EP0899506A2 - Combustion device - Google Patents

Abstract

The opening surface (17) of the flow rectifier(18) is larger than the entry surface (19) of the spin producer(100). The ratio of the opening surface to the entry surface is greater than or equal to 3. The flow rectifier comprises a holed plate hood (12), on which are end flanges (11). The spin producer comprises at least two hollow, conical part bodies inter-engaged in the flow direction. The adjacent walls of the part bodies in their longitudinal extent from tangential channels for a combustion airflow and in the conical hollow space formed by the part bodies is at least one fuel nozzle.

Description

Technical field

The invention is based on a burner device according to the preamble of first claim.

State of the art

When designing modern incineration plants, especially gas turbine plants, play an economic and environmental perspective increasingly important role. In this context, one strives to Individual components of a gas turbine plant in which energy is converted in their properties of energy conversion in terms of protecting natural Optimizing resources and in particular while avoiding high emission values.

The heart of the energy conversion in gas turbine systems is the burner device, in which gas and / or liquid fuel is mixed with pre-compressed air and ignited. The burner devices usually consist of a swirl generator through which the combustion air is swirled, a device for injecting fuel and a downstream combustion chamber in which the fuel-air mixture is burned. The combustion of the fuel atomized in air should take place as completely as possible, so that the entire fuel burns while developing the highest possible temperatures. On the one hand, the most complete possible combustion of the fuel contributes to optimal energy conversion, which essentially determines the efficiency of the entire gas turbine system, and on the other hand, the emission gases NO _x and CO ₂ gases can be considerably reduced at the highest possible combustion temperatures, thereby reducing the environmental impact can be positively influenced.

In addition to the optimization of burner devices that are as homogeneous as possible Atomizing fuel and thus causing uniform combustion, it occurs particularly when operating modern burner devices such as these described for example in European Patent EP 0 321 809 B1 are that the compressed air in the swirl generator surrounding Plenum of the burner device as free as possible in an undisturbed air flow Turbulence and is available in a directed manner. Modern burner devices, as can be seen from the publication cited above, have, for example, a conical swirl generator / burner that runs lengthways has provided narrow inlet slots on the outside of its cone, through which the the air flow required for the mixing of fuel and air is.

On the basis of Figures 1a and 1b representing the prior art Problems are shown with the flow guidance within a plenum are connected, into which an air flow is as turbulence-free as possible in inlet openings of a burner provided in the plenum.

A housing G is shown in FIG. 1 a, into which the inlet openings 4, 5 Gas streams 1, 2 are blown in. At a stagnation point A of the two gas flows 1, 2, hereinafter called partial beams, the speed disappears in the statistical Medium. In addition, the limit streamlines of the two partial beams reach 1, 2, which run through the stagnation point A, the same static at this point Pressure. For these reasons, the total pressure on both Limit streamlines are the same. As a rule, the two partial beams 1, 2 are experienced on their way from the compressor diffuser, through the cooling system of the combustion chamber to different friction losses to the air hood / plenum of the combustion chamber because the entry speeds into the plenum 6 of the combustion chamber are not accurate are the same. For this reason, the partial jets 1, 2 have different total pressures on. Moved by the total pressure difference of the two partial jets 1, 2 the stagnation point A of the two partial beams is imperative (as shown in FIG. 1b) in the immediate vicinity of the inlet opening of the partial jet with the smaller one Total pressure.

Due to the flow characteristics of several gas flows introduced into the interior of a housing to their mutual mixing or merging, is ideal in Figure 1b Air supply shown of a burner 9, which is arranged within a plenum 6 is severely impaired.

The plenum 6 is surrounded by a housing wall G and points to the left Side two inlet openings 4, 5 for two gas flows 1, 2, which run along the inner wall of the housing 3 are directed into the interior of the plenum 6. The gas flows 1, 2 meet in an area around the point of impact A of which results from a common, free gas flow 7 into the interior of the plenum 6. Ideally, the common, free gas stream 7 should be in a gap-like shape Enter the inlet opening 8 of the burner 9 and there with gaseous and / or mixed liquid fuel and brought to ignition in a combustion chamber 15 become.

Due to the above flow effects, however, the common, free gas flow does not result in an undisturbed, uniform flow, but is subject to an inconsistent lateral movement relative to the burner inlet opening 8 and also has very strong turbulent flow components. However, this usually leads to severe impairments of the aerodynamic properties of the burner 9, not least due to poor combustion impact, which significantly reduces the burner's emission values become. It can also be used in conjunction with turbulence effects within the Burner, which are initiated by the joint gas flow 7 entering, reignition effects occur, which extinguish the burning flame or overheat being able to lead.

Presentation of the invention

The invention is based, with a burner device of the beginning mentioned type to further develop such that the swirl generator / burner flow is homogeneous in every operating state.

According to the invention, this is achieved by the features of the first claim.

The essence of the invention is therefore that a flow straightener is located upstream of the swirl generator arranged to rectify the inflow to the swirl generator is.

The advantages of the invention include the fact that the inflow homogenized to the burner with low pressure drops. Thereby the emission of pollutants through a homogeneous mixture formation in the Burning zone can be minimized. The risk of flashbacks is minimized and flame pulsations avoided. This is especially true because of the flow straightener also acts as a damping element, the pressure fluctuations / Compensates for pulsations in the combustion air supply. Such a flow straightener is also ideal for retrofitting in existing ones Burner devices.

Further advantageous embodiments of the invention result from the subclaims and the description.

Brief description of the drawing

In the drawing, an embodiment of the invention is shown schematically.

Fig. 1a

Prinzipskizze zur Verdeutlichung des Ausbreitungsverhaltens zweier in einem Gehäuse geführten Gasströme,

Fig. 1b

Querschnittsdarstellung durch ein Plenum mit idealen Strömungsverhältnissen,

Fig. 2

einen Brenner mit einem Strömungsgleichrichter;

Fig. 3

einen Brenner mit einem Strömungsgleichrichter und mit anschliessender Brennkammer;

Fig. 4

einen Drallerzeuger in perspektivischer Darstellung, entsprechend aufgeschnitten;

Fig. 5

einen Schnitt durch den 2-Schalen-Drallerzeuger, nach Fig. 4;

Fig. 6

einen Schnitt durch einen 4-Schalen-Drallerzeuger;

Fig. 7

einen Schitt durch einen Drallerzeuger, dessen Schalen schaufelförmig profiliert sind;

Fig. 8

eine Darstellung der Form der Uebergangsgeometrie zwischen Drallerzeuger und Mischrohr.

Show it:

Fig. 1a

Principle sketch to illustrate the propagation behavior of two gas flows in a housing,

Fig. 1b

Cross-sectional representation through a plenum with ideal flow conditions,

Fig. 2

a burner with a flow straightener;

Fig. 3

a burner with a flow straightener and with a subsequent combustion chamber;

Fig. 4

a swirl generator in a perspective view, cut open accordingly;

Fig. 5

a section through the 2-shell swirl generator, according to Fig. 4;

Fig. 6

a section through a 4-shell swirl generator;

Fig. 7

a step through a swirl generator, the shells of which are profiled in the shape of a scoop;

Fig. 8

a representation of the shape of the transition geometry between the swirl generator and the mixing tube.

Only the elements essential for understanding the invention are shown.

Way of carrying out the invention

According to FIG. 2, a flow straightener 18 is arranged around the swirl generator / burner in order to avoid a discontinuous movement of the inflowing combustion air and turbulent flow components relative to the inlet opening 8 of the burner. This flow straightener 18 essentially consists of a perforated plate hood 12 and possibly of end flanges, for example of an upper end flange 11 and a lower end flange 10. The upper end flange can also be perforated. The flow straightener 18 surrounds the swirl generator so that the air flowing into the swirl generator must flow through the flow straightener 18. By means of the flow straightener 18, uneven distributions of the inflow to the burner are compensated for and the gas flow 7 entering the inlet opening 8 is largely homogenized. The configuration of the perforated plate hood 12 and the end flanges shown here also enables easy installation in existing burner configurations, since the largest outside diameter of the flow straightener 18 corresponds to the largest outside diameter of the burner.
The flow straightener 18 has an opening surface 17 which determines the characteristic of the flow straightener 18 in relation to an inlet surface 19 of the burner. The entry area 19 is determined by the area of the inlet openings of the burner. The opening surface 17 of the flow straightener is chosen larger than the inlet surface 19 of the burner. This keeps pressure losses at the flow straightener as small as possible. However, the opening area 17 of the flow straightener must not be chosen to be any larger than the entry area 19 of the burner, since otherwise the flow straightener no longer homogenizes the gas flows. If the ratio of opening area 17 to entry area 19 is greater than or equal to three (opening area / entry area 3 3), the losses are below 15%. If the ratio of opening area 17 to entry area 19 is greater than six (opening area / entry area> 6), the losses are below 5%. A particularly preferred range from opening surface 17 to inlet surface 19 is therefore in the range from three to six, since the losses here are relatively small and nevertheless an excellent homogenization of the inflow to the burner is achieved. The flow straightener 18 also serves as a damping element which compensates for pulsations / pressure fluctuations from the air supply to the burner, for example from the compressor.

Fig. 3 shows the overall structure of a burner with a flow straightener 18. Initially, a swirl generator 100 is effective, the design of which in the the following Fig. 4-7 is shown and described in more detail. It is about in this swirl generator 100 around a conical structure, the tangential several times from a tangentially incoming and through the flow straightener 18 rectified combustion air flow 115 is applied. The The flow that forms here is based on a flow downstream of the swirl generator 100 provided transition geometry seamlessly transferred into a transition piece 200, in such a way that no separation areas can occur there. The configuration this transition geometry is described in more detail in FIG. 8. This Transition piece 200 is through on the outflow side of the transition geometry a tube 20 extends, both parts of the actual mixing tube 220 des Form burner. Of course, the mixing tube 220 can be made from a single one Consist of pieces, i.e. then that the transition piece 200 and tube 20 into one only contiguous structures are fused, the characteristics of each part are preserved. Downstream of the tube 20 is located the actual combustion chamber 30, which here only through the flame tube is symbolized. The mixing tube 220 meets the condition that downstream of the swirl generator 100 a defined mixing section is provided, in which a perfect premixing of fuels of different types is achieved. This Mixing section, ie the mixing tube 220, furthermore enables loss-free Flow guidance, so that it is also in operative connection with the transition geometry cannot initially form a backflow zone, which means over the length of the Mixing tube 220 exerted influence on the quality of the mixture for all types of fuel can be. This mixing tube 220 has yet another property, which is that in the mixing tube 220 itself the axial speed profile has a pronounced maximum on the axis, so that backfire the flame from the combustion chamber is not possible. However, it is correct that with such a configuration this axial velocity towards the wall falls off. In order to prevent re-ignition in this area, the mixing tube 220 in the flow and circumferential direction with a number regularly or irregularly distributed holes 21 of different cross-sections and directions provided, through which an amount of air into the interior of the mixing tube 220 flows, and along the wall an increase in speed is indicated. Another way to achieve the same effect is that the Flow cross section of the mixing tube 220 on the outflow side of the transition channels 201, which form the transition geometry already mentioned, a narrowing experiences what the overall speed level within the Mixing tube 220 is raised. In the figure, the outlet corresponds to the transition channels 201 the narrowest flow cross section of the mixing tube 220. Die named transition channels 201 therefore bridge the respective cross-sectional difference, without negatively influencing the flow formed. If the chosen precaution in guiding the pipe flow 40 along the Mixing tube 220 triggers an intolerable pressure loss, can counteract this Remedy can be created by not at the end of the mixing tube in the figure shown diffuser is provided. At the end of the mixing tube 220 closes a combustion chamber 30, wherein between the two flow cross sections a cross-sectional jump is present. Only here does a central backflow zone form 50, which has the properties of a flame holder. Forms there is a flow within this cross-sectional jump during operation Edge zone, in which by the prevailing negative pressure Vertebral detachments occur, this leads to an increased ring stabilization the backflow zone 50. The combustion chamber 30 has a number at the end face Openings 31 through which an amount of air jumps directly into the cross section streams, and there lower others contribute to the ring stabilization the backflow zone 50 is strengthened. In addition, it should not go unmentioned that the generation of a stable backflow zone 50 also a sufficiently high one Twist number in a pipe required. If this is initially undesirable, you can stable return flow zones through the supply of small, strongly swirled air flows generated at the end of the tube, for example by tangential openings become. It is assumed here that the amount of air required for this in is about 5-20% of the total air volume.

In order to better understand the structure of the swirl generator 100, it is advantageous to if at least FIG. 5 is used at the same time as FIG. 4. Furthermore, in order not to make this Fig. 4 unnecessarily confusing, are the after the Figure 3 schematically shown guide plates 121a, 121b only hinted at been. The following is the description of FIG. 4 as needed referred to the figures mentioned.

The first part of the burner according to FIG. 3 forms the swirl generator shown in FIG. 4 100. This consists of two hollow conical partial bodies 101, 102, which are nested in a staggered manner. The number of conical Partial body can of course be larger than two, like the figures 4 and 5 show; this depends in each case, as will be explained in more detail below will depend on the mode of operation of the entire burner. It is with certain Operating constellations are not excluded, one from a single To provide a spiral existing swirl generator. The transfer of the respective Central axis or longitudinal symmetry axes 201b, 202b of the tapered partial body 101, 102 to each other in the neighboring wall, in a mirror image Arrangement, each a tangential channel, i.e. an air inlet slot 119, 120 (Fig. 5), through which the combustion air 115 in the interior of the swirl generator 100, i.e. flows into the cone cavity 114 of the same. The cone shape of the one shown Partial body 101, 102 in the direction of flow has a certain fixed Angle on. Of course, depending on the operational use, the partial bodies can 101, 102 an increasing or decreasing cone inclination in the flow direction have, similar to a trumpet. Tulip. The latter two Shapes are not recorded in the drawing, since they are easy for the expert are sensitive. The two conical partial bodies 101, 102 each have one cylindrical initial part 101a, 102a, which also, analogous to the conical partial bodies 101, 102, run offset from one another, so that the tangential air inlet slots 119, 120 available over the entire length of the swirl generator 100 are. A nozzle 103 is preferred in the area of the cylindrical starting part for a liquid fuel 112, the injection 104 approximately with the narrowest cross section of that formed by the tapered partial body 101, 102 Cone cavity 114 coincides. The injection capacity and the type this nozzle 103 depends on the given parameters of the respective Brenners. Of course, the swirl generator 100 can be purely conical, that is, without cylindrical starting parts 101a, 102a. The tapered body 101, 102 each further have a fuel line 108, 109, which runs along the tangential air inlet slots 119, 120 arranged and with injection openings 117 are provided, through which preferably a gaseous Fuel 113 is injected into the combustion air 115 flowing through there is how the arrows 116 symbolize this. These fuel lines 108, 109 are preferably at the latest at the end of the tangential inflow, prior to entering the cone cavity 114, this by an optimal Obtain air / fuel mixture. The one brought up through the nozzle 103 As mentioned, fuel 112 is normally a liquid Fuel, forming a mixture with another medium easily is possible. This fuel 112 is injected into the cone cavity at an acute angle 114 injected. A nozzle is thus formed from the nozzle 103 Fuel spray 105, the rotating combustion air flowing in tangentially 115 is enclosed. In the axial direction, the concentration of the injected fuel 112 continuously through the incoming combustion air 115 degraded to mix in the direction of evaporation. Becomes a introduced gaseous fuel 113 via the opening nozzles 117 happens the formation of the fuel / air mixture directly at the end of the air inlet slots 119, 120. Is the combustion air 115 additionally preheated, or for example enriched with a recirculated flue gas or exhaust gas, this helps sustained evaporation of liquid fuel 112 before this mixture flows into the downstream stage. The same considerations apply even if liquid fuels are supplied via lines 108, 109 should. When designing the tapered partial bodies 101, 102 with regard to the taper angle and the width of the tangential air inlet slots 119, 120 are on to adhere to narrow limits so that the desired flow field of the Combustion air 115 can set at the output of the swirl generator 100. General is to say that a reduction in the tangential air inlet slots 119, 120 the faster formation of a backflow zone already in the area of Swirl generator favors. The axial speed within the swirl generator 100 can be achieved by a corresponding axial feed, not shown Change the combustion air flow. A corresponding swirl generation is prevented the formation of flow separations within the swirl generator 100 downstream mixing tube. The design of the swirl generator 100 is suitable furthermore, the size of the tangential air inlet slots 119, 120 to change, with which without changing the overall length of the swirl generator 100 relatively large operational bandwidth can be captured. Of course the partial bodies 101, 102 can also be displaced relative to one another in another plane, whereby even an overlap of the same can be provided. It is further possible, the partial body 101, 102 by a counter-rotating Interlacing movement in a spiral. So it is possible to change the shape the size and configuration of the tangential air inlet slots 119, 120 to vary as desired, with which the swirl generator 100 without changing its overall length is universally applicable.

5 now shows the geometric configuration of the guide plates 121a, 121b. They have a flow introduction function, and this, accordingly their length, the respective end of the tapered partial body 101, 102 in the direction of flow extend towards the combustion air 115. The channeling the combustion air 115 into the cone cavity 114 can be opened or closing the guide plates 121a, 121b by one in the area of the entrance thereof Channel in the cone cavity 114 pivot point 123 are optimized, this is particularly necessary if the original gap size of the tangential Air inlet slots 119, 120 are to be changed dynamically. Of course these dynamic arrangements can also be provided statically, by making required baffles an integral part with the tapered Part form bodies 101, 102. The swirl generator 100 can also be used without Baffles are operated, or other aids can be provided for this become.

6 shows, compared to FIG. 5, that the swirl generator 100 now consists of four partial bodies 130, 131, 132, 133 is constructed. The associated longitudinal symmetry axes for each sub-body are marked with the letter a. To this Configuration is to be said that it is due to the lower generated with it Twist strength and in cooperation with a correspondingly enlarged Slot width is best suited, the bursting of the vortex flow on the downstream side to prevent the swirl generator in the mixing tube, thus causing the mixing tube to can fulfill the intended role.

FIG. 7 differs from FIG. 6 in that the partial bodies 140 here 141, 142, 143 have a blade profile shape which is used to provide a certain Flow is provided. Otherwise, the mode of operation of the swirl generator stayed the same. The admixture of fuel 116 in the combustion air flow 115 happens from inside the blade profiles, i.e. the fuel line 108 is now integrated in the individual blades. Here, too, are the longitudinal axes of symmetry to the individual parts of the body Letter a marked.

8 shows the transition piece 200 in a three-dimensional view. The transition geometry is body for a swirl generator 100 with four parts, accordingly 6 or 5, built. Accordingly, the transition geometry as a natural extension of the upstream partial bodies, four transition channels 201 on, whereby the conical quarter area of said partial body is extended until the wall of the tube 20 resp. of the mixing tube 220 cuts. The same considerations also apply if the swirl generator comes from another Principle, as that described in Fig. 4, is constructed. The down area of the individual transition channels 201 running in the direction of flow has a spiral shape in the flow direction, which has a describes crescent-shaped course, corresponding to the fact that present the flow cross section of the transition piece 200 in the flow direction flared. The swirl angle of the transition channels 201 in the flow direction is selected so that the pipe flow then up to the cross-sectional jump there is still a sufficiently large distance at the combustion chamber inlet, to achieve a perfect premix with the injected fuel. Furthermore, the measures mentioned above also increase the Axial speed on the mixing tube wall downstream of the swirl generator. The transition geometry and effect the measures in the area of the mixing tube a significant increase in the axial speed profile towards the center of the Mixing tube out, so that the risk of early ignition is decisively counteracted becomes.

Of course, the invention is not limited to that shown and described Embodiment limited. The geometry of the flow straightener can be chosen differently than shown. So the geometry of the perforated sheet hood and the flanges and the inlet openings of the perforated sheet hood be designed differently.

Reference list

1

Gas flow

2nd

Gas flow

3rd

Housing inner wall

4th

Injector, inlet opening

5

Injection nozzle, inlet opening

6

plenum

7

Common or free gas flow

8th

Inlet opening

9

Swirl generator / burner

10th

Lower end flange

11

Upper end flange

12th

Perforated sheet hood

15

Combustion chamber

17th

Opening area

18th

Flow straightener

19th

Entry surface burner

20th

pipe

21

Holes, openings

30th

Combustion chamber

31

Openings

40

Flow, pipe flow in the mixing pipe

50

Backflow zone

100

Swirl generator

101

Partial body

102

Partial body

101a

Cylindrical starting parts

102b

Cylindrical starting parts

101b

Longitudinal symmetry axes

102b

Longitudinal symmetry axes

103

Fuel nozzle

104

Fuel injection

105

Fuel spray (fuel injection profile)

108

Fuel lines

109

Fuel lines

112

Liquid fuel

113

Gaseous fuel

114

Cone cavity

115

Combustion air (combustion air flow)

116

Fuel injection from lines 108, 109

117

Fuel nozzles

119, 120

Tangential air inlet slots

121a, 121b

Baffles

123

Pivot point of the guide plates

130, 131, 132, 133

Partial body

131a, 131a, 132a, 133a

Longitudinal symmetry axes

140, 141, 142, 143

Vane-shaped partial body

140a, 141a, 142a, 143a

Longitudinal symmetry axes

200

Transition piece

201

Transition channels

220

Mixing tube

A

Stagnation point

G

Housing, plenum housing

Claims (8)

Burner device comprising a swirl generator (9, 100) for a combustion air stream (1, 2, 115) and a combustion chamber (15) arranged downstream of the swirl generator (9, 100),
characterized,
that a flow straightener (18) is arranged upstream of the swirl generator (9, 100) to rectify the inflow to the swirl generator (9, 100). Burner device according to claim 1,
characterized,
that the opening area (17) of the flow straightener (18) is larger than the entry area (19) of the swirl generator (9, 100). Burner device according to claim 2,
characterized,
that the ratio of opening area (17) to entry area (19) is greater than or equal to three (opening area / entry area ≥ 3). Burner device according to claim 1,
characterized,
that the ratio of opening area (17) to entrance area (19) is in the range from three to six (6 ≥ opening area / entrance area ≥ 3). Burner device according to Claims 1 to 4,
characterized,
that the flow straightener (18) consists of a perforated sheet hood (12). Burner device according to claim 5,
characterized,
that end flanges (10, 11) are arranged on the perforated sheet metal hood (12). Burner device according to one of Claims 1 to 6,
characterized,
that the swirl generator (9) consists of at least two hollow, conical partial bodies (101, 102; 130, 131, 132, 133; 140, 141, 142, 143) nested one inside the other in the flow direction, that the respective longitudinal symmetry axes (101b, 102b; 130a , 131a, 132a, 133a; 140a, 141a, 142a, 143a) of these partial bodies are offset with respect to one another, in such a way that the adjacent walls of the partial bodies in their longitudinal extension form tangential channels (119, 120) for a combustion air flow (115), and in that at least one fuel nozzle (103) is arranged from the conical cavity (114). Burner device according to one of Claims 1 to 7,
characterized,
that a mixing section (220) is arranged downstream of the swirl generator (100), that the mixing section (220) downstream of the swirl generator (100) within a first section part (200) is a transition channel (201) running in the direction of flow for transferring a swirl generator (100) Flow (40) in the downstream flow cross-section (20) of the mixing section (220) downstream of the inflow channels (201).

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