The present application relates generally to gas turbine engines and more particularly relates to a vortex breaker for use in fuel plenums of combustor swozzle vanes.
Various types of combustors are known and used in gas turbine engines. In turn, these combustors generally use different types of fuel nozzles depending upon the type of fuel in use. For example, most natural gas fired systems operate using lean premixed flames. In these systems, fuel is mixed with air upstream of the reaction zone to create a premixed flame. One example is a “swozzle” (swirler+nozzle) in which the fuel ports are positioned about a number of extending vanes so as to inject the fuel into the air stream. Alternatively in systems using syngas or other types of fuels, diffusion nozzles may be used to inject the fuel and the air directly into the combustion chamber due to the generally higher reactivity of the fuel.
Current combustor designs, however, focus on fuel flexibility with respect to the use of natural gas and other types of fuels. As a result, operational issues may arise when switching from one type of fuel to another while using the same components. For. example, syngas may have a much higher volumetric flow rate as opposed to natural gas because of its higher reactivity. The design of the combustor thus should accommodate these varying characteristics.
There is thus a desire for improved combustor components in specific and improved turbine components in general that can provide greater fuel flexibility while maintaining system efficiency and limiting overall emissions. Specifically, such fuel flexible systems should accommodate natural gas and other types of fuels without extensive equipment changeovers.
The present application thus provides a manifold for use with a gas turbine. The premix manifold may include a fuel passage and a swozzle vane in communication with the fuel passage. The swozzle vane may include a fuel plenum in communication with one or more fuel holes and a vortex breaker positioned about the fuel holes.
The present application further describes a method of modifying a recirculation vortex about one or more fuel holes within a fuel plenum of a manifold vane. The method may include the steps of flowing fuel through a fuel passage, turning the flow of fuel about ninety degrees into the fuel plenum so as to create the recirculation vortex therein, and positioning a vortex breaker about the fuel holes so as to modify the recirculation vortex.
The present application further describes a premix manifold for use with a gas turbine. The premix manifold may include a fuel passage and a swozzle vane in communication with the fuel passage. The swozzle vane may include a fuel plenum in communication with one or more fuel holes. The fuel plenum may be positioned at about a ninety degree turn from the fuel passage. The swozzle vane further may include a vortex breaker positioned about the fuel holes so as to reduce a recirculation vortex within the fuel plenum.
These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numbers refer to like elements throughout the several views,
In use, the fuel is injected through the fuel holes 180 of the swozzle 150 and into the air passage 130. The primary purpose of the swozzle 150 is to inject the fuel into the air stream and introduce swirl so as to promote good mixing. The fuel mixes with the air in the burner tube 140 and then enters into a combustion zone or liner within the combustor 30.
Specifically, the premixed fuel enters the premix manifold 100, passes through the premixed fuel passages 120, and passes into the vanes 160 and the fuel plenums 170 of each swozzle 150. The fuel from the premixed fuel passages 120, however, takes a roughly ninety degree (90°) turn 165 when entering the fuel plenum 170 inside each vane 160.
The fuel thus may form a recirculation vortex 175 within the fuel plenum 170 when making this turn 165. Such a recirculation vortex 175 may swirl behind one or more of the fuel holes 180. For lower BTU gases (higher volumetric flow gasses as opposed to natural gas), the recirculation vortex 175 inside the fuel plenum 170 may result in a non-uniform fuel flux distribution through each fuel hole 180. Such a non-uniform fuel flux may provide uneven fuel jet penetration into the air passage 130. As a result, these recirculation vortexes 175 may lead to flame holding and higher emission due to poor fuel/air mixing. The strength of the recirculation vortexes 175 may increase with the volumetric flow rate.
Specifically, the dominant mechanism for flame holding or flashback may be the recirculation vortexes 175 behind the fuel holes 180. The non-uniform fuel flux may result in higher jet penetration through some of the fuel holes 180. These higher jets may form stronger recirculation vortexes 175 behind the jets and hence the chance for flame holding or flashback may be increased. The non-uniform fuel flow also may result in smaller jet penetration for other fuel holes 180. The fuel through the smaller jets may flow close to the vane wall and may not fully mix with the air stream. Such poor mixing thus may result in higher emissions.
Any number of the vortex breakers 210 may be used. The size, shape, number, and location of the vortex breakers 210 may depend upon the nature and speed of the fuel flowing therein, although it appears that the best location for the vortex breaker 210 may be nearer to the center of the recirculation vortex. The vortex breaker 210 may be used at any place inside the passage where fuel is being injected into the air for premixing. Although the vortex breaker 210 shown here is used in a swozzle fuel plenum 200, it also may be used in any other plenum where an excessive pressure drop needs to be controlled. The vortex breaker 210 may be used with any fluid that may create recirculations in a flow path.
As compared to the fuel plenums 170 without the vortex breakers 210, the fuel plenums 200 with the vortex breaker 210 have a more even pressure drop across each of the fuel holes 180. This even pressure loss thus may result in a more uniform fuel flux. Moreover, the overall pressure drop may be reduced by weakening the recirculation vortex 175. The vortex breakers 210 or similar designs also may be used within fuel pegs.
The vortex breaker 210 thus helps to reduce or eliminate the recirculation vortex 175 and hence provides a more uniform fuel flux through each of the fuel holes 180. The more uniform fuel flux thus may increase flame holding margins and reduce emissions by improving overall mixing. Improved flame holding also may increase the life of the premix manifold 100 as a whole and help to reduce overall maintenance costs. Likewise, improved flame holding may reduce outage time due to premixer failure. As above, improved flame holding largely increases fuel flexibility of the turbine 10 as a whole so as to accommodate different kinds of fuels without adverse effect on operability. The vortex breaker 210 helps in reducing the recirculation vortex inside the fuel plenum and thereby improves the operability with different fuels. Eliminating the recirculating vortex also should help in eliminating or reducing flow and combustion induced instabilities.
It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.