EP1855054B1 - Method for supplying fuel to a premix burner - Google Patents

Description

Technical area

The invention relates to a device with a premix burner, a fuel supply and a control unit for operating a gas turbine, wherein the premix burner has at least one burner shell at least partially delimiting an axially extending premixing chamber, with one directed into the premixing chamber via the burner cup Premix gas supply, wherein the premix gas is mixed with combustion air and ignited downstream, outside the premix burner.

State of the art

Premix burners of the aforementioned type are well known for operating gas turbine plants and have different premix burner geometries. So is in the EP 0 321 809 B1 a cone-shaped premix burner consisting of several burner shells, a so-called double-cone burner, whose burner shells are composed in such a way that tangential air inlet slots for the combustion air are formed along the burner axis. At the inflow edges of the burner shells formed thereby are provided outlet openings for the premix gas, which are distributed in the direction of the burner axis. The injection of the premix gas through the outlet openings along the inflow edges of the burner shells leads due to the burner shell geometry in conjunction with the combustion air supply to a swirling mixing of the premix gas and the combustion air supply.

Another premix burner geometry is in the WO 93/17279 shown, in which the premix burner is formed with an additional conical inner body. Also in this case, the premix gas is fed into the premix burner via respective exit openings arranged along the axially extending air inlet slots, where the premix gas is mixed with combustion air and ignited downstream within the combustion chamber.

Now it is possible to make optimizations by suitable choice of the arrangement, size, number of outlet openings and their mutual distance with regard to the quality of the combustion. In particular, the emission values, the extinguishing behavior of the flame forming in the combustion chamber, the flame backflow behavior and the flame stability can be decisively influenced by a suitable choice of the abovementioned parameters.

However, the optimization possibilities described above quickly reach their limits if one wishes to take measures to optimize the burner behavior not only with a fixed burner geometry and with an ideal combustion state. Thus, it is almost impossible to keep the combustion behavior at a virtually constant optimum level with a structurally predetermined arrangement of outlet openings along certain areas of the burner shells, the combustion behavior under different load and ambient conditions. It has been found that an optimized arrangement of outlet ports for the premix gas supply within the premix burner, which has been optimally designed for the use of a particular type of machine, for example, for use in an annular combustion chamber, poor or not at all for use in another Machine type, for example, for use in a silo combustion chamber, use.

Also occur during the use of a burner creeping burner system changes that are caused by fatigue and lead, for example, to an increase in leakage air currents. Due to the fixed predetermined arrangement of Premixgasdurchtrittsöffnungen, which are themselves subject to no or only negligible aging phenomena, the aging-related changes can not be compensated jeodch, whereby a deterioration of the combustion process with increasing duration of the burner is inevitable.

Existing premix gas supply systems are typically optimized for the medium and high load ranges of gas turbines in terms of low emissions and cushioned combustion oscillations. In order to start the combustion process and to reach the middle load range of the gas turbine, pilot stages are usually used. Usually, pilot gas is fed into the interior of the premix burner in the center of the premix burner axis via a burner lance, which mixture is mixed with combustion air and brought to ignition. Only after reaching a certain load range, the pilot gas supply is switched off and the Premixgaszufuhr be put into operation. In the same way, such switching occurs when the gas turbine is shut down, in which the premix gas supply is switched off and the pilot gas supply is switched on. In the switching processes, however, high combustion oscillations occur within the burner system, which are associated with strong pressure fluctuations, which in turn have an immediate and disturbing effect on the load behavior of the gas turbine, which is consequently subjected to large load oscillations.

When a gas supply system is shut down both when the gas turbine is raised and lowered, it is necessary to purify the shut-off gas supply lines with inert gas in order to re-ignite the gas To exclude supply line into it and to avoid their damage. The amount of inert gases required for the purification of the gas supply takes on a considerable extent and not least also leads to high operating costs of such burner systems.

Finally, with the presently known premix burners, it is almost impossible to operate the premix burner with different types of fuel, such as liquid or gaseous fuel, especially as the burner lance generally arranged centrally in the burner axis for supplying pilot gas, as mentioned above, for powering up the gas turbine and for the lower load range is required, is located in close proximity to the central liquid fuel nozzle. Unintended ignition interactions between the two fuel outlets can not be excluded.

The two writings DE-A1-44 46 945 and EP-A1-0 592 717 disclose gas-powered premix burners in which combustion air is introduced at least approximately tangentially into the pre-mixing chamber of the burner. Fuel is injected via a plurality of nozzles arranged in the longitudinal direction of the premixing chamber and mixed with the combustion air. The nozzles are divided into at least two groups with different fuel supply.

Presentation of the invention

The invention has the object of providing a device with a premix burner, a fuel supply and a control or regulating unit according to the preamble of claim 1 such that the above-mentioned prior art disadvantages are avoided. In particular, it is necessary to take measures at the premix burner, so that an optimized adaptation of the premix burner behavior in the entire load range of the gas turbine is possible. This should in particular be done without great technical and design effort and be feasible with only a small cost.

The solution of the problem underlying the invention is specified in claim 1. The concept of the invention advantageously further features are the subject of the dependent claims and the description, in particular with reference to the figures refer.

The idea underlying the invention is the axial stepped supply of premix gas along the flanks of the burner shells by the burner shells are divided into at least two axially successively arranged areas, which are each supplied via Premixgaszuführleitungen separated. The separate areas along the burner shells are arranged axially behind one another in the direction of flow of the premix burner, wherein it has been recognized according to the invention that more than 60% of the total premix gas supply is to be made via the upstream first region for starting up the gas turbine and that the load is required for the further startup Gas turbine to full load a gradual or continuous redistribution of Premixgaszuführung on the downstream of the first area adjacent areas takes place.

Due to the axial subdivision of the Premixgaszuführung along the burner bowls of the premix burner and in particular the stepwise supply of the individual areas with premix gas, it is possible to completely dispense with the supply of pilot gas, even in the case of starting and in lower load ranges of the gas turbine.

The elimination of a pilot gas stage is associated with a number of advantages, resulting not least by the elimination of the connected by the switching of pilot gas to Premixgaszufuhr Brennkammeroszillationen.
With the mode of operation of a premix burner according to the invention, it is now possible to operate a gas turbine from startup to full load without a pilot gas stage. The continuous or incremental connection of individual areas, via which premix gas enters the interior of the premix burner, takes place with the aid of provided in the individual Premixgaszuführleitungen control or regulating units, which are formed in the simplest case as a controllable throttle valves.

Due to the advantageous omission of a pilot gas supply, it is particularly possible to atomize liquid fuel through a central, projecting into the burner mouth injection nozzle, which in turn is suitably surrounded by a tubular combustion air flow.

An embodiment designed according to the invention for the targeted supply control of premix gas for the burner shells of the premix burner subdivided into different regions is set out in the following description with reference to the figures. An essential aspect of the device described in detail below is the separate, metered premix gas supply to the individual, axially successively arranged regions along the burner shells, through which the premix gas is injected into the interior of the premix burner.

Brief description of the invention

Figur 1

schematische Querschnittsdarstellung durch einen kegelförmig ausgebildeten Vormischbrenner,

Figur 2

Diagrammdarstellung zur Betriebsweise der in Figur 1 dargestellten Ausführungsform,

Figur 3

schematisierter Plan zum Verlauf von Zufuhrleitungen zur Versorgung des Vormischbrenners mit Premixgas,

Figur 4

Ausführungsbeispiel eines Regelventils.

The invention will now be described by way of example without limitation of the general inventive idea by means of embodiments with reference to the drawing. Show it:

FIG. 1

schematic cross-sectional view through a cone-shaped premix burner,

FIG. 2

Diagram representation of the mode of operation of in FIG. 1 illustrated embodiment,

FIG. 3

schematic plan for the course of supply lines for supplying the premix burner with premix gas,

FIG. 4

Embodiment of a control valve.

Ways to carry out the invention, industrial applicability

In FIG. 1 is a schematic representation of a longitudinal section through a cone-shaped Vormischbrenner shown. The premix burner has cone-shaped burner shells 1, 2 along which premix gas outlet openings 3 are provided in the axial direction of the burner longitudinal axis A, through which premix gas can be fed into the interior of the premix burner. The burner shells 1, 2 are divided into two differently separated regions, stage S1 and stage S2, which are supplied with premix gas by different premix gas supply lines 4, 5. As tangential in the direction of the conical shape is by not in the FIG. 1 shown air inlet slots supply air led into the interior of the premix burner, which mixes with the premix gas 6 to a fuel air mixture.

Optionally, a liquid fuel atomization direction 7 can be provided in the center of the premix burner, which allows mixing operation or switching from gaseous fuel to liquid fuel. The supply of liquid fuel takes place with the aid of a known atomizing nozzle, which generates a conically spreading atomizing cloud within the premix burner. For protection against the Premixgasaustrittsöffnungen 3 and for purposes of shape stabilization, the spreading liquid fuel cloud is surrounded by a protective air jacket.

To start the gas turbine, that is to ignite the premix burner, a pilot is not, as is common in the prior art, made, but in the illustrated in the embodiment two-stage premix burner each area of the burner shell is supplied with a Premixgaszufuhr upstream in the premix burner is arranged. In the exemplary embodiment, this is the area stage 1, which is operated for starting and for operating the premix burner in the low load range with more than 60% of the total Premixgaszuführung.

Out FIG. 2 An overview diagram emerges from which the percentage distribution of the premix gas distribution between area S1 and area S2 increases can be found. The fields entered in black correspond to the portion of the premix gas exiting via region 1, the brighter fields in each case to the premix gas fraction which reaches the interior of the burner via region S2 of the premix burner. As mentioned above, in the ignition, the lion's share (ie, more than 90%) of the entire premix gas supply flows over the region S1 into the interior of the premix burner. In the lower load range (idle), the proportion of the premix gas emerging over the region S2 increases slightly. In the case of the half-load state, both areas S1 and S2 are supplied with premix gas in approximately equal parts. In full-load operation, slightly more premix gas enters the premix burner via area S2 than over area 1. The in FIG. 2 shown Premixgaszuteilung on the areas S1 and S2 by means of a control unit, which can gradually or continuously make the division ratio of the Premixgaszuteilung on the areas S1 and S2. In the simplest case, these are coupled throttle valves, which are respectively provided in the individual Premixgaszuführleitungen 4 and 5.

Another possibility of controlled premix gas supply to the separate areas of the premix burner is shown in the schematic representation according to FIG FIG. 3 refer to. Again, it is in accordance with the embodiment FIG. 3 around a cone-shaped premix burner, which has two regions S1 and S2, via which premix gas enters the interior of the premix burner separately. In a common supply line 8, via which premix gas is supplied to the premix burner, a main control valve 9 is provided. Via the main control valve 9, the direct inflow of premix gas to the area S1 of the premix burner can be regulated. In the supply line between the main control valve 9 and the outlet region S1 of the premix burner, a crossing point 10 is provided at which a portion of the premix gas is discharged into a branch line 11. In the branch line 11, a further control unit in the form of a spring-loaded pressure relief valve 12 is provided, which will be described in more detail below with reference to FIG. 4 is described. A bypass line 13 whose flow cross-section is small enough or in the a corresponding throttle element 14 is provided, ensures that when the control valve 12 is closed, a small premix gas flow to the region S2 of the premix burner can be supplied.

This in FIG. 3 shown supply system for premix gas to the two areas S1 and S2 of the premix burner now has the following operation. After opening the main control valve 9, the area S1 of the premix burner is supplied with premix gas. The gas pressure within the supply line which supplies the region S1 with premix gas as well as also in the branch line 11 is not yet able to open the overpressure valve subjected to spring force. Only a small proportion of premix gas passes via the bypass line 13 to the area S2 of the premix burner and exits there into the interior of the premix burner. This corresponds to the state when starting the gas turbine or when igniting the premix burner. After the start-up phase, the prevailing in the branch line 11 Premixgasdruck increases, which is able to open the spring-loaded throttle valve 12 continuously, whereby an increasing proportion of flowing through the main control valve 9 premix gas flows through the pressure relief valve 12 into the area S2. If the supply gas pressure continues to increase, the overpressure valve 12 opens completely, as a result of which a large proportion of the premix gas can reach the region S2 of the premix burner. By dimensioning the supply lines and adjusting the response of the pressure relief valve 12, it is possible to optimize the behavior of the premix burner in terms of emission and vibration behavior. Thus, it is possible, without the need for a pilot gas supply and using only a single control valve, namely the pressure relief valve 12, to realize a premix burner for operating a gas turbine over the entire load range.

Such a pressure relief valve is as an advantageous embodiment in FIG. 4 shown. The pressure relief valve 12 has a conically shaped piston 15, the spring-loaded by a spring 16 gas-tight rests on a mating contour 17. Now, the piston 15 by means of gas pressure (see Arrow on the left side of the throttle valve) is pressurized, so the pressure acting on the piston 15 gas pressure can compress the spring 16 against a stop 18. This opens a gap between the piston 15 and the mating contour 17, whereby gas can pass through the pressure relief valve to the right. Depending on the choice of the spring force of the spring element 16 and the dimensioning of the piston size, the gas pressure-dependent flow rate of the premix gas by the pressure relief valve 12 is set individually. With the aid of suitable dimensioning of the pressure relief valve 12 and the branch line 11 and the throttle element 14 involved in the premix gas supply, it is possible to optimize the combustion process in a manner known per se. Also with the in FIG. 3 illustrated embodiment, it is possible to a targeted Premixgaszuteilung on the stages S1 and S2 of the burner bowls of the premix burner according to the diagram in FIG FIG. 2 to obtain.

With the device according to the invention with a premix burner, a fuel supply and a control or regulation unit, a number of advantages associated: By the graduated Premixgaszuführung in the premix burner this can be used in significantly larger range limits than just single-stage premix burner.

With the help of in FIG. 3 illustrated embodiment, only a single Premixgaszuleitung is required.

By using a control unit designed as a pressure relief valve 12, only a single control unit is required to operate the premix burner.

The retrofitting to existing premix burner systems is easy to carry out, especially since the use of two or more separate Premixgaszuleitungssystemen is not required.

The targeted supply of a minimum proportion of premix gas in the second area of the premix burner via the bypass line, it is not necessary to clean this supply line with natural gas. Tests have shown that the system according to the invention only causes low pulsations in the starting behavior. With the individual Premixgaszuteilung on the different areas of the premix burner, it is possible to make appropriate optimizations even when occurring aging phenomena.
Due to the possible omission of a pilot gas supply, any pulsations that occur when switching between pilot gas to Premixgaszufuhr can be avoided.

The entire device is structurally simple and inexpensive to produce.

LIST OF REFERENCE NUMBERS

1.2

burner shells

3

Premixgasaustrittsöffnungen

4.5

Premixgaszuführleitungen

6

premix gas

7

Flüssigbrennstoffzerstäubungseinrichtung

8th

supply line

9

Main control unit

10

intersection

11

branch line

12

Pressure relief valve

13

bypass line

14

throttle element

15

piston

16

feather

17

mating contour

18

attack

S1, S2

Areas 1, 2 for the staged Premixgasaustritt

A

Brenner

Claims (3)

1. Device with a premix burner, a fuel supply and a control or regulator unit for operating a gas turbine, wherein the premix burner has at least one burner shell (1, 2) which at least partially delimits an axially extending premix chamber, and a premix gas supply directed into the premix chamber via the burner shell (1, 2), wherein the premix gas (6) is mixed with combustion supply air inside the premix burner and is ignited downstream outside the premix burner, wherein at least two physically separated regions (S1, S2) are provided axially along the burner shell (1, 2), via which regions premix gas (6) can be fed into the premix chamber and which are connected to separate premix gas supply lines (4, 5), wherein a first region (S1) is provided in the burner shell (1, 2) and arranged upstream in the premix burner, and at least one second region (S2) is arranged downstream of the first region (S1) in the premix burner, and a regulator or control unit is provided which is connected to the premix gas supply lines (4, 5) and divides the premix gas supply to the individual regions depending on the load range of the gas turbine,
   characterised in that
   the premix gas supply line (5) of the first region (S1) is provided with a choke valve (9), that an intersection point (10) is provided between the choke valve (9) and the first region (S1), from which point a branch line (11) leads to the second region (S2), and that the control or regulator unit is provided between the intersection point (10) and the second region (S2).
2. Device as claimed in claim 1, characterised in that the control or regulator unit is an overpressure valve (12) subjected to spring force.
3. Device according to claim 1 or 2, characterised in that when the first region (S1) is supplied with premix gas (6), a bypass line (13) is provided between the intersection point (10) and the second region (S2) and ensures a minimum supply of premix gas (6) to the second region (S2) insofar as the first region (S1) is supplied with premix gas.

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