WO2011054771A2

WO2011054771A2 - Premixed burner for a gas turbine combustor

Info

Publication number: WO2011054771A2
Application number: PCT/EP2010/066535
Authority: WO
Inventors: Madhavan Poyyapakkam; Anton Winkler; Khawar Syed; Andrea Ciani
Original assignee: Alstom Technology Ltd
Priority date: 2009-11-07
Filing date: 2010-10-29
Publication date: 2011-05-12
Also published as: US20120285172A1; US8490398B2; EP2496883A2; WO2011054771A3; EP2496883B1

Abstract

The disclosure relates to a burner (1) for a single combustion chamber or first combustion chamber of a gas turbine, with an injection device (7) for the introduction of at least one gaseous and/or liquid fuel into the burner (1), wherein the injection device (7) has at least one body (22) which is arranged in the burner (1) with at least one nozzle (15) for introducing the at least one fuel into the burner (1), wherein the at least one body (22) is located in a first section (18) of the burner (1) with a first cross-sectional area at a leading edge of the at least one body (22) with reference to a main flow direction (14) prevailing in the burner (1), wherein downstream of said body (22) a mixing zone (2) is located with a second cross-sectional area, and at and/or downstream of said body (22) the cross-sectional area is reduced, such that the first cross-sectional area is larger than the second cross-sectional area.

Description

PREMIXED BURNER FOR A GAS TURBINE COMBUSTOR

TECHNICAL FIELD

The present invention relates to a burner in particular for a first of a sequential combustion chamber of a gas turbine or a single combustor only, with an injection device for the introduction of at least one gaseous and/or liquid fuel into the burner.

PRIOR ART

In order to achieve a high efficiency, a high turbine inlet temperature is required in standard gas turbines. As a result, there arise high NOx emission levels and higher life cycle costs. These problems can be mitigated with a sequential combustion cycle, wherein the compressor delivers nearly double the pressure ratio of a conventional one. The main flow passes the first combustion chamber (e.g. using a burner of the general type as disclosed in EP 1 257 809 or as in US 4,932,861, also called EV combustor, where the EV stands for environmental), wherein a part of the fuel is combusted. After expanding at the high-pressure turbine stage, the remaining fuel is added and combusted (e.g. using a burner of the type as disclosed in US 5,431,018 or US 5,626,017 or in US 2002/0187448, also called SEV combustor, where the S stands for sequential). Both combustors contain premixing burners, as low NOx emissions require high mixing quality of the fuel and the oxidizer.

(S)EV-burners are currently designed for operation on natural gas and oil only. The subsequent mixing of the fuel and the oxidizer at the exit of the mixing zone is just sufficient to allow low NOx emissions (mixing quality), to avoid thermo acoustic pulsations and to avoid flashback (residence time).

SUMMARY OF THE INVENTION

It is an object of the present invention to provide new premixed burner concept (applicable to a 1st stage combustor in a 2-stage combustion system or to a single combustion burner system). The concept shall provide rapid mixing achievable e.g. for highly reactive fuels with acceptable burner pressure drops. This invention shall further provide rapid fuel-air mixing occurring in short burner-mixing lengths. The improved burner shall be usable in particular (but not exclusively) for high reactivity conditions, i.e. for a situation where high reactivity fuels, specifically MBtu fuels, shall be burned in such a burner.

Specifically, the improvement relates to a burner for a single combustion chamber or first combustion chamber of for example a gas turbine, with an injection device for the introduction of at least one gaseous and/or liquid fuel into the burner, wherein the injection device has at least one body which is arranged in the burner with at least one nozzle for introducing the at least one fuel into the burner, wherein the at least one body is located in a first section of the burner with a first cross-sectional area at a leading edge of the at least one body with reference to a main flow direction prevailing in the burner, wherein downstream of said body a mixing zone is located with a second cross-sectional area. According to the invention, at and/or downstream of said body the cross- sectional area is reduced, such that the first cross-sectional area is larger than the second cross-sectional area. In other words the cross-section available for the flow of combustion gases at the leading edge of the at least one body is larger than the cross-section available for the flow of combustion gases in the mixing zone. This reduction of the cross-section typically leads to an increase of the flow velocity along this flow path.

The proposed concept can be applied in the context of annular combustors but also in the context of can-annular combustors wherein individual burner cans feed hot combustion gas into respective individual portions of the arc of the turbine inlet vanes. Each can includes a plurality of main burners disposed in a ring around a central pilot burner, as illustrated for example in US 6,082,111 or in EP 1434007.

The design preferably features aerodynamically facilitated axial fuel injection with mixing enhancement via small sized vortex generators. As a result, the premixed burner is designed to operate for increased fuel flexibility without suffering on high NOx emissions or flashback. The proposed burner configuration is applicable for both annular and can- annular combustors. Flame stabilization is achieved by pushing the vortex breakdown occurrence to the burner exit. The burner velocities, the axial pressure gradient as well as the dimensional in the bodies and optionally arranged vortex generators are varied to control the vortex breakdown to occur near the burner exit.

The possible range of applications of the proposed burner is broad. The burner can be used for gas turbines, for boilers, water heaters, etc. It can be implemented in can-annular, or annular combustors, and it can be operated with multiple or single fuel, or a different variety of fuels (natural gas, H2, Oil, LBTU fuels etc.)

The key advantages of the proposed system and of preferred embodiments thereof can be summarised as follows:

• Higher burner velocities (i.e. lower residence times) which also allow to accommodate highly reactive fuels

• Lower burner pressure drop for achieving desired fuel air mixing performance. · Small scale mixing achieved with flute/vortex generator injectors rely less on the large scale vortex structures.

• Flame stabilization at the burner exit can be achieved by controlling or delaying the vortex breakdown through modifying the burner axial pressure gradient.

According to a first preferred embodiment of the proposed burner, the second cross- sectional area is at least 10%, more preferably at least 20%, even more preferably at least

30%, smaller than the first cross-sectional area. Typically it is around 40% smaller than the first cross-sectional area. By having such a reduced cross-section the main flow velocity is increased making it possible to use high reactivity fuels or to apply high inlet temperatures as the residence time in the mixing section is substantially reduced.

According to a further preferred embodiment, in the first section the flow cross-sectional area of the burner is continuously reducing, so in the section where the bodies are arranged, the cross-sectional area is continuously reducing.

Normally in this case, the body has a longitudinal extension essentially along the main flow direction, and the flow cross-sectional area of the burner is continuously reducing from the first cross-sectional area at least over a length of the longitudinal extension, preferably over 1 1/2 or twice the length of this longitudinal extension.

Generally injection is possible cross-flow but preferably in-line, so the injection angle is preferably lower than 90° and the injection device injects fuel under this angle lower than 90° with respect to the main flow direction of the air flow. In other words the proposed system is particularly suitable for in-line fuel injection. So according to a further preferred embodiment, the injection device injects fuel essentially along the main flow direction. This allows to have higher reactivity conditions as the fuel is carried downstream very rapidly and it in addition to that allows to use low pressure carrier gas.

Fuel can thus be injected under an essentially zero angle with respect to the main flow direction of the air flow (full in-line injection) however it can also be injected at a slight inclination with respect to the main flow direction, so for example at an angle thereto of less than 30°, preferably of less than 15°.

It is particularly preferred a so-called lance type injection devices are used. In this case the at least one body is configured as a streamlined body which has a streamlined cross- sectional profile and which extends with a longitudinal direction perpendicularly to or at an inclination to a main flow direction prevailing in the burner, the at least one nozzle having its outlet orifice at or in a trailing edge of the streamlined body. The body in accordance with this aspect of the invention has two lateral surfaces (normally at least for one central body essentially parallel to the main flow direction and converging, i.e. inclined for the others). In this case, preferentially upstream of the at least one nozzle on at least one lateral surface there is located at least one vortex generator.

The gist of this aspect of the invention is to merge the vortex generator aspect and the fuel injection device into one single combined vortex generation and fuel injection device. By doing this, mixing of fuels with oxidation air and vortex generation take place in very close spatial vicinity and very efficiently, such that more rapid mixing is possible and the length of the mixing zone can be reduced. It is even possible in some cases, by corresponding design and orientation of the body in the oxidising air path, to completely omit flow conditioning elements as the body may also take over the flow conditioning. All this is possible without severe pressure drop along the injection device such that the overall efficiency of the process can be maintained.

In one burner at least one such injection device is located in the first section, preferably at least two such injection devices are located within one burner, even more preferably three such injection devices or flutes are located within one burner. Typically in case of three flutes the central one is arranged essentially parallel to the main flow of oxidising medium, while the lateral ones are arranged in a converging manner, essentially parallel to sidewalls converging towards the mixing section.

In order to have a sufficiently efficient vortex generation to produce higher circulation rates at a minimum pressure drop, preferentially the vortex generator has an attack angle in the range of 15-40°, preferably in the range of 15-20° and/or a sweep angle in the range of 40-70°, preferably in the range of 55-65°.

Generally speaking, vortex generators as they are disclosed in US 5,80,360 to as well as in US 5,423,608 can be used in the present context, the disclosure of these two documents being specifically incorporated into this disclosure.

At least two nozzles (typically at least four, or six) are arranged at different positions along said trailing edge (in a row with spacings in between), wherein upstream of each of these nozzles at least one vortex generator is located. It is possible to have two vortex generators on opposite sides of the body for one nozzle or for a pair of nozzles.

Generally "upstream" in the context of the vortex generators relative to the nozzles is intending to mean that the vortex generator generates a vortex at the position of the nozzle. The vortex generators may also be upstream facing in order to bring the vortices closer to the fuel injection location.

Preferably vortex generators to adjacent nozzles (along the row) are located at opposite lateral surfaces of the body. Even more preferably more than three, most preferably at least four, nozzles are arranged along said trailing edge and vortex generators are alternatingly located at the two lateral surfaces.

Preferentially, downstream of each vortex generator there are located at least two nozzles for fuel injection at the trailing edge.

A further preferred embodiment is characterised in that the streamlined body extends across the entire flow cross section between opposite walls of the burner. Typically these opposite walls between which the streamlined bodies extend are parallel, while the sidewalls joining these two parallel walls are converging towards the mixing section. It is however also possible that these opposite walls converge as well, in this case in a side view the streamlined body is have a trapezoidal shape.

The profile of the streamlined body can be parallel to the main flow direction. It can however also be inclined with respect to the main flow direction at least over a certain part of its longitudinal extension wherein for example the profile of the streamlined body can be rotated or twisted, for example in opposing directions relative to the longitudinal axis on both sides of a longitudinal midpoint, in order to impose a mild swirl on the main flow. The vortex generator(s) can also be provided with cooling elements, wherein preferably these cooling elements are effusion/film cooling holes provided in at least one of the surfaces (also possible is internal cooling such as impingement cooling) of the vortex generator. The film cooling holes can be fed with air from the carrier gas feed also used for the fuel injection to simplify the setup. Due to the in-line injection of the fuel, lower pressure carrier gas can be used, so the same gas supply can be used for fuel injection and cooling.

Also the body can be provided with cooling elements, wherein preferably these cooling elements are given by internal circulation of cooling medium along the sidewalls (also possible is impingement cooling) of the body and/or by film cooling holes, preferably located near the trailing edge. Again the cooling elements can be fed with air from the carrier gas feed also used for the fuel injection.

As mentioned above, normally the fuel is injected from the nozzle together with a carrier gas stream (typically the fuel is injected centrally and a carrier gas circumferentially encloses the fuel jet), wherein the carrier gas air is low pressure air with a pressure in the range of 10-20 bar, preferably in the range of 16-20 bar. As in-line injection is used, a lower pressure can be used for the carrier gas.

The streamlined body can have a symmetric cross-sectional profile, i.e. one which is mirror symmetric with respect to the central plane of the body (while however this symmetry does not include necessarily also the vortex generators, these may also be mounted asymmetrically on such a symmetric profile).

The streamlined body can also be arranged centrally in the burner with respect to a width of a flow cross section.

The streamlined body can be arranged in the burner such that a straight line connecting the trailing edge to a leading edge extends parallel to the main flow direction of the burner.

A plurality of separate outlet orifices of a plurality of nozzles can be arranged next to one another and arranged at the trailing edge.

At least one slit-shaped outlet orifice can be, in the sense of a nozzle, arranged at the trailing edge.

Furthermore the present invention relates to the use of a burner as defined above for the combustion under high reactivity conditions, preferably for the combustion at high burner inlet temperatures and/or for the combustion of MBtu fuel, normally with a calorific value of 5000-20,000 kJ/kg, preferably 7000-17,000 kJ/kg, more preferably 10,000-15,000 kJ/kg, most preferably such a fuel comprising hydrogen gas.

Further embodiments of the invention are laid down in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1 shows the proposed burner arrangement in a perspective view;

Fig. 2 shows such a primary burner with reduced exit cross-section area in an axial cut; Fig. 3 shows in a) the streamlined body in a view opposite to the direction of the flow of oxidising medium with fuel injection parallel to the flow of oxidising medium, in b) a side view onto such a streamlined body, in c) a cut perpendicular to the central plane of the streamlined body in d) the corresponding fuel mast fraction contour at the exit of the burner, in e) a schematic sketch how the attack angle and a sweep angle of the vortex generator are defined, , wherein in the upper representation a side elevation view is given, and in the lower representation a view onto the vortex generator in a direction perpendicular to the plane on which the vortex generator is mounted are given, in f) a perspective view onto a body and its interior structure, and in g) in a cut perpendicular to the longitudinal axis;

Fig. 4 shows in a) the streamlined body in a view opposite to the direction of the flow of oxidising medium with fuel injection inclined to the flow of oxidising medium, in b) a side view onto such a streamlined body, in c) a cut perpendicular to the central plane of the streamlined body, and

Fig. 5 shows in a) a side view onto a streamlined body with inverted vortex generators , in b) a cut perpendicular to the central plane of the streamlined body. DESCRIPTION OF PREFERRED EMBODIMENTS

The invention relates in particular (but not exclusively) to combustion of fuel air mixtures having lower ignition delay times and higher flame speeds. This is achieved by an integrated approach, which allows higher velocities of the main flow and in turn, a lower residence time of the fuel air mixture in the mixing zone. The challenge regarding the fuel injection is twofold with respect to the use of hydrogen rich fuels and fuel air mixtures:

• Hydrogen rich fuels may change the penetration behavior of the fuel jets. The penetration is determined by the cross section areas of the burner and the fuel injection holes, respectively.

• The second problem is that depending on the type of fuel or the temperature of the fuel air mixture, the reactivity of the fuel air mixture change.

The present invention in particular it relates to the stabilised propagating flame regime of burners.

For each temperature and mixture composition the laminar/turbulent flame speeds and the ignition delay time changes. As a result, hardware configurations must be provided offering a suitable operation window. For each hardware configuration, the upper limit regarding the fuel air reactivity is given by the flashback safety.

In the framework of a H2 premixed burner the flashback risk is increased, as the residence time in the mixing zone exceeds the ignition delay time of the fuel air. Mitigation can be achieved in several ways:

• The inclination angle of the fuel can be adjusted to decrease the residence time of the fuel.

• The reactivity can be slowed down by diluting the fuel air mixture with nitrogen or steam, respectively.

• The length of the mixing zone can be kept constant, if in turn the main flow velocity is increased. However, then normally a penalty on the pressure drop must be taken.

• By implementing more rapid mixing of the fuel and the oxidizer, the length of the mixing zone can be reduced while maintaining the main flow velocity.

The main goal of this invention is to evolve an improved premixer configuration, wherein the latter two points are addressed.

In order to allow capability for highly reactive fuels, the injector is designed to perform

• flow conditioning,

· injection and

• mixing

• flame stabilization

simultaneously. As a result, the injector can save burner pressure loss, which is currently utilized in the various devices along the flow path. If the combination of flow conditioning device, vortex generators and injector is replaced by the proposed invention, the velocity of the main flow can be increased in order to achieve a short residence time of the fuel air mixture in the mixing zone.

Figure 1 shows how in the proposed burner the cross-sectional area is reduced to accommodate higher burner velocities in order to help in operating the burner safely for highly reactive fuels and operating conditions. The vortex break down location is controlled so as to provide flame stabilization in addition to sudden burner-liner expansion. The burner cross-sectional area is varied in particular in section 18 to allow for gradual change in the axial pressure gradient in order to delay the vortex breakdown occurrence. More specifically in figure 1, which is a perspective representation of a burner according to the invention, where the top wall of the burner has been removed, the main flow of oxidizing medium, typically from the compressor, enters along arrow 8 at the inlet side 6 of the actual burner 1.

Within a converging portion 18, there are located three injection devices 7, which in this case are structured as streamlined bodies 22. These are arranged within the flow path with essentially parallel longitudinal axes while only the central plane of the central streamlined body is essentially parallel to the flow direction 8 while the outer two streamlined bodies or fluids 22 are inclined with respect to the flow direction 8. More specifically, in the converging portion 18 of the burner, the burner walls 3 are converging and the central planes of the flutes 22 are located essentially parallel to these inclined walls. At the trailing edges 24 of these burners there are located nozzles 15, which inject fuel.

Downstream of this converging portion, the length of which is typically longer than the lengths of the flutes 22, there follows a reduced burner cross sectional area 19. The actual mixing space or mixing zone 2 is therefore in this case formed by the portion of the converging portion 18 which is located downstream of the trailing edge 24 of the flutes 22, and by the reduced burner cross sectional area 19. In this area 19 the cross section of the flow path is essentially constant. Downstream of this area 19 the flow expands at the transition 13 where the backside wall 13 of the combustion space or combustion chamber 4 is located. At this outlet side 5 or burner exit vortex break down takes place and it is at or just downstream of this where the flame is controlled to be located.

The combustion chamber 4 is bordered by the combustion chamber walls 12.

Figure 2 shows a set-up, where the proposed burner area is reduced considerably. The higher burner velocities help in operating the burner safely at highly reactive conditions. In figure 3 a proposed burner is shown with reduced exit cross-section area. In this case downstream of the inlet side 6 a fuel injection device according to the invention is located, which is given as a streamlined body 22 extending with its longitudinal direction across the two opposite walls 3 of the burner. At the position where the streamlined body 22 is located the two walls 3 converge in a converging portion 18 and narrow down to a reduced burner cross-sectional area 19. This defines the mixing space 2 which ends at the outlet side 5 where the mixture of fuel and air enters the combustion chamber or combustion space 4 which is delimited by walls 12.

Several more specific embodiments of the inline injection with flute/VG concept shall be presented below.

Embodiment 1:

The first embodiment to this concept is to stagger the vortex generators 23 embedded on the bodies or flutes 22 as shown in Figure 3. The vortex generators 23 are located sufficiently upstream of the fuel injection location to avoid flow recirculations. The vortex generator attack and sweep angles are chosen to produce highest circulation rates at a minimum pressure drop.

Normally such vortex generators have an attack angle a in the range of 15-20° and/or a sweep angle β in the range of 55-65°, for a definition of these angles reference is made to Fig. 3e), where for an orientation of the vortex generator in the air flow 14 as given in figure 3a) the definition of the attack angle a is given in the upper representation which is an elevation view, and the definition of the sweep angle β is given in the lower representation, which is a top view onto the vortex generator.

As illustrated the body 22 is defined by two lateral surfaces 33 joined in a smooth round transition at the leading edge 25 and ending at a small radius/sharp angle at the trailing edge 24 defining the cross-sectional profile 48. Upstream of trailing edge the vortex generators 23 are located. The vortex generators are of triangular shape with a triangular lateral surface 27 converging with the lateral surface 33 upstream of the vortex generator, and two side surfaces 28 essentially perpendicular to a central plane 35 of the body 22. The two side's surfaces 28 converge at a trailing edge 29 of the vortex generator 23, and this trailing edge is typically just upstream of the corresponding nozzle 15.

The lateral surfaces 27 but also the side surfaces 28 maybe provided with effusion/film cooling holes 32.

The whole body 22 is arranged between and bridging opposite the two walls 3 of the combustor, so along a longitudinal axis 49 essentially perpendicular to the walls 3. Parallel to this longitudinal axis there is, according to this embodiment, the leading edge 25 and the trailing edge 24. It is however also possible that the leading edge 25 and/or the trailing edge are not linear but are rounded.

At the trailing edge the nozzles 15 for fuel injection are located. In this case fuel injection takes place along the injection direction 35 which is parallel to the central plane 35 of the body 22. Fuel as well as carrier air are transported to the nozzles 15 as schematically illustrated by arrows 30 and 31, respectively. Typically the fuel supply is provided by a central tubing, while the carrier air is provided in a flow adjacent to the walls 33 to also provide internal cooling of the structures 22. The carrier airflow is also used for supply of the cooling holes 23. Fuel is injected by generating a central fuel jet along direction 34 enclosed circumferentially by a sleeve of carrier air.

The staggering of vortex generators 23 helps in avoiding merging of vortices resulting in preserving very high net longitudinal vorticity. The local conditioning of fuel air mixture with vortex generators close to respective fuel jets improves the mixing. The overall burner pressure drop is significantly lower for this concept. The respective vortex generators produce counter rotating vortices which at a specified location pick up the axially spreading fuel jet.

In somewhat more detail three bodies 22 according to a modification of this first embodiment arranged within an annular secondary combustion chamber are given in perspective view in figure 3f, wherein the bodies are cut perpendicularly to the longitudinal axis 49 to show their interior structure, and in a cut perpendicular to the longitudinal axis in figure 3g.

In the cavity formed by the outer wall 59 of each body on the trailing side thereof there is located the longitudinal inner fuel tubing 57. It is distanced from the outer wall 59, wherein this distance is maintained by distance keeping elements 53 provided on the inner surface of the outer wall 59.

From this inner fuel tubing 57 the branching off tubing extends towards the trailing edge 29 of the body 22. The outer walls 59 at the position of these branching off tubings is shaped such as to receive and enclose these branching off tubings forming the actual fuel nozzles with orifices located downstream of the trailing edge 29.

In the essentially cylindrically shaped interior of the branching off tubings there is located a cylindrical central element 50 which leads to an annular stream of fuel gas. As between the wall of the branching off tubings and the outer walls 59 at this position there is also an essentially annular interspace, this annular stream of fuel gas at the exit of the nozzle is enclosed by an essentially annular carrier gas stream.

Towards the leading edge of the body 22 in the cavity formed by the outer wall 59 of the body in this embodiment there is located a carrier air tubing channel 51 extending essentially parallel to the longitudinal inner fuel tubing channel 57. Between the two channels 57 and 51 there is an interspace 55. The walls of the carrier air tubing channel 51 facing the outer walls 59 of the body 22 run essentially parallel thereto again distanced therefrom by distancing elements 53. In the walls of the carrier air tubing channel 51 there are located cooling holes 56 through which carrier air travelling through channel 51 can penetrate. Air penetrating through these holes 56 impinges onto the inner side of the walls 59 leading to impingement cooling in addition to the convective cooling of the outer walls 59 in this region.

Within the walls 59 there are provided the vortex generators 23 in a manner such that within the vortex generators cavities 54 are formed which are fluidly connected to the carrier air feed. From this cavity the effusion/film cooling holes 32 are branching off for the cooling of the vortex generators 23. Depending on the exit point of these holes 32 they are inclined with respect to the plane of the surface at the point of exit in order to allow efficient film cooling effects.

Embodiment 2:

Another embodiment of this concept as shown below in Figure 4, is to direct the fuel at a certain angle (can be increased up to 90°). In this case, the fuel is directed into the vortices and this has shown to improve mixing even further.

More specifically in this case there are, along the row of nozzles 15, a first set of three nozzles 15, which are directing the fuel jet 34 out of plane 35 at one side of plane 35, and the second set of nozzles 15' directing the corresponding fuel jet out of plane at the other side of plane 35. The more the fuel jets 34 are directed into the vortices the more efficient the mixing takes place.

Embodiment 3:

Another embodiment of this concept is to invert the vortex generators (facing upstream) as shown in figure 5. This helps in bringing the vortices closer to the fuel injection location with out producing adverse flow recirculations. The fuel injection locations can be varied with the vortex generator locations to improve the interaction of vortices with the fuel jet. Embodiment 4:

Another embodiment of inline injection will involve providing 2 fuel jets (injected at an angle) per VG. This would improve the mixing further since each fuel jet is conditioned by the surrounding vortex.

Embodiment 5:

Another embodiment involves increasing the number of flutes 22 and completely replaces the current outlet guide vanes of the high-pressure turbine. This provides better mixing and arrest adverse flow variations arising from the high-pressure turbine. In summary, at least the following advantages of the injection concept according to the invention when compared to existing premixed burners can be given:

• Inline injection offers better mixing performance at very low burner pressure drops.

• Savings in the burner pressure drop obtained with the proposed inline injection allows to burn highly reactive fuels and operating conditions. The existing designs pose operational issues for highly reactive fuels.

• Inline injection provides better control of fuel residing close to the burner walls when compared to the cross flow injection concepts. This provides higher flashback margin for the inline injection design.

• Reduced burner length resulting in reduction in cooling requirements. Possibility to replace burner effusion cooling air with TBC coated burner.

• Possibility to mitigate thermo acoustic pulsations due to increased fuel-air mixture asymmetry at the burner exit.

• Sufficiently high burner velocities in the entire burner length to avoid flame holding due to F/A mixture residing in recirculation regions.

• Inline fuel injection with appropriate vortex break down control ensures appropriate flame stabilization needed for premixed combustion..

LIST OF REFERENCE SIGNS burner 29 trailing edge of 23

mixing space, mixing zone 30 fuel gas feed

burner wall 31 carrier gas feed

combustion space 32 effusion/film cooling holes outlet side, burner exit 33 lateral surface of 22 inlet side 34 ejection direction of injection device fuel/carrier gas mixture main flow from compressor 35 central plane of 22 fuel mass fraction contour at 36 leading edge of 23

burner exit 5 48 cross-sectional profile of 22 combustion chamber wall 49 longitudinal axis of 22 transition between 3 and 12 50 central element

flow of oxidising medium 51 carrier air channel fuel nozzle 52 interspace between 37 and 51 converging portion of 3 53 distance keeping elements reduced burner cross- 54 cavity within 23

sectional area 55 interspace between 51 and 36 streamlined body, flute 56 cooling holes

vortex generator on 22 57 inner fuel tubing, longitudinal trailing edge of 22 part

leading edge of 22 58 branching off tubing of inner injection direction fuel tubing

lateral surface of 23 59 outer wall of 22

side surface of 23

Claims

1. Burner (1) for a single combustion chamber or first combustion chamber in particular of a gas turbine, with an injection device (7) for the introduction of at least one gaseous and/or liquid fuel into the burner (1), wherein the injection device (7) has at least one body (22) which is arranged in the burner (1) with at least one nozzle (15) for introducing the at least one fuel into the burner (1), wherein the at least one body (22) is located in a first section (18) of the burner (1) with a first cross-sectional area at a leading edge of the at least one body (22) with reference to a main flow direction (14) prevailing in the burner (1), wherein downstream of said body (22) a mixing zone (2) is located with a second cross- sectional area, and at and/or downstream of said body (22) the cross-sectional area is reduced, such that the first cross-sectional area is larger than the second cross- sectional area.

2. Burner (1) according to claim 1, wherein the second cross-sectional area is at least

10%, more preferably at least 20%, even more preferably at least 30%, smaller than the first cross-sectional area.

3. Burner (1) according to any of the preceding claims, wherein in the first section (18) the flow cross-sectional area of the burner is continuously reducing.

4. Burner (1) according to any of the preceding claims, wherein the body (22) has a longitudinal extension essentially along the main flow direction (14), and wherein the flow cross-sectional area of the burner is continuously reducing from the first cross-sectional area at least over a length of the longitudinal extension, preferably over twice the length of the longitudinal extension.

5. Burner (1) according to any of the preceding claims, wherein the injection device (7) injects fuel essentially along the main flow direction (14) or at an angle thereto of less than 90°, preferably of less than 30°, more preferably of less than 15°.

6. Burner according to any of the preceding claims, wherein the at least one body is configured as a streamlined body (22) which has a streamlined cross-sectional profile (48) and which extends with a longitudinal direction (49) perpendicularly or at an inclination to a main flow direction (14) prevailing in the burner (1), the at least one nozzle (15) having its outlet orifice at or in a trailing edge (24) of the streamlined body (22), wherein the body (22) has two lateral surfaces (33), and wherein preferably upstream of the at least one nozzle (15) on at least one lateral surface (33) there is located at least one vortex generator (23).

7. Burner (1) according to claim 6, wherein the vortex generator (23) has an attack angle in the range of 15-20° and/or a sweep angle in the range of 45-75°, preferably of 55-65°.

8. Burner (1) according to any of the preceding claims, wherein at least two nozzles (15) are arranged at different positions along a trailing edge (24) of the body (22), wherein upstream of each of these nozzles (15) at least one vortex generator (23) is located, and wherein preferably vortex generators (23) to adjacent nozzles (15) are located at opposite lateral surfaces (33), and wherein even more preferably more than three, most preferably at least four, nozzles (15) are arranged along said trailing edge (24) and vortex generators (23) alternatingly located at the two lateral surfaces (33).

9. Burner (1) according to any of the preceding claims 6-8, wherein downstream of each vortex generator (23) there are located at least two nozzles (15).

10. Burner (1) according to any of the preceding claims 6-9, wherein the streamlined body (22) extends across the entire flow cross section between opposite walls (3) of the burner (1).

11. Burner (1) according to any of the preceding claims, wherein at least two bodies (22), preferably in the form of streamlined bodies are arranged in the first section (18), wherein preferably , preferably between 3 streamlined bodies are arranged in the first section (18) with their longitudinal axes (49) are arranged essentially parallel to each other and with their central planes (35) arranged converging towards the mixing section (2).

12. Burner (1) as claimed in any of the preceding claims, wherein at least one body (22) is a streamlined body (22, and wherein the profile of the streamlined body (22) is inclined with respect to the main flow direction (14) at least over a certain part of its longitudinal extension wherein preferably the profile of the streamlined body (22) is rotated or twisted in opposing directions relative to the longitudinal axis on both sides of a longitudinal midpoint, in order to impose a mild swirl on the main flow.

13. Burner (1) according to any of the preceding claims 6-10, wherein the vortex generator (23) is provided with cooling elements (32), wherein preferably these cooling elements (32) are film cooling holes provided in at least one of the surfaces (27, 28) of the vortex generator (23), and wherein even more preferably the film cooling holes (32) are fed with air from the carrier gas feed (31) also used for the fuel injection.

14 . Burner (1) according to any of the preceding claims, wherein the body (22) is provided with cooling elements, wherein preferably these cooling elements are given by internal circulation of cooling medium along the sidewalls (33) of the body (22) and/or by film cooling holes, preferably located near the trailing edge (24), and wherein most preferably the cooling elements are fed with air from the carrier gas feed (31) also used for the fuel injection.

15. Burner (1) according to any of the preceding claims, wherein the fuel is injected from the nozzle (15) together with a carrier gas stream, and wherein the carrier gas air is low pressure air with a pressure in the range of 10-25 bar, preferably in the range of 16-20 bar.

16. The burner as claimed in one of the preceding claims, wherein body (22) is a streamlined body (22), and wherein the streamlined body (22) has a cross- sectional profile (48) which is mirror symmetric with respect to the central plane (35) of the body (22).

Use of a burner (1) according to any of the preceding claims for the combustion under a high reactivity conditions, preferably for the combustion at high burner inlet temperatures and/or for the combustion of MBtu fuel.