EP2233836B1 - Swirler, method for reducing flashback in a burner with at least one swirler and burner - Google Patents

Description

The present invention relates to a swirl generator with a central fuel distributor element and to a burner with at least one swirl generator. In addition, the invention relates to a method for avoiding flashback in a burner comprising at least one swirl generator with a central fuel distributor element.

Gas turbine burners with a central fuel distributor elements and the swirl generators surrounding the fuel distributor elements are, for example, in DE 10 2007 004 394 A1 , in US 2004/0055306 A1 and in US 6,082,111 described. At the in US 2004/055306 A1 and in US 6,082,111 described the swirl generator extends from the central fuel distributor element to a surrounding the central fuel distributor element, an axial flow channel for combustion air limiting wall. The burners each comprise a plurality of such arrangements. In such burners, the profiles of the fuel injected into the flow channel are designed such that only very little fuel is supplied to the zone around the central fuel distributor element, so that only a very lean mixture forms in this zone. The reason for this is that a flashback should be avoided. In fact, a zone of reduced flow velocity is created in the vortices that form downstream of the central distribution element. If too much fuel is injected in the vicinity of the central distributor element, it may happen that this central region is supplied with too low a flow rate with too much fuel, which can lead to flashback, which in the case of high loads very high temperatures downstream of the swirl generator are connected. However, the very lean mixture in the region of the central fuel distributor element leads, by reducing the quality of the mixture, to an increase in the NO _x emissions, which, however, are accepted in order to avoid a flashback.

To avoid a flashback is in DE 10 2007 004 394 A1 proposed to recesses the swirl vanes near the central fuel distributor element such that the swirl vanes near the central fuel distributor element are shorter in the axial direction than remote from the distributor element. As a result, the curvature of the swirl vanes in the circumferential direction is not made as wide in the vicinity of the central fuel distributor element as far away from the central distributor element. In this way it is achieved that the air flowing through the flow channel near the distributor element undergoes less swirl and thereby flows faster in the axial direction than further away from the distributor element. At the inner edge of the swirl blades facing the distributor element, a cylindrical wall can also be present in the region of the recess, which separates the channel section with little vortex formation from the channel section with high vortex formation.

The US 2008/0280238 A1 discloses a burner having a centrally located pilot burner and an outer wall surrounding the central pilot burner, defining an axial combustion air flow passage, and a partition wall surrounding the central pilot burner and located radially inwardly of the outer wall, forming the flow passage into a radially inner passage section and a radially outer passage section separates. In the radially inner channel portion, a flow unifying aperture is arranged, whereas in the outer channel portion swirl blades are arranged, which extend in the radial direction to the outer wall and the flowing combustion air impose a tangential flow component. An annular fuel distributor ring extends around the outside wall and around the outside feeds fuel lines which extend through the outer channel section and protrude into the inner channel section.

The DE 10 2008 044448 A1 discloses a gas turbine pre-mixer having a central hub and an outer wall surrounding the hub, wherein the flow channel located between the hub and outer wall is divided by a partition wall into an inner and an outer channel section. In both the inner and in the outer channel portion swirl vanes are arranged, which impart a twist to the flow.

Compared to the cited prior art, it is an object of the present invention to provide an advantageous swirl generator and an advantageous burner. A further object of the present invention is to provide an advantageous method for avoiding flashback in a burner with at least one swirl generator.

The above objects are achieved by a swirl generator according to claim 1, a burner according to claim 10 and a method for avoiding flashback according to claim 11. The dependent claims contain advantageous embodiments of the invention.

A swirl generator according to the invention comprises a central fuel distributor element, an outer wall surrounding the central fuel distributor element and defining an axial flow channel for combustion air, swirl vanes extending radially to the outer wall and imparting a tangential flow component to the flowing combustion air, and radially surrounding the central fuel distributor element inside the outer wall partition. The partition separates the flow channel into a radially inner channel section and a radially outer channel section. Here, the partition in the axial direction of the swirl generator at least over the axial Length of the swirl blades, but in particular also extend beyond the axial length. The radially inner channel section passes the combustion air without imparting a tangential flow component, fuel pipelines extending through the radially inner channel section to the swirl vanes in the radially outer channel section.

By completely avoiding a tangential component in the inner channel region, a flow of high axial flow velocity enveloping this element around the central fuel distributor element can be generated which reliably helps to prevent a flashback. But also the generation of a counter-rotation in the inner channel section, ie a swirl whose orientation is opposite to the swirl in the outer channel section, can help prevent flashback, as this positively influences the flow conditions in the vortex downstream of the central fuel distributor element.

The complete avoidance of a tangential flow component in the inner channel section can be achieved in particular in that no swirl vanes are present in this channel section at all. To supply fuel to the swirl vanes present in the radially outer channel section, fuel pipes extend through the radially inner channel section to the swirl vanes in the radially outer channel section. To avoid stalls on the fuel pipes, these advantageously have a circular or drop-shaped cross section.

In order to achieve a particularly uniform fuel profile in the inner channel section, it is advantageous if there are fuel outlet openings in the fuel piping. These can in particular be arranged so that they the fuel substantially perpendicular to the flow direction of the combustion air in the radially inner channel section into the combustion air. Likewise, in the swirl vanes in the radially outer channel section fuel outlet openings may be present, which may be arranged in particular so that they inject the fuel substantially perpendicular to the flow direction of the combustion air in the radially outer channel section into the combustion air. As a result, a uniform fuel profile can also be achieved in the radially outer channel section. However, the injection direction does not necessarily have to be perpendicular to the flow direction of the combustion air. Rather, the injection direction can basically be chosen freely. Thus, for example, as an alternative or in addition to the supply perpendicular to the flow direction of the combustion air, the fuel can also be supplied perpendicular to the radial direction and / or opposite to the flow direction of the combustion air flowing through the flow channel and / or parallel to the flow direction of the combustion air flowing through the flow channel. Other directions and combinations not expressly stated are also possible: this applies both to the fuel supply in the inner duct section and to the fuel supply in the outer in the outer duct section.

In order to further increase the axial flow velocity in the vicinity of the central fuel distributor element, the dividing wall may at least partially have a conical shape, wherein the opening cross section of the radially inner channel section decreases in the direction of flow of the combustion air.

In a development of the swirl generator according to the invention, the dividing wall projects beyond the outflow-side end of the outer wall. This development can be realized both in a conical partition, as well as in a non-conical partition.

The relatively complicated compared to swirl generators according to the prior art geometric shape of the invention Swirl generator can be realized advantageously when the swirl generator is designed as a casting. Once a casting model is made, the cost of producing the swirl generator of the present invention as a casting is not significantly different from the production cost of prior art swirlers.

An inventive burner is equipped with at least one swirl generator according to the invention. As a result, the advantages described with respect to the swirl generator can be realized in a burner, which in particular can be a gas turbine burner.

The invention also provides a method of preventing flashback in a combustor comprising at least one swirl generator with a central fuel distribution element and an outer wall surrounding the central fuel distribution element defining an axial combustion air flow passage. The combustion air flowing through the flow channel is imparted a tangential flow component in a radially outer channel region. In contrast, in a radially inner region, the combustion air flowing through the flow channel does not impart a tangential flow component, fuel being directed through fuel conduits which extend through the radially inner channel section to the swirl vanes in the radially outer channel section.

The advantages which can be achieved with the method according to the invention with regard to avoiding a flashback have already been described with reference to the swirl generator according to the invention. This description is referred to to avoid repetition.

A particularly uniform fuel profile can be generated when fuel is supplied to the combustion air flowing through the flow channel. The fuel can in this case in particular perpendicular to the flow direction of the is mixed by the flow channel flowing combustion air and / or perpendicular to the radial direction. An admixing substantially opposite to the flow direction of the combustion air flowing through the flow channel and / or parallel to the flow direction of the combustion air flowing through the flow channel is possible alternatively or in addition to the aforementioned variants.

• Figur 1 zeigt eine Gasturbine in einer stark schematisierten Darstellung.
• Figur 2 zeigt einen Gasturbinenbrenner in einer perspektiveschen Darstellung.
• Figur 3 zeigt einen Drallerzeuger des Brenners aus Figur 2 in einer perspektivischen Darstellung.
• Figur 4 zeigt den Drallerzeuger aus Figur 3 in einer teilweise geschnittenen Darstellung.
• Figur 5 zeigt den Drallerzeuger aus Figur 3 in einem Schnitt entlang seiner Längsachse.
• Figur 6 zeigt eine alternative Ausgestaltung des Drallerzeugers in einer teilweise geschnittenen Darstellung.
• Figur 7 zeigt eine weitere alternative Ausgestaltung des Drallerzeugers in einer teilweise geschnittenen Darstellung.

Further features, properties and advantages of the present invention will become apparent from the following description of embodiments with reference to the accompanying figures.

• FIG. 1 shows a gas turbine in a highly schematic representation.
• FIG. 2 shows a gas turbine burner in a perspective view.
• FIG. 3 shows a swirl generator of the burner FIG. 2 in a perspective view.
• FIG. 4 shows the swirl generator FIG. 3 in a partially cut representation.
• FIG. 5 shows the swirl generator FIG. 3 in a section along its longitudinal axis.
• FIG. 6 shows an alternative embodiment of the swirl generator in a partially sectioned view.
• FIG. 7 shows a further alternative embodiment of the swirl generator in a partially sectioned view.

The following is based on FIG. 1 showing a highly schematic sectional view of a gas turbine, explaining the structure and function of a gas turbine. The gas turbine 1 comprises a compressor section 3, a combustion section 4, which in the present embodiment comprises a plurality of tube combustion chambers 5 with burners 6 arranged thereon, but in principle may also comprise an annular combustion chamber, and a turbine section 7. A rotor 9, also called a runner, extends extending through all sections and carries in the compressor section 3 compressor blade rings 11 and the turbine section 7 turbine blade rings 13. Between adjacent compressor blade rings 11 and between adjacent turbine blade rings 13 are wreaths of compressor vanes 15 and wreaths of turbine vanes 17 arranged, extending from a housing 19 of the gas turbine 1 extend radially in the direction of the rotor 9.

During operation of the gas turbine 1, air is sucked through an air inlet 21 into the compressor section 3. There, the air is compressed by the rotating compressor blades 11 and directed to the burners 6 in the combustion section 4. In the burners 6, the air is mixed with a gaseous or liquid fuel and the mixture is burned in the combustion chambers 5. The hot combustion exhaust gases under high pressure are then supplied as working medium to the turbine section 7. On their way through the turbine section, the combustion exhaust gases impart impulses to the turbine blades 13, relaxing and cooling. Finally, the expanded and cooled combustion exhaust gases exit the turbine section 7 through an exhaust 23. The transmitted pulse results in a rotational movement of the rotor that drives the compressor and a consumer, such as an electric current generator or an industrial machine. The rings of turbine vanes 17 serve as nozzles for conducting the working medium in order to optimize the momentum transfer to the turbine blades 13.

FIG. 2 shows a burner 6 of the combustion section 4 in a perspective view. As main components, the burner 6 comprises a fuel distributor 27, eight fuel nozzles 29 extending from the fuel distributor 27 and eight swirl generators 31 arranged in the region of the tips of the fuel nozzles 29. The fuel distributor 27 and the fuel nozzles 29 together form a burner housing through which fuel lines extend Extend injection openings, which are arranged within the swirl generator 31 and therefore in FIG. 2 are not recognizable. Through a number of pipe sockets (not shown), the burner can be connected to fuel supply lines. By means of a flange 35, the burner 6 can be attached to a tube combustion chamber so that the fuel nozzles 29 point towards the interior of the combustion chamber.

Although the in FIG. 2 As shown burner 6 has eight fuel nozzles 29, it is also possible to equip it with a different number of fuel nozzles 29. The number of fuel nozzles can be greater than or less than eight, for example For example, six fuel nozzles or twelve fuel nozzles may be present, each having its own swirl generator. Furthermore, a pilot fuel nozzle is usually arranged in the center of the burner. The pilot fuel nozzle is in for clarity FIG. 2 not shown.

During the combustion process, air from the compressor is passed through the swirl generators 31 where it is mixed with fuel. Subsequently, the air-fuel mixture is then burned in the combustion zone of the combustion chamber 5 to form the working medium.

In FIG. 3 a swirl generator of the burner 6 is shown in a perspective view. The swirl generator 31 has a central fuel distributor element 37 which is surrounded by an outer wall 39, which forms an axial flow channel for compressor air. In the flow channel 41 also a central fuel distributor element 37 surrounding and located radially within the outer wall 39 dividing wall 42 is present, which separates the flow channel 41 into a radially inner channel portion 43 and a radially outer channel portion 45. From the dividing wall 42, swirl vanes 47 extend in the radial direction through the radially outer channel section to the outer wall 39. The swirl vanes 47 mediate the flowing through the radially outer channel section 45 compressor air a tangential flow component, so that the air after passing through the swirl generator 31 forms a vortex.

In the radially inner channel section 43 no swirl vanes are present. Instead, starting from the central fuel distributor element 37, fuel pipelines 49 extend in the radial direction to the dividing wall 42 FIG. 4 , which shows a partially sectioned view of the swirl generator 31, can be seen, the fuel pipes 49 have a teardrop-shaped cross section in order to avoid a stall at the trailing edge of the pipes 49.

Instead of a drop-shaped cross-section, however, the pipelines 49 may in principle also have a round cross-section.

The fuel conduits 49 are arranged to be aligned with the swirl vanes 47 in the radially outer passage portion so that a fuel passage 51 may extend in a straight line from the central fuel distributor 37 through the fuel conduits 49 to the swirl vanes 47. The fuel channels 51 are in particular in FIG. 5 which shows a sectional view through the swirl generator 31 along its longitudinal axis. By means of the fuel channels 51, outlet openings 53 in the swirl vanes 47 and outlet openings 55 in the fuel pipes 49 are supplied with fuel. The outlet openings 53, 55 are arranged so that the fuel is injected substantially perpendicular to the flow direction of the compressor air in the radially outer channel portion 45 and the radially inner channel portion 43.

The swirl generator design described causes the compressor air flowing through the radially inner channel section 43 to be imparted with no twist. As a result, the flow velocity of this compressor air in the axial direction is higher than in the compressor air flowing through the radially outer channel section 45, in which part of the axial flow is converted into a tangential flow component. Due to the higher axial flow rate in the radially inner channel portion, ie, in the area adjacent to the central fuel distribution element 37, the emergence of low axial flow rate zones downstream of the central fuel distribution element 37 can be avoided, which in turn results in avoiding flashbacks. This allows more fuel to be injected in the vicinity of the central distributor element 37 compared to the prior art, which reduces the NO _x emissions during combustion.

The partition 42 extends at least over the entire axial length of the swirl vanes 47 in the radially outer channel section 45, so that the supply of a tangential flow component in the radially inner channel section 43 can be reliably avoided. In the present embodiment, the partition wall 42 also extends in the axial direction beyond the arrival and trailing edges of the swirl vanes 47 in order to avoid influencing the compressor air flowing through the radially inner channel section 43 by the swirling air flowing in the radially outer channel section 45.

An alternative embodiment of the swirl generator 31 is shown in FIG FIG. 6 shown. Elements corresponding to the swirl generator of the first embodiment are shown in FIG FIG. 6 are denoted by the same reference numerals as in the first embodiment and will not be explained again to avoid repetition.

The swirl generator 131 of the second embodiment differs from the swirl generator 31 of the first embodiment only by its partition wall 142. Unlike the first embodiment, the partition wall 142 of the second embodiment has a conical portion 144 which causes the opening cross section of the radially inner channel portion 43 reduced toward the output of the swirl generator 131 out. By the conical portion 144, the flow velocity of the compressor air flowing through the radially inner passage portion 43 increases in comparison with the swirl generator 31 of the first embodiment. The central fuel distributor element 37 can thus be surrounded by an air jacket, which has a particularly high axial flow velocity and thus particularly reliably avoids the formation of regions with low flow velocity, and consequently the formation of flashbacks.

Although the partition 142 in the present embodiment only has a conical portion 144 downstream, it may also be conical over its entire axial length.

A third embodiment of the swirl generator according to the invention is in FIG. 7 shown in a partially sectioned view. As with the swirl generator of the second embodiment, even in the swirl generator of the third embodiment, all those elements which do not differ from the first embodiment are denoted by the same reference numerals as in the first embodiment and will not be described again.

The swirl generator 231 of the third exemplary embodiment differs from the swirl generator of the first exemplary embodiment in that swirl blades 149 are also present in the radially inner channel section 43. In contrast to the swirl blades 47 in the radially outer channel section 45, however, suction side and pressure side of the blades are reversed, so that the compressor air in the radially inner channel section through the compressor blades 159 a tangential component is taught, which has a reverse orientation with respect to the axial flow direction than the tangential component, which is imparted to the compressor air in the radially outer channel section 45 by the swirl blades 47 located there. Also by this measure can be avoided flashbacks. Like the fuel piping 49 in the first two embodiments, the swirl vanes 149 in the radially inner passage section 43 have fuel channels 51 and fuel outlets 155 arranged to inject the fuel substantially perpendicular to the flow direction of the air flowing through the radially inner passage section 43.

Although the swirler 231 of the third embodiment is shown in FIG FIG. 7 is shown with a cylindrical partition wall 42, the swirl generator according to the third embodiment also be equipped with an at least partially conical partition, as has been described with reference to the second embodiment.

In the embodiments illustrated in the figures, the partitions do not protrude beyond the downstream end of the respective outer wall. However, the dividing walls can also be extended downstream, as shown in the figures, so that they protrude beyond the downstream end of the outer wall. This applies regardless of whether a partition is conical or not.

The relatively complex geometric shape of the swirl generator according to the described embodiments can be realized in an advantageous manner when the swirl generators are produced as castings.

Claims (13)

1. Swirl generator (31, 131, 231) having

   - a central fuel distributor element (37),

   - an outer wall (39) enclosing the central fuel distributor element (37) and bounding an axial flow channel (41) for combustion air,

   - swirl vanes (47), which extend in a radial direction to the outer wall (39) and give the flowing combustion air a tangential flow component,

   - a separating wall (42, 142) enclosing the central fuel distributor element (37) and being positioned radially within the outer wall (39), which divides the flow channel (41) into a radially inner channel segment (43) and a radially outer channel segment (45),
   characterised in that
   the radially inner channel segment (43) allows the combustion air to pass without giving it a tangential flow component, wherein fuel lines (49) extend through the radially inner channel segment (43) to the swirl vanes (47) in the radially outer channel segment (45).
2. Swirl generator (31, 131, 231) according to claim 1,
   characterised in that
   the separating wall (42, 142) extends in an axial direction at least over the axial length of the swirl vanes (47).
3. Swirl generator (31, 131) according to claim 1 or claim 2,
   characterised in that
   swirl vanes (47) are only present in the radially outer channel segment (45).
4. Swirl generator (31, 131) according to one of claims 1 to 3,
   characterised in that
   the fuel lines (49) have a circular or teardrop-shaped cross section.
5. Swirl generator (31, 131, 231) according to one of claims 1 to 4,
   characterised in that
   fuel outlet openings (55, 155) are present in the fuel lines (49).
6. Swirl generator (31, 131, 231) according to one of claims 1 to 5,
   characterised in that
   fuel outlet openings (53) are present in the swirl vanes (47) in the radially outer channel segment.
7. Swirl generator (131) according to one of claims 1 to 6,
   characterised in that
   the separating wall (142) at least partially has a conical form (144), with the opening cross section of the radially inner channel segment (43) decreasing in the flow direction of the combustion air.
8. Swirl generator (31, 131, 231) according to one of claims 1 to 7,
   characterised in that
   the separating wall projects beyond the downstream end of the outer wall (39).
9. Swirl generator (31, 131, 231) according to one of claims 1 to 8,
   characterised by
   its embodiment as a cast part.
10. Burner (6) having at least one swirl generator (31, 131, 231) according to one of claims 1 to 9.
11. Method for preventing flashback in a burner (6), which comprises at least one swirl generator (31, 131, 231) having a central fuel distributor element (37) and an outer wall (39) enclosing the central fuel distributor element and bounding an axial flow channel (41) for combustion air, wherein the combustion air flowing through the flow channel (41) is given a tangential flow component in a radially outer channel region (45),
    characterised in that
    in a radially inner channel region (43) the combustion air flowing through the flow channel (41) is not given a tangential flow component, wherein fuel is passed through fuel lines (49) which extend through the radially inner channel segment (43) to the swirl vanes (47) in the radially outer channel segment (45).
12. Method according to claim 11,
    characterised in that
    fuel is supplied to the combustion air flowing through the flow channel (41).
13. Method according to claim 12,
    characterised in that
    fuel is supplied to the combustion air flowing through the flow channel (41) perpendicular to the flow direction of the combustion air flowing through the flow channel and/or perpendicular to the radial direction and/or counter to the flow direction of the combustion air flowing through the flow channel and/or parallel to the flow direction of the combustion air flowing through the flow channel.

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