EP2927599A1 - Method for regulating a distribution of fuel at different burner stages - Google Patents

Abstract

The invention relates to a method for controlling a distribution of fuel to predetermined burner stages of at least one burner of a machine during stationary machine operation.

Description

The present invention relates to a method for controlling a distribution of fuel to predetermined burner stages of at least one burner of a machine during a stationary engine operation, wherein the engine is in particular a gas turbine having a plurality of burners.

In the case of gas turbines, it is known to influence the emissions and the combustion stability or the buzzing behavior via the distribution of fuel to different burner stages, which must be minimized or at least kept below predetermined limit values. One problem, however, is that both emissions and combustion stability are affected by a wide variety of disturbances, such as environmental conditions, aging effects, pollution, engine load or the like, and the precise interactions between combustion stability and emissions and the disturbances are on the other hand only insufficiently known. A direct regulation of fuel distribution has not been used for these reasons. A known in the prior art solution to the problem provides to deposit in the control technology based on empirical values maps that allocate values to the fuel supply or their distribution to the individual burner stages for each operating state of the gas turbine. As far as known disturbance variables are detected metrologically, the maps can be supplemented by correction functions, such as an ambient temperature-dependent modulation of the guided to the individual burner stages fuel components. As a result, however, it can be stated that, despite such a map-based control system, there are always repeated emissions or inadmissible heavy hum. Based on this prior art, it is an object of the present invention to provide an alternative method with which the combustion stability and the emission are influenced via the fuel supply to the individual burner stages.

1. a) Definieren von Grenzwerten verschiedener Regelgrößen, wobei die Regelgrößen zumindest eine Bewertungsgröße für die Verbrennungsstabilität und eine Bewertungsgröße für den NOx-Anteil im Abgas umfassen;
2. b) Erfassen und Zwischenspeichern der Regelgrößen unter Verwendung geeigneter Messeinrichtungen während des stationären Maschinenbetriebs, wobei die den einzelnen Brennerstufen während des stationären Maschinenbetriebs zugeführten Brennstoffvolumenströme bekannte Ausgangsgrößen darstellen;
3. c) Vergleichen der in Schritt b) zwischengespeicherten Regelgrößen mit den zugeordneten Grenzwerten und, wenn im Rahmen dieser Vergleiche eine Überschreitung zumindest eines Grenzwertes festgestellt wird,
4. d) Verändern des Brennstoffvolumenstroms zu einer ersten Brennerstufe um einen vorbestimmten Wert;
5. e) erneutes Erfassen und Zwischenspeichern der Regelgrößen unter Verwendung der Messeinrichtungen;
6. f) Bewerten, ob zumindest eine der in Schritt e) zwischengespeicherten Regelgrößen eine Verbesserung oder eine Verschlechterung gegenüber einer der in Schritt b) zwischengespeicherten Regelgrößen darstellt;
7. g) Wiederholen der Schritte d) bis f), bis in Schritt f) eine Verbesserung zumindest einer Bewertungsgröße erfasst wird; und
8. h) Durchführen der Schritte b) bis g) für weitere vorbestimmte Brennerstufen des Brenners, insbesondere für sämtliche Brennerstufen des Brenners.

To achieve this object, the present invention provides a method for controlling a distribution of fuel to predetermined burner stages of at least one burner of a machine during stationary machine operation, comprising the steps of:

1. a) defining limit values of different controlled variables, the controlled variables comprising at least one combustion stability assessment variable and an NOx emission assessment value;
2. b) detecting and buffering the controlled variables using suitable measuring devices during stationary machine operation, wherein the fuel volume flows supplied to the individual burner stages during stationary engine operation represent known output variables;
3. c) comparing the control values temporarily stored in step b) with the assigned limit values and, if an excess of at least one limit value is detected in the context of these comparisons,
4. d) changing the fuel volume flow to a first burner stage by a predetermined value;
5. e) re-acquiring and temporarily storing the controlled variables using the measuring devices;
6. f) assessing whether at least one of the control variables buffered in step e) represents an improvement or deterioration compared with one of the control variables buffered in step b);
7. g) repeating steps d) to f) until, in step f), an improvement in at least one evaluation variable is detected; and
8. h) performing steps b) to g) for further predetermined burner stages of the burner, in particular for all burner stages of the burner.

In other words, a control is proposed according to the invention in which by gradual change of the fuel supply to the individual burner stages improved fuel allocation is determined by trial and error to keep the NOx content in the exhaust gas and the combustion stability below the predetermined limits. By slightly varying the individual manipulated variables in the form of the fuel volume flows fed to the individual burner stages and observing the effect on the combustion stability and the NOx fraction in the exhaust gas, it can be determined whether the new setting represents an improvement or not. An essential advantage of the method according to the invention is that an optimization of the fuel distribution always takes place automatically with changes in the ambient conditions or aging-related changes in the machine components, regardless of whether the influence of the changes on the combustion stability and / or on the NOx content in the exhaust gas are known or not. Furthermore, the commissioning time of the machine can be carried out within a very short period of time thanks to the method according to the invention. Conventional devices can be used as measuring devices. Measuring devices for determining the proportion of NOx in the exhaust gas are well known in the prior art. For example, sound sensors, pressure sensors or the like can serve as measuring devices for detecting the combustion stability. Whether the machine is in steady-state operation can be determined, for example, by monitoring the machine output.

According to an embodiment of the present invention, if after performing a modification step in step d), no deterioration of an evaluation amount is detected in step f), the fuel volume flow in the newly performed step d) becomes equal by a predetermined value Direction as in the previous step d) changed. If the fuel volume flow has been increased in the previous step d), for example, it will be increased again in the step d) which has been carried out again. On the other hand, if the fuel volume flow was reduced in the previous step d), then it is also reduced in the renewed step d).

Preferably, if, after performing a fuel volume flow change in step d), a deterioration of an evaluation variable is detected in step f), the fuel volume flow change performed in the previous step d) is reversed in the step d) carried out again. This prevents further deterioration from taking place.

Advantageously, if after a reversal of a previous change in fuel volume flow, the fuel volume flow again corresponds to the output variable, the fuel volume flow in the step d) carried out again changed by a predetermined value against the original direction. Thus, if the fuel volume flow has been increased when step d) is carried out for the first time, it will now be reduced on the basis of the initial variable. If it was reduced when the step d) was carried out for the first time, it is now increased on the basis of the starting variable.

According to one embodiment of the method according to the invention, if in step c) both an exceedance of the limit value for the combustion stability as well as an exceedance of the limit value for the NO x fraction in the exhaust gas are determined, only an improvement in step f) the evaluation parameter for the combustion stability or only an improvement in the evaluation of the NOx component in the exhaust gas considered. In other words, one of the controlled variables receives a priority.

Preferably, the steps b) to g), after having been carried out in accordance with step h) for all of the predetermined burner stages, are carried out again for the first burner stage. In other words, an execution of the complete process cycle is followed by another process cycle so that the control can respond to changing disturbances.

The portion of the fuel volume flow by which the fuel supply of a burner stage is increased or reduced in step d) is preferably subtracted from the fuel volume flow of at least one of the other burner stages or at least added to one of the other burner stages, so that the total fuel flow volume supplied to the burner stages is kept constant , Accordingly, the machine performance is influenced only slightly or not at all by the regulation according to the invention. The splitting of that portion of the fuel volume flow by which the fuel supply of a burner stage in step d) is increased or reduced to the other burner stages can be effected, for example, in equal proportions, proportionally to the current fuel distribution or in another manner.

Advantageously, the method according to the invention is terminated when no exceeding of limit values is detected in step c) or the machine leaves the stationary mode. The latter can be determined, for example, by monitoring the machine performance.

The settings of the fuel volume flows to the individual burner stages, which are carried out in the context of carrying out steps b) to h), are preferably stored in matrices clustered according to engine power and ambient temperature. A restart of the machine can then be carried out based on a stored matrix, which is used as a map.

Other features and advantages of the present invention will become apparent from the following description of a method according to an embodiment of the present invention with reference to the accompanying drawings which show a schematic flow chart.

The method described below is for controlling a distribution of fuel to different burner stages of a plurality of annularly arranged burners of a gas turbine during a stationary gas turbine operation. Each burner includes a pilot burner and a plurality of premix burners. The pilot burner defines a first burner stage of a burner. The premix burners of each burner form a second and a third burner stage. All pilot burners are supplied with fuel via a common first loop. Likewise, all premix burners of the second burner stage and all premix burners of the third burner stage are each supplied with fuel via a common second or third ring line.

It should be noted at this point that the number of burner stages is basically variable, as far as at least two burner stages are provided, which are supplied with fuel separately from each other.

In order to carry out the method according to the invention, in a first step S1, a limit value for an evaluation parameter for the combustion stability or the buzzing behavior is determined. Further, in step S1, a threshold value for a NOx amount evaluation quantity in the exhaust gas is defined. The limit values each form upper limits which should not be exceeded during stationary gas turbine operation.

In a second step S2, the evaluation parameter for the combustion stability and the evaluation quantity for the NOx content in the exhaust gas during stationary engine operation are detected using suitable measuring devices, and cached, wherein the amounts of fuel that are supplied to the individual firing stages during steady-state operation, are known. The stationary gas turbine operation can be determined, for example, by monitoring the engine power. For example, sound sensors, pressure sensors or the like can serve as measuring devices for detecting the combustion stability. As a measuring device for determining the NOx content in the exhaust gas, devices based on various measuring principles are available, which directly determine the proportion of NOx.

In a subsequent step S3.1, the measurement results cached in step S2 are compared with the limit values defined in step S1. If it is found in the context of such a comparison that none of the limit values has been exceeded, then step S2 is carried out again. If, on the other hand, it is determined in step S3 that at least one of the limit values has been exceeded, the fuel supply to the first burner stage is changed by a predetermined value in a further step S4.1. In other words, the first burner stage is now supplied with a predetermined amount of more or less fuel.

Then, the combustion stability evaluation amount and the NOx amount evaluation amount in the exhaust gas are newly detected and latched in step S5.1 using the aforementioned measuring devices.

In step S6.1, it is then assessed whether at least one of the control variables buffered in step S5.1 represents an improvement over one of the control variables buffered in step S2. If it is determined in step S6.1 that the change of the fuel supply in step S4.1 did not result in a deterioration of an evaluation variable, the fuel supply to the first burner stage in step S4.2 again becomes a predetermined value in the same direction as in step S4 .1 changed. If the fuel supply was increased in step S4.1, then it is in Step S4.2 increased again. On the other hand, if the fuel supply was reduced in step S4.1, it is also reduced in step S4.2. Then, the control variables are detected again using the measuring devices in step S5.2 and buffered. Subsequently, it is evaluated in step S6.2 whether at least one of the control variables buffered in step S5.2 represents an improvement compared to the control variables buffered in step S5.2. If it is again determined in step S6.2 that the fuel supply in step S4.2 did not result in a deterioration of an evaluation variable, in step S4.3 the fuel supply is again changed in the same direction by a predetermined value, whereupon steps S5.3 and S6.3 are carried out in an analogous manner.

If it is determined in step S6.n (n = 2, 3...) That a deterioration of at least one evaluation variable has taken place, then the fuel supply is reset to that of step S4.n-1. Thereafter, the above-described procedure is sequentially applied to the second and the third burner stage.

If it is determined in step S6.1 that a deterioration of at least one evaluation variable has taken place compared to the evaluation variables detected and buffered in step S2, then in step S4.2 at least one further modification step is performed against the direction selected in step S4.1 starting from the starting point , Thus, if the fuel supply of the first burner stage was increased in step S4.1 relative to the fuel supply of the first burner stage in step S.2, it is reduced starting from the starting point in step S4.2. If it was reduced in step S4.1, it is now increased in step S4.2. Thereafter, steps S5.2 and S6.2 are performed. If it is determined in step S6.n (n = 2, 3...) That a deterioration of at least one evaluation variable has taken place, then the fuel supply is reset to that of step S4.n-1. Thereupon, the previously described Procedure sequentially applied to the second and the third burner stage.

If both exceeding of the limit value for the combustion stability and the exceeding of the limit value for the NOx content in the exhaust gas are determined in step S3, then only an improvement in the evaluation parameter for the combustion stability or in step S4.1 Improvement of the evaluation parameter for the NOx content in the exhaust gas is taken into account. In other words, one of the scores is given priority.

If the distribution of the fuel has been regulated for all burner stages in the context of the steps described above, the method described above is applied again to the first burner stage. In other words, the process then starts all over again.

The method is terminated as soon as the gas turbine leaves the stationary mode or if no exceeding of limit values is determined in step S3.

The settings of the fuel supply to the individual burner stages, which were made in the context of carrying out the method according to the invention, are stored in matrices clustered according to machine performance and ambient temperature. A restart of the machine can then be based on a stored matrix, which is then used as a map. As soon as the machine returns to stationary machine operation after restarting, the method according to the invention is carried out again.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be made by those skilled in the art can be derived without departing from the scope of the invention.

Claims (10)

A method of controlling a split of fuel at predetermined burner stages of at least one burner of a machine during stationary engine operation, comprising the steps of: a) defining limit values of different controlled variables, the controlled variables comprising at least one combustion stability assessment variable and an NOx emission assessment value; b) detecting and buffering the controlled variables using suitable measuring devices during stationary machine operation, wherein the fuel volume flows supplied to the individual burner stages during stationary engine operation represent known output variables; c) comparing the control values temporarily stored in step b) with the assigned limit values and, if an excess of at least one limit value is detected in the context of these comparisons, d) changing the fuel volume flow to a first burner stage by a predetermined value; e) re-acquiring and temporarily storing the controlled variables using the measuring devices; f) assessing whether at least one of the control variables buffered in step e) represents an improvement or deterioration compared with one of the control variables buffered in step b); g) repeating steps d) to f) until, in step f), an improvement in at least one evaluation variable is detected; and h) performing steps b) to g) for further predetermined burner stages of the burner, in particular for all burner stages of the burner. Method according to Claim 1, in which, if after performing a modification step in step d) no deterioration of a valuation variable in step f) is detected, the Fuel volume flow in the re-performed step d) by a predetermined value in the same direction as in the previous step d) is changed. The method of claim 1 or 2, wherein, after performing a fuel volume flow change in step d) a deterioration of a rating in step f) is detected, in the step d) carried out again the fuel volume flow change performed in the previous step d) is reversed. Method according to Claim 3, in which, after a previous change in the fuel volume flow has been reversed, the fuel volume flow again corresponds to the output variable, the fuel volume flow in the renewed step d) is changed by a predetermined value against the original direction. Method according to one of the preceding claims, in which, if in step c) both the exceeding of the limit value for the combustion stability and the exceeding of the limit value for the NOx component in the exhaust gas is determined, in step f) only an improvement in the evaluation parameter for the combustion stability or only an improvement in the evaluation quantity for the NOx content in the exhaust gas is taken into account. Method according to one of the preceding claims, in which the steps b) to g), after they have been carried out in step h) for all of the predetermined burner stages, are carried out again for the first burner stage. Method according to one of the preceding claims, in which that proportion of the fuel volume flow by which the fuel supply of a burner stage in step d) is increased or decreased, is subtracted from the fuel volume flow of at least one of the other burner stages or at least added to one of the other burner stages, so that the the Burner stages total supplied total fuel flow is kept constant. Method according to one of the preceding claims, characterized in that this is terminated when in step c) no exceeding of limit values is detected or the machine leaves the stationary operation. Method according to one of the preceding claims, in which the settings of the fuel volume flows to the individual burner stages, which are carried out in the context of performing the steps b) to h), are stored in arrays clustered according to engine power and ambient temperature. The method of claim 9, wherein a startup of the machine is based on a stored die.

Images