Patent Application
20120125004
The subject matter disclosed herein relates to a premixer for use with a gas turbine engine combustor.
In gas turbine engines, premixed air and fuel are combusted within combustors that are disposed upstream from turbines in which mechanical energy is derived from the high temperature fluids produced by the combustion. Electrical energy is then generated from the mechanical energy and transmitted to electrical circuits. The combustors typically include fuel nozzles having premixing passages in which the air and fuel are mixed with one another. This premixing increases the tendency of the combustible materials to fully combust, which leads to decreases in amounts of emissions produced by the engine. As such, an increased degree of premixing corresponds to a decrease in an amount of the emissions.
Such increased premixing has been achieved by the use of large swirl vanes and/or large numbers of swirl vanes in swirlers disposed at or near upstream ends of the premixing passages. The swirl vanes redirect the flow of combustible materials to facilitate mixing of fuel and air. However, the large swirl vanes and/or the large numbers of swirl vanes add to the overall weight and cost of the fuel nozzles and, despite their use, it may be the case that at least air entry in to the premixing passage is axial or radial but not a mix of axial and radial flows.
According to one aspect of the invention, a combustor premixer is provided and includes a burner tube having a bell mouth-shaped opening, a plurality of tubular bodies telescopically disposed within the burner tube to deliver combustible materials to a premixing passage defined between the burner tube and an outermost one of the plurality of tubular bodies and a plurality of swirler vanes arrayed circumferentially in the opening, each one of the plurality of swirler vanes including a body extending along a radial dimension from the burner tube to the outermost tubular body and a leading edge protruding upstream from the opening.
According to another aspect of the invention, a combustor premixer is provided and includes an annular shroud an annular wall disposed within the shroud to define premixing and fuel passages, the premixing passage extending downstream from a shroud upstream end and radially inwardly from a divergent point at the shroud upstream end to a convergent point, the fuel passage being configured to deliver fuel to the premixing passage proximate to the divergent point and a centerbody having an innermost tube to define an interior passage and being loadable within the wall to define an intermediate passage, the intermediate passage being fluidly communicative with the interior passage via first holes formed in the innermost tube, the fuel passage via second holes formed in the wall downstream from the first holes, and the premixing passage via third holes formed in the wall downstream from the second holes and proximate to the convergent point.
According to yet another aspect of the invention, a combustor premixer is provided and includes an annular burner tube, an annular inner wall formed to define a fuel passage and a centerbody formed to define an interior, the burner tube, the inner wall and the centerbody being telescopically arranged such that the burner tube and the inner wall define a premixing passage having a convergent upstream end and a downstream portion, the premixing passage being fluidly communicative with the fuel passage at the upstream end, the inner wall and the centerbody define an intermediate passage having an upstream end and a divergent downstream portion, the intermediate passage being fluidly communicative with the fuel passage and the interior at the upstream end and with the premixing passage at respective borders of corresponding upstream ends and downstream portions; and the combustor premixer further comprising a plurality of swirler vanes arrayed circumferentially in the premixing passage, each one of the plurality of swirler vanes including a body extending along a radial dimension from the burner tube to the inner wall and a leading edge protruding upstream from an opening of the premixing passage.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
With reference to
The burner tube 20 includes an annular shroud 21 extending from an upstream end 22 in a downstream direction through a tubular portion 23. The annular shroud 21 bulges at the upstream end 22 to form a bell mouth-shaped opening 25 with a dome-type design. In operation, compressor discharge air exhausted from, for example, a compressor of a gas turbine engine, flows toward a head end of the gas turbine engine in the upstream direction and, as the compressor discharge air approaches the bell mouth-shaped opening 25, flows radially inwardly toward the plurality of tubular bodies 30, smoothly turns toward the axial direction due to the bell mouth-shaped opening 25 with the dome-type design and then flows axially downstream through the plurality of swirler vanes 40. The plurality of swirler vanes 40 imparts an angular momentum to the air entering the bell moth-shaped opening 25 such that the air swirls at a predefined angle set to allow for sufficient axial movement of the air and to encourage full premixing of the air with fuel.
Compressor discharge air may also flow through shroud side holes 26 that are formed in the annular shroud 21. The shroud side holes 26 may be formed downstream from the plurality of swirler vanes 40 and, in some embodiments, may be formed substantially proximate to trailing edges 43 thereof. The shroud side holes 26 reduce numbers and effects of low velocity zones caused by, for example, boundary layer blowing.
The plurality of tubular bodies 30 are telescopically disposed within the annular shroud 21 of the burner tube 20 and are formed to deliver combustible materials to a premixing passage 31. The premixing passage 31 is defined between the annular shroud 21 and an outer surface 32 of an outermost tubular body 33 of the plurality of tubular bodies 30. The air entering the bell mouth-shaped opening 25 and flowing through the swirler vanes 40 proceeds through the premixing passage 31 where it is premixed with the fuel delivered by the plurality of tubular bodies 30. The positioning of the swirler vanes 40 upstream from the premixing passage 31 provides for increased premixing distance. In addition, a pressure along the premixing passage 31 is maintained at a substantially uniform level.
The plurality of swirler vanes 40 is arrayed circumferentially in the bell mouth-shaped opening 25. Each one of the plurality of swirler vanes 40 includes a relatively thin body 41 as compared to the circumferential length of the bell moth-shaped opening to decrease weight, a leading edge 42 and a trailing edge 43. The body 41 of each one of the plurality of swirler vanes 40 extends along a radial dimension from the leading edge and the inner diameter of the annular shroud 21 to the outer surface 32 of the outermost tubular body 33. The leading edge 42 protrudes upstream from the bell mouth-shaped opening and the trailing edge 43 is angled to encourage the angular flow of the air. The protrusion of the leading edge 42 provides for relatively slight axial/radial to tangential momentum at the upstream end 22 and thereby a relatively smooth air entrance. In accordance with embodiments, each of the plurality of swirler vanes 40 is substantially spiral shaped along the radial dimension. With this construction, cross-sections of the annular shroud 21 and the plurality of the swirler vanes 40 have a dome-shaped configuration 44 or some other similar configuration.
As shown in
Air entering the bell mouth-shaped opening 25 mixes with fuel entering the premixing passage 31 at the first and second locations 50, 51 and this mixing is encouraged and facilitated as the combustible materials converge toward the hub 60. In addition, as shown in
The plurality of tubular bodies 30 further includes a centerbody 35. The centerbody 35 is loadable into a breach defined within the plurality of the tubular bodies 30 to define an intermediate passage 36 and includes an innermost tube 37. The innermost tube 37 is formed to define an interior passage 38 that is receptive of a purge air supply.
The outer surface 32 of the outermost tubular body 33 forms the hub 60 as an annular inner wall 61 that is telescopically disposed partially within the annular shroud 21 to define an upstream section of the premixing passage 31. The annular inner wall 61 further includes an outer wall portion 321 and an inner wall portion 322 that diverge from one another at a division point at a downstream edge thereof, which is proximate to the upstream end 22 to define fuel passage 62. As noted above, the premixing passage 31 extends downstream from the upstream end 22 and converges radially inwardly from a divergent point proximate to the first location 50 at the upstream end 22 to a convergent point proximate to the second location 51, which is axially interposed between the upstream end 22 and the downstream narrowing tubular portion 23.
The fuel passage 62 is configured to deliver fuel to the premixing passage 31 proximate to the divergent point at the upstream end 22 via fuel holes 63. The intermediate passage 36 is fluidly communicative with the interior passage 38 via first holes 70 that are formed in the innermost tube 37. In addition, the intermediate passage 36 is fluidly communicative with the fuel passage 62 via second holes 71 that are formed in the annular inner wall 61 at an axial location that is downstream from that of the first holes 70. The intermediate passage 36 is also fluidly communicative with the premixing passage 31 via third holes 72 that are formed in the annular inner wall 61 at an axial location that is downstream from the second holes 71 and proximate to the convergent point and the secondary location 51. The first holes 70, the second holes 71 and the third holes 72 may be distributed and angled to mitigate dynamics and the decrease recirculation behind jets.
Thus, purge air, which enhances mixing and which is supplied to the intermediate passage 36 and the interior passage 38 flows through the first holes 70 and mixes with fuel flowing from the fuel passage 62 through the second holes 71 in the intermediate passage 36. This fuel and air mixture then flows into the premixing passage 31 via the third holes 72 where it is mixed with the combustible materials already present in the premixing passage 31. The eventual fuel and air mixture continues to flow through the downstream narrowing tubular portion 23 and maintains pressure due to the radial narrowing of the premixing passage 31 in the downstream direction. The radial narrowing may be defined with the annular inner wall 61 diverging in the downstream direction from the secondary location 51.
The fuel holes 63, the first holes 70, the second holes 71 and the third holes 72 may be arrayed circumferentially about there respective walls/tubes and may be spaced from one another in substantially uniform or non-uniform intervals.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
