Gas turbine nozzle trailing edge fillet

This invention relates generally to gas turbine components (e.g., nozzle segments), and more particularly to turbine airfoils.

A gas turbine engine includes a compressor that provides pressurized air to a combustor where the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to at least one turbine that extracts energy therefrom to power the compressor and provide useful work. The turbine commonly includes a stationary turbine nozzle followed by a turbine rotor.

The turbine nozzle comprises a row of circumferentially side-by-side nozzle segments each including one or more stationary airfoil-shaped vanes mounted between inner and outer band segments defining platforms for channeling the hot gas stream into the turbine rotor. Each of the vanes includes pressure and suction sidewalls that are connected at a leading edge and a trailing edge. The airfoil section typically has a broad, blunt leading edge having a region of high curvature on the suction side transitioning from the leading edge to a thinned trailing edge portion.

Stress (e.g., thermal stress) on the thinned trailing edge portion can lead to undesirable issues on the trailing edge portion at its connection to the platforms which can significantly reduce the life of the nozzle segment.

One exemplary but nonlimiting aspect of the disclosed technology relates to a nozzle segment for a gas turbine engine. The nozzle segment comprises an arcuate inner endwall having an inner platform and an airfoil body extending outwardly from the inner platform toward an arcuate outer endwall. The airfoil body includes opposed pressure and suction sidewalls extending between a leading edge and a trailing edge of the airfoil body and a first inner fillet blending into the inner platform. The first inner fillet has a height, wherein the airfoil body includes a first trailing edge fillet blending into the inner platform at a trailing edge of the airfoil body. The first trailing edge fillet has a height greater than the height of the first inner fillet.

Another exemplary but nonlimiting aspect of the disclosed technology relates to a nozzle segment for a gas turbine engine. The nozzle segment comprises an arcuate inner endwall having an inner platform, an arcuate outer endwall having an outer platform, and an airfoil body extending outwardly from the inner platform and inwardly from the outer platform. The airfoil body includes opposed pressure and suction sidewalls extending between a leading edge and a trailing edge of the airfoil body and a first trailing edge fillet blending into the inner platform at a trailing edge of the airfoil body, wherein a height of the first trailing edge fillet is at least 5% of a total radial length of the airfoil body between the inner and outer platforms. Further, the trailing edge of the airfoil body is locally bowed along a span of the airfoil body so as to form a curved structure in the radial direction of the airfoil body.

The accompanying drawings facilitate an understanding of the various examples of this technology. In such drawings:

FIG. 1 is a perspective view of an turbine nozzle segment according to an example of the disclosed technology;

FIG. 2 is a cross-sectional view taken along the line 2 - 2 in FIG. 1 ;

FIG. 3 is a partial perspective view of a trailing edge of a vane of the nozzle segment of FIG. 1 ;

FIG. 4 is a partial side view of a trailing edge portion of the vane of FIG. 3 near an inner endwall;

FIG. 5 is a partial perspective view of a trailing edge of a vane having a bowed trailing edge portion in accordance with an example of the disclosed technology; and

FIG. 6 is a partial side view of a trailing edge portion of a vane near an outer endwall in accordance with an example of the disclosed technology.

Referring to FIGS. 1-3 , an exemplary nozzle segment 10 in accordance with an example of the disclosed technology is shown. A plurality of such nozzle segments 10 are assembled in circumferential side-by-side fashion to build up a turbine nozzle. The nozzle segment 10 includes one or more airfoils or vanes 12 each having a leading edge 14 , a trailing edge 16 , a root 18 , a tip 20 , and spaced-apart pressure and suction sidewalls 22 and 24 , respectively. An arcuate outer endwall 26 having an outer platform 28 is attached to the tips 20 of the vanes 12 . An arcuate inner endwall 30 having an inner platform 32 is attached to the roots 18 of the vanes 12 . The outer and inner endwalls 26 and 30 define the outer and inner radial boundaries, respectively, of the primary gas flowpath through the nozzle segment 10 .

The nozzle segment 10 is typically formed from a high-temperature capable metallic alloy such as known nickel or cobalt-based “superalloys.” The nozzle segment may be cast as a single unit, or it may be assembled from individual components or sub-assemblies.

FIG. 2 is a cross-sectional view taken along the line 2 - 2 in FIG. 1 and illustrates the airfoil section of the vanes 12 . The suction sidewall 24 of each vane 12 extends rearward from the leading edge 14 , and has a high curvature section 34 between relatively less curved forward and aft portions 36 and 38 , respectively, of the suction sidewall 24 .

A throat 40 defining the minimum cross-sectional flow area is defined between an aft portion 42 of the pressure sidewall of vane 12 and the aft portion 38 of the suction sidewall 24 of an adjacent vane 12 . The area of the throat 40 is a key dimension affecting the aerodynamic performance of the nozzle segment 10 . It is therefore desirable to maintain the actual area of the throat 40 as close as possible to the intended design value.

As shown in FIG. 3 , the vane 12 includes an inner fillet 50 near the inner platform 32 . The inner fillet 50 forms a concave portion that blends into the platform 32 . The inner fillet 50 may extend around the entire periphery of the vane 12 . The inner fillet 50 may have a simple curved cross-sectional profile having any suitable radius of curvature r 1 and a height d 1 as those skilled in the art will recognize.

In the illustrated example, a trailing edge fillet 60 is disposed at the trailing edge 16 of the vane 12 between opposing end portions of the inner fillet 50 , as shown in FIGS. 3 and 4 . The trailing edge fillet 60 has an increased height d 2 as compared to the height d 1 of the inner fillet 50 . As shown in FIG. 4 , the height d 2 is measured from a transition point B where the trailing edge fillet 60 blends into the trailing edge of the vane 12 , as those skilled in the art will understand. The trailing edge fillet 60 is taller than conventional fillets. Specifically, the height d 2 of the trailing edge fillet 60 is greater than 5% (e.g., 5% to 20%) of the total radial extent or length (height) of the vane 12 from the inner platform 32 to the outer platform 28 . Preferably, the height d 2 is greater than 10% (e.g., 15%) of the height of the vane 12 .

The trailing edge fillet 60 may also have an increased width d 3 as compared to a similar dimension of the inner fillet 50 (or a conventional fillet). As shown in FIG. 4 , the width d 3 is measured from the transition point B to an end point C of the trailing edge fillet. Preferably, the width d 3 is 80% to 300% of the height d 2 . The curved segment BC is modeled as a conic segment in accordance with the particular lengths of d 2 and d 3 and having a rho value within the range of 0.3-0.5, as one skilled in the art will understand.

Due to the width d 3 of the trailing edge fillet 60 , the chord length of the inner endwall 32 is increased thereby reducing the local throat 40 . In order to maintain the spanwise throat distribution, the trailing edge sections of the vanes 12 are bowed along the radial direction of the vanes 12 , as shown in FIG. 5 . That is, the trailing edge portion of the vane 12 is bowed so as to preserve the intended size of the throat. This causes the nozzle trailing edge 16 to be locally bowed thus preserving the throat width and thereby leading to a reduction in secondary flows (i.e., increased aerodynamic efficiency).

The trailing edge 16 of the vane 12 at its connection to the inner endwall 30 may be offset by a distance d 4 from the point at which the trailing edge 16 connected to the inner endwall 30 before bowing (or from a radially extending line through a point on the trailing 16 circumferentially farthest from the trailing edge/inner endwall connection). The offset d 4 may be within a range of 3-6% of the total radial extent (height) of the vane 12 from the inner platform 32 to the outer platform 28 .

FIG. 6 illustrates a trailing edge portion of a vane 12 near the outer endwall 26 . Similar to the intersection of the vane 12 and the inner endwall 30 , the vane 12 may have fillets in order to blend into the outer endwall 26 .

As shown in FIG. 6 , the vane 12 includes an outer fillet 150 near the outer platform 28 and a trailing edge fillet 160 . The outer fillet 150 and the trailing edge fillet 160 are similar to the inner fillet 50 and the trailing edge fillet 60 described above. The ranges for the dimensions d 1 ′, d 2 ′, d 3 ′ and r 1 ′ are respectively the same as the dimensions d 1 , d 2 , d 3 and r 1 described above. Similarly, the curved segment B′C′ is modeled in the same manner as the segment BC above. It is noted however that the particular values of the dimensions d 1 ′, d 2 ′, d 3 ′ and r 1 ′ as well as the shape of the segment B′C′ may be different from the values of the dimensions d 1 , d 2 , d 3 and r 1 and the shape of the segment BC.

The trailing edge 16 of the vane 12 may also be bowed near the outer endwall 26 , as shown in FIG. 5 . The offset of the bow at the outer endwall 26 may be within the same range as the offset d 4 of the bow at the inner endwall 30 .

The larger trailing edge fillets 60 , 160 increase the cross-sectional area at the junctions between the vanes 12 and the inner and outer platforms 32 and 28 and thus cause the vanes to better withstand stress. The trailing edge fillets cause a reduction in the amount of cracking at the trailing edge junction over the life of the nozzle segment, thus significantly increasing the useful life of the nozzle segment. Further, by bowing the trailing edge junction portions, the throat is maintained and therefore aerodynamic efficiency is not sacrificed.

While the invention has been described in connection with what is presently considered to be the most practical and preferred examples, it is to be understood that the invention is not to be limited to the disclosed examples, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.