DE19545310B4 - premix - Google Patents

Abstract

premix (1), for mixing fuel and combustion air (9) before the Ignition, essentially consisting of at least two partial cone shells (10) with associated Teilkegelachsen and entrance channels (4) for the combustion air (9), characterized in that the premix burner (1) essentially of a straight hollow cone, limited by an outer one Cone sheath (14) and an inner cone sheath (15) is formed, in the at least two inlet channels tangential to the inner Cone sheath and along a straight cone shroud of the cone sheath (14, 15) are arranged, wherein the Teilkegelachsen formed thereby Part cone shells (10) lie on a common cone axis (2) and that at the downstream End of premix burner (1) a cross-sectional change in the form of a nozzle (8) is arranged.

Description

Technical area

The The invention relates to a premix burner for mixing fuel and combustion air before the ignition, consisting essentially of at least two partial cone shells with associated Teilkegelachsen and entrance channels for the Combustion air.

State of the art

Such premix burners are known, for example from the EP-B1-0 321 809 , By virtue of the premix burner designed as a swirl burner, comprising at least two partial cone bodies which are nested in the flow direction and whose respective cone axes are offset relative to a central axis, tangential channels are formed. Through the tangential channels, the combustion air enters the burner interior and is set in rotation. The fuel is injected into the rotating air and mixed with it. At the burner outlet creates a defined dome-shaped recirculation zone at the top of the ignition. The flame itself is stabilized by the recirculation zone in front of the burner, without the need for a mechanical flame holder. The thermoacoustic behavior of such burners is usually stable and they are characterized by a simple and inexpensive construction.

Becomes the burner with gaseous Fuel operated, this is in the area of the two Particle shells formed tangential channels in the walls of the two partial body longitudinal distributed gas inlet openings intended. In gas operation, the mixture formation begins with the combustion air thus already in the zone of the entrance channels.

At the tip of the cone shells is a fuel nozzle for liquid fuel arranged. The fuel is at an acute angle in the hollow cone injected. The resulting conical fuel profile is tangential incoming Air enclosed. In the axial direction, the concentration of the Fuel continuous as a result of mixing with the compressed Air evened.

By the two or more subcone axes facing the Center axis are offset, the double-cone burner is not axially symmetric. This can lead to aerodynamic problems, as in the burner interior formed vortex has two or more axes corresponding to the Teilkegelachsen. This may cause the backflow zone move between the different axes and it can lead to instabilities of Flame come.

From the EP 0321 809 B1 is described a premix burner of the above type, which includes by Teilkegelschalen a conically expanding in the flow direction swirl space. The partial conical shafts which can be assigned to the partial conical shells run separately and in each case off-center to the burner axis, so that the above-mentioned flame stability also prevails in this burner. Of the US 5,307,634 A On the other hand, a cylindrical premix burner is to be taken which has composite cylindrical shells whose cylinder axes coincide.

Presentation of the invention

Of the Invention is based on the object with a cone-shaped Premix burner the aero-dynamic properties of the premix burner to improve and the backflow zone too stabilize.

According to the invention this is achieved in that the premix burner essentially from a straight hollow cone, bounded by an outer cone sheath and a inner cone shell, is formed, in the at least two inlet channels tangentially to the inner cone sheath and along a straight cone sheath line the cone sheath are arranged and that the Teilkegelachsen the thereby formed Teilkegelschalen lie on a common cone axis. Further, at the downstream End of the premix burner arranged a cross-sectional change in the form of a nozzle.

The Advantages of the invention are, inter alia, that the inside the premix burner rotating combustion air only rotated around the cone axis. This leads to a stable flow the flow around the cone axis and thus to a stable flame.

It is particularly appropriate when the premix burner in the flow direction is divided into at least two areas, wherein the inlet channels in the Areas are arranged so that each opposing twisting the combustion air is created. As a result, the mixing of combustion air and fuel improves.

Since a nozzle is located at the downstream end of the premix burner, the premixing distance of the burner is lengthened, thereby extending the premixing distance of the burner and thereby allowing premixing of fuel and combustion air at a higher level, resulting in a significant reduction in NOx emissions leads. Further, no special adapter is needed here, making aerodynamic Pro avoided and costs of the nozzle are minimized.

It is advantageous if the nozzle a Venturi nozzle is. By connecting to the convergent part of the nozzle divergent part becomes an outer one Corner recirculation of the flow prevented. This will ensure that the vortex energy to Forming the recirculation zone is used and the flame stability is high.

It is advantageous that starting from the top of the sub-cone shells a downstream into the Inside the Vormischbrenners extending food lance arranged is, which is substantially symmetrical to the cone axis and that at the downstream At least one fuel nozzle is arranged at the end of the feed lance. The axial Distance between return flow zone and fuel nozzle is shortened by the projecting into the burner interior food lance. Thereby will the backflow zone in each Load range stabilized in the axial direction and pulsations avoided. By injecting the fuel is passed through the fuel nozzle in the vicinity of the Rückströmzone is also less Fuel needed to stabilize the flame. Thus, it is also at partial load operation possible, operate the premix burner with low nitrogen oxide emissions.

The outer surface The food lance also serves as a shear surface, the mixing of gaseous Fuel and combustion air supports and thus the pollutant emission lowers.

By the positioning of the fuel nozzle in the vicinity of the return flow zone can be the injection angle the fuel nozzle for liquid fuel elevated become. This makes the premix when using liquid fuels improved and the nitrogen oxide emissions lowered.

It is particularly appropriate when the food lance downstream at least to the bottom Third of the premix burner extends. This prevents a knockback the flame front to the burner interior.

Further it is appropriate the food lance from a lance tube and a fuel line arranged therein to build. As a result, through the lance tube, a part of the combustion air be blown, thereby mixing the fuel and Air supported becomes. In addition, the flame is prevented from reaching the end of the Food lance attached.

moreover it is appropriate at the downstream To arrange an air-assisted atomizing nozzle at the end of the lance tube. This allows liquid Burn fuel with low pollutant emissions.

It is advantageous between the lance tube and the fuel line a swirler to arrange. This allows the injected through the lance tube Air can be imparted to any spin, reducing the mixing is further optimized.

Short description of the drawing

In the drawing is an embodiment of Invention illustrated by a premix burner.

It demonstrate:

1 a Vormischbrenner in perspective view;

2 a partial longitudinal section of the premix burner along the level II-II in 1 ;

3 a partial cross section through the premix burner along the level III-III in 1 ;

4 a partial cross section through the premix burner along the level IV-IV in 1 ;

5 a partial longitudinal section through a modified premix burner;

6 a partial cross section through the premix burner along the plane VI-VI in 5 ;

7 a partial longitudinal section through a modified premix burner;

8th a partial longitudinal section through a modified premix burner with Venturi nozzle;

9 a partial longitudinal section through a modified premix burner with a feed lance;

10 the detail X out 9 ;

11 a partial cross section through the feed lance along the plane XI-XI in 10 ,

It are only for the understanding the invention essential elements shown. The flow directions the work equipment are represented by arrows.

Way to execute the invention

To 1 there is a premix burner 1 , a so-called cone burner, essentially of several identical cone shells 10a . 10b . 10c and 10d (hereinafter: 10 ). The part cone axes the partial cone shells 10 lie on a common cone axis 2 , Such a cone burner 1 can be produced, for example, by casting.

For a better understanding of the structure of the premix burner, it is advantageous to 1 the cuts after 2 . 3 and 4 consulted. The premix burner 1 is essentially formed by a straight hollow cone with an outer conical surface 14 and an inner cone sheath 15 , as well as by in the hollow cone embedded inlet channels 4a . 4b . 4c and 4d (hereinafter: 4 ) with a minimum width 5 , The outer cone coat 14 and the inner cone sheath 15 also define the maximum thickness 11 the cone burner wall. The opening angle of the inner and outer conical shells may also vary, whereby the thickness of the conical burner wall depends on the height of the conical burner 1 becomes. Geometrically, the inlet channels 4 formed by a plane, with the cone axis 2 as a plane element, with the hollow cone formed from inner and outer cone sheath 14 . 15 is cut. The entrance channels 4 run tangentially to the inner cone sheath 15 and along a straight cone sheath line from the top of the premix burner 1 to its downstream end burner exit 20 , The inlet channels are thus corresponding to the opening angle of the cone relative to the cone axis 2 inclined. By the number of entrance channels 4 becomes the number of partial cone shells 10 Are defined. At the upstream beginning of the entrance channels 4 , at the transition to the outer cone coat 14 , are the entrance channels 4 designed so that the flow of the inflowing medium does not detach. The application of well-known flow criteria thus causes the flow at the inlet channels 4 does not replace. Essentially, the entry channels expand 4 upstream, causing the Teilkegelschalen 10 obtained a wing-like profile. By the width 5 the inlet channels, the opening angle of the inner cone sheath 15 and the height of the premix burner 1 is essentially that in the combustion air 9 created swirl and an optimal premix of the concentric air / fuel layers set.

For the injection of gaseous fuel are in the region of the inlet channels 4 inflow 6 arranged. These inflow openings 6 be over completely arranged in the sub-cone shells feed channels 7 fueled. At the top of the premix burner 1 is a non-illustrated, fuel nozzle 3 arranged, for example, an air-assisted nozzle or a pressure atomizer. The fuel nozzle 3 is supplied via a fuel lance, not shown, with fuel. The fuel nozzle 3 may also be designed in addition to the injection of gaseous fuel. The premix burner 1 is at his burner exit 20 on a front panel 18 mounted, with the front panel 18 limited to the combustion chamber.

The compressed combustion air generated in a compressor not shown 9 occurs over the tangential channels 4 inside the premix burner 1 one. Due to the tangential incoming combustion air 9 gets the air 9 rotated in the interior of the premix burner, wherein the swirl number increases in the flow direction.

In gas mode, the mixture formation begins with the combustion air 9 in the zone of the entrance channels 4 by means of the inflow openings 6 , At the burner exit 20 arises through the rotating combustion air 9 a homogeneous fuel concentration over the applied cross section. It is created at the burner outlet 20 in the front panel 18 limited combustion chamber, a defined dome-shaped Rückströmzone 21 , at the top of which the ignition takes place. The same happens when operating with liquid fuel. The liquid fuel is through the fuel nozzle 3 injected and the formed conical fuel profile is from the tangential incoming combustion air 9 enclosed. In the downstream, axial direction, the concentration of the fuel is continuously reduced by the mixed combustion air.

In 5 and 6 is the premix burner 1 by means of a plane perpendicular to the cone axis 2 divided into two areas A and B. Through these areas now different directions of rotation of the combustion air 9 induced in the interior of the premix burner. In area A, the combustion air rotates counterclockwise in the flow direction (see 3 ). In area B, the combustion air rotates in the direction of flow in a clockwise direction (see 6 ). Of course, the regions A and B can also be designed such that in the region A the combustion air rotates clockwise in the flow direction and counterclockwise in the region B. This will result in better mixing in the premix burner 1 achieved. The size and number of areas A and B is arbitrary and must be adapted to the respective conditions such as fuel, compressor pressure, etc.

To 7 the premix burner is suitable 1 excellent for attaching a nozzle 8th at the downstream end of the premix burner. At the nozzle 8th it may be, for example, a pipe, a Venturi nozzle or, as shown, a convergent nozzle. Such a nozzle essentially introduces an additional mixing section for mixing combustion air and fuel. Through the convergent nozzle 8th the axial component of the vortices is increased, so that the number of vertebrae decreases. This leads to an additional premixing and thus to an improved mix quality and to a lower pollutant emission.

In 8th shows a Venturi nozzle 12 located at the downstream end of the premix burner 1 is arranged. The venturi nozzle 12 consists of a convergent part and a downstream divergent part. The second divergent part of the venturi nozzle, acting as a diffuser, reduces the axial component of the fuel-air flow, resulting in an increase in the number of swirls until the critical vortex number is reached and a return flow zone 21 is produced. The controlled expansion provided by the second divergent part of the Venturi nozzle reduces the outer corner recirculation and ensures that the vortex energy is used to form the central recirculation zone 21 is used.

Of course it is the invention is not limited to the embodiment shown and described. The Number of partial cone shells is arbitrary. The premix burner can provided with two or more tangential entry slots become.

at Partial load, if the operation of the premix burner by injection of gaseous Fuel in the range of tangential channels no longer guaranteed is over the fuel nozzle arranged at the tip of the cone shells gaseous fuel injected. Due to the large axial distance between Rückströmzone and fuel nozzle is however, the danger that the axial position of the flame changes and it thereby comes to pulsations. Continues to rise, due to the large axial distance between Rückströmzone and fuel nozzle, the Amount of needed Fuel, resulting in increased Pollutant emission can lead.

To 9 is symmetrical to the cone axis 2 of the premix burner 1 starting from the through the partial cone body 10 formed tip a downstream extending food lance 50 arranged. It consists of a lance tube 52 and a fuel line disposed therein 53 , The axial position of the downstream end of the feed lance 50 is preferably at least in the lower third of the premix burner 1 , ie the food lance can also be from the premix burner 1 protrude. For example, the food lance 50 up to twenty percent of the axial height of the premix burner from the premix burner 1 protrude. Inside the lance tube 52 , preferably near the downstream end, is a swirler 56 arranged.

To 10 and 11 exists the swirl body 56 from several deflecting bodies 57 between the inner wall of the lance tube and the fuel line 53 are arranged. Inside the fuel line 53 is an annular outer fuel supply passage 55 and an inner fuel supply passage 54 arranged. By means of the inner channel 54 becomes one at the downstream end of the fuel line 53 located fuel nozzle 58 Fuel supplied. This nozzle 58 is designed as a dual nozzle for the injection of liquid and gaseous fuels. The outer channel 55 branches over the deflecting body 57 in an outer fuel supply channel 55a inside the downstream end of the lance tube 52 from. The through the outer channel 55 subsidized liquid fuel 30 is thereby to the downstream end of the lance tube 52 guided. The at the downstream end of the lance tube 52 located outer edge of the lance tube serves as a sputtering edge 67 , The outer wall of the lance tube 52 serves as additional shear surface, which is the mixing of combustion air 9 and gaseous fuel further supported. The axial position of the return flow zone 21 is determined by the axial position of the downstream end of the feed lance 50 fixed. This prevents the backflow zone from axially displacing and pulsing therewith.

At partial load, when operating the premix burner 1 by injection of gaseous fuel 31 in the area of the tangential channels 4 is no longer guaranteed, gaseous fuel through the nozzle 58 injected. The gaseous fuel thereby becomes near the backflow zone 21 injected, whereby pulsations between full load and part load operation can be avoided. Next is the required amount of fuel passing through the nozzle 58 must be injected, reduced, as the fuel directly into the backflow zone 21 is injected.

Through the cavity between the lance tube 52 and fuel line 53 also becomes combustion air 9a promoted. The extracted by the lance tube combustion air content 9a can be up to 25% of the total air flow. Through the swirl body 56 becomes the combustion air 9a set in rotation. The nature and strength of the swirl must be adapted to the respective circumstances of the premix burner who the. For example, the swirl body 56 be interpreted that the swirl generated by him opposite to the spin of the premix burner 1 runs. This increases the mixing of combustion air 9 . 9a and fuel and additionally prevents repelling the Rüchströmzone 21 and thus the flame to the downstream end of the food lance 50 ,

Will the premix burner 1 operated with liquid fuel, the fuel by means of dining lance 50 injected. This is done by means of the outer channel 55 , about the liquid fuel 30 to the spray edge 67 is encouraged. By means of the lance tube 52 subsidized air 9a This creates an air-assisted atomizing nozzle 22 (English airblast atomizer) formed. To improve the atomization may need the air 9a opposite the air 9 be further compressed.

Next can be liquid fuel through the fuel nozzle 58 be injected. Because of the axial position of the nozzle 58 inside the premix burner 1 can the spray angle of the nozzle 58 be very large. This will cause the mixing of air 9 . 9a and fuel improves.

Of course it is the invention is not limited to the embodiment shown and described. The dual nozzle can also be from two nozzles be constructed, in which case the inner feed channel adapted accordingly must become. The outside fuel feed can also be routed from the fuel line into the lance tube.

1

premix (Cone burner)

2

cone axis

3

fuel nozzle

4

inlet channels

4a-4d

inlet channel

5

width inlet channel

6

inflow

7

feed

8th

jet

9 9a

compacted combustion air

10

Cone shell

10a-10d

Partial cone shell

11

maximum Thick cone burner wall

12

Venturi nozzle

14

outer cone shell

15

internal cone shell

18

front panel

20

burner outlet

21

dome-shaped return flow zone

22

air-assisted atomizing nozzle

30

liquid fuel

31

gaseous fuel

50

dining lance

52

lance tube

53

fuel line

54

internal fuel feed

55, 55a

outer fuel feed

56

swirler

57

deflecting

58

fuel nozzle

67

atomization

68

Gas supply line

A, B

Cone burner areas

Claims (9)

Premix burner ( 1 ), for mixing fuel and combustion air ( 9 ) prior to ignition, consisting essentially of at least two partial cone shells ( 10 ) with associated sub-cone axes and inlet channels ( 4 ) for the combustion air ( 9 ), characterized in that the premix burner ( 1 ) consisting essentially of a straight hollow cone, bounded by an outer cone sheath ( 14 ) and an inner cone sheath ( 15 ) is formed, in the at least two inlet channels tangent to the inner conical surface and along a straight cone surface line of the conical surface ( 14 . 15 ) are arranged, wherein the pitch cone axes of the thus formed Teilkegelschalen ( 10 ) on a common cone axis ( 2 ) and that at the downstream end of the premix burner ( 1 ) a cross-sectional change in the form of a nozzle ( 8th ) is arranged. Premix burner according to claim 1, characterized in that the premix burner is subdivided into at least two regions (A, B) in the flow direction and that the inlet channels in the regions (A, B) are arranged in such a way that a respective opposite directional twisting of the combustion air ( 9 ) arises. Premix burner according to claim 1, characterized in that in the region of the inlet channels ( 4 ) Inflow openings ( 6 ) are arranged for injection of gaseous fuel. Premix burner according to claim 1, characterized in that at the apex of the premix burner ( 1 ) a fuel nozzle ( 3 ) is arranged for injection of liquid fuels. Premix burner according to claim 1, characterized in that the cross-sectional change a Venturi nozzle ( 12 ). Premix burner according to claim 1, characterized in that starting from the tip of the sub-cone shells ( 10a - 10d ) one downstream into the interior of the premix burner ( 1 ) extending food lance ( 50 ) is arranged, which is substantially coaxial with the cone axis ( 2 ) and that at the downstream end of the food lance ( 50 ) at least one fuel nozzle ( 58 ) is arranged. Premix burner according to claim 6, characterized in that the food lance ( 50 ) downstream to at least the lower third of the premix burner ( 1 ). Premix burner according to claim 6, characterized in that the food lance ( 50 ) essentially from a lance tube ( 52 ) and one in it arranged fuel line ( 53 ) and that at the downstream end of the fuel line ( 53 ) the fuel nozzle ( 58 ) is arranged. Premix burner according to claim 8, characterized in that at the downstream end of the lance tube ( 52 ) an air-assisted atomizing nozzle ( 22 ) and between the lance tube ( 52 ) and the fuel line ( 53 ) A swirl body is arranged.