Patent Application
20150110616
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:
Referring to
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.
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
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
The trailing edge fillet 60 may also have an increased width d3 as compared to a similar dimension of the inner fillet 50 (or a conventional fillet). As shown in
Due to the width d3 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
The trailing edge 16 of the vane 12 at its connection to the inner endwall 30 may be offset by a distance d4 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 d4 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.
As shown in
The trailing edge 16 of the vane 12 may also be bowed near the outer endwall 26, as shown in
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.
