CN205717331U - Fuel nozzle in gas turbine combustor - Google Patents

Abstract

A fuel nozzle in a gas turbine combustor comprising: an elongated central body; an elongated peripheral wall formed about the central body so as to define a primary flow annulus therebetween; a primary fuel supply and a primary air supply in conjunction with an upstream end of the primary flow annulus in fluid communication; and a pilot nozzle. pilot nozzles may be formed in the center body and include: axially elongated mixing tubes defined within the center body wall; fuel ports positioned on the mixing tubes for connecting each to an auxiliary fuel supply; and an auxiliary air supply configured to be in fluid communication with the inlet of each of the mixing tubes. The plurality of mixing tubes may be formed as diagonal mixing tubes configured to induce a vortex about the central axis in a common discharge therefrom.

Description

Fuel nozzles in gas turbine combustors

technical field

The present invention generally relates to a gas turbine engine that combusts a hydrocarbon fuel mixed with air to generate a high temperature gas flow that drives turbine blades to rotate a shaft attached to the blades. More particularly, but not by way of limitation, the present invention relates to combustor fuel nozzles that include pilot nozzles that premix fuel and air for lower NOx.

Background technique

Gas turbine engines are widely used to generate power for many applications. A conventional gas turbine engine includes a compressor, combustor and turbine. In a typical gas turbine engine, a compressor provides compressed air to a combustor. Air entering the burner mixes with fuel and burns. The hot gases of combustion are exhausted from the combustors and flow into the blades of the turbine to rotate a turbine shaft connected to the blades. Some of the mechanical energy of the rotating shaft drives the compressor and/or other mechanical systems.

Since government regulations discourage the release of nitrogen oxides into the atmosphere, the formation of gas turbine engines as a by-product of operation strives to be kept below allowable levels. One way to meet such regulations is to move from diffusion flame burners to burners employing lean fuel and air mixtures, which use a fully premixed mode of operation to reduce, for example, nitrogen oxides (commonly denoted NOx) and nitrogen monoxide (CO ) emissions. These combustors are variously referred to in the art as dry low NOx (DLN) combustion systems, dry low emissions (DLE) combustion systems, or lean premixed (LPM) combustion systems.

The fuel-air mixture affects both the level of nitrogen oxides produced in the hot gases of combustion of the gas turbine engine and the performance of the engine. Gas turbine engines may employ one or more fuel nozzles to intake air and fuel to facilitate fuel-air mixing in the combustor. Fuel nozzles may be located at the head end of the combustor and may be configured to draw in a flow of air to be mixed with the fuel input. Typically, each fuel nozzle may be internally supported by a center body located on the interior of the fuel nozzle, and a guide may be mounted at the downstream end of the center body. So-called swozzles may be mounted to the outside of the center body and upstream of the guides, for example as described in U.S. Patent No. 6,438,961, which is hereby incorporated by reference in its entirety for each kind of purpose. The swozzle has curved vanes extending radially from a center body across an annular flow passage from which fuel is directed into the annular flow passage for entrainment into the airflow passing through the vane swirl of the swozzle.

Various parameters describing the combustion process in gas turbine engines are associated with the production of nitrogen oxides. For example, higher gas temperatures in the combustion reaction zone are responsible for the production of larger amounts of nitrogen oxides. One way to reduce these temperatures is by premixing the fuel-air mixture and reducing the fuel-to-air ratio that is burned. As the ratio of fuel to air burned decreases, the amount of nitrogen oxides also decreases. However, there is a tradeoff to the performance of the gas turbine engine. Because when the ratio of combusted fuel to air is reduced, the propensity of the flame of the fuel nozzle to go out increases and thus makes the operation of the gas turbine engine unstable. Diffusion flame type guides have been used for better flame stabilization in the burner, but doing so increases NOx. Accordingly, there remains a need for an improved pilot nozzle assembly that provides flame holding benefits while also minimizing the NOx emissions typically associated with pilot nozzles.

Utility model content

The present application thus describes a fuel nozzle for a gas turbine engine. The fuel nozzle may include: an axially elongated central body; an axially elongated peripheral wall formed around the central body so as to define a primary flow annulus therebetween; a primary fuel supply and a primary air supply connected to the primary an upstream end of the flow annulus in fluid communication; and a pilot nozzle. A pilot nozzle may be formed in the center body comprising: axially elongated mixing tubes defined within the center body wall, each of the mixing tubes having an inlet defined by an upstream face of the pilot nozzle and an outlet through the pilot nozzle. extending between outlets formed by the downstream face; a fuel port positioned between the inlet and outlet of each of the mixing tubes for connecting each of the mixing tubes to an auxiliary fuel supply; and an auxiliary air supply, It is configured to be in fluid communication with the inlet of each of the mixing tubes. The plurality of mixing tubes may be formed as canted mixing tubes configured to induce a vortex about the central axis in a common discharge therefrom.

Description of drawings

Figure 1 shows a block diagram of an exemplary gas turbine in which embodiments of the present invention may be used;

2 is a cross-sectional view of an exemplary combustor such as may be used in the gas turbine shown in FIG. 1;

3 includes views in part perspective and part in section depicting an exemplary combustor nozzle in accordance with certain aspects of the present invention;

Figure 4 shows a more detailed cross-sectional view of the burner nozzle of Figure 3;

Figure 5 shows an end view taken along the line of sight marked 5-5 in Figure 4;

Figure 6 includes a simplified side view of a mixing tube that may be used in a pilot nozzle;

7 illustrates a simplified side view of an alternative mixing tube having an oblique configuration in accordance with certain aspects of the present invention;

8 shows a cross-sectional view depicting an exemplary pilot nozzle having a diagonal mixing tube according to certain aspects of the present invention;

Fig. 9 shows a side view of an oblique mixing tube according to an exemplary embodiment of the present invention;

Figure 10 includes a perspective view of the mixing tube of Figure 9;

Figure 11 shows a side view of a diagonal mixing tube according to an alternative embodiment of the present invention;

Figure 12 shows a side view of a diagonal mixing tube according to another alternative embodiment of the present invention;

Figure 13 shows a side view of another embodiment in which linear mixing tubes are combined with diagonal mixing tubes;

Figure 14 includes a perspective view of the mixing tube of Figure 13;

Figure 15 shows an inlet view of the mixing tube of Figure 13;

Figure 16 shows an exit view of the mixing tube of Figure 13;

Figure 17 shows a side view of another embodiment comprising a counter-rotating helical mixing tube according to certain other aspects of the present invention;

Figure 18 includes a perspective view of the mixing tube of Figure 17;

Figure 19 shows an inlet view of the mixing tube of Figure 17;

Figure 20 shows an exit view of the mixing tube of Figure 17;

Figure 21 shows an exit view of an alternative embodiment of a mixing tube including an outboard component to the discharge direction;

Figure 22 shows an exit view of an alternative embodiment of a mixing tube including an inboard component to the discharge direction;

Figure 23 schematically illustrates the results of a directional flow analysis with a linear or axially oriented mixing tube; and

Figure 24 schematically shows the results of a directional flow analysis with a mixing tube oriented tangentially obliquely.

detailed description

Aspects and advantages of the invention are set forth in the following description, or may be obvious from the description, or may be taught by practice of the invention. Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical designations to refer to features in the drawings. Like or similar numerals in the drawings and description may be used to refer to like or like parts of the embodiments of the present invention.

It will be appreciated that each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. It should be understood that the ranges and limits mentioned herein include all sub-ranges falling within the stated limits, and unless otherwise stated, include the limits themselves.

Additionally, certain terms have been chosen to describe the invention and its component subsystems and parts. These terms have been chosen as far as possible based on terminology commonly used in this technical field. However, it will be appreciated that these terms are often interpreted differently. For example, an element that may be referred to herein as a single component may be referred to elsewhere as consisting of a plurality of components, or an element that may be referred to herein as comprising a plurality of components may be referred to elsewhere as a single component. In understanding the scope of the present invention, attention should be paid not only to the specific terms used, but also to the accompanying description and context, as well as the structure, configuration, function and/or use of the referenced and described components, including the The manner in which the term is related to several figures and, of course, the precise use of the term in the appended claims. Furthermore, while the following examples are shown with respect to certain types of turbine engines, the techniques of the present disclosure may also be applicable to other types of turbine engines, as would be understood by those of ordinary skill in the relevant art.

Given the nature of turbine engine operation, several descriptive terms may be used throughout this application to explain the function of the engine and/or subsystems or components included therein, and it may prove beneficial to define these terms at the beginning of this chapter. Accordingly, unless otherwise stated, these terms and their definitions follow. The terms "forward" and "rearward", without further specificity, refer to directions relative to the orientation of the gas turbine. That is, "forward" refers to the front or compressor end of the engine, and "rearward" refers to the rear or turbine end of the engine. It will be appreciated that each of these terms may be used to indicate movement or relative position within the engine. The terms "downstream" and "upstream" are used to indicate a position within a particular conduit relative to the general direction of flow moving therethrough. (It will be appreciated that these terms refer to a direction relative to expected flow during normal operation, which should be clearly apparent to anyone of ordinary skill in the art.) The term "downstream" refers to the direction along which a fluid flows through a specific The direction of the pipeline, while "upstream" refers to the opposite direction. Thus, for example, the primary flow of working fluid through a turbine engine, which begins as air moving through the compressor and then becomes combustion gases within the Beginning at a location upstream of the front end and terminating at a location downstream towards the aft end of the turbine. With respect to orientation within describing common types of combustors, as discussed in more detail below, it will be appreciated that compressor discharge air typically enters the combustor through impingement ports towards the rear end of the combustor (relatively The aforementioned compressor/turbine positioning) centered on the longitudinal axis of the combustor and defining a front/rear distinction. Once in the combustor, compressed air is directed through a flow annulus formed around the internal chamber toward the front end of the combustor, where the air flow enters the internal chamber and reverses its flow direction, traveling toward the rear end of the combustor. In another scenario, however, coolant flow through the cooling passage can be treated in the same way.

Additionally, terminology describing position relative to the axis may be used herein considering the configuration of the compressor and turbine about a central common axis, as well as the cylindrical configuration common to many combustor types. In this regard, it will be appreciated that the term "radial" refers to movement or position perpendicular to an axis. In connection with this, it may be required to describe the relative distance from the central axis. In such cases, for example, a first component would be described as being “radially inward” with respect to, or “inboard of,” a second component if the first component was positioned closer to the central axis than the second component. On the other hand, if a first component is positioned further from the central axis than a second component, then the first component will be described herein as being “radially outward” with respect to or “outboard” the second component. Additionally, it will be appreciated that the term "axial" refers to movement or position parallel to an axis. Finally, the term "circumferential" refers to movement or position about an axis. As stated, while these terms may be applied with respect to a common central axis extending through the compressor and turbine sections of the engine, these terms may also be used with respect to other components or subsystems of the engine. For example, in the case of cylindrical combustors (as is common for many gas turbine machines), the axis that gives these terms a relative meaning is the longitudinal central axis extending through the center of the cross-sectional shape, which is initially cylindrical, but It transitions to a more annular profile as it approaches the turbo.

Referring to FIG. 1 , a simplified diagram of portions of a gas turbine system 10 is shown. Turbine system 10 may use liquid or gaseous fuels, such as natural gas and/or hydrogen-rich syngas, to operate turbine system 10 . As described, a plurality of fuel-air nozzles of the type described more fully hereinafter (or, as referred to herein, "fuel nozzles 12") draw in the fuel supply 14, mix the fuel with the air supply, And directing the fuel-air mixture into the combustor 16 for combustion. The combusted fuel-air mixture produces hot pressurized exhaust gas, which may be channeled through turbine 18 toward exhaust outlet 20 . As the exhaust gas passes through turbine 18 , the gases force one or more turbine blades to rotate shaft 22 along the axis of turbine system 10 . As shown, shaft 22 may be connected to various components of turbine system 10 , including compressor 24 . Compressor 24 also includes blades that may be coupled to shaft 22 . As shaft 22 rotates, blades within compressor 24 also rotate, compressing air from air intake 26 through compressor 24 and into fuel nozzles 12 and/or combustor 16 . Shaft 22 may also be connected to a load 28, which may be a vehicle or a stationary load such as, for example, a generator in a power plant or a propeller on an aircraft. It will be appreciated that load 28 may include any suitable device capable of being driven by the rotational output of turbine system 10 .

FIG. 2 is a simplified diagram of a cross-sectional view of portions of the gas turbine system 10 schematically depicted in FIG. 1 . As schematically shown in FIG. 2 , turbine system 10 includes one or more fuel nozzles 12 located in a head end 27 of combustor 16 in gas turbine engine 10 . Each illustrated fuel nozzle 12 may include multiple fuel nozzles integrated together into groups and/or individual fuel nozzles, wherein each illustrated fuel nozzle 12 relies at least substantially or entirely on internal structural support (e.g., load bearing load fluid path). Referring to FIG. 2 , the system 10 includes a compressor section 24 for pressurizing gas, such as air, flowing into the system 10 via an air inlet 26 . In operation, air enters turbine system 10 through air intake 26 and may be pressurized in compressor 24 . It should be understood that while the gas may be referred to herein as air, the gas may be any gas suitable for use in gas turbine system 10 . Pressurized air discharged from compressor section 24 flows into combustor section 16, which is generally characterized by a plurality of combustors 16 (only one of which is shown in FIGS. out). Air entering combustor section 16 is mixed with fuel and combusted within combustion chamber 32 of combustor 16 . For example, fuel nozzles 12 may inject a fuel-air mixture into combustor 16 at an appropriate fuel-air ratio for optimal combustion, emissions, fuel consumption, and power output. Combustion produces hot pressurized exhaust gas, which then flows from each combustor 16 to turbine section 18 ( FIG. 1 ) to drive system 10 and generate power. The hot gases drive one or more blades (not shown) within turbine 18 to rotate shaft 22 and thus compressor 24 and load 28 . Rotation of shaft 22 causes blades 30 within compressor 24 to rotate and draw in and pressurize air received through air intake 26 . However, it should be readily understood that combustor 16 need not be constructed as described above and illustrated herein, and may generally have any configuration that allows pressurized air to be mixed with fuel, combusted, and diverted to turbine section 18 of system 10 .

Turning now to FIGS. 3-5 , an exemplary configuration of a premixing pilot nozzle 40 (or simply "pilot nozzle 40") is presented in accordance with certain aspects of the present invention. The pilot nozzle 40 may include a number of mixing tubes 41 within which a fuel and air mixture is formed for combustion within the combustion chamber 32 . FIGS. 3 to 5 illustrate an arrangement by which fuel and air can be supplied to several mixing tubes 41 leading to nozzles 40 . Another such fuel-air delivery configuration is provided with respect to FIG. 8 and it should be understood that other fuel and air supply configurations are possible and these examples should not be construed as limiting unless indicated in the appended claims set.

As described in FIGS. 3 , 4 and 5 , the mixing tube 41 can have both linear and axial configurations. In these cases, each mixing tube 41 may be configured such that fluid flow therefrom exits in a direction parallel to the central axis 36 of the fuel nozzle 12 (or, as used herein, includes a "discharge direction"), or alternatively Specifically, discharge in a direction that is at least not oriented obliquely tangentially with respect to the central axis 36 of the fuel nozzle. As used herein, such mixing tubes 41 may be referred to as "axial mixing tubes." Accordingly, axial mixing tube 41 may be oriented such that it is generally parallel to central axis 36 of fuel nozzle 12 , or alternatively, axial mixing tube 41 may be oriented to include a radially oblique orientation relative to central axis 36 , As long as the mixing tube has no tangential oblique components. Other mixing tubes 41 , referred to as "slanted mixing tubes," may include such a tangentially angled or slanted orientation such that each is slanted or tangentially slanted relative to the central axis 36 of the fuel nozzle 12 . Release the fuel and air mixture in the direction of . As described below, this type of configuration may be used to create a swirl pattern within the combustion zone after release, which improves certain performance aspects of the pilot nozzle 40 and thereby improves the performance of the fuel nozzle 12 .

As shown, the fuel nozzle 12 may include an axially elongated peripheral wall 50 defining an outer envelope of the component. The peripheral wall 50 of the fuel nozzle 12 has an outer surface and an inner surface, the inner surface facing the outer surface and defining an axially elongated interior cavity. As used herein, the central axis 36 of the nozzle 12 is defined as the central axis of the fuel nozzle 12 , which in this example is defined as the central axis of the peripheral wall 50 . The fuel nozzle 12 may also include a hollow axially elongated center body 52 disposed within the cavity formed by the peripheral wall 50 . Considering the concentric configuration shown between peripheral wall 50 and central body 52 , central axis 36 may be common to each component. Centerbody 52 may be axially bounded by walls defining upstream and downstream ends. The primary air flow passage 51 may be defined in an annular space between the outer surface of the central body 52 and the peripheral wall 50.

The fuel nozzle 12 may also include an axially elongated hollow fuel supply line, which will be referred to herein as a “center supply line 54 ,” extending through the center of the center body 52 . An elongated internal passage or secondary flow annulus 53 is defined between the outer wall of the center body 52 and the center supply line 54 , which can extend axially toward the pilot nozzle 40 from a forward position adjacent the head end 27 . A central supply line 54 may similarly extend axially between the forward ends of the central body 52 where it may form a connection to a fuel source (not shown) through the head end 27 . The central supply line 54 may have a downstream end that is arranged at the rear end of the central body 52 and may provide a supply of fuel that is ultimately injected into the mixing tube 41 of the pilot nozzle 40 .

The main fuel supply to the fuel nozzles 12 may be directed to the combustion chamber 32 of the combustor 16 through a plurality of swirler vanes 56, as shown in FIG. The fixed vane of the annular belt 51. According to aspects of the present invention, the swirler vanes 56 may define a so-called “swozzle” type fuel nozzle in which a plurality of vanes 56 extend radially between the center body 52 and the peripheral wall 50 . As shown schematically in FIG. 3 , each swirler vane 56 of the swozzle is desirably provided with an internal fuel conduit 57 terminating in a fuel injection port 58 through which the main fuel supply (which flows from Arrows) are introduced from the fuel injection port 58 into the main air flow guided through the main flow annulus 51 . As this primary air flow is directed relative to the swirler vanes 56 , a swirl pattern is imparted which, it will be appreciated, promotes mixing of the air and fuel supply within the primary flow annulus 51 . Downstream of the swirler vanes 56 , the swirling air and fuel supply brought together within the flow annulus 51 may continue to mix before being expelled into the combustion chamber 32 for combustion. As used herein, the primary flow annulus 51 may be referred to as the "parent nozzle" when distinguished from the pilot nozzle 40, and the fuel-air mixture brought together within the primary flow annulus 51 may be referred to as originating from the " Inside the "Female Nozzle". When these designations are used, it will be appreciated that fuel nozzle 12 includes parent nozzles and pilot nozzles, and that each of these injects a separate fuel and air mixture into the combustion chamber.

The center body 52 may be described as comprising axially stacked sections, with the pilot nozzle 40 being the axial section disposed at the downstream or rear end of the center body 52 . According to the exemplary embodiment shown, pilot nozzle 40 includes a fuel plenum 64 disposed about the downstream end of central supply line 54 . As shown, fuel plenum 64 may be in fluid communication with central supply line 54 via one or more fuel ports 61 . Accordingly, fuel may travel through supply line 54 to enter fuel plenum 64 via fuel port 61 . Pilot nozzle 40 may also include an annular centerbody wall 63 disposed radially outward from fuel plenum 64 and desirably concentric about central axis 36 .

As mentioned, the pilot nozzle 40 may include a plurality of axially elongated hollow mixing tubes 41 disposed immediately outside of the fuel plenum 64 . The pilot nozzle 40 may be axially bounded by an upstream face 71 and a downstream face 72 . As shown, the mixing tube 41 may extend axially through the centerbody wall 63 . A plurality of fuel ports 75 may be formed in the centerbody wall 63 for supplying fuel from the fuel plenum 64 into the mixing tube 41 . Each of the mixing tubes 41 may extend axially between an inlet 65 formed by an upstream face 71 of the pilot nozzle 40 and an outlet 66 formed by a downstream face 72 of the pilot nozzle 40 . So configured, air flow can be directed from the auxiliary flow annulus 53 of the center body 52 into the inlet 65 of each mixing tube 41 . Each mixing tube 41 may have at least one fuel port 75 in fluid communication with fuel plenum 64 such that fuel flow exiting fuel plenum 64 is passed into each mixing tube 41 . The resulting fuel-air mixture may then travel downstream in each mixing tube 41 and may then be injected into combustion chamber 32 from outlet 66 formed through downstream face 72 of pilot nozzle 40 . It will be appreciated that, considering the linear configuration and axial orientation of mixing tube 41 shown in FIGS. . Although the fuel-air mixture tends to diffuse radially from each mixing tube 41 after injection into the combustion chamber 32, applicants have found that radial diffusion is not significant. In fact, studies have shown that the equivalence ratio (i.e., the air/fuel ratio) at the section of the combustion outlet plane 44 located directly downstream of the outlet 66 of each mixing tube 41 may be The equivalence ratio left at the section of the combustion outlet plane 44 at almost twice. The high equivalence ratio at a location just downstream of the outlet 66 of each mixing tube 41 can continuously and efficiently ignite the fuel-air mixture passing through the parent nozzle, and thus can ignite the fuel-air mixture even when the flame is in a lean blowout ("LBO") condition. Used to stabilize flames when operating nearby.

6 and 7 include simplified side views comparing different orientations of a single mixing tube 41 within pilot nozzle 40 relative to central axis 36 of fuel nozzle 12 (ie, as may be defined by peripheral wall 50 ). Figure 6 shows the mixing tube 41 having an axial configuration, which is the configuration discussed above with respect to Figures 3-5. As noted, the mixing tube 41 is aligned generally parallel to the central axis 36 so that the fuel-air mixture discharged therefrom (i.e., from the outlet 66) has a discharge direction extending downstream approximately parallel to the central axis 36 of the fuel nozzle 12. direction ("discharge direction")80.

As shown in FIG. 7 , according to an alternative embodiment of the present invention, the mixing tube 41 includes an angled outlet section 79 at the downstream end that is angled or tangentially angled relative to the central axis 36 of the fuel nozzle 12 . Towards. Constructed in this manner, the fuel-air mixture flowing from the outlet 66 has a discharge direction 80 extending from and following the tangential oblique orientation of the oblique outlet section 79 . As used herein, angled outlet section 79 may be defined with respect to an acute tangential angle 81 relative to axial reference line 82 (which, as used herein, is defined as a reference parallel to central axis 36 ). line) is formed in the downstream direction.

As discussed in more detail below, performance advantages for pilot nozzles 40 may be realized by configuring several mixing tubes to include this oblique orientation. Typically, mixing tubes 41 may each be similarly constructed and arranged in parallel, although certain embodiments discussed in greater detail below include exceptions to this. The extent to which the oblique outlet section 79 of the mixing tube 41 is tangentially angled, ie the magnitude of the tangential angle 81 formed between the discharge direction 80 and the axial reference line 82 , can vary. It will be appreciated that the tangential angle 81 may depend on several criteria. Furthermore, while results may be optimal at certain values, various levels of desired performance benefits may be achieved across a wide range of values for tangential angle 81 . Applicants have been able to identify several preferred embodiments which will now be disclosed. According to one embodiment, the tangential angle 81 of the oblique mixing tube 41 comprises a range between 10° and 70°. According to another embodiment, the tangential angle 81 comprises a range between 20° and 55°. Finally, according to the last embodiment, the mixing tube 41 is preferably configured such that the tangential angle 81 is between approximately 40° and 50°.

Although the simplified version shown in Figure 7 shows only one mixing tube 41, each of the mixing tubes 41 may have a similar configuration and may be oriented parallel with respect to each other. When the angled orientation is applied consistently to each of the plurality of mixing tubes 41 included in the pilot nozzle 40 , it will be appreciated that the tangential orientation of the discharge direction is directly downstream of the downstream face 72 of the pilot nozzle 40 Create a vortex. As discovered for the applicant, this vortex can be used to achieve certain performance advantages which will be described in more detail below. According to one exemplary embodiment, the mixture exiting the mixing tube 41 may be made to "co-swirl" with the swirling fuel-air mixture exiting the primary flow annulus 51 (i.e., wherein the primary flow annulus 51 comprises a swirling flow In the case of the vane 56).

As described with respect to several alternative embodiments provided below, the mixing tube 41 may be configured to achieve this tangentially angled discharge direction 80 in a number of ways. For example, a mixing tube 41 comprising linear segments joined at elbows (as in Figure 7) may be used to angle the discharge direction. In other cases, as provided below, mixing tube 41 may be curved and/or helically formed to achieve a desired discharge direction. Additionally, a combination of linear segments and curved or helical segments may be used, as well as any other geometry that allows the exit flow of the mixing tube 41 to exit at a tangential angle relative to the central axis 36 of the primary flow annulus 51 .

8-12 illustrate an exemplary embodiment including a mixing tube 41 having an angled or oblique configuration according to the present invention. FIG. 8 shows an exemplary helical configuration for the mixing tube 41 and is also arranged to show an alternative preferred configuration through which fuel and air may be delivered to the mixing tube 41 leading to the nozzle 40 . In this case, the outboard fuel passage 85 is arranged within the center body wall 63 and extends axially from the upstream connection with the fuel conduit 57, as shown in Figures 3 and 4, which also supplies fuel to the swirl flow The port 58 of the vane 56. Thus, considering the configuration of FIG. 8 , instead of delivering fuel from fuel plenums positioned radially inward with respect to mixing tube 41 , fuel is delivered from fuel passage 85 arranged at the immediate outer side of mixing tube 41 .

It will be appreciated that the outboard fuel passages 85 may be formed as several discrete tubes or annular passages formed around the circumference of the center body 52 to coincide with the location of the mixing tube 41 as desired. One or more fuel ports 75 may be formed to fluidly connect outboard fuel passage 85 to each of mixing tubes 41 . In this manner, the upstream end of each of the mixing tubes 41 may be connected to a fuel source. As further illustrated, an auxiliary flow annulus 53 may be formed within the center body 52 and extend axially therethrough for delivering an air supply into each of the inlets 65 of the mixing tube 41 . Unlike the embodiment of FIGS. 3 and 4 , it will be appreciated that the centrally disposed central supply line 54 of the central body 52 is not used to deliver fuel to the mixing tube 41 . Even so, a central supply line 54 may be included to provide or allow for other fuel types for the fuel nozzles 12 . In any event, the internal passage or auxiliary flow annulus 53 may be formed as an elongated passage defined between a central structure, such as the outer surface of the central supply line 54 , and the inner surface of the central body wall 63 . Other configurations are also possible.

Similar to the configuration taught in FIG. 7 , each of the mixing tubes 41 may include an angled outlet section 79 that is angled tangentially relative to the central axis 36 of the fuel nozzle 12 . In this manner, the discharge direction 80 for the fuel-air mixture moving through the mixing tube 41 may be similarly oblique relative to the central axis 36 of the fuel nozzle 12 . According to the preferred embodiment of FIGS. 8 to 10 , each of the mixing tubes 41 comprises an upstream linear section 86 transitioning into a downstream helical section 87 which is curved around the central axis 36 as indicated. In one embodiment, the fuel ports 74 are located in the upstream linear section 86 and the downstream helical section 87 facilitates mixing of the fuel and air causing the components to change direction within the mixing tube 41 . This change in direction has been found to create secondary flow and turbulence that promotes mixing between the fuel-air moving therethrough such that a well-mixed fuel-air mixture emerges from the mixing tube 71 in the desired angled exit direction.

According to a preferred embodiment, a plurality of mixing tubes 41 are arranged around the circumference of the pilot nozzle 40 . For example, between ten and fifteen tubes may be defined within the center body wall 63 . The mixing tubes 41 may be spaced at regular circumferential intervals. The discharge direction 80 defined by the angled outlet section 79 may be configured such that it coincides with or is in the same direction as the direction of the vortex formed by the swirler vanes 56 within the primary flow annulus 51 . More specifically, according to a preferred embodiment, angled outlet section 79 may be angled in the same direction as swirler vanes 56 so as to create a flow that swirls in the same direction about central axis 36 .

Another exemplary embodiment is provided in FIG. 11 which includes a mixing tube 41 having a curved helical form for the entire mixing length of the mixing tube 41. As used herein, the mixing length of the mixing tube 41 is the axial length between the location of the initial (ie, furthest upstream) fuel port 75 and the outlet 66 . It will be appreciated that each of the mixing tubes 41 may include at least one fuel port 75 . According to alternative embodiments, each mixing tube 41 may include a plurality of fuel ports 75 . Fuel ports 75 may be spaced axially along the mixing length of mixing tube 41 . However, according to the preferred embodiment, the fuel port 75 is positioned or concentrated toward the upstream end of the mixing tube 41, which causes the fuel and air to gather together very early, so more can occur before the combined flow is injected from the outlet 66 into the combustion chamber 32. the mix of.

According to another embodiment, as shown in FIG. 12 , the angled portion of mixing tube 41 may be limited to a section immediately downstream of mixing tube 41 , which is shown to represent an axially narrow length adjacent outlet 66 . With this configuration, beneficial results can still be achieved since the desired rotation pattern can still be induced in the common discharge from the mixing tube 41 . However, the level of fuel-air mixing within mixing tube 41 may be less than optimal.

Figures 13 to 16 illustrate additional embodiments in which linear and helical mixing tubes 41 are combined. 13 and 14 respectively illustrate a preferred manner in which linear axial mixing tubes 41 (i.e., those extending parallel to the central axis 36) may be arranged within the centerbody wall 63 of the nozzle 40 together with the oblique mixing tubes 41. Side view and perspective view. As shown, the oblique mixing tube 41 may be formed helically. It will be appreciated that the angled mixing tube 41 may also be formed with a linear segmented configuration including bends or elbow joints between segments, such as the example of FIG. 12 . It will be appreciated that FIG. 15 provides an inlet view showing the inlet 65 of the axial and oblique mixing tube 41 on the upstream face 71 of the pilot nozzle 40 . FIG. 16 provides an outlet view showing a representative configuration of the outlet 66 of the axial and diagonal mixing tube 41 on the downstream face 72 of the pilot nozzle 40 . According to an alternative embodiment, the oblique mixing tubes 41 may be configured to co-rotate, ie swirl about the central axis 36 in the same direction as the swirling mixing of the female nozzles of the main flow annulus 51 .

Both axial and diagonal mixers can be supplied from the same air and fuel sources. Alternatively, each of the different types of mixing tubes may be fed from a different supply so that the levels of fuel and air reaching the mixing tubes are significantly different or controllable. More specifically, it will be appreciated that supplying each tube type with its own controllable air and fuel supply enables mechanical operational flexibility which may allow adjustment or adjustment of the fuel-to-air ratio or equivalence ratio within the combustion chamber . Different settings may be used throughout a range of loads or operating levels, which, as discovered by the applicants of the present disclosure, provides an approach to address specific areas of concern that may occur at different engine load levels.

For example, in the run-down mode of operation, when the combustion temperature is lower relative to the base load, CO is the emission of major concern. In these cases, the equivalence ratio can be increased to increase the tip zone temperature in degrees for improved CO combustion. This is because the angled mixing tube acts to direct the parent nozzle reactants back to the nozzle tip, the temperature in the tip region (ie, the tip of the nozzle) can remain cooler than if the tubes were not tangentially angled. In some cases, this can contribute to excess CO in the combustor's exhaust. However, by adding or increasing axial momentum through the addition of axial mixing tubes (as shown in Figures 13-16), the amount of recirculation flow can be varied, limited or controlled, and thus, achieved for controlling tip zone temperature device. This method can thus be used as an additional way of improving combustion characteristics and emission levels when the engine is operating in certain modes.

According to other embodiments, for example, the present invention includes the use of conventional control systems and methods for manipulating the level of air flow between two different types of mixing tubes. According to one embodiment, the gas flow to the axial mixing tube 41 may be increased to prevent cooler reaction products from the parent nozzle from being directed back into the tip region of the pilot nozzle 40 . This can be used to increase the temperature of the extremity zone, which can reduce the level of CO.

In addition, the combustion dynamics can have a strong correlation with the shear forces in the reaction zone. By adjusting the amount of air directed through each of the different types of mixing tubes (ie, oblique and axial), the amount of shear can be adjusted to a level that positively affects combustion. This can be achieved by configuring the metering holes to deliver uneven air volumes to different types of mixing tubes. Alternatively, active control devices may be installed and actuated via conventional methods and systems in order to vary the air supply level during operation. Additionally, control logic and/or control feedback loops can be created so that control of the device is responsive to the operating mode or measured operating parameter. As mentioned, this may result in changes in control settings depending on the operating mode of the engine (such as when operating at full load or a reduced load level) or in response to measured operator parameter readings. These systems may also include the same type of control method for varying the amount of fuel supplied to different types of mixing tubes. This can be achieved through pre-configured component configurations (ie, orifice sizes, etc.) or through more active real-time control. It will be appreciated that operating parameters (such as temperature within the combustion chamber, sound changes, reactant flow patterns) and/or other parameters related to combustor operation may be used as part of the feedback loop in these control systems.

It will be appreciated that these types of control methods and systems are also applicable to other embodiments discussed herein, including any of those embodiments that involve combining mixing tubes in the same pilot nozzle with different configurations or swirl directions (including, for example, the counter-swirl embodiments discussed with respect to FIGS. way of the discharge direction of the radial component). Additionally, these types of control methods and systems are applicable to other embodiments discussed herein, including any of those embodiments that involve combining mixing tubes with different configurations or swirls in the same pilot nozzle. direction (such as the reverse scroll embodiment discussed with respect to FIGS. 17-20 ).

Additionally, these methods and systems are applicable to pilot nozzle configurations in which each of the mixing tubes is configured in the same manner and aligned parallel to each other. In these situations, the control system is operable to control the combustion process by varying the air and/or fuel separation between the parent nozzle and the pilot nozzle to affect combustion characteristics. According to other embodiments, the control method and system may be configured such that fuel and/or air supply levels are varied unevenly around the circumference of the pilot nozzle, which may be used, for example, to interrupt certain flow patterns, or to prevent unwanted sound generation. These actions may be taken on a priority basis or in response to detected anomalies. For example, fuel and air supplies can be increased or decreased for specific subsets of mixing tubes. The action may be taken on a predetermined periodic basis, in response to measuring an operating parameter or other condition.

FIGS. 17-20 illustrate additional exemplary embodiments in which the angled mixing tube 41 has a counter-vortex configuration defined within the centerbody wall 63 . 17 and 18 illustrate side and perspective views, respectively, of a representative configuration of the counter-vortex helical mixing tube 41 within the centerbody wall 63 . It will be appreciated that FIG. 19 provides an inlet view of the pilot nozzle 40 illustrating a representative configuration of the inlet 65 of the counter-vortex helical mixing tube 41 on the upstream face 71 of the pilot nozzle 40 . FIG. 20 provides an exit view of the pilot nozzle 40 illustrating the preferred manner in which the outlet 66 of the counter-vortex helical mixing tube 41 may be arranged on the downstream face 72 of the pilot nozzle 40 . It will be appreciated that the addition of counter-vortex oblique mixing tubes 41 can be used in the manner discussed above to control the temperature of the tip region of the nozzle. In addition, the oblique mixing tube of the counter-vortex promotes greater mixing in the tip region due to the increased shear induced by the pilot flow through the counter-vortex, which is advantageous for certain operating conditions.

21 and 22 illustrate an alternative embodiment in which a radial component is added to the discharge direction of the mixing tube 41 . It will be appreciated that Figure 21 shows an exit view of an alternative embodiment of the mixing tube including an outboard component to the discharge direction. In contrast, Figure 22 shows an exit view of an alternative embodiment of the mixing tube including an inboard component to the discharge direction. In these ways, the angled mixing tubes of the present invention can be configured to have both radial and tangential components in the discharge direction. According to an alternative embodiment, the mixing tube may be configured with a discharge direction having a radial component but no circumferential component. Thus, inboard and outboard radial components can be added to either the axial or diagonal mixing tubes. According to an exemplary embodiment, the angle of the inner and/or outer radial component may comprise a range between 0.1° and 20°. As mentioned above, a radial component can be included on a subset of mixing tubes and thus can be used to manipulate the shear effect of the pilot nozzles to advantageously control recirculation.

FIG. 23 schematically shows the results of a directional flow analysis of a pilot nozzle 40 with an axial mixing tube 41 comprising an axial outlet section, while FIG. 24 schematically shows the results of an oblique mixing tube 41 with an oblique outlet section. Results of a directional flow analysis. As shown, the axial mixing tube 41 may oppose the reverse flow created by the swirl caused by the parent nozzle, which may compromise flame stability and increase the likelihood of lean blowout. In contrast, the angled outlet section may be configured to swirl the pilot reactant around the fuel nozzle axis in the same direction as the swirl formed in the main or master nozzle. As the results indicate, this vortex proved to be beneficial, as the pilot nozzle now works in cooperation with the parent nozzle to create and/or reinforce the central recirculation zone. As shown, the recirculation zone associated with the angled mixing tube includes many more pronounced and concentrated recirculations that result in entrained reactants returning to the outlet of the fuel nozzle from a location far downstream. It will be appreciated that the central recirculation zone is the basis for swirl stable combustion as the products of combustion are directed back to the nozzle outlet and fresh reactants are introduced in order to ensure ignition of those reactants and thereby continue the process. Thus, angled mixing tubes can be used to improve recirculation and thereby further stabilize combustion, which can be used to further stabilize a lean fuel-air mixture that can allow for lower NOx emission levels. Additionally, as discussed, pilot nozzles with angled mixing tubes may allow for performance benefits related to CO emissions levels. This is achieved due to the enrichment cycle forming a localized hot zone at the exit of the fuel nozzle, which attaches the nozzle flame and allows further CO burnout. Additionally, the significant recirculation created by the angled mixing tubes of the present invention can aid in CO burnout by mixing the products produced during combustion with the CO back into the central recirculation zone so that the CO escapes without being burned. The chances of getting out are as small as possible.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (22)

1. A fuel nozzle in a gas turbine combustor, said fuel nozzle comprising: an axially elongated central body; an axially elongated peripheral wall formed about the center body so as to define a primary flow annulus therebetween, wherein the peripheral wall defines a central axis of the fuel nozzle; a primary fuel supply and a primary air supply in fluid communication with the upstream end of the primary flow annulus; and a pilot nozzle comprising a downstream section of the central body, the pilot nozzle comprising: axially elongated mixing tubes defined within the centerbody wall, each of said mixing tubes being between an inlet defined by an upstream face of said pilot nozzle and an outlet formed by a downstream face of said pilot nozzle elongation between a fuel port positioned between the inlet and the outlet of each of the mixing tubes for connecting each of the mixing tubes to an auxiliary fuel supply; and an auxiliary air supply configured to be in fluid communication with the inlet of each of the mixing tubes; Wherein the plurality of said mixing tubes comprises a diagonal mixing tube which is angled relative to said central axis of said fuel nozzle so as to induce a downstream swirl in a common discharge therefrom. 2. The fuel nozzle of claim 1, wherein at said outlet formed by said downstream face of said pilot nozzle, said angled mixing tubes each include said tangentially angled orientation of the central axis; wherein said common discharge comprises a combined fuel and air discharge from said plurality of said diagonal mixer tubes; and Wherein the inclined mixing tube is configured such that the vortex of the common discharge swirls in the same direction as the vortex induced by the swirler vanes of the main flow annulus. 3. The fuel nozzle of claim 1 wherein said angled mixing tubes each include an outlet section comprising an axially narrow downstream region of said angled mixing tube adjacent said outlet a section configured to impart an exit direction to the discharge of fuel and air therefrom; wherein the angled mixing tube is configured such that the discharge direction defines an acute tangential discharge angle extending downstream relative to the central axis of the fuel nozzle; and The tangential discharge angle includes angles between 10° and 70°. 4. The fuel nozzle of claim 1 wherein said mixing tubes each include an outlet section comprising an axially narrow downstream section of said mixing tube adjacent said outlet, said outlet region the segment defines a central axis passing therethrough; and Wherein the angled mixing tube is configured such that continuation of the central axis of the outlet section includes an acute tangential discharge angle relative to a downstream continuation of the central axis of the fuel nozzle. 5. The fuel nozzle of claim 4, wherein each of said mixing tubes of said pilot nozzle comprises said inclined mixing tubes and are arranged parallel with respect to each other; wherein said peripheral wall and said central body wall each comprise a cylindrical shape, and wherein said peripheral wall is concentrically disposed about said central body wall; and Wherein said tangential discharge angle comprises an angle between 10° and 70°. 6. The fuel nozzle of claim 4, wherein said center body comprises axially stacked sections including: a forward section including said secondary fuel supply and said secondary air supply; and configured to the rear section of the pilot nozzle; wherein said front section of said central body comprises: an axially extending central supply line; and, an auxiliary flow annulus formed around said central supply line, said auxiliary flow annulus extending towards said central body extending axially between the connection to the air source formed by the upstream end of the , and the upstream face of the pilot nozzle; and Wherein the central body wall defines an outer wall of the central body and defines an outer boundary of the auxiliary flow annulus. 7. The fuel nozzle of claim 6 wherein said primary flow annulus comprises a swozzle comprising: a plurality of swirler vanes extending radially across the primary flow annulus; and a fuel passage extending through the swirler vane to connect a fuel port formed through an outer surface of the swirler vane to a fuel plenum; wherein said swirler vanes comprise a tangentially angled orientation relative to said central axis for causing downstream flow therefrom to swirl about said central axis in a first direction; and Wherein the fuel ports of each of the slanted mixing tubes include lateral fuel ports for injecting fuel through openings formed through sidewalls of the slanted mixing tubes. 8. The fuel nozzle of claim 7, wherein from the connection formed by the angled mixing tube, the fuel port extends in an outboard direction to connect with the auxiliary fuel supply; and Wherein said auxiliary fuel supply comprises fuel passages formed just outside said diagonally cut mixing tube and within said centerbody wall. 9. The fuel nozzle of claim 8, wherein the fuel plenum is disposed inboard of the swirler vane; and wherein the fuel passage extends axially from a connection formed by the fuel plenum to the downstream face of the pilot nozzle and includes a connection therebetween to the fuel port of the inclined mixing tube . 10. The fuel nozzle according to claim 7, wherein from the connection formed by the mixing tube, the fuel port extends in an inboard direction to match the internal fuel pressure formed at the downstream end of the central supply line. room connections; and Wherein said fuel port for each of said angled mixing tubes includes an upstream position relative to air flow therethrough. 11. The fuel nozzle of claim 7, wherein each of said angled mixing tubes includes a plurality of said fuel ports; and Wherein the plurality of fuel ports includes an upstream concentration relative to air flow therethrough. 12. The fuel nozzle of claim 7, wherein each of said angled mixing tubes is configured to accept air flow through said inlet and fuel flow through said fuel port for passage through said fuel port. discharge its mixture through the said outlet; wherein said outlet is in fluid communication with a combustion chamber of said burner, wherein the angled mixing tubes each include a mixing length defined between an upstream fuel port and the outlet; and Wherein, for said mixing length, said oblique mixing tubes each comprise a segmented configuration comprising an upstream segment and a downstream segment to each side of a junction, said junction markings for said Diagonal mixing tube changes direction. 13. The fuel nozzle of claim 12 wherein said angled mixing tubes each comprise a configuration wherein said upstream segment is linear and said downstream segment is curved. 14. The fuel nozzle of claim 12 wherein said angled mixing tubes each comprise a configuration wherein said upstream segment is linear and said downstream segment is linear. 15. The fuel nozzle of claim 12 wherein said angled mixing tubes each comprise a configuration wherein said upstream segment is curved and said downstream segment is linear. 16. The fuel nozzle of claim 12 wherein said angled mixing tubes each comprise a configuration wherein said upstream segment is curved and said downstream section is curved. 17. The fuel nozzle of claim 12 wherein said angled mixing tubes each comprise a configuration wherein said upstream segment is linear and axially oriented and said downstream segment is curved and helically formed about the central axis of the fuel nozzle; and Wherein the upstream section includes a mixing length that is less than half the mixing length of the diagonal mixing tube. 18. The fuel nozzle of claim 7, wherein said angled mixing tubes each include a mixing length defined between an upstream fuel port and said outlet; and Wherein, for said mixing length, said diagonal mixing tubes each comprise a non-segmented configuration, wherein said mixing tubes maintain a constant form over said mixing length. 19. The fuel nozzle of claim 7, wherein said tangential discharge angle comprises an angle between 20° and 55°. 20. The fuel nozzle of claim 19 wherein said angled mixing tubes comprise a parallel orientation relative to each other such that said tangential discharge angles of said angled mixing tubes comprise parallel Configuration. 21. The fuel nozzle of claim 20 wherein said angled mixing tube is configured such that said swirl of said common discharge flows along said swirler as entrained by said primary flow annulus The direction of flow downstream of the vortex generated by the vanes defines the first directional vortex. 22. The fuel nozzle of claim 21 wherein said pilot nozzle includes between five and twenty-five of said angled mixing tubes; and Wherein said angled mixing tubes are circumferentially spaced at regular intervals within said centerbody wall.