Patent Application
20130255261
The invention relates generally to combustors and more particularly to swirlers for combustion chambers.
Typically gas turbines include combustion chambers having swirlers along with fuel nozzles (or swozzles) therein. Each of the swirlers within a nozzle includes one or more passages for delivering a mixture of fuel and air (or air only) to a combustion chamber. The swozzles are used for stabilizing the flame and improving the mixing of the fuel and air prior to ignition. The swirler includes a plurality of vanes extending from the nozzle and having an aerodynamic profile. The swirler vanes often include passages which provide fuel to fuel holes on a surface of the swirler vanes. As fuel exits the fuel holes, it mixes with fluid, typically air, passing the swirler vanes. Typically the swirler vanes have a turn near the trailing edge of the swirler vane that may produce flow separations in the swirler or downstream of the swirler which increases the potential of flash back and flame holding to occur. To solve such flow problems, one common approach is to modify the vane profile. This modification requires new casting processes and casting tooling for each iteration.
Accordingly, there is an ongoing need for increasing the swirler performance.
In accordance with an embodiment of the invention, a combustion swirler is provided. The combustion swirler includes multiple vanes axially extending from an annular first body portion of the combustion swirler. The combustion swirler also includes an annular second body portion enclosing the multiple vanes for directing a flow of combustion fluid. Each of the vanes comprises an aerodynamic blade body comprising a leading edge with a plurality of first tubercles and a trailing edge with a plurality of second tubercles.
In accordance with another embodiment of the invention, a gas turbine is provided. The gas turbine includes a combustion swirler located upstream of a combustion region of the gas turbine. Further, the combustion swirler includes multiple vanes axially extending from an annular first body portion of a combustion air swirler. The gas turbine also includes an annular second body portion of the swirler enclosing the multiple vanes for directing a flow of combustion fluid. Each of the vanes includes an aerodynamic blade body having a leading edge with multiple first tubercles and a trailing edge with multiple second tubercles.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters are not exclusive of other parameters of the disclosed embodiments.
A perspective view of the combustion swirler 11 is shown in
Each of the multiple swirl vanes 12 includes an aerodynamic blade body comprising a leading edge 22 with a plurality of first tubercles 24. The first tubercles 24 are protrusions with sinuous curves at the leading edge 22. This will help generate a couple of counter rotating vortices around the leading edge 22 resulting in elimination of a flow separation close to a trailing edge 28 such that a lower swirl angle can be used while maintaining a same amount of swirl of the air or the mixture of fuel and air. This will be translated in terms of reduction in the pressure drop generated across the combustion swirler 11. Such a reduction in pressure drop leads to an increase in thermal efficiency of the gas turbine having the combustion swirler 11. Further, the leading edge 22 with the plurality of first tubercles 24 causes elimination of the trailing edge wake region, thereby resulting in improved flame static stability. In one embodiment, the leading edge 22 with the plurality of first tubercles 24 causes a high speed flow of the combustion fluid without forming any wake region.
The aerodynamic blade body of each of the multiple swirler vanes 12 having the trailing edge 28 includes a plurality of second tubercles. In one embodiment, the second tubercles comprise serrations or notches 26 which define individual teeth or chevrons. As the center body 14 rotates along with the swirler vanes 12 during operation, the plurality of serrations or notches 26 helps in reducing separation or a wake region in a boundary layer flow of the combustion fluid between the swirler vanes 12 and around a region of the trailing edge 28. Also, the serrations or notches 26 are expected to create increased turbulence levels which will be translated in terms of lower NOx emissions. In another embodiment, the trailing edge 28 includes a plurality of second tubercles comprising protrusions with sinuous curves. The plurality of second tubercles may also help in generating multiple vortexes for enhancing the mixing of combustion fluid and fuel.
The plurality of first tubercles 24 may be evenly spaced along the leading edge 22 and provide for improved air and fuel mixing in the combustor over other embodiments for combustion chambers wherein such tubercles are not present on the leading edge of swirler vanes. The tubercles 26 may be evenly spaced along the trailing edge 28 and generate vortexes that enhance the air-fuel mixing in the combustor. The plurality of first tubercles 24 causes stall delays and reduces air flow separation. Further, the plurality of second tubercles 26 results in reduction of a wake region around the trailing edge of swirler vanes. Therefore, the reduction in the wake region helps to lessen the severity of flash back and flame holding. This embodiment also helps mitigate noise generation attributed to flow separation. Moreover, the elimination of the wake region improves the dynamics stability of the combustor section since combustion dynamics generated due to flow break down is alleviated.
Advantageously, the combustion swirler improves the air-fuel mixing as well as flame static stability of the combustor chambers. This is translated in terms of a high pressure drop (such as, for example, about 3%) across the combustion swirler with a combustion region of a gas turbine in accordance with one embodiment. The pressure drop is primarily due to a blockage caused by the combustion swirler. Typically a high swirl angle is chosen to account for the flow separation that occurs at the trailing edge of the combustion swirler. In the present invention, a smaller angle of the swirl vane results in the same degree of swirl and thus the pressure drop is reduced. Consequently, the present invention leads to enhanced performance of the combustion swirler due to the flame static stability and reduced pressure drop.
Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
