope of the invention. [0012] FIG 1 is a cross sectional suction side view of a prior art turbine blade with two triple pass serpentine flow cooling circuits.

[0013] FIG 2 is a cross sectional top view of a prior art turbine blade with two triple pass serpentine flow cooling circuits. [0014] FIG 3 is a cross sectional pressure side view of a prior art turbine blade internal ceramic casting core with two triple pass serpentine flow cooling circuits.

[0015] FIG 4 is a cross sectional side view of an exemplary embodiment of the present invention. [0016] FIG. 5 is a detailed cross sectional suction side view of an integration of cooling circuits of an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0017] Broadly, an embodiment of the present invention provides a turbine blade and method of cooling. The turbine blade having multiple aft flowing cooling circuits formed within the blade including at least a leading edge circuit and a trailing edge circuit. Each cooling circuit includes a first pass channel flowing aft with two substantially 180-degree turns at a tip end and a root end of the blade providing a second pass channel, and a third pass channel. The leading edge circuit starts along a leading edge of the blade and the trailing edge circuit starts along a mid-chord area of the blade with the third pass channel located along a trailing edge area of the blade. A tip axial cooling passage comprising a first opening and a second opening connects the leading edge circuit to the trailing edge circuit, integrating the at least two multiple pass serpentine flow cooling circuits.

[0018] A blade of a gas turbine receives high temperature gases from a combustion system in order to produce mechanical work of a shaft rotation. Due to the high temperature gases, a cooling system may be provided to reduce the temperature levels throughout the blade.

[0019] A gas turbine cooling system may perform two basic functions. The first function may be to provide direct cooling of components exposed to gas path temperature that is higher than material temperature limits. The second function may be that of turbine environmental control. Air at correct pressure and temperature may be provided at various critical points to ensure that design environment is maintained throughout the turbine. [0020] In certain embodiments, air for cooling the rotor and rotating blades may be extracted from the axial compressor discharge at a combustor shell. The compressor discharge air may pass through an air-to-air cooler and may be filtered for rotor cooling. Direct cooling may occur at the turbine spindle blade root end along one or more stages. The turbine stationary vanes may be cooled by both internal bypassing and external bleeding lines.

[0021] An effective step that can be taken to increase the power output and improve the efficiency of a gas turbine engine may be to increase the temperature at which heat is added to the system, that is, to raise the turbine inlet temperature of the combustion gases directed to the turbine. Increases in efficient turbines have lead to an increase in the temperature that must be withstood by the turbine blades and rotor. The result is that to use the highest desirable temperatures, some form of forced cooling may be desirable. This cooling may be in the form of air bled from the compressor at various stages, and ducted to critical elements in the turbine. Although emphasis is placed on cooling the initial stages of vanes and blades, air may be also directed to other vanes, blade rings and discs.

[0022] Being furthest from the inlet of cooling air, a trailing edge corner of the blade tends to be the one of the hottest portions of the blade after cooling. Better cooling to a tip section of a blade without using additional cooling air is desirable. Embodiments of the present invention provide a blade that may allow for the reduction in temperature of the tip section of the blade without the use of additional cooling air. The cooling air that may be provided can stay within the turbine providing cooling for as long as possible.

[0023] As is illustrated in Figs. 4 and 5, a turbine rotor blade 10 includes a pressure side 38 (not shown), and suction side 40 (not shown), a leading edge 24 and a trailing edge 26. The turbine rotor blade 10 may include at least two cooling circuits, a leading edge circuit 12 and a trailing edge circuit 14. Each cooling circuit may include a serpentine style path that may include multiple pass cooling channels such as a first pass cooling channel 16, a second pass cooling channel 18, and a third pass cooling channel 20. The first pass cooling channel 16 may be in the radial direction towards a tip end 44 of the blade 10. The second pass cooling channel 18 may be in the radial direction towards a root end 42 of the blade 10. The third pass cooling channel 20 may start in the radial direction towards the tip end 44 of the blade 10. The multiple pass cooling channels help move flow of air 36 from the leading edge 24 to the trailing edge 26 in order to help reduce the blade temperature throughout the blade 10.

[0024] The multiple pass cooling channels are connected through substantially 180-degree turns along a tip end 44 and a root end 42 of the blade 10 that change the direction of the multiple cooling channels as the air flow 36 moves aft. The leading edge circuit 12 may include the first pass cooling channel 16 located along the leading edge 24 of the blade 10. The leading edge circuit 12 may then flow aft with two substantially 180-degree turns at the tip end 44 and the root end 42 of the blade 10 providing the second pass cooling channel 18 and the third pass cooling channel 20. The trailing edge circuit 14 may include the first pass cooling channel 16 located in an approximately mid-chord area 46 of the blade 10. The trailing edge circuit 14 may then flow aft with two substantially 180-degree turns at the tip end 44 and the root end 42 of the blade 10 providing the second pass cooling channel 18 and the third pass cooling channel 20. The third pass cooling channel 20 may be located along the trailing edge 26 of the blade 10.

[0025] The third pass cooling channel 20 of the trailing edge circuit 14 may open axially aft ward towards and through the trailing edge 26 of the blade 10. In certain embodiments, a plurality of trailing edge pin banks 30 and/or trailing edge exit holes 32 may be aligned along the trailing edge 26 allowing for the cooling air flow 36 to exit aft ward along the trailing edge 26 of the blade 10 and out of the blade 10.

[0026] A tip axial cooling passage 22 may include a first opening 48 and a second opening 50. The tip axial cooling passage 22 may connect the leading edge circuit 12 to the trailing edge circuit 14, integrating the at least two multiple pass flow cooling circuits. In certain embodiments, the trailing edge circuit 14 may be positioned below the tip axial cooling passage 22. The cooling air 36 flowing through the leading edge circuit 12 may then flow through the tip axial cooling passage 22. The cooling air 36 flowing through the trailing edge circuit 14 may merge with the cooling air 36 flowing through the tip axial cooling passage 22 near a trailing edge tip corner 28. The cooling air 36 merging near the trailing edge tip corner 28 may decrease the temperature in that particular area without the need for additional cooling air.

[0027] Figure 2 shows the trailing edge tip corner 28 of the prior art being one of the hottest areas along the blade 10 and the cooling circuit. The hottest portions run along the tip end 44 of the blade 10. The temperature of the blade 10 increases near the end of the trailing edge circuit 14 and along the tip end 44 along the leading edge of the blade 10 as shown in Figure 1 through Figure 3. Allowing additional cooling air 36 to enter the trailing edge tip corner 28 area through the tip axial cooling passage 22, the temperature of the trailing edge tip corner 28 may decrease. A decrease in temperature may increase the life of the component.

[0028] Figures 4 and 5 show the path of the cooling air 36 through the tip axial cooling passage 22 in further detail. The first opening 48 of the tip axial cooling passage 22 may connect to the third pass cooling channel 20 of the leading edge circuit 12. A substantially 90-degree turn from the leading edge circuit 12 to the tip axial cooling passage 22 may move the cooling air 36 flowing through the leading edge circuit 12 aft away from the mid portion of the squealer tip 52 and towards the trailing edge 26 of the blade 10.

[0029] The second opening 50 of the tip axial cooling passage 22 may connect with the trailing edge circuit 14. In certain embodiments, the tip axial cooling passage 22 may connect through the third pass cooling channel 20 of the trailing edge circuit 14. The cooling air 36 flowing through the exit of the tip axial cooling passage 22 may pass through a plurality of trailing edge pin banks 30 and/or a plurality of trailing edge exit holes 32.

[0030] In certain embodiments, at least one tip film cooling hole 34 may be drilled from the squealer tip 52 of the blade 10 to the tip axial cooling passage 22. At least one radial passage may be provided to discharge the cooling air radially outwardly at the tip end 44 of the blade 10. The at least one tip film cooling hole 34 may provide bleeding access into a tip cavity or the pressure side 38 of the blade 10.

[0031] The cooling flow split between the leading edge circuit 12 and the trailing edge circuit 14 may be adjusted to achieve more uniform metal temperatures within the blade 10. The adjustment may be in the form of varying the thickness of the multiple channels, adjusting the length of the multiple channels, or the like.

[0032] In certain embodiments, the trailing edge circuit 14 may have a smaller length than the prior art in order to position the tip axial cooling passage 22 above the trailing edge circuit 14.

[0033] While specific embodiments have been described in detail, those with ordinary skill in the art will appreciate that various modifications and alternative to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims, and any and all equivalents thereof.

Claims

CLAIMS What is claimed is:

1. A turbine rotor blade (10) comprising:

at least two integrated multiple pass serpentine flow cooling circuits formed within the blade (10) to provide cooling for the blade (10) comprising;

a leading edge circuit (12) comprising a first pass channel (16) located along a leading edge (24) of the blade (10) and flowing aft with two substantially 180-degree turns at a tip end (44) and a root end (42) of the blade (10) providing a second pass channel (18) and a third pass channel (20);

a trailing edge circuit (14) comprising a first pass channel (16) located in a mid-chord area (46) of the blade (10) and flowing aft with two substantially 180-degree turns at the tip end (44) and the root end

(42) of the blade (10) providing a second pass channel (18) and a third pass channel (20), wherein the third pass channel (20) is located along a trailing edge (26) of the blade (10); and

a tip axial cooling passage (22) comprising a first opening (48) and a second opening (50), wherein the tip axial cooling passage

(22) connects the leading edge circuit (12) to the trailing edge circuit (14), integrating the at least two multiple pass serpentine flow cooling circuits.

2. The turbine rotor blade according to claim 1, wherein the trailing edge circuit (14) is positioned below the tip axial cooling passage (22), wherein cooling air (36) flowing through the leading edge circuit (12) and the trailing edge circuit (14) merge near a trailing edge tip corner (28) of the blade (10).

3. The turbine rotor blade according to claims 1 or 2, wherein a substantially 90-degree turn along the first opening (48) of the tip axial cooling passage (22) connects to the third pass channel (20) of the leading edge circuit (14).

4. The turbine rotor blade according to any of the claims 1 to 3, wherein the second opening (50) of the tip axial cooling passage (22) exits through a plurality of trailing edge pin banks (30) and/or a plurality of trailing edge exit holes (32) along the trailing edge (26) of the blade (10).

5. The turbine rotor blade according to any of the claims 1 to 4, further comprising at least one tip film cooling hole (34) drilled from a squealer tip (52) of the blade (10) to the tip axial cooling passage (22).

6. A method for increasing cooling to a trailing edge tip corner (28) of a turbine blade (10), comprising:

providing a tip axial cooling passage (22) comprising a first opening (48) and a second opening (50);

connecting the first opening (48) of the tip axial cooling passage (22) to an end of a third pass channel (20) of a leading edge circuit (12), wherein the leading edge circuit (12) comprises a first pass channel (16) located along a leading edge (24) of the blade (10) and flowing aft with two substantially 180-degree turns at a tip end (44) and a root end (42) of the blade (10) providing a second pass channel (18) and the third pass channel (20);

connecting the second opening (50 of the tip axial cooling passage (22) to a trailing edge circuit (14), wherein the trailing edge circuit (14) comprises a first pass channel (16) located in a mid-chord area (46) of the blade (10) and flowing aft with two substantially 180-degree turns at the tip end (44) and the root end (42) of the blade (10) providing a second pass channel (18) and a third pass channel (20), wherein the third pass channel (20) is located along a trailing edge (26) of the blade (10);

sending cooling air (36) through the leading edge circuit (12) and the trailing edge circuit (14), wherein the cooling air (36) flowing through the leading edge circuit (12) then flows through the tip axial cooling passage (22) and into the trailing edge circuit (14), merging with the cooling air (36) in the trailing edge circuit (14).

7. The method according to claim 6, wherein a cooling flow split between the leading edge circuit (12) and the trailing edge circuit (14) is adjusted to achieve more uniform metal temperatures within the blade (10).

8. The method according to claims 6 or 7, wherein the tip axial cooling passage (22) is positioned above the first pass channel (16) and the second pass channel (18) of the trailing edge circuit (14).

9. The method according to any of claims 6-8, wherein the second opening (50) of the tip axial cooling passage (22) opens into the third pass channel (20) of the trailing edge circuit (14) approximate to the trailing edge tip corner (28).

10. The method according to any of claims 6-9, wherein the second opening (50) of the tip axial cooling passage (22) exits through a plurality of trailing edge pin banks (30) and/or a plurality of trailing edge exit holes (32) along the trailing edge (26) of the blade (10).

1 1. The method according to any of claims 6-10, further comprising at least one tip film cooling hole (34) drilled from a squealer tip (52) of the blade (10) to the tip axial cooling passage (22).