JPH07247801A - Rotor assembly for gas-turbine engine and self-supporting wheel structure - Google Patents

Abstract

PURPOSE: To provide a rotor assembly for gas turbine engines, capable of reducing the cooling air quantity necessary for cooling the rotor assembly. CONSTITUTION: A rotor assembly comprises plural rotor discs 40 and disc spacer arms 80 structured to transmit axial load and bending moment between adjacent discs. The spacer arms comprise cooling fins 120 for convectively cooling themselves. The cooling fins are arranged to the spacer arms to reduce thermal distortion, and thereby reduce bending stress transmitted to the discs. The spacer arms comprise body parts 86 adjacent to relatively high temperature seal cavity 63, and the relatively high temperature seal cavity can be ventilated by cooling air from a relatively low temperature rotor-bore cavity 60.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to rotor disk spacer arm structures in gas turbine engines.
In particular, it relates to a disk spacer arm mechanism having a finned structure. The finned disc spacer arm is preferably a self-supporting wheel structure.

[0002]

BACKGROUND OF THE INVENTION A rotor structure in a gas turbine engine may include a plurality of blade carrying rotor disks separated by annular disk spacer arms. U.S. Pat. No. 3,647,313, assigned to General Electric Company, discloses a compressor rotor structure having disks separated by annular spacer arms and a cooling system for the rotor structure. There is. To increase engine cycle efficiency, it is desirable to minimize the amount of cooling air used to cool the rotor and spacer arms.

US Pat. No. 3,056,579 assigned to General Electric Company discloses a composite disc structure. The composite disc structure includes a first suspended linear portion that performs a heat shield function and a second suspended linear portion.
And an axially aligned stiffening member, the stiffening member may have the shape of a tubular spacer. The cooling fins are shown as being disposed on a catenary heat shield or heat shield. However, US Patent No. 30565
The No. 79 finned heat shield can actually result in poor performance. Centrifugal load generated on the catenary shield (as described in column 3, lines 63-66);
The load due to heat and pressure is transmitted to the disc rim.
This load transfer to the disc rim is due to the following facts: the catenary shield is, by design, not a self-supporting wheel structure capable of bearing its own centrifugal load. Therefore, the additional centrifugal load due to the additional weight of the fins provided on the catenary shield increases the disc rim stress by increasing the centrifugal load transmitted to the disc rim. Thus, fins added to structures that are not self-supporting wheel structures require extra cooling air or disc rim material to maintain disc rim stress at acceptable levels for a given operating temperature. there is a possibility. The additional weight of the fins also increases hoop stress in the catenary shield.

Moreover, the fins located on the heat shield do not effectively reduce the thermal strain of the disk spacer arm structure and the resulting stresses on the spacer arm and adjacent disks. Temperature gradients in the disk spacer arms may deform the disk spacer arms, resulting in deleterious bending stresses in the spacer arms and adjacent disk rims. The disc rim is where the spacer arm transmits a bending load between adjacent discs. Such bending stresses occur especially during transient operating conditions, in which the spacer arm responds to temperature changes more quickly than the adjacent disks or connecting flanges.

In addition, gas turbine engineers seek to increase turbine operating temperature to improve engine efficiency while keeping turbine component temperatures within acceptable limits with a minimal amount of cooling air.

[0006]

Therefore, one advantage of the present invention is that it reduces the amount of cooling air required to cool the rotor disk assembly. Another advantage of the present invention is that it reduces thermally induced strain on the disk spacer arm structure.

Another advantage of the present invention is that it reduces bending stresses in the spacer arms and adjacent disk rims. Additionally, a finned disk spacer arm structure can be provided that has a plurality of fins extending into a relatively cool cooling air cavity in which the rotor hub is supported.

Another advantage of the present invention is to provide a disk spacer arm that is cooled without imparting centrifugal load to the disk rim to which the spacer arm is mounted. Further, it is possible to provide spacer arm cooling fins that are cooler than the rest of the self-supporting disc spacer arm during operation, and thus the cooling fins are centrifugal hoops that would otherwise be supported by the outer body of the spacer arm. It bears part of the load, which increases the temperature capability of the outer body of the spacer arm and
It reduces the amount of cooling air required in the cavity outside the spacer arm.

[0009]

SUMMARY OF THE INVENTION One or more cooling fins are provided on a radially inner surface of a disk spacer arm structure for a gas turbine engine. This disc spacer structure can transmit an axial load and a bending moment between adjacent rotor discs. The spacer arm is preferably a self-supporting wheel structure in which wheel loads centrifugally generated on the spacer arm during maximum engine operation are locally supported by the spacer arm and not on adjacent rotor disc rims. . The cooling fins are preferably circumferentially continuous load paths for tensile hoop loads. The cooling fins extend into the cooler rotor bore cavity and may be cooler than the rest of the spacer arm structure during operation. The relatively cool fins have a tendency to contract with respect to the rest of the spacer arm, and are preferably spaced from the disc spacer arm, to provide thermal strain to the spacer arm and
The disc rim stress generated by such spacer arm strain is reduced. Further, by designing a continuous circumferential fin that rotates cooler than the rest of the spacer arm, the fin is subjected to hoop tension and, without such fins, is supported by the relatively hot outer body of the spacer arm. Bearing a relatively large portion of the expected tensile centrifugal hoop load. That is, reducing the load and stress on the outer body of the spacer arm increases the temperature capability of the outer body of the spacer arm and, for a given turbine operating temperature, requires in the cavity outside the spacer arm. The amount of air for cooling the spacer arm is reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a known high bypass gas turbine engine 10. As will be apparent to those skilled in the art, the disclosed axial machine, although shown in cross-section, extends circumferentially about the engine axis 14. Engine 10
Includes a fan 12 that receives an air stream 18.
A low pressure compressor (LPC) 20 is provided downstream of the fan 12,
A high pressure compressor (HPC) 22, a combustor 24, a high pressure turbine (HPT) 28, and a low pressure turbine (LPT) 30 are arranged. A shaft 32 connects the high pressure turbine 28 to the high pressure compressor 22, and a shaft 34 connects the high pressure turbine 3 to the low pressure turbine 3.
0 is connected to the low pressure compressor 20 and the fan 12. Fan 12, compressors 20 and 22, and turbines 28 and 30 are rotatably mounted about common engine axis 14 as is well known in the art.

A part of the air flow 18 leaving the fan 12 becomes a fan bypass flow 19 to generate the main thrust of the engine 10. The remainder of air stream 18 becomes core stream 23, which is compressed by compressors 20 and 22. A portion of the core stream 23 exiting the HPC 22 is combusted with fuel in a combustor 24 into a hot gas stream 25. Hot gas stream 25 expands through HPT 28 and LPT 30. Turbines 28 and 30
The expansion of gas stream 25 therein drives compressors 22 and 20 via shafts 32 and 34, respectively.

FIG. 2 is a schematic enlarged view of a part of the engine 10 shown in FIG. 1, and shows a downstream portion of the HPT 28 and the LPT 30.
And the upstream part of the. The LPT 30 may include a plurality of rotor disks 40 supported on the shaft 34 via shaft extensions 36. Each rotor disk has a hub 42 extending radially inward into the bore cooling cavity 60, a web 44 extending radially outward from the hub 42, and a web 44.
Extending radially outward from the rotor disc 40
And a rim 46 forming the outer periphery of the. Adjacent rotor discs 40 are interconnected by a disc spacer arm structure 80, which supports the adjacent rotor discs and imparts to the discs by expansion of gas flow 25 through LPT 30. It transmits the axial thrust load. The spacer arm structure 80 may be rigidly attached to the adjacent disks so as to be integral therewith, and may transmit a bending moment between the adjacent disks.

Each rotor disk 40 carries a row of blades 48 which, as is well known in the art, each dovetail root which is supported within a shouldered slot 47 of the disk rim 46. Contains 49. A plurality of rows of vanes 52 between each row of blades 48,
It extends radially inward from the case 54. The LPT rotor disk 40 may be cooled by air extracted from the upstream compressor. A conduit 62 (FIG. 1) may guide a portion of the core airflow 23 extracted from the HPC 22 into an opening 53 in a case 54 surrounding the LPT 30. The extracted air is designated by the reference numeral 64 in FIG.
It is a relatively low temperature compared to 5. The cooling air 64 is the stationary blade 52.
Enter the internal passage 55 of the. The air 64 cools the vanes 52,
Some of it is exhausted into the gas stream 25 through the plurality of vane holes. A part of the air 64 shown by the reference numeral 66 in FIG. 2 flows through the plurality of openings 57 of the stator vane inner structure 51 and flows into the annular chamber 6.
Enter 1. The annular chamber 61 may have an upstream boundary set by the HPT rotor disc 29 and a downstream boundary set by a stationary annular seal 68 extending radially inward from the structure 51. Cooling air 66 flows through a radial gap between stationary seal 68 and swivel seal 69 supported by HPT 29 and enters bore cooling cavity 60.

Referring to FIG. 3, cooling air 66 within the cavity 60 flows against the disk hub 42 and also cools the disk rim 46 and the radially inner surface 83 of the spacer arm. An annular seal cavity 63 extends circumferentially between stream 25 and spacer arm 80. Also, cooling air 6
A portion of 6 can be flushed below the root 49 by the dovetail slot 47, which allows the disc rim 46
Can be cooled and the seal cavity 63 can be partially ventilated to reduce the inflow of hot gas stream 25 into the circumferentially extending seal cavity 63. The cavity 63 may be set by a blade base 45 and a stationary vane base 55 having radially outer boundaries extending axially and circumferentially, and a radially inner boundary having a radially outer surface 85 of the spacer arm 80. Can be set by The seal cavity 63 includes the moving blade base 45 and the stationary blade base 5 which are adjacent to each other.
The gas flow 25 communicates with the gas flow 25 through the gaps between the gas flow 25 and the gas flow path 5, respectively. The seal cavity 63 may act as an annular buffer cavity between the hot gas stream 25 and the spacer arm 80.

A seal land 98 extending in the circumferential direction is bolted to the lower side of the stationary vane base 55 and faces the rotary shaft seal teeth 96 of the rotary shield 92 extending in the circumferential direction. The flow of the gas 25 inside the blades 45 and 55 is suppressed. The shield 92 may be bolted at the bolt connection 90 between adjacent disk spacer arms. The shield 92 may be provided with circumferentially spaced radial passages 94 that direct cooling air between the shield 92 and the spacer arms 80 and further into the dovetail slot 47.

Each spacer arm 80 includes a spacer arm first end 82 integral with an adjacent disc rim 46, a spacer arm second end 84 which may include a radially inwardly extending connecting flange 88, and a first end. A circumferentially continuous spacer arm body portion 86 may extend between the end 82 and the second end 84. The body portion 86 may include a radially inner surface 83 and a radially outer surface 85.

The spacer arm inner surface 83 faces the rotor bore cavity 60, while the spacer arm outer surface 85 faces the seal cavity 63. The temperature of the gas in the cavity 60 is lower than the temperature of the gas in the cavity 63. The portion of the cooler air 66 that passes through the dovetail slot 47 is
3 ventilation and cooling of the main body 86 of the spacer arm 80,
In particular, it helps to cool the outer surface 85. To the extent that the portion of cooling air 66 directed into the seal cavity 63 does not completely ventilate the cavity 63 and a portion of the gas stream 25 enters the cavity 63,
Spacer arms 80 may isolate the relatively hot gas stream 25 from the radially inner relatively cold cavity 60. Cavity 6
It is desirable to reduce the amount of cooling air 66 used to ventilate 3 and cool outer surface 85. This is because such cooling air causes performance deterioration.

Applicants have found that thermal gradients in spacer arm 80 under engine operating conditions can cause the spacer arm to warp radially outward, as shown in phantom in FIG. I found that there is. Since the disk 40 and the flange 88 act as a heat absorbing source, the central portion of the spacer arm main body 86 becomes hotter than the spacer arm first end 82 and the second end 84.
The temperature of the spacer arm body also depends on the inner surface 83 (cavity 60
The inner surface (facing the cooler air) to the outer surface 85
It rises radially outwards to (the surface of the cavity 63 facing the relatively hot air). The resulting spacer arm strain is detrimental. The spacer arm is a structure capable of transmitting a force and a bending moment between the adjacent disks, and thermal strain of the spacer arm may generate bending stress in the spacer arm. It is supported by 46.

Since the spacer arm 80 shown in FIG. 3 can be dimensioned to be a self-supporting wheel structure that bears its own centrifugal hoop load, it is necessary to support such wheel load with adjacent disks. There is no. In other words, if the spacer arms were separated from the adjacent discs into individual rotating components and rotated at various engine operating speeds and temperatures, the disc spacer arms would not rupture and would be unacceptably deformed. do not do. Thus, the spacer arm, which is a self-supporting wheel structure, bears its own centrifugally generated load and does not centrifugally load adjacent disc rims. As is well known, the hoop stress generated in a rotating wheel rim is proportional to the wheel mass, the average rim radius, the square of the angular velocity, and inversely proportional to the cross-sectional area of the rim. Given the maximum rotational speed and spacer arm material, the spacer arm cross-sectional area can be calculated to keep the spacer arm stress within the acceptable range of spacer arm material, without support by adjacent disc rims. R. Roark
W. Young, "Stress and Strain Equations (Form
ulas for Stress and Strain) ”5th edition, pages 564-5
Page 72, Timothenko and Goodier, Theory of Elasticity, Second Edition, pages 69-73, and Harris, Introduction to Stress Analysis. 1959
The annual edition, pages 250-260, describes the calculation of stresses in rotating discs and should be referred to here.

4 and 5 show a preferred embodiment of the present invention. At least one, and preferably a plurality of cooling fins 120 extend from the surface 83 of the spacer arm body into the relatively cold cavity 60. Referring to FIG. 5, fins 120 may have tapered sidewalls 122 extending from relatively thick fin bases 124 to relatively thin fin tips 126. The taper increases the fin surface area for convective heat transfer and increases the fillet radius where the sidewall 122 meets the spacer arm surface 83.

Fins 120 provide convective cooling to spacer arm 80. Exposing the fins 120 to the cooling air 66 used to cool the disk hub 42 may facilitate thermal matching between the hub temperature and the fin temperature. As mentioned above, thermal gradients in the spacer arms cause the spacer arms to curve radially outward. Applicants have found that spacing the cooling fins to the disk spacer arms can reduce the bending stresses transferred to the rotor disk due to thermal gradients in the spacer arms. In FIG.
The middle point c of the spacer body is the spacer arm first end 82.
And at a distance L from the second end 84. Since the disk 40 and the flange 88 act as a heat sink, the spacer arm 80 becomes relatively hot at the midpoint c of the spacer arm body and relatively cold at the first end 82 and the second end 84. The fins 120 should be centered around the midpoint c and are preferably spaced near the midpoint c. In FIG. 5, the separation distance l from the midpoint c to the fin is shorter than half the distance L from the midpoint c to the spacer arm end. The fin tips 126 are cooled by the air 66, tend to contract radially inward with respect to the relatively hot spacer arm body 86, and resist the outward bending of the spacer arm body.

The fins 120 are preferably circumferentially continuous, in which case the relatively cool tip 126 provides a 360 degree load path for tensile hoop stress when contracted against the spacer arm 80. Relatively low temperature tip 1
The tensile hoop stress generated at 26 resists radial outward strain of spacer arm 80. As the temperature difference between the spacer arm outer surface 85 and the fin tips 126 increases, the portion of the fin 120 that bears the tensile hoop load increases (ie, a relatively large portion of the fin 120 cross-sectional area is in compression). No, it will be pulled). Therefore, as the temperature of surface 85 increases (and the temperature difference between surface 85 and fin tip 126 increases), the fins carry more tensile hoop load. A greater portion of the centrifugal load on the spacer arm is supported by the fins 120 and a lesser centrifugal load is supported by the body portion 86.
Spacer arm body 86 may operate at relatively high temperatures due to reduced loads and stresses on body 86. Therefore, less cooling air 66 is required to cool and vent the cavity 63 through the slots 47.

The fins 120 preferably extend substantially radially inward from the spacer arms. The fin axis A-A is then oriented radially and is substantially perpendicular to the engine axis 14. The fins may extend perpendicularly from the surface 83, but such a shape results in an axial offset between the base 124 and the tip 126, so that the tip 126 is radiused relative to the arm 80. Fins 120 as they contract inwardly
A local bending stress is generated in the base 124 of the.

The spacer arm 80 of FIGS. 4 and 5 is preferably a self-supporting wheel structure, and the fins 120 added to such a structure may be used during engine operation.
No centrifugal load is applied to the disk rim 46, and the centrifugal load carried by the fins 120 is not carried by the disk rim 46. The fins 120, spacer arms 80 and disks 40 may be forged as a unitary piece of high strength superalloy, eg Inconel 718.

An example of the relevant dimensions (FIG. 5) of one embodiment of a finned spacer arm structure forming a self-supporting wheel structure is as follows. However, the maximum rotation speed of the disk and spacer arm assembly is approximately 40
The maximum metal temperature of the spacer arm is about 1200 ° F. Length l and length L are about 0.16 inches and about 0.59 inches, fin radial height h is about 0.24 inches, and spacer arm thickness t is about 0.07 inches. be able to. The axial width w of the fin tip 126 can be about 0.05 inches and the sidewall 122 is tapered at the fin tip 126 by 7-8 degrees. Radius R1, R2, R3,
R4, R5 and R6 are measured from axis 14 and are 12.15 inches, 12.08 inches, 12.05 inches, 11.41 inches, 12.20 inches and 12.3, respectively.
It can be 6 inches. Axial widths E and F can be about 0.25 inches and 0.16 inches, respectively.

The height h of the fin 120 is preferably much smaller than the radius R1 or R2 of the fin tip. The height h of the fins 120 is preferably defined to provide a beneficial temperature differential between the fin tips 126 and the surface 85 to minimize weight gain of the spacer arm assembly. The increase in temperature difference associated with fin height h is non-linear and decreases as fin height h increases. In the above example, fins having a height h less than 2% of the tip radius R1 or R2 provide a suitable temperature difference and minimize the weight gain of the spacer arm assembly.

The preferred embodiment of the present invention has been described above.
It will be appreciated that various modifications are possible within the scope of the invention.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a known high bypass gas turbine engine.

FIG. 2 is an enlarged view of a part of the schematic diagram of FIG. 1, showing in part the high and low pressure turbine sections.

FIG. 3 is an enlarged view of a portion of the schematic of FIG. 2, showing adjacent rotor disks separated by disk spacer arms.

FIG. 4 is a schematic cross-sectional view showing a disk spacer arm with fins according to the present invention.

5 is an enlarged view of the disk spacer arm with fins shown in FIG. 4. FIG.

[Explanation of symbols]

 40 rotor disk 42 disk hub 60 rotor bore cavity 63 seal cavity 80 disk spacer arm 82 spacer arm first end 83 spacer arm inner surface 84 spacer arm second end 85 spacer arm outer surface 86 spacer arm body 120 cooling fin 122 fin side wall 124 fin base 126 fin tip

Claims (20)

[Claims] 1. A plurality of rotor disks each supported in a cavity for rotation about an engine axis; and (b) extending axially from one of the disks. Gas turbine with circumferentially continuous disk spacer arms configured to transfer loads between adjacent disks; and (c) at least one cooling fin extending from the spacer arms into the cavity. Engine rotor assembly. 2. The rotor assembly according to claim 1, wherein each cooling fin is circumferentially continuous. 3. The rotor assembly of claim 1, wherein the spacer arm is a self-supporting wheel structure. 4. The rotor assembly of claim 1, wherein a plurality of cooling fins are disposed on the spacer arm to reduce bending stresses in the spacer arm due to thermal strain on the spacer arm. 5. The disk spacer arm is configured to transmit an axial load and a bending moment between adjacent rotor disks of a gas turbine engine, and the spacer arm comprises (a) an adjacent rotor disk. A rigidly attached first end of the spacer arm, (b) a second end of the spacer arm axially spaced from the first end, and (c) a relatively high temperature gas flow radially outward in the radial direction. A spacer arm body extending between the spacer arm first end and a second end to isolate it from the inner relatively cool cavity; and (d) the relatively cool temperature from the spacer arm body. The rotor assembly of claim 1, including at least one cooling fin extending within the cavity. 6. The rotor assembly according to claim 5, wherein each cooling fin is circumferentially continuous. 7. The rotor assembly of claim 5, wherein the spacer arm is a self-supporting wheel structure. 8. The rotor assembly according to claim 5, wherein a plurality of spacer arm cooling fins are arranged around a midpoint of the spacer arm main body. 9. The rotor assembly of claim 5, wherein the spacer arm first end is integral with a rotor disk. 10. The rotor assembly of claim 5, wherein the adjacent rotor disks include rotor disk hubs extending within the radially inner relatively cooler cavities. 11. The rotor assembly of claim 5, wherein each cooling fin has tapered sidewalls extending from a relatively thick radially outer base to a relatively thin radially inner tip. 12. (a) A plurality of rotor disks each including a plurality of blades extending in a hot gas flow; and (b) a structure for transmitting a load between adjacent rotor disks. A first surface bounding a relatively hot cavity that is in communication with the hot gas stream;
A structural disc spacer arm having a second surface bounding a relatively cool cavity; and (c) extending from the disc spacer arm into the relatively cool cavity. A rotor assembly for a gas turbine engine comprising at least one cooling fin, and (d) means for directing cooling air into the relatively hot cavity. 13. The rotor assembly according to claim 12, wherein each cooling fin is circumferentially continuous. 14. The rotor assembly of claim 12, wherein the spacer arm is a self-supporting wheel structure. 15. A plurality of cooling fins extending from the disk spacer arm into the relatively cool cavity are disposed about the spacer arm body midpoint. The rotor assembly according to claim 12. 16. The rotor assembly of claim 12, wherein each cooling fin has tapered sidewalls extending from a relatively thick radially outer base to a relatively thin radially inner tip. 17. The spacer arm includes a first end fixed to an adjacent rotor disk, the adjacent rotor disk including a rotor disk hub extending into the relatively cold cavity. The rotor assembly according to claim 12. 18. A means for directing cooling air from said relatively cold cavity to said relatively hot cavity.
2. The rotor assembly according to 2. 19. The spacer arm includes a first end fixed to an adjacent rotor disk, the adjacent rotor disk including a rotor disk hub extending into the relatively cold cavity. The rotor assembly according to claim 18. 20. A self-supporting wheel structure mounted for rotation about an axis and configured to carry a hoop load, the body delimiting a relatively hot cavity. And at least one circumferential continuous cooling fin extending from the structure into a relatively cool cavity, the cooling fin for reducing the hoop load carried by the body. A self-supporting wheel structure in which a load is transferred from the main body to the cooling fins due to a temperature difference between the main body and the cooling fin.