Process to operate a gas turbine combustor

Technical area

The present invention relates to a method for operating a combustion chamber for a gas turbine, wherein the combustion chamber has a combustion chamber and a plurality of burners each arranged at an inlet of the combustion chamber.

State of the art

So that as few pollutants as possible are formed during the operation of such a combustion chamber, the supply of the individual burners takes place with a very lean fuel-oxidizer mixture, ie with comparatively large λ values. To avoid thermoacoustic pressure pulsations, it is fundamentally possible to divide the burners of the combustion chamber into two burner groups and to supply the burners of the two burner groups with fuel-oxidizer mixtures which, although lean, have different λ values. The document<patcit id="pcit0001" dnum="DE19545311A1"><text>DE 19545311 A1</text></patcit> discloses a method of operating a combustor having two burner groups, wherein the burner groups may be operated with different numbers of air and fuel streams. In the case of burners whose fuel-oxidizer mixture has a smaller λ value, more fuel is thus available for conversion, which leads to higher temperatures during the combustion reaction in the combustion chamber and thus to a reduction of the pressure pulsations.

It has been found, however, that when operating the combustion chamber with two burner groups whose burners are operated with different λ values, the total pollutant emission increases, in particular the emission of NO_x and visible flue gases (so-called "yellow plume") while at the same time decreasing the stability of the homogeneous combustion reaction in the combustion chamber.

Presentation of the invention

Here the invention wants to remedy the situation. The invention, as characterized in the claims, deals with the problem of providing for a combustion chamber of the type mentioned an improved operating method, which in particular allows a reduction of the pollutant emission and stabilization of the homogeneous combustion reaction.

According to the invention, this problem is solved by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of ​​supplying an additional fuel flow to the burners of the burner group which is operated with the larger λ value. The invention uses the knowledge that in a conventional operation with two burner groups, which differ from each other by different lean λ values, only in those burners, which are operated with the smaller λ value, a stationary flame front arises in the combustion chamber, the allows a stable homogeneous combustion reaction. In contrast, it comes in the burners, which are operated with the larger λ value, not in the combustion chamber to form such a flame front, so that there runs off combustion reaction generates lower temperatures. Of particular interest is the knowledge that the formation of the stationary flame front increases the flow resistance in the burners, which are operated with the lower λ values. This leads to an uneven distribution of the oxidator current supplied in common to all burners. As a result, an increased oxidizer current occurs at the burners operated at larger λ values. As a result, interactions occur between the reaction zones of the burners of the two burner groups within the combustion chamber. For example, this increases the extinction limit of the stationary flame front. Furthermore, the stability of the combustion reaction in the stationary flame front can be reduced. This leads to an uneven distribution of the oxidator current supplied in common to all burners. As a result, an increased oxidizer current occurs at the burners operated at larger λ values. As a result, interactions occur between the reaction zones of the burners of the two burner groups within the combustion chamber. For example, this increases the extinction limit of the stationary flame front. Furthermore, the stability of the combustion reaction in the stationary flame front can be reduced. This leads to an uneven distribution of the oxidator current supplied in common to all burners. As a result, an increased oxidizer current occurs at the burners operated at larger λ values. As a result, interactions occur between the reaction zones of the burners of the two burner groups within the combustion chamber. For example, this increases the extinction limit of the stationary flame front. Furthermore, the stability of the combustion reaction in the stationary flame front can be reduced. For example, this increases the extinction limit of the stationary flame front. Furthermore, the stability of the combustion reaction in the stationary flame front can be reduced. For example, this increases the extinction limit of the stationary flame front. Furthermore, the stability of the combustion reaction in the stationary flame front can be reduced.

Due to the injection according to the invention of an additional fuel flow in those burners which are operated with the larger λ value, a stationary flame front can now also be established in these burners in the combustion chamber. As a result, the flow resistance also increases in these burners. As a result, the total of the burners supplied Oxidatorstrom is distributed more evenly on the burners of the two burner groups, whereby the aforementioned interactions are reduced. Overall, the extinguishing temperature limit can be lowered by the inventive measure in all burners, whereby at the same time the stability of the homogeneous combustion reaction is increased. Furthermore, the entry of a cold Oxidatorstroms is suppressed in the combustion chamber. For the combustion chamber this means

Of particular advantage is an embodiment in which the additional fuel stream is injected into the burners of the second burner group in such a way that the additionally supplied fuel does not mix within these burners or only slightly with the oxidizer supplied to these burners. In other words, the mixing of the additionally supplied fuel with the oxidizer takes place only in the combustion chamber, so that there specifically the combustion reaction in the form of the stationary flame front can be established and stabilized. The additional fuel stream thus passes directly into the flame front without prior mixing and reaction with the oxidizer. Particularly useful is an embodiment in which the burners are each designed as a premix burner, in which the fuel streams are fed to the burners, the fuel within the respective burner mixes with the oxidizer supplied to that burner. The invention thus clearly differentiates between the fuel streams for premixing with the oxidizer and the additional fuel stream which is supplied to the burners having the larger λ value in the fuel-oxidizer mixture. It has been found that the injection of the additional fuel stream, in particular without mixing with the Oxidatorstrom, leads to the desired stabilization of the combustion reaction and the desired reduction of pollutant emissions, while in this respect a lowering of the λ value in the premix burners of the second burner group would not be effective.

Brief description of the drawings

A preferred embodiment of the invention is illustrated in the drawing and will be explained in more detail in the following description.

The only <figref idrefs="f0001">Fig. 1</figref> shows a highly simplified schematic representation of a section of a combustion chamber according to the invention.

Ways to carry out the invention

Corresponding <figref idrefs="f0001">Fig. 1</figref> has a combustion chamber 1 according to the invention a combustion chamber 2, which is preferably designed annular. A longitudinal center line of this annular combustion chamber 2 extends perpendicularly from top to bottom parallel to the plane of the drawing. Accordingly, the illustration in FIG<figref idrefs="f0001">Fig. 1</figref> only a limited peripheral portion of the combustion chamber 2. The combustion chamber 1 has a plurality of burners 3, which in two burner groups 4, namely a first burner group 4th_I and a second burner group 4_II are divided. The burner groups 4 are in<figref idrefs="f0001">Fig. 1</figref> characterized by curly braces. Accordingly, the individual burners 3 are either the first burner group 4_I or the second burner group 4_II assigned and accordingly with 3_I or 3_II designated. The individual burners 3 are arranged next to one another at an inlet 13 of the combustion chamber 2. In the case of an annular combustion chamber 2, a circumferentially distributed arrangement of the burners 3 expediently takes place. The burners 3 arranged side by side in the circumferential direction can form a burner ring. Likewise, embodiments are possible in which two or more radially spaced burner rings are formed at the inlet 13 of the combustion chamber 2. Each burner group 4 contains one or more burners 3, wherein the burners 3 of the individual burner groups 4 can alternate in the circumferential direction, so that one or more burners 3 of one group 4 follow in the circumferential direction to one or more burners 3 of the other group 4.

For both burner groups 4 and thus for all burners 3, a common oxidizer supply 5 is provided which supplies the burners 3 with the required oxidizer, in particular air. An oxidizer flow 6 generated by the oxidizer supply 5 is in<figref idrefs="f0001">Fig. 1</figref> symbolized by arrows.

Furthermore, the combustion chamber 1 for the burner 3_I the first burner group 4_I a common first fuel supply 7. One of the first fuel supply 7 to the burners. 3_I the first burner group 4_I supplied first fuel stream 8 is symbolized by arrows. In a corresponding manner is to supply the burner. 3_II the second burner group 4_II provided with fuel, a second fuel supply 9, wherein a thus provided second fuel flow 10 is symbolized by arrows. The fuel used is preferably natural gas.

According to the invention, the combustion chamber 1 is now also equipped with an additional fuel supply 11, with the aid of which the second burner group 4_II or their burner 3_II an auxiliary fuel stream 12, also represented by arrows, can be supplied.

According to a preferred embodiment, the burners 3 are in each case premix burners in which the oxidant supplied in each case mixes intensively with the respectively supplied fuel before the fuel-oxidant mixture thus formed enters the combustion chamber 2. For example, oxidizer and fuel are supplied radially in the respective burner 3 and acted upon by a twist, resulting in a particularly intensive mixing.

For example, for this purpose, the additional fuel stream 12 in the burners. 3_II the second burner group 4_II axially introduced into the burner 3 at the burner head, ie at an end remote from the combustion chamber 2. In principle, it is also possible to inject the additional fuel stream 12 in each case by means of a fuel lance, which then centrally in the respective burners 3_II is arranged.

Of particular importance is now that the additional fuel supply 11 is designed so that the additionally supplied additional fuel stream 12 to the respective burner. 3_II flows through virtually unhindered, without causing a strong mixing with the oxidizer. In this way, the additional fuel stream 12 passes virtually unmixed into the combustion chamber. 2

In the preferred embodiment shown here, the geometry of the burner 3 at the inlet 13 is designed so that a sudden cross-sectional enlargement results in the transition into the combustion chamber 2. In conjunction with a swirling action of the fuel-oxidizer mixture, a collapse of the swirl system thereby occurs in the combustion chamber 2, whereby a recirculation zone can arise within the combustion chamber 2 downstream of each burner 3, which can contribute to the stabilization of a flame front 14.

The combustion chamber 1 according to the invention operates as follows:<ul><li>During operation of the combustion chamber 1, it is supplied with a predetermined oxidizer stream 6 via the oxidizer supply 5. Depending on the desired power of the combustion chamber 1, a total fuel flow is determined, which must be burned in the combustion chamber 2 in order to provide the desired combustion chamber performance. A suitable controller, not shown here, now determines a suitable proportion factor for each burner group 4, which defines the distribution of the total fuel flow to the two burner groups 4. It is envisaged that the burner. 3_I the first burner group 4_I be operated with a fuel-oxidizer mixture whose λ-value is indeed greater than 1, but smaller than the λ value in the fuel-oxidizer mixture, with which the burner. 3_II in the second burner group 4_II operate. This requirement ensures that both the burner 3_I the first burner group 4_I as well as the burners 3_II the second burner group 4_II run lean. It is important that the burners 3_I the first burner group 4_I each more fuel is supplied, as the burners. 3_II the second burner group 4_II, As a result, at least downstream of the burner 3 in the combustion chamber 2_I the first burner group 4_I each establish a stationary flame front 14.</li></ul>

According to the invention now the burners. 3_II the second burner group 4_II additionally the additional fuel stream 12 is supplied. This can be downstream of the burner. 3_II the second burner group 4_II in the combustion chamber 2 also each form a stationary flame front 14. Overall, a comparatively homogeneous temperature distribution can thereby be achieved in the combustion chamber 2. At the same time pollutant emissions, in particular the emissions of NO_x, of CO and of visible flue gases. Furthermore, the homogeneous combustion reaction in the combustion chamber 2 is stabilized by lowering the extinguishing temperature limit to a relatively low temperature. By the establishment of a stationary flame front 14 also downstream of the burner. 3_II the second burner group 4_II also turns on these burners 3_II essentially the same throughflow resistance as at the burners 3_I the first burner group 4_I on. As a result, an essentially uniform distribution of the oxidizer stream 6 to the individual burners 3 automatically sets in, which makes a significant contribution to the desired stabilization and homogenization of the reactions in the combustion chamber 2. Furthermore, the injection of the additional fuel stream 12 according to the invention makes it possible to select the proportion factors for the division of the total fuel flow such that the λ values ​​in the burners 3 of the two burner groups 4 only differ relatively little from one another. This measure also leads to a homogeneous temperature distribution in the combustion chamber 2 and thus in particular to a reduction of NO_x-Education.

Preferably, the additional fuel flow 12 is dimensioned so that the combustion reaction downstream of the associated burner. 3_II Of particular interest in this case may be an embodiment in which the amount of additional fuel stream 12 is just as large as the amount difference between the first fuel stream 8 and the second fuel flow 10. In this way, each burner is 3_II the second burner group 4_II ultimately fed the same amount of fuel as each burner. 3_I the first burner group 4_I, Alternatively or additionally, the dimensioning of the additional fuel flow 12 may also be selected so that ultimately both in the combustion chamber 2 downstream of the burner. 3_II the second burner group 4_II as well as downstream of the burner 3_I the first burner group 4_I sets a combustion reaction at about the same λ value.

LIST OF REFERENCE NUMBERS

<dl id="dl0001" compact="compact"><dt>1</dt><dd>combustion chamber</dd><dt>2</dt><dd>combustion chamber</dd><dt>3</dt><dd>burner</dd><dt>4</dt><dd>burner group</dd><dt>5</dt><dd>Oxidatorversorgung</dd><dt>6</dt><dd>oxidant</dd><dt>7</dt><dd>first fuel supply</dd><dt>8th</dt><dd>first fuel flow</dd><dt>9</dt><dd>second fuel supply</dd><dt>10</dt><dd>second fuel stream</dd><dt>11</dt><dd>Additional fuel supply</dd><dt>12</dt><dd>Additional fuel stream</dd><dt>13</dt><dd>Admission of 2</dd><dt>14</dt><dd>flame front</dd></dl>