JPH08261417A - Pre-mixing burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the emission of polluting components of liquid fuel or gaseous fuel by arranging a gasifying section extending to the burner front of a mixture burner under a nozzle and coupling the nozzle which feeds the liquid or gaseous fuel with a vortex generator. SOLUTION: At least, one fuel nozzle 12 is arranged inside a through flow path in the operation of a mixture burner 12 with liquid fuel 12a. In the direct upstream of the fuel nozzle 12, at least another vortex generator 4 is arranged. In the down stream of the atomization of the liquid fuel 12a by the synergy of the fuel nozzle 12 and the vortex generator 4, a gasifying section 6 having an enough length is arranged and the gasification of the liquid fuel is completed before the liquid fuel reaches a burner front 9. In the operation with gaseous fuel 5a, the mixture burner 1 is supplemented by a series of blowing-in lances in the downstream of the vortex generator 4 arranged in the direction of circumference and around the inner wall of the cross section of the through flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to at least one tubular passage extending axially or substantially axially for supplying combustion air, means arranged in the tubular passage for generating a swirl, and fuel. It relates to a premix burner which has as a main component a supply nozzle and a method of operating such a premix burner.

[0002]

2. Description of the Related Art According to the specification of EP-0321809,
Burners are known which enable premixed combustion and which have the series of advantages detailed in the literature. This burner consists mainly of at least two hollow, conical sub-parts which are fitted in and out in the flow direction, the longitudinal symmetry axes of which are offset from one another, and adjacent wall parts of the sub-parts are provided. Is a longitudinal extension of the sub-body and forms a tangential passage for the combustion air flow into the burner. Liquid fuel is preferably blown in through the central nozzle in the hollow space formed by the sub-members, whereas in the hollow region formed by the partial bodies, it is passed through a further nozzle which lies in the region of the tangential passage in the region of longitudinal extension. Gas fuel is supplied. In this burner, the "premixed mode (Prem
flame stabilization in the "ix mode)" is provided by the increase of vortex flow along the cone. As a result, a counterflow zone (also called backflow bubble) is formed on the burner axis at the burner outlet, where the critical swirl number is governed according to the regulations, combined with a rapid cross-sectional expansion by the combustion chamber. Ignition is performed at the weir point. However,
In this case, under certain circumstances, flame stabilization may be insufficient at partial load. The occurrence of such inadequacy is solved in two ways in this burner. That is, 1. Preload with the lowest partial load range (Premi
x) be adapted to the operating point (this is the case for burners operating in the atmosphere with smoke gas recycling); Adding fuel via the head stage (burner axis) in the partial load range, which is used in gas turbine operation.

Neither solution is always satisfactory. In case (1) the pressure drop over the burner may increase with load, or in case (2) the emission of harmful Nox components may increase due to the transition from premix mode to diffusion mode. Because. In addition, 2% of the air in the burner described above is required to cool the burner front. Only in the flame range is this air introduced into the combustion space or chamber and thus is only incompletely mixed with the previously injected fuel. This raises the flame temperature by about 20 °. Therefore, in this case, there is a potential danger that the Nox emission amount will increase. It has to be taken into consideration that the burner can also be operated with liquid fuel in the premix operation without a higher emission of harmful constituents.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object of the present invention described in the claims is to provide a premixing burner and its operating method even in the case of operation using a liquid fuel. It is an object of the present invention to provide a structure in which the same low emission of harmful components can be obtained even when operating with a gaseous fuel. A further object of the invention is to maximize the operational reliability of the premix burner.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a premixing burner as mentioned at the outset, wherein the means for generating a vortex in the passage through which the combustion air flows is a vortex generator, and the premixing burner is arranged radially. A nozzle for delivering liquid or gaseous fuel, which nozzle is operatively connected to at least one swirl generator, and there is a vaporization section below the nozzle which extends to the burner front of the premix burner. It was solved by

[0006]

An advantage of the present invention is that the burner can be operated in premixed operation with liquid or gaseous fuels at very low emission values without changing its structure. This allows the type of fuel to be changed as required during the course of operation without changing the burner configuration accordingly.

Another advantage of the present invention is the cooling of the thermally heavily loaded front wall of the burner (hereinafter referred to as the burner front) and the bypassing of the cooling air flowing along the loaded wall to the burner front. The burner is not damaged even if it is done and the flame backlashes inside the burner.

The burner has a simple geometrical shape and the length of the vaporization and mixing section can be chosen appropriately. After refueling, there are no built-in components in the flow zone, so that the flow is optimally guided. The free choice of the vaporization and mixing section allows the vaporization and mixing section to be provided with radial deflections which avoid the mixing zone from direct flame radiation.

Advantageous configurations of the solution to the subject of the invention are disclosed in the dependent claims.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Members that are not necessary for understanding the present invention are omitted.
The flow direction of the medium is indicated by the arrow. The same parts in different figures are given the same reference numerals.

The drawing shows a rotationally symmetrical premix burner 1 as can be seen from the central axis 14. The premix burner 1 can consist of a single tube or several tubes can be arranged in a ring around the central axis 14. The premix burner 1 is characterized by an inflow passage 8 extending radially and circumferentially, in particular in the region of the burner front 9. Through the inflow passage 8, the above-mentioned burner front 9
Cooling air 7 for continuously cooling the air flows. The cooling air flow is guided along the outer shell of the premix burner 1 by the turning portion. The heated cooling air is preferably and appropriately introduced into the premix burner 1 after the cooling process has ended. The cooling itself performed here is convection cooling.
In this case, the tube guide of the premix burner can be perforated in the circumferential and axial directions so that jet cooling, especially film cooling, can be performed. At the beginning of the premix burner 1, a vortex fluid 200 (hereinafter referred to as a vortex flow generator) is provided. This swirl generator gives a swirl to the incoming combustion air 2. The structure of the vortex generator 200 will be described in detail with reference to FIGS. 2 to 12. This combustion air 2 can be fresh air or a mixture formed by the returned smoke gas. In this case, both the fresh air and the mixture can be selectively enriched with fuel. Further, the combustion air 2 can be thermally pretreated depending on the operation type. The actual fuel injection into the premix burner 1 is performed downstream of the swirl generator 200 described above.
When operating the premix burner 1 with a liquid fuel 12a, at least one fuel nozzle 12 is arranged in the throughflow passage. This fuel nozzle 12 is preferably designed as a spray nozzle. Immediately upstream of this fuel nozzle 12 is arranged at least one further swirl generator 4. The swirl generator 4 is caused to flow through the injected fuel immediately downstream, at an axial direction, a radial direction or at a predetermined angle. Liquid fuel 12 prepared by fuel nozzle 12
The a is continuously given a vortex by the combustion air flow directed based on the configuration of the vortex generator 4, whereby the liquid fuel is finely atomized with a droplet size of <20 μm. The above-mentioned vortex generators 4, which can also be arranged in a plurality on the inner wall of the flow cross section, have the shape of a vane grid over the outer circumference or are described in EP-0321809. It can have an appropriately modified shape of the burner evaluated immediately. Of course, this vortex generator 4 is
00 technology.
The vortex flow generator 200 provided on the upstream side at the start end of the premix burner 1 can be omitted depending on the conditions.
In this case, it should be noted that during normal operation of the vortex generator, the subsequent acceleration of the combustion air, which takes place there, provides an improvement in the subsequent process. The vortex generators 200 are arranged differently in the inflow zone 3 around the inner and outer passage walls 17 of the flow cross section.
A sufficiently long vaporization section 6 is provided on the downstream side of the atomization of the supplied liquid fuel 12a performed by the mutual dependence of the fuel nozzle 12 and the vortex generator 4, and the liquid fuel reaches the burner front 9. It must be possible to finish the previous vaporization. The cross section of the premix burner is preferably kept constant from the swirl generator 4 to the end of the boss, ie in the region of the burner front 9, after which the vortex breakdown is caused by a diffuser-like expansion and an additional This is achieved by a dramatic expansion of the combustion chamber 16 into the cross section 10. The backflow zone 11 thus formed also allows the premix burner 1 to operate under extremely low fuel conditions. For operation with the gaseous fuel 5a, the premix burner 1 is supplemented with a series of injection lances 5 in the circumferential direction and downstream of the swirl generator 4 provided around the inner wall of the throughflow cross section. To be done. In this case, each swirl generator 4 is provided with one suitable fuel injection. This better achieves the desired fuel ratio for each longitudinal vortex. For operation at low partial loads, additional fuel nozzles 15 can be provided for the liquid and / or gaseous fuels 12a, 5a, for example at the end of the boss. Generally speaking, the premixing burner 1 can be operated in Dual operation without exception. Downstream of the main fuel injections 12a, 5a, the cross-section guide of the premix burner 1 has a radial deflection in the form of a bulge 13. This deflector prevents flame radiation from affecting the fuel spray and igniting the fuel spray. In the described arrangement, the fuel nozzle 12 is operated at a very high mass flow ratio, so that the required degree of vaporization of the liquid fuel 12a is achieved without difficulty.

In FIGS. 2, 3 and 4, the actual inflow zone 3 is not shown. In contrast, shown is the flow of combustion air 2 indicated by the arrow. It also indicates the flow direction. As shown in these figures, the vortex generators 200, 201, 202 consist of three triangular faces that are exposed to the flow. These surfaces are one roof surface 210 and two side surfaces 211 and 213.
Is. These surfaces extend in the flow direction at a predetermined angle to their longitudinal direction. Vortex generators 200, 201,
202, a vortex generator, preferably a right-angled triangle, is fixed on its longitudinal side to the previously mentioned passage wall 17, preferably in a gas-tight manner. The eddy current generator forms a contact portion by forming a point angle α on its narrow side. The abutment is designed as a sharp connecting edge 216 and lies perpendicular to each passage wall 17. The passage wall 17 is aligned with the side surface. Both sides 211, 213 forming the apex angle α are shown in FIG.
Are symmetrical in shape, size, and orientation, and are located on opposite sides of a symmetry axis 217 that extends in the same direction as the passage axis.

The roof surface 210 extends laterally with respect to the passageway through which it is constructed with a very narrow edge 215.
Therefore, it is in contact with the same passage wall 17 as the side surfaces 211 and 213. The longitudinal edges 212, 214 of the roof surface 210 are aligned with the longitudinally oriented edges of the side surfaces 211, 213 projecting into the flow passages. The roof surface 210 extends at an angle of attack θ with respect to the passage wall 17, and the longitudinal edges 212 and 214 of the roof surface 210 together with the connecting edge 16 are pointed 218.
Is formed. Of course, the vortex generators 200, 20
1, 202 may also have a bottom surface that is secured to passage wall 17 in any suitable manner. Such a bottom surface has nothing to do with the mode of action of this member.

The mode of operation of the vortex generators 200, 201, 202 is as follows. When flowing around the edges 212 and 214, the main stream 2 is converted into a pair of opposite vortices. This is shown diagrammatically in the drawing. The vortex axis is located within the axis of this main stream 2. Vortex number and location of vortex breakdown (backflow zone = Nortex Breakdow
n) is determined by choosing the angle of attack θ and the tip angle α appropriately, if the latter is desired. As the angle rises,
The vortex strength or the number of vortices is increased, and the vortex breakdown location moves upstream to the range of the vortex generators 200, 201, 202 themselves. Depending on the use, both said angles θ and α are determined by a constitutive given and by the process itself. The only further points that this swirl generator has to be adapted are the length and the height, as will be explained in more detail with the aid of FIG.

In FIG. 2, both sides 211, 213
The connecting edge 216 of the above forms the downstream edge of the vortex generator 200. The edge 215 of the roof surface 210 extending transversely to the passage through which the medium flows is the edge initially loaded by the passage flow.

FIG. 3 shows a so-called half vortex generator based on the vortex generator of FIG. In the eddy current generator 201 shown in FIG. 3, only one of the two side surfaces has a tip angle α / 2. The other side is straight and oriented in the flow direction. In contrast to symmetrical vortex generators, in this case only one vortex is generated on the tilted side, as shown schematically in the drawing. Therefore, there is no eddy current neutral zone downstream of this eddy current generator, and the flow is forced to swirl.

FIG. 4 differs from FIG. 2 in that the sharp mating edge 216 of the vortex generator 202 is where the passage flow is initially loaded. As can be seen from the state shown, both opposite vortices change their direction.

FIG. 5 shows the geometry of the swirl generator 200 incorporated in the passage 3. Usually, the height h of the coupling edge 216 is equal to the passage height H or the height of the passage portion assigned to the vortex generator, and the generated vortex is the vortex generator 2.
Just downstream of 00, it is already large enough and is tuned to fill a full passage height H. As a result, the velocity distribution in the loaded cross section becomes uniform. Another criterion that can influence the selected ratio h / H of both heights is the pressure drop as the medium flows around the vortex generator 200. It can be seen that the pressure loss coefficient also increases as the ratio h / H increases.

The vortex generators 200, 201, 202 are primarily used where two streams are to be mixed together. The main stream 2 has a rim 215 that is oriented laterally in the direction of the arrow.
Alternatively, it flows toward the connecting edge 216. In each case, the secondary flow in the form of a gaseous and / or liquid fuel with an increased proportion of supporting air has a mass flow which is significantly smaller than the main flow. This secondary flow is introduced into the main flow downstream of the vortex generator in the case shown, as can be seen in particular in FIG.

The vortex generators 200 are distributed over the outer and inner walls of the passage 3 at a distance from each other. Of course, the vortex generators can also be arranged side by side so that no intermediate space remains in the passage wall 17 even in the circumferential direction. What is ultimately decisive for the choice of the number and arrangement of the vortex generators is the vortex flow to be generated.

FIGS. 6-12 show another possible configuration for introducing fuel into the main combustion air stream. These variations can be combined with each other and with central fuel injection in various ways.

In FIG. 6, in addition to the passage wall holes 220 downstream of the swirl generator, the fuel is laterally adjacent to the side faces 211, 213 and on the same passage wall 17 where the swirl generator is located. It is also blown through the wall holes 221 existing along 211 and 213. By introducing fuel through the wall holes 221, additional impulses are imparted to the generated vortex, which prolongs the life of the vortex generator.

In FIGS. 7 and 8, the fuel is injected through the slit 222 or the wall hole 223. in this case,
The slit 222 or wall hole 223 is the same as the passage wall 1 just before the edge 215 of the roof surface 210 that extends transversely to the passage through which the medium passes and in which the swirl generator is arranged.
7 along the edge 215. Wall hole 223
Or, the geometric shape of the slit 222 is such that the fuel is supplied into the main stream 2 at a predetermined injection angle and the vortex generator disposed downstream is used as a protective film to generate a vortex flow with respect to the now hot main stream 2. It is selected to be nearly shielded by flowing around the vessel.

In the example described below, the secondary flow is first introduced into the hollow interior of the vortex generator via the passage wall 17 via a guide (not shown) (compare previous description). This provides internal cooling of the vortex generator without additional measures.

In FIG. 9, the fuel is on the roof surface 210,
Immediately following and alongside the edge 215 extending transversely to the passage through which the medium flows, the medium is blown through a wall hole 224. In this case, the eddy current generator is cooled more from the outside than from the inside. When the secondary stream flowing out flows around the roof surface 210, it forms a protective layer that shields the hot mainstream 2.

In FIG. 10, the fuel is a wall hole 22 that is arranged in a stack on the roof surface along the axis of symmetry 217.
It is blown in through 5. Due to this variation, the passage wall 17 is particularly good and protected from the hot mainstream 2.
This is because the fuel is first introduced to the outer circumference of the vortex.

In FIG. 11, fuel is injected through the wall holes 226 in the edges 212 and 214 extending in the longitudinal direction of the roof surface 210. This solution ensures good cooling of the vortex generator. This is because the fuel flows out at the end of the vortex generator and thus completely flushes the inner wall of the member. In this case, the secondary flow flows directly into the generated vortex, which results in the flow ratio being defined.

In FIG. 12, the blow is in the region of the sides 211 and 213 on the one hand the longitudinal edges 212 and 21.
4 and on the other hand in the area of the connecting edge 216 via a wall hole 227. This variation is functionally similar to that of FIG. 6 (hole 221) and FIG. 11 (hole 226).

[Brief description of drawings]

FIG. 1 is a view showing a ring-shaped premix burner.

FIG. 2 is a perspective view of an eddy current generator.

FIG. 3 is a diagram showing a modified embodiment of the eddy current generator.

FIG. 4 is a diagram showing a variation of the arrangement of the vortex generator shown in FIG.

FIG. 5 is a view showing a vortex generator in the premix passage.

FIG. 6 illustrates a fuel supply variation associated with a swirl generator.

FIG. 7 illustrates a fuel supply variation associated with a swirl generator.

FIG. 8 shows a fuel supply variation associated with a swirl generator.

FIG. 9 illustrates a fuel supply variation associated with a swirl generator.

FIG. 10 illustrates a fuel supply variation associated with a swirl generator.

FIG. 11 illustrates a fuel supply variation associated with a swirl generator.

FIG. 12 shows a fuel supply variation associated with a swirl generator.

[Explanation of symbols]

 1 Premix Burner 2 Combustion Air, Main Flow 3 Inflow Zone 4 Vortex Generator 5 Blow Lance 5a Gaseous Fuel 6 Vaporizing Section 7 Cooling Air 8 Cooling Air Inflow Passage 9 Burner Front 10 Combustion Chamber Cross Section 11 Backflow Zone 12 Fuel Nozzle 12a Liquid fuel 13 Bulging portion 14 Central axis 15 Fuel nozzle 16 Combustion chamber 17 Passage wall 200, 201, 202 Vortex generator 210 Roof surface 211, 213 Side surface 212, 214 Longitudinal edge 215 Horizontal edge 216 Coupling edge 217 Axis of symmetry 218 Tip 220-227 Hole for blowing fuel L, h Dimensions of vortex generator H Height of passage α Tip angle θ Angle of attack

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Claims (13)

[Claims] 1. At least one tubular passage extending axially or substantially axially for supplying combustion air, means arranged in the tubular passage for generating a vortex, and a nozzle supplying fuel. In the premix burner, which has as a main component, the passage (3) through which the combustion air (2) flows
In the vortex generator (4, 20
0,201,202), the premix burner (1) is arranged radially and is liquid (12a) or gaseous (5a)
Nozzles (5, 12) for feeding the fuel of the at least one swirl generator (4, 20).
0, 201, 202) and there is a vaporization section (6) below the nozzle (5, 12) that extends to the burner front (9) of the premix burner (1). Let's say the pre-mix burner. 2. A premix burner according to claim 1, wherein the vaporization section (6) has a bulge (13) which projects radially with respect to the axial plane of the combustion chamber (16). 3. The premix burner as claimed in claim 1, wherein the vaporization section (6) transitions into the combustion chamber (16) under a jump in cross section. 4. The burner front (9) is cooled air (7).
The mixing burner according to claim 1, which is cooled by. 5. Mixing burner according to claim 1, characterized in that the premixing burner (1) has a ring-shaped flow cross section. 6. The vortex generator (200) has three faces extending in the flow direction and exposed to the flow, one of these faces forming a roof face (210) and the other two faces being side faces. (211, 213) are formed, and the side surface (21
1, 213) are aligned with the same wall segment of the passage (3) and form an acute angle (α) with each other, the roof surface (210) is attached to the same wall segment of the passage (3), The edge (215) extending laterally with respect to (3) has a side surface (2).
The roof surface (210)
The longitudinal edges (212, 214) of the
13. The front of claim 1, which is aligned with the longitudinal edge of 13) projecting into the passageway (3) and forms an angle of attack (θ) with the wall segment of the passageway (3). Mixed burner. 7. The tip angle (α) of the vortex generator (200).
Both side surfaces (211, 213) forming the
Premix burner according to claim 6, which is arranged symmetrically with respect to 7). 8. A connecting edge (116) for connecting both side surfaces (211, 213) forming a sharp angle (α, α / 2) to each other.
The edges (21) oriented in the longitudinal direction of the roof surface (210).
Premix burner according to claim 6, characterized in that it forms a tip (218) with 2,214) and the connecting edge (216) is located at the radius of the circular passage (3). 9. Joining edge (216) and / or roof surface (21)
Premix burner according to claim 8, characterized in that the longitudinal edges (212, 214) of (0) are at least substantially sharply configured. 10. The symmetry axis (2) of the vortex generator (200).
17) extends parallel to the passage axis, the connecting edges (216) of both sides (211, 213) forming the downstream edge of the vortex generator (200) and the roof surface (21).
0) of the edge (21) extending transversely to the passage (3).
Premix burner according to any one of claims 1 or 6 to 8, wherein 5) is the edge initially loaded by the combustion air (2). 11. The ratio of the height (h) of the vortex generator to the height (H) of the passage (3) is such that the generated eddy current fills the passage (3) immediately downstream of the vortex generator (200). 2. The premix burner of claim 1, wherein the premix burner is selected to fill the height (H) and the full height (h) of the passage section associated with the vortex generator (200). 12. At least one tubular passage extending axially or substantially axially for supplying combustion air, means for generating a swirl in the tubular passage, and a nozzle for supplying fuel. In the method of operating a premix burner, which has as a main component, the premix burner is operated with a liquid (12a) or gaseous (5a) fuel and a nozzle (12) for the liquid fuel (12a). ) Is directly treated with at least one swirl generator (4) to form a minimized spray of liquid fuel (12a) blown from a nozzle, for the gaseous fuel (5a) The nozzle (5) may be the same and / or another vortex generator (200, 20
1,202) for optimizing the combustible mixture in the subsequent vaporization section and at the end of the premix burner for the combustion chamber (1
A backflow zone (11) formed there at the transition to 6)
How to drive a premix burner to stabilize the flame front by. 13. Process according to claim 12, in which the operation of the premix burner is maintained at low partial load with a separate fuel nozzle (15) arranged in the vaporization section (6).