GB2161220A

GB2161220A - Gas turbine stator vane assembly

Info

Publication number: GB2161220A
Application number: GB08515742A
Authority: GB
Inventors: David Glenn Cherry; Dean Thomas Lenahan; Harvey Michael Maclin; Mikio Suo
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1984-07-02
Filing date: 1985-06-21
Publication date: 1986-01-08
Also published as: IT1185174B; DE3523145A1; IT8521411A0; FR2568938A1; FR2568938B1; GB8515742D0; JPS6123803A; GB2161220B

Abstract

A gas turbine's stator nozzle is made up of segments comprising one or more vanes 26 and integral inner and outer circumferential platform segments 36, 38 extending from the suction side 30 of the foil(s). By so locating the joint line between the adjacent segments on the high pressure side of the foils, leakage of coolant air through the joints from radially outward space 46 is reduced. Moreover any such leakage tends to flow across the segments as shown by arrows 52, thereby cooling these surfaces. <IMAGE>

Description

SPECIFICATION Stator Vane Gas turbine engines generally include a compressor for compressing air flowing through the engine, a combustor in which fuel is mixed with the compressed air and ignited to form a high energy gas stream, and a turbine which includes a rotor for driving the compressor. The turbine comprises a number of blades connected to the rotor and located aft of the combustor and within the gas flowpath so as to extract useful energy from the gas flow. In order to optimize the amount of energy extracted, an array of vanes is typically interposed between the combustor and turbine blades to turn the gas stream. By imparting a circumferential velocity component to the flow, higher turbine blade speeds are attainable.

Atypical vane array comprises a plurality of circumferentially positioned airfoils radially mounted between inner and outer shrouds or bands. In the past, two types of vane arrays have been employed, namely, a single array of vanes in which the inner and outer bands are continuous with essentially no breaks, and those in which the bands are segmented and include one or more airfoils per segment.

Stator vanes with segmented bands have a gap between adjacent segments. This gap permits differential thermal expansion of the segments thereby preventing the segments from buckling.

However, the gap also allows the hot gases from the flowpath to leak out or allows higher pressure cooling air on the back side of the band to leak into the flowpath. In addition, the split line interrupts the smooth passage between adjacent vanes, thereby reducing aerodynamic performance of the vane array, especially in the high velocity flow fields typical of compressor drive turbines.

Objects of the Invention It is an object of the present invention to provide a new and improved stator vane sector for a gas turbine engine.

It is another object of the present invention to provide a new and improved stator vane sector with an improved flowpath band surface.

It is a further object of the present invention to provide a new and improved stator vane sector with improved band cooling over those heretofore known.

It is yet a further object of the present invention to provide a new and improved stator vane sector with lower performance losses attributable to cooling air leakage.

Summary of the Invention The stator vane sector according to one form of the present invention comprises an airfoil with outer and inner circumferential band segments. The airfoil has a pressure side and a suction side and radially outer and inner ends. The circumferential band segments are integral with the outer and inner ends, respectively, and extend away from the suction side of the airfoil.

Brief Description of the Drawings Figure 1 is a schematic view of a gas turbine engine embodying the present invention.

Figure 2 is a perspective view of stator vane sectors according to one form of the present invention.

Figure 3 is a perspective view of a stator vane sector according to an alternate form of the present invention.

Detailed Description of the Invention Figure 1 shows a gas turbine engine 10 with fan 12, compressor 14, combustor 16, high pressure turbine 18, and low pressure turbine 20. Interposed between combustor 16 and high pressure turbine 18 is turbine stator 22. Stator 22 includes a plurality of circumferentially disposed airfoils which impart a circumferential component to the gas flow from combustor 16 to increase the blade speed of turbine 18.

Figure 2 shows in greater detail a portion of stator 22 according to one form of the present invention.

Stator 22 includes a plurality of circumferentially disposed stator vane sectors 24. Each sector 24 comprises an airfoil 26 having a pressure side 28 and suction side 30. In addition, each airfoil 26 has a radially outer end 32 and a radially inner end 34.

Stator vane sector 24 further comprises outer circumferential band segment 36 and inner circumferential band segment 38.

In a preferred embodiment, outer and inner band segments 36 and 38 may be formed integral with outer and inner airfoil ends 32 and 34, respectively.

However, band segments 36 and 38 may be otherwise joined to ends 32 and 34, respectively, by brazing, diffusion bonding, or other permanent fastening means. Each band segment 36 and 38 extends away from suction side 30 of airfoil 26.

Each of band segments 36 and 38 includes an axially directed recess 40 at the end of the segment furthest away from airfoil 26. Each airfoil 26 similarly includes a recess 42 which follows the contour of airfoil 26 and which generally aligns with recess 40 of an adjacent stator vane sector 24. When so positioned, a split line 43 is defined by the intersection of each band segment and the pressure side of the adjacent airfoil. This line represents a leakage path between the inner flowpath 44 and each space 46 radially outside flowpath 44. In order to reduce leakage therebetween, appropriate sealing means along this line may be employed. For example, a shim 48 mateable with recesses 40 and 42 may be used.

In operation, hot gases will flow through inner flowpath 44 of stator 22. The back side of outer and inner band segments 36 and 38 can be cooled by providing high pressure cooling air into each space 46. Such cooling air will be at a higher pressure than the gas in flowpath 44 and will therefore tend to leak into flowpath 44 through the split lines 43 shown.

Since pressure side 28 is at a higher pressure than suction side 30, locating the split line in this highest pressure region will reduce the amount of leakage into flowpath 44. To the extent that leakage does occur, the cooling air will tend to flow across the inner surfaces of band segments 36 and 38, as shown by arrow 52, thereby providing cooling to these surfaces. Thus, leakage is reduced and, to the extent that it exists, is utilized effectively for band cooling. It should be noted that since the region nearest the pressure side 28 is at the highest pressure, gases in flowpath 44 in this region will be at the lowest velocity. Accordingly, the leakage air which enters flowpath 44 in this region, will create the lowest aerodynamic loss possible.

In prior art segmented turbine stators, the split line tends to interrupt the smooth flow of gas between vanes. This occurs because the split line does not follow the flow field and consequently crosses the split line. Since the flow field tends to follow the contour of the vane in the vicinity of the pressure side, split line 43 has a reduced tendency to create flow disturbances.

Figure 3 shows an alternate form of the present invention. The stator vane sector shown therein includes a plurality of circumferentially positioned airfoils. For example, the embodiment shows a first airfoil 26a and a second airfoil 26b. The airfoils are positioned so that suction side 30 of airfoil 26a faces second airfoil 26b. Furthermore, each of the airfoils of sector 24 are aligned so that the suction side of each airfoil faces the same circumferential direction, shown by arrow 50. Outer and inner band sections 36 and 38 extend away from the suction side 30 of first airfoil 26a as shown.

In operation, sector 24 shown in Figure 3 will function in a manner similar to that shown in Figure 2. Again, the positioning of the split line on the pressure side reduces the amount of leakage into flowpath 44. However, the cooling effect on bands 36 and 38 from the cooling air leakage which occurs will not extend along the surface of bands 36 and 38 between airfoils 26a and 26b.

It will be clear to those skilled in the art that the present invention is not limited to the specific embodiments described and illustrated herein. Nor is the invention limited to turbine stators. Rather, it applies equally to rotors and stators employed in turbomachinery.

It will be understood that the dimensions and proportional and structural relationships found in the drawings are illustrated by way of example only and these illustrations are not to be taken as the actual dimensions or proportional structural relationships used in the stator vane sector of the present invention.

Numerous modifications, variations, and full and partial equivalents can be undertaken without departing from the invention as limited only by the spirit and scope of the appended claims.

Claims

1. A stator vane sector comprising: an airfoil having a pressure side and a suction side and radially outer and inner ends; and outer and inner circumferential band segments integral with said outer and inner ends, respectively, and extending away from said suction side.

2. In a gas turbine engine, first and second circumferentially arranged stator vane sectors, each sector comprising: an airfoil having a pressure side and a suction side and radially outer and inner ends; and outer and inner circumferential band segments integral with said outer and inner ends, respectively, and extending away from said suction side; wherein said sectors are joinable along outer and inner lines defined by the intersection of said respective band segments of said first vane with said airfoil pressure side of said second vane.

3. A stator vane sector comprising: a plurality of circumferentially positioned airfoils, commencing with a first airfoil, each airfoil having radially outer and inner ends and a pressure side and a suction side, wherein the suction side of said first airfoil faces the other airfoils and the suction side of each of said airfoils facing a first circumferential direction; and outer and inner circumferential band segments integral with said outer and inner ends, respectively, and extending away from the suction side of said first airfoil.

4. A stator vane sector substantially as hereinbefore described.