EP2191200B1 - Premix stage for a gas turbine burner - Google Patents

Abstract

The premixing stage (2) has a premixing channel (3) for supplying a combustion air mass flow to a gas turbine combustion chamber. A fuel nozzle is arranged in the premixing channel such that a fuel mass flow is introduced into the premixing channel in a peripheral direction around an inclined angle and is mixed with the combustion air mass flow. A fuel mass flow control unit is provided for controlling a fuel mass flow (12) such that twist of a combustion air-fuel mixture can be adjustable. A hole (6) is provided as the fuel nozzle in an outer wall (4). An independent claim is also included for a method for adjusting twist of a combustion air-fuel mixture.

Description

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 stream is formed. The hot gas stream is expanded in the turbine, which drives the compressor and provides a net output. 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 in terms of 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 to provide a premixing stage for a gas turbine combustor and a gas turbine combustor with the premix stage, wherein the gas turbine combustor has a high full load capacity and at the same time a further 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 supplied to the gas turbine burner, at least one first fuel nozzle, which is arranged in the premixing channel such that a first fuel mass flow in the circumferential direction by a first angle and introduced into the Vormischkanal is mixable with the combustion air mass flow, and a fuel mass flow control means for controlling the first fuel mass flow such that the swirl of the combustion air-fuel mixture is adjustable, wherein the premixing channel has an outer wall in which as the first fuel nozzle at least a first hole is provided which at least at the outlet into the interior of the premixing channel in its circumferential direction by the first angle is arranged inclined and the first fuel mass flow from outside the outer wall through the first hole in the interior of the premixing channel with high tangential velocity can be introduced, wherein in the outer wall as a second fuel nozzle at least one zw eites hole is provided which extends at least at the exit into the interior of the premixing channel perpendicular to the circumferential direction and the second fuel mass flow is introduced from outside the outer wall through the second hole in the interior of the premixing channel, whereby the second Brennstroffmassenstrom is introduced into the premixing channel without twisting, so that the second fuel mass flow does not act on the combustion air-fuel mixture with a twist.

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 can be adjusted by means of the premixing stage according to the invention, so that different operating points in the gas turbine burner according to the invention at different predetermined swirl intensities of the combustion air-fuel mixture are operable. 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 has at least one second fuel nozzle arranged in the premixing channel such that a second fuel mass flow can be introduced into the premixing channel in its circumferential direction by a second angle, which is a right angle to the circumferential direction of the premixing channel, and can be mixed with the mass flow of combustion air wherein the second angle is different from the first angle, and the fuel mass flow controller is configured to control the first and second fuel mass flow such that with a corresponding split of a given total fuel mass flow to the first fuel nozzle than the first fuel mass flow and to the second fuel nozzle second fuel mass flow of the swirl of the combustion air-fuel mixture 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 predetermined and controlled to define the combustion conditions in the gas turbine combustor.

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 swirl 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. Thereby, both the swirl of the combustion air-fuel mixture and the stoichiometric ratio between the fuel and the combustion air in the combustion air-fuel mixture are adjustable.

The premixing channel has an outer wall in which as the first fuel nozzle at least a first hole is provided, which is arranged 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 outer wall through the first Hole in the interior of the premixing channel high tangential velocity 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.

In the outer wall is provided as the second fuel nozzle at least a second hole, at least at the outlet into the interior of the premixing channel perpendicular to its circumferential direction runs and the second fuel mass flow from outside the outer wall through the second hole in the interior of the premix channel can be introduced.

Thus, the second fuel mass flow in the premixing channel can be introduced twist-free, so that the swirl of the combustion air-fuel mixture can be at least not 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.

Thereby, the first fuel mass flow and the second fuel mass flow are distributed evenly distributed in the premixing duct over the circumference, so that the mixing of the first fuel mass flow, the second fuel mass flow and the combustion air is uniform and thus loss.

Furthermore, 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 and / or at the pressure side of the vane as a second fuel nozzle at least one fourth hole at the suction side of the vane as a first fuel nozzle are provided, and from within the vane a third fuel mass flow through the third hole and a fourth fuel mass flow through the fourth hole in the interior of the premix channel can be introduced.

By means of the guide vane, the combustion air mass flow is deflected, whereby the swirling of the combustion air mass flow can be accomplished. The third fuel mass flow enters the mass air flow through the third hole on the suction side of the vane, so that the third fuel mass flow attenuates the swirl of the mass air flow. The fourth fuel mass flow enters the mass air flow through the fourth hole on the pressure side of the vane, so that the fourth fuel mass flow amplifies the swirl of the mass air flow. Thus, by means of a predetermined determination of the ratio between the third fuel mass flow and the fourth 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 swirl impingement of the combustion air mass flow in the premixing duct and thus the swirl influence by the third and the fourth fuel mass flow are evenly distributed over the circumference of the premixing duct. 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.

Fig. 1

einen Querschnitt durch eine Vormischstufe eines erfindungsgemäßen Gasturbinenbrenners,

Fig. 2

einen Längsschnitt der Vormischstufe der Gastur- binenbrennkammer und

Fig. 3

eine perspektivische Darstellung der Vormischstufe der Gasturbinenbrennkammer.

In the following, the invention is based on a preferred embodiment of a gas turbine combustor according to the invention explained with reference to the accompanying schematic drawings. It shows:

Fig. 1

a cross section through a premixing stage of a gas turbine burner according to the invention,

Fig. 2

a longitudinal section of the premixing stage of Gasturbinenbrennkammer and

Fig. 3

a perspective view of the premixing stage of the gas turbine combustor.

Like it out Fig. 1 to 3 It can be seen that 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 is arranged concentrically around the inner wall 5 and thereby forms 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 in the in Fig. 1 shown cross section in the outer wall 4 inclined by a first angle 14 to the circumferential direction of the premixing channel 3. 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 in Fig. 1 seen the first fuel mass flow 12 with a twist is associated with a clockwise direction of rotation. 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 channel 3, so that the second fuel mass flow 13 does not act on the combustion air-fuel mixture 11 with a twist.

Thus, depending on how large the first fuel mass flow 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 is acted upon by the guide vanes 8 of the combustion air mass flow with swirl. The guide vanes 8 are designed as hollow profile guide vanes, wherein gaseous fuel is present in the interior of the guide vanes 8.

On the suction side of the guide vanes 8, a plurality of third holes 9 is provided through which a third 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 fourth 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 third fuel mass flow 12 causes an amplification of the swirl of the combustion air-fuel mixture 11, whereas the fourth fuel mass flow 13 causes a reduction in the swirl of the combustion air-fuel mixture 11. Thus, depending on the strength of the third fuel mass flow 12 and the fourth fuel mass flow 13, the twist 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 fuel flowing out of the premixing channel 3 can be adjusted when the ratio of the fuel mass flow flowing through the first and second holes 6, 7 and the fuel mass flow flowing through the third and fourth holes 9, 10 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 accomplished by means of a fuel mass flow control device (not shown) while maintaining a constant total fuel mass flow.

Claims (9)

1. Premixing stage for a gas turbine burner (1), with a premixing duct (3), by means of which a combustion-air mass flow can be supplied to the gas turbine burner (1), with at least one first fuel nozzle (6, 9) which is arranged in the premixing duct (3) in such a way that a first fuel mass flow (12) can be introduced, inclined at a first angle (14), into the premixing duct (3) in the circumferential direction of the latter and can be mixed with the combustion-air mass flow, and with a fuel mass flow control device for controlling the first fuel mass flow (12) in such a way that the swirl of the combustion-air/fuel mixture (11) arising therefrom can be set, the premixing duct (3) having an outer wall (4) in which there is provided as the first fuel nozzle at least one first hole (6) which, at least at the outlet into the inner space of the premixing duct (3), is arranged, inclined at the first angle (14), in the circumferential direction of the latter, and the first fuel mass flow being capable of being introduced from outside the outer wall (4) through the first hole (6) into the interior of the premixing duct (3) at high tangential velocity, characterized in that there is provided in the outer wall (4), as a second fuel nozzle, at least one second hole (7) which, at least at the outlet into the inner space of the premixing duct (3), runs perpendicularly to the circumferential direction of the latter, and the second fuel mass flow (13) can be introduced from outside the outer wall (4) through the second hole into the interior of the premixing duct (3), with the result that the second fuel mass flow (13) is introduced, swirl-free, into the premixing duct (3), so that the second fuel mass flow (13) does not act with a swirl upon the combustion-air/fuel mixture (11).
2. Premixing stage according to Claim 1, the first and the second holes (6, 7) being distributed uniformly over the circumference of the premixing duct (3) and being arranged alternately.
3. Premixing stage according to Claim 2, the premixing duct (3) having at least one guide vane (8) with a hollow profile for acting with a swirl upon the fuel mass flow, at least one third hole (9) being provided as a first fuel nozzle on the suction side of the guide vane (8) and/or at least one fourth hole (10) being provided as a second fuel nozzle on the pressure side of the guide vane (8), and also a third fuel mass flow (12) being capable of being introduced from inside the guide vane (8) through the third hole (9) into the interior of the premixing duct (3) and a fourth fuel mass flow (13) being capable of being introduced from inside the guide vane (8) through the fourth hole (10) into the interior of the premixing duct (3).
4. Premixing stage according to Claim 3, the premixing duct (3) having a guide vane ring which is formed by a plurality of the guide vanes (8).
5. Premixing stage according to one of Claims 1 to 4, the first and/or the second holes (6, 7) being arranged downstream of the guide vane (8) in the premixing duct (3).
6. Premixing stage according to Claim 1, the premixing duct (3) having a ring of hollow guide vanes (8) for acting with a swirl upon the combustion-air mass flow.
7. Gas turbine burner having a premixing stage according to one of Claims 1 to 6.
8. Gas turbine combustion chamber having a gas turbine burner according to Claim 7.
9. Method for setting the swirl of a combustion-air/fuel mixture (11) of a premixing stage according to one of Claims 1 to 8, in which, in order to vary the swirl present in the combustion-air/fuel mixture, a fuel mass flow can additionally be introduced in the circumferential direction into the combustion-air/fuel mixture.

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