WO2009040218A1

WO2009040218A1 - Premix stage for a gas turbine burner

Info

Publication number: WO2009040218A1
Application number: PCT/EP2008/061499
Authority: WO
Inventors: Eberhard Deuker; Jürgen MEISL; Bernd Prade
Original assignee: Siemens Aktiengesellschaft
Priority date: 2007-09-25
Filing date: 2008-09-01
Publication date: 2009-04-02
Also published as: ATE514039T1; EP2191200A1; EP2042807A1; EP2191200B1

Abstract

A premix stage for a gas turbine combustion chamber has a premix channel, by way of which a combustion air mass flow may be supplied to the gas turbine combustion chamber, at least one first fuel nozzle, which is situated in the premix channel such that a first fuel mass flow may be introduced into the premix channel in the peripheral direction thereof inclined by a first angle and can be mixed with the combustion air mass flow, and a fuel mass flow control unit for controlling the first fuel mass flow such that the twist of the combustion air-fuel mixture can be set.

Description

description

Premix stage for a gas turbine burner

The invention relates to a premix stage for a gas turbine combustor, a gas turbine combustor with the premix stage, and a method for adjusting a swirl of a premix stage.

A gas turbine has a compressor, a combustion chamber and a turbine. In the combustion chamber, a combustion air-fuel mixture is brought to the ignition, whereby a hot gas flow is produced. The hot gas flow is released in the turbine, which drives the compressor and provides useful power. The net power may be, for example, a shaft power for driving a generator in a power plant.

In the gas turbine both liquid and gaseous fuels can be burned in the combustion chamber. Conventionally, a premix combustion is used in the gas turbine, in which the fuel and the combustion air are passed through a burner as evenly as possible premixed into the combustion chamber. In this case, the combustion air-fuel mixture has a large excess of air, whereby the combustion in the combustion chamber is lean. As a result, the flame temperature in the combustion chamber is uniformly low, so that the formation of hot spots in the combustion chamber is prevented. Thus, the nitrogen oxide formation in the combustion chamber is low.

The combustion air-fuel mixture is subjected to a twist in the burner of the combustion chamber, whereby the flow field of the flame and the mixing processes in the flame are improved and thus the stability of the flame in the combustion chamber is increased. As a measure of the swirl, which is applied to the combustion air-fuel mixture, the swirl number is known. The swirl number is formed from the Ratio of the velocity components in the circumferential direction and in the main flow direction of the combustion air-fuel mixture flow.

The operating behavior of the combustion chamber or the burner is highly dependent on the swirl number. For example, a swirl number is desired for full load operation, in which there is good thermoacoustic stability in the combustion chamber. However, if the combustion chamber is operated at the same swirl number in a partial load operation, the combustion takes place in the combustion clamp to form a high CO concentration, so that the outflowing hot gas has a high CO emission. Thus, the full load operation with optimal combustion conditions and the partial load operation with only poor combustion conditions are faced.

Conventionally, a swirl number is selected for the combustion air-fuel mixture, which represents a compromise with regard to the combustion conditions in full load operation and in partial load operation. The swirl number may for example be selected such that a predetermined operating specification in part-load operation, such as a maximum permissible CO emission, is still complied with and in full load operation, the combustion chamber still has a reasonably high performance. However, this power is lower than the maximum achievable performance of the combustion chamber at full load, whereby the operation of the gas turbine from an energetic point of view is not optimal.

The object of the invention is a Vormischstufe for a

Gas turbine burner and a gas turbine burner with the pre-mixing stage to create, the gas turbine burner has a high full load capacity and at the same time another low-emission operating range.

Another task is to specify a method for this purpose. The premixing stage according to the invention for a gas turbine burner has a premixing duct, with which a combustion air mass flow can be fed to the gas turbine combustor, at least one first fuel nozzle, which is arranged in the premixing duct such that a first fuel mass flow into the premixing duct in its circumferential direction by a first angle and fuel mass flow control means for controlling the first fuel mass flow such that the swirl of the combustion air-fuel mixture is adjustable to be inclinable and miscible with the combustion air mass flow;

The gas turbine burner according to the invention has the premixing stage.

The operating behavior of the gas turbine burner is dependent on the swirl, which has the combustion air-fuel mixture. Thus, for part-load and full-load operation of the gas turbine burner, for example, achieving good thermoacoustic stability or low CO emission is only possible if the swirl of the combustion air-fuel mixture has a corresponding strength. This swirl intensity is adjustable by means of the premixing stage according to the invention, so that in the gas turbine burner according to the invention different operating points at different predetermined swirl intensities of the combustion air-fuel mixture can be operated. Thus, according to predetermined target parameters of the gas turbine combustor, such as the thermoacoustic stability and / or the CO emission can be achieved by adjusting the twist of the combustion air-fuel mixture.

The premixing stage preferably has at least one second fuel nozzle which is arranged in the premixing channel in such a way that a second fuel mass flow can be introduced into the premixing duct in its circumferential direction inclined at a second angle and can be mixed with the combustion air mass flow, the second angle being from the first Angle is different, and the fuel mass flow control Direction for controlling the first and second fuel mass flow is set up such that with a corresponding distribution of a given total fuel mass flow to the first fuel nozzle as the first fuel mass flow and the second fuel nozzle as a second fuel mass flow of the swirl of the combustion air-fuel Ge - Mix is adjustable.

The combustion in the gas turbine combustor is further adjusted via the stoichiometric ratio between the total fuel mass flow and the mass air flow of the combustion air. The total fuel mass flow is usually chosen such that in the gas turbine combustion chamber, the combustion proceeds under excess oxygen, so it is lean. Thus, in addition to the swirl of the combustion air-fuel mixture, the total fuel mass flow is preset and controlled in order to define the combustion conditions in the gas turbine combustion chamber.

When the total total fuel mass flow through the first fuel nozzle is given as the first fuel mass flow into the premixing passage, the swirl of the combustion air-fuel mixture is defined by the magnitude of the first angle. In an analogous manner, the spin of the combustion air-fuel mixture is defined by the magnitude of the second angle when the total total fuel mass flow through the second fuel nozzle is added as the second fuel mass flow into the premix channel. By the first and the second angle of the swirl region is predetermined, which is available for adjusting the twist of the combustion air-fuel mixture. Depending on how the total fuel mass flow is distributed to the first fuel nozzle as the first fuel mass flow and to the second fuel nozzle as the second fuel mass flow, the spin is adjustable within the range defined by the first and second angles. As a result, both the swirl of the combustion air-fuel mixture and the stoichiometric ratio between see the fuel and the combustion air in the combustion air-fuel mixture adjustable.

It is preferred that the premixing channel has an outer wall in which as the first fuel nozzle at least a first hole is provided which is inclined at least at the outlet into the interior of the premixing channel in its circumferential direction by the first angle and the first fuel mass flow from outside the Outside wall through the first hole in the interior of the premixing channel high tangential speed can be introduced.

As a result, the first angle is determined by the position of the exit of the hole in the interior of the premixing channel. Further, the first fuel mass flow is determined by the narrowest cross section of the first hole and the pressure difference across the first hole. Thus, the first fuel mass flow may be controlled by a pressure variation of the fuel from outside the outer wall and / or by a cross-sectional variation of the first hole.

Furthermore, it is preferred that at least one second hole is provided in the outer wall as the second fuel nozzle, which extends at least at the outlet into the interior of the pre-mixing channel perpendicular to the circumferential direction and the second fuel mass flow from outside the outer wall through the second hole in the Inside the Vormischkanals can be introduced.

Thus, the second fuel mass flow in the premixing channel can be introduced without twisting, so that the swirl of the combustion air-fuel mixture can at least not be increased by increasing the second fuel mass flow. If the combustion air in the premixing duct upstream of the second hole is already flooded, the introduction of the second fuel mass flow leads to a reduction of the twist of the combustion air-fuel mass flow. It is preferable that the first and second holes are uniformly distributed over the circumference of the premix channel and arranged alternately.

As a result, the first fuel mass flow and the second fuel mass flow are distributed uniformly over the circumference thereof in the premixing duct, so that the mixing of the first fuel mass flow, the second fuel mass flow and the combustion air is uniform and thus low-loss.

Alternatively, it is preferred that the premixing channel has at least one guide vane with a hollow profile for swirling the mass flow of combustion air, at least one third hole on the suction side of the vane as the first fuel nozzle and / or at least one fourth hole on the pressure side of the vane as the second fuel nozzle are provided, and from within the guide vane, the first fuel mass flow through the third hole and the second fuel mass flow through the fourth hole in the interior of the premixing channel can be introduced.

By means of the guide vane, the combustion air mass flow is deflected, whereby the swirl impingement of the combustion air mass flow can be accomplished. The first fuel mass flow enters the mass air flow through the third hole on the suction side of the vane, so that the first fuel mass flow attenuates the swirl of the mass air flow. The second fuel mass flow enters the mass air flow through the fourth hole on the pressure side of the vane, so that the second fuel mass flow amplifies the swirl of the mass air flow. Thus, by means of a predetermined determination of the ratio between the first fuel mass flow and the second fuel mass flow, the influence of the two fuel mass flows on the swirl of the combustion air-fuel mixture can be adjusted. Preferably, the premixing channel has a vane ring which is formed by a plurality of the guide vanes.

As a result, the swirling of the combustion air mass flow in the premixing channel and thus the swirl influence by the first and the second fuel mass flow over the circumference of the premixing duct is evenly distributed. Thus, the mixing operations in the premix channel are uniform and low loss.

The first and / or the second holes are preferably arranged in the premixing channel downstream of the guide blade. The second holes may also be arranged upstream of the swirl generator or in the swirl generator.

Thereby, in combination, the first, second, third and fourth holes can be used as a means for adjusting the twist of the combustion air-fuel mixture. Thus, the swirl of the fuel-combustion air mixture is adjustable over a wide range.

In the following the invention will be explained with reference to a preferred embodiment of a gas turbine combustor according to the invention with reference to the accompanying schematic drawings. It shows:

1 shows a cross section through a premixing stage of a gas turbine burner according to the invention, Fig. 2 shows a longitudinal section of the premixing stage of the gas turbine combustor and

Fig. 3 is a perspective view of the premixing stage of the gas turbine combustor.

As can be seen from FIGS. 1 to 3, a gas turbine burner 1 has a premixing stage 2 with a premixing channel 3. The premixing stage 2 has an inner wall 5 and an outer wall 4 which are concentric about the inner wall 5 is arranged, thereby forming the premixing channel 3 together with the inner wall 5.

Distributed over the circumference of the outer wall 4 are provided in this ten pairs of first holes 6 and second holes 7. The first holes 6 and the second holes 7 are each equally spaced over the circumference uniformly distributed and arranged alternately. The first holes 6 are arranged in the cross-section shown in Fig. 1 in the outer wall 4 at a first angle 14 to the circumferential direction of the premixing channel 3 inclined. The second holes 7 are arranged to extend in the outer wall 4 in the radial direction of the premixing channel 3, so that a second angle 15 to the circumferential direction of the premixing channel 3 is a right angle.

On the outside of the outer wall 4 is gaseous fuel with an overpressure compared to the pressure in the premixing channel 3 at. As a result, the gaseous fuel flows through the first holes 6 as a first fuel mass flow 12 and through the second holes 7 as a second fuel mass flow 13. The first fuel mass flow 12 flows obliquely into the premixing channel 3, so that the first fuel mass flow 12 is seen in FIG is twisted with a twist with a clockwise direction. In the premixing channel 3 is combustion air, which mixes with the first fuel mass flow 12, so that the resulting combustion air-fuel mixture 11 is subjected to the swirl. The second fuel mass flow 13 flows radially into the premixing duct 3, so that the second fuel mass flow 13 does not impart a swirl to the combustion air-fuel mixture 11.

Thus, depending on how large the first Brennstoffmassen- ström 12 and / or the second fuel mass flow 13 is selected, the swirl of the combustion air-fuel mixture 11 can be adjusted. Further, the premixing stage 2 has a plurality of vanes 8 arranged in the premixing channel 3 as a vane ring. The guide vanes 8 cause a deflection of the combustion air mass flow, so that by the guide vanes 8 of the combustion air mass flow is subjected to swirl. The guide vanes 8 are designed as Hohlprofilleitschaufein, wherein 8 is present in the interior of the vanes gaseous fuel.

On the suction side of the guide vanes 8, a plurality of third holes 9 is provided, through which a first fuel mass flow 12 can escape. On the pressure side of the guide vanes 8, a plurality of fourth holes 10 is provided, through which a second fuel mass flow 13 can escape. The fuel mass flows 12, 13, which enters the combustion air mass flow through the third and / or fourth holes 9, 10, mix with it and form the combustion air-fuel mixture. The first fuel mass flow 12 causes an amplification of the swirl of the combustion-air fuel mixture 11, whereas the second fuel mass flow 13 causes a lowering of the swirl of the combustion air-fuel mixture 11. Thus, depending on the strength of the first fuel mass flow 12 and the second fuel mass flow 13, the swirl of the combustion air-fuel mixture 11 can be adjusted.

The first holes 6 and the second holes 7 are located downstream of the trailing edge of the guide vanes 8, so that by an appropriate distribution of the fuel mass flows 12, 13 on the first and / or the second and / or the third and / or the fourth holes 6, 7, 9, 10, the twist of the combustion air-fuel mixture 11 is adjustable.

In particular, the swirl of the total mass flow of combustion air flowing out of the premixing channel 3 can be set if the ratio of the fuel mass flow flowing through the first and second holes 6, 7 and the fuel mass flowing out through the third and fourth holes 9, 10. senstrom is varied, the sum of both fuel mass flows is constant.

The method according to the invention thus envisages distributing the fuel mass flow over the guide vanes and via the first and second holes 6, 7 so that the most favorable swirl in the entire fuel / combustion air mixture 11 is set for the respective operating conditions, thus ensuring low emissions to achieve a constant combustion. For amplification (weakening) of the twist impressed by the guide vanes, the fuel mass flow supplied via the holes 6, 7 can be increased (reduced).

The control of the fuel mass flows 12, 13 through the first and / or the second and / or the third and / or the fourth holes 6, 7, 9, 10 is effected by means of a fuel mass flow control device (not shown) while maintaining a constant total fuel mass flow. stelligbar.

Claims

claims

A premixing stage for a gas turbine combustor (1), comprising a premixing duct (3) for supplying a combustion air mass flow to the gas turbine combustor (1), at least one first fuel nozzle (6, 9) arranged in the premixing duct (3) arranged that a first fuel mass flow (12) in the Vormisch- channel (3) in its circumferential direction by a first angle (14) is introduced inclined and mixable with the combustion air mass flow, and a fuel mass flow control means for controlling the first fuel mass flow (12) in such a way that the swirl of the combustion air-fuel mixture (11) is adjustable.

2. Premixing stage according to claim 1, wherein the premixing stage (2) has at least one second fuel nozzle (7, 10) which is arranged in the premixing channel (3) such that a second fuel mass flow (13) is introduced into the premixing channel (3). in its circumferential direction inclined about a second angle (15) can be introduced and mixed with the Brennluftmas- senstrom, the second angle (15) from the first angle (14) is different, and the fuel mass flow control device for controlling the first and the second Fuel mass flow (12, 13) is arranged such that with a corresponding distribution of a given total fuel mass flow to the first fuel nozzle (6, 9) as the first fuel mass flow (12) and the second fuel nozzle (7, 10) as a second fuel mass flow (13) the swirl of the combustion air-fuel mixture (11) is adjustable.

3. premix stage according to claim 1 or 2, wherein the premixing channel (3) has an outer wall (4) in which as the first fuel nozzle at least a first hole (6) is provided which at least at the outlet into the interior of the premix channel (3). in the circumferential direction about the first angle (14) is arranged inclined and the first fuel mass flow from outside the outer wall (4) through the first hole (6) into the interior of the premixing channel (3) with high tangential velocity can be introduced.

4. premix stage according to claim 3, wherein in the outer wall (4) as the second fuel nozzle at least a second hole (7) is provided which at least at the outlet into the interior of the premixing channel (3) perpendicular to the circumferential direction and the second Fuel mass flow (13) from outside the outer wall (4) through the second hole in the interior of the premixing duct (3) can be introduced.

5. Premixing stage according to claim 4, wherein the first and the second holes (6, 7) are evenly distributed over the circumference of the premixing channel (3) and arranged alternately.

6. Premixing stage according to claim 2, wherein the premixing channel (3) has at least one guide blade (8) with a hollow profile for swirling the combustion air mass flow, at least one third hole (9) being provided on the suction side of the guide blade (8) as the first fuel nozzle. and / or on the pressure side of the guide vane (8) as the second fuel nozzle at least a fourth hole (10) are provided, and from within the guide vane (8) of the first fuel mass flow (12) through the third hole (9) and the second fuel mass flow (13) through the fourth hole (10) into the interior of the premixing duct (3) can be introduced.

A premixing stage according to claim 6, wherein the premixing duct (3) comprises a vane ring formed by a plurality of the vanes (8).

8. premix stage according to one of claims 3 to 7, wherein the first and / or the second holes (6, 7) in the premixing channel (3) are arranged downstream of the guide vane (8).

9. premixing stage according to claim 1, wherein the premixing channel (3) has a ring of hollow guide vanes (8) for swirling the Brennluftmassen- current.

10. Gas turbine burner with a premixing stage according to one of claims 1 to 9.

11. Gas turbine combustor with a gas turbine burner according to claim 10.

12. A method for adjusting the swirl of a combustion air-fuel mixture (11) a premixing stage according to one of claims 1 to 9, wherein for changing the present in the combustion air-fuel mixture swirl a fuel mass flow in the circumferential direction in the combustion air fuel Mixture is additionally einbringbar.