Abstract:
A burner insert for a gas turbine combustion chamber is provided. The burner insert includes a burner insert wall including a cold side and a hot side, an edge delimiting the burner insert wall. The edge includes an edge bar extending at least partially circumferentially and projecting beyond the cold side. A burner opening for inserting a burner is formed in the burner insert wall.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US National Stage of International Application No. PCT/EP2009/061854, filed Sep. 14, 2009 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 08018907.9 EP filed Oct. 29, 2008. All of the applications are incorporated by reference herein in their entirety. 
     FIELD OF INVENTION 
     The present invention relates to a burner insert for a gas turbine combustion chamber, which comprises a burner opening for inserting a burner. The invention also relates to a gas turbine. 
     BACKGROUND OF INVENTION 
     Gas turbine combustion chambers comprise a burner-side end and a turbine-side end. The turbine-side end is open and enables the hot combustion gases produced in the combustion chamber to flow out to the turbine. At the burner-side end a burner insert is often present which comprises a heat-resistant hot side and a cooled cold side. The burner is inserted into an opening in the burner insert. When the gas turbine is operating, cold air which as a rule comes from the compressor flows along the cold side from the burner opening of the burner insert to its outer edge, from where the cold air flows into the combustion chamber. An example of a burner insert in a can-type combustion chamber is described in US 2005/0016178 A1. 
     In the case of annular combustion chambers, in other words combustion chambers which extend in annular fashion around the turbine rotor, as a rule a plurality of burner inserts is arranged side by side in the circumferential direction of the annular combustion chamber. The cold air flowing past the cold side of the burner side then flows between the radially outer wall and the radially inner wall of the combustion chamber into the combustion chamber. In addition, cold air can also be introduced into the combustion chamber through gaps between adjacent burner inserts in the circumferential direction. Such an annular combustion chamber is described for example in EP 1 557 607 A1. Alternatively, it is also possible to direct the cold air towards the burner opening instead of away from the burner opening of the burner insert and then to introduce said cold air into the combustion chamber through an annular gap between the edge of the burner opening and the inserted burner, as is described in EP 1 767 855 A1. 
     A burner insert for an annular combustion chamber is illustrated schematically in  FIG. 1 . The figure shows a sectional perspective view of the cold side  103  of a burner insert for an annular combustion chamber. In the center of the cold side  103  of the burner insert  100  is situated an opening  105 , into which the burner can be inserted. The burner insert is secured by means of an annular bar  107  in the section  109  of the burner insert  100  projecting beyond the cold side on a support structure in the gas turbine housing. 
     During operation of the gas turbine combustion chamber, pressure fluctuations may occur therein which can excite the burner insert to high-frequency oscillations. These stress the burner insert and shorten its useful life. In order to stiffen the burner insert and to direct the cold air, the cold side  103  of the burner insert  100  is provided with ribs  111 . Furthermore, support bolts  113  are present, which are indicated only schematically in  FIG. 1 . The bolts  113  and the ribs  111  constitute contact sections by means of which the cold side comes into contact with the support structure in the gas turbine housing. With regard to such types of burner inserts, the formation of an uneven gap can occur along the circumferential edge of the burner insert, which can lead to an excess supply of cold air at points having an enlarged gap. Furthermore, on account of the fact that the support bolts  113  are also present in addition to the ribs  111 , a static overdeterminacy results because the burner insert  100  should simultaneously bear both on the ribs  11  and also on the bolts. 
     SUMMARY OF INVENTION 
     Compared with this prior art, the object of the present invention is to make available an advantageous burner insert for a gas turbine combustion chamber. A further object is to make available an advantageous gas turbine combustion chamber and an advantageous gas turbine. 
     The first object is achieved by a burner insert as claimed in the claims, the second object by a gas turbine combustion chamber as claimed in the claims and a gas turbine as claimed in the claims respectively. The dependent claims contain advantageous embodiments of the invention. 
     A burner insert according to the invention for a gas turbine combustion chamber has a burner insert wall having a cold side and a hot side. A burner opening for inserting a burner is formed in the burner insert wall. The burner insert has an outer edge delimiting the burner insert wall, with an at least partially circumferential edge strip projecting beyond the cold side. In this situation, the edge can be formed to be largely circular, for instance in the case of a can-type combustion chamber, or, for example in the case of an annular combustion chamber, can have the form of the edge of an annular segment. Other contours are also possible in principle, depending on the form of the combustion chamber. 
     The edge strip of the burner insert according to the invention results in an increase in the resonance frequencies compared with a burner insert according to the prior art as has been described with reference to  FIG. 1 . The vibration stress on the burner insert during operation of the combustion chamber is therefore reduced in comparison with the burner insert from the prior art. Furthermore, during operation of the gas turbine combustion chamber the edge strip can bear completely on the support structure in the gas turbine housing, such that a uniform gap, preferably a zero gap, is present along the entire edge. In order to not interrupt the cold air flow in the presence of a zero gap, in a development of the invention the edge strip is provided with openings for the passage of cooling fluid. In order to implement the openings, the edge strip can have castellations, between which the openings are formed, and/or can be equipped with through-holes, drilled holes for example. As a result of the fact that defined openings can be produced in the edge strip by means of the castellations, or the holes, it is possible to exactly set the cold air quantity passing through the edge strip by suitable choice of the castellation size or of the free diameter of the holes. In the case of castellations, these can be produced for instance by interrupting the edge strip. It is however advantageous if the edge strip is not interrupted and instead the edge strip projects further beyond the cold side in the castellation regions than in the remaining regions of the edge strip. In addition to the openings described, further forms of openings are also conceivable, slots for example. 
     By preference, the edge strip runs around the entire edge of the burner insert. The stiffness of the edge of the burner insert is then particularly high. 
     In a special embodiment of the burner insert according to the invention, the burner opening is surrounded by an annular wall region projecting beyond the cold side and provided with an annular bar. Otherwise, the burner insert wall is flat in form, in other words no further structures exist, such as for instance the ribs present in the prior art. In the case of the burner insert according to the invention, such types of ribs are superfluous because it has become clear that a uniform distribution of the cold air also takes place without such ribs. A stiffening function of the ribs is also not required in the burner insert according to the invention. 
     Overall, the burner insert according to the invention enables savings to be achieved in terms of cold air usage because no non-uniform gap dimensions occur which may result in a surplus in the cold air supply. The reduced cold air feed into the combustion chamber consequently results in a reduction in harmful emissions from the gas turbine and to higher turbine inlet temperatures, which in turn enables an increase in the efficiency of the gas turbine. In the case of openings in the edge gap, for example in the form of castellations or through-openings, it is moreover possible through suitable choice of the opening cross-sections to set the quantity of cold air flowing into the combustion chamber in a defined manner. Furthermore, it is possible to set a zero gap between the front surface of the edge strip or the castellations and the support structure or the combustion chamber wall. Finally, the design of the burner insert according to the invention also makes possible a reduction in costs because the stiffening bolts are dispensed with and therefore fewer components are required in comparison with the burner insert described in the introduction. 
     A gas turbine combustion chamber according to the invention comprises at least one burner, at least one combustion chamber wall surrounding a combustion chamber interior and at least one burner-side combustion chamber end wall. It incorporates a burner insert according to the invention, the burner insert wall of which forms the combustion chamber end wall, whereby the hot side of the burner insert wall faces the combustion chamber interior. In the combustion chamber according to the invention the combustion chamber wall can in the case of a can-type combustion chamber be embodied in a cylindrical shape. In the case of an annular combustion chamber, two combustion chamber walls are however present, namely one radially outer and one radially inner combustion chamber wall. 
     The advantages which can be achieved by using the burner insert according to the invention can thus be implemented in the gas turbine combustion chamber according to the invention. 
     In the gas turbine combustion chamber according to the invention, between the combustion chamber end wall formed by the at least one burner insert and the at least one combustion chamber wall a gap may be present which enables cold air to flow away from the cold side of the burner insert into the combustion chamber. 
     In the case of a gas turbine combustion chamber embodied as an annular combustion chamber and having an annular combustion chamber interior formed between an inner combustion chamber wall and an outer combustion chamber wall, the burner-side combustion chamber end wall can in particular be formed by a number of burner inserts arranged side by side in the circumferential direction of the combustion chamber. Gaps may be present between adjacent burner inserts, which enable cold air to flow in between the burner inserts into the annular combustion chamber. 
     A gas turbine according to the invention is equipped with at least one gas turbine combustion chamber which is embodied as a gas turbine combustion chamber according to the invention. Furthermore, the gas turbine according to the invention incorporates a cooling fluid reservoir, for example a combustion chamber plenum being connected to the output of a compressor, whereby the cold side of the burner insert wall has a flow connection with the cooling fluid reservoir. Such a gas turbine makes it possible to implement the advantages of a combustion chamber having a burner insert according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features, attributes and advantages of the present invention will emerge from the description which follows of an exemplary embodiment with reference to the attached figures. 
         FIG. 1  shows a burner insert according to the prior art. 
         FIG. 2  shows a partial longitudinal section of a gas turbine. 
         FIG. 3  shows a partial sectional perspective view of an annular combustion chamber. 
         FIG. 4  shows a burner insert according to the invention. 
         FIG. 5  shows the edge of the burner insert from  FIG. 4 . 
         FIG. 6  shows a detail view of the edge of the burner insert. 
         FIG. 7  shows a detail view of the edge of a modified burner insert. 
         FIG. 8  is a schematic illustrating a burner insert arranged on a support structure which is affixed on a housing of gas turbine. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
       FIG. 2  shows a longitudinal section of a gas turbine  1  which comprises a compressor section  3 , a combustion chamber section  5  and a turbine section  7 . A shaft  9  extends through all the sections of the gas turbine  1 . In the compressor section  3  the shaft  9  is equipped with rings of compressor blades  11  and in the turbine section  7  with rings of turbine blades  13 . Rings of compressor guide vanes  15  are situated between the rings of blades in the compressor section  3  and rings of turbine guide vanes  17  are situated between the rings of blades in the turbine section  7 . The guide vanes extend from the housing  19  of the gas turbine unit  1  essentially in the radial direction to the shaft  9 . 
     During operation of the gas turbine  1 , air  23  is drawn in through an air inlet  21  of the compressor section  3  and compressed by the compressor blades  11 . The compressed air is fed to a combustion chamber  25  arranged in the combustion chamber section  5 , which in the present exemplary embodiment is embodied as an annular combustion chamber, into which a gaseous or liquid fuel is also injected by way of at least one burner  27 . The air/fuel mixture produced thereby is ignited and combusted in the combustion chamber  25 . The hot combustion exhaust gases flow along the flow path  29  from the combustion chamber  25  into the turbine section  7  where they expand and cool and in doing so transfer momentum to the turbine blades  13 . In this situation, the turbine guide vanes  17  serve as jets for optimizing the transfer of momentum to the blades  13 . The rotation of the shaft  9  brought about by the transfer of momentum is used in order to drive a load, for example an electrical generator. The expanded and cooled combustion gases are finally discharged from the turbine  1  through an outlet  31 . 
     The annular combustion chamber  25  of the gas turbine represented in  FIG. 2  is illustrated in  FIG. 3  in a partial sectional perspective view. The outer combustion chamber wall  33  can be seen, and also the inner combustion chamber wall  35 . Both the outer combustion chamber wall  33  and also the inner combustion chamber wall  35  are equipped with a hot gas resistant lining which is formed from heat shield elements  37 . Ceramic heat shield elements are used as heat shield elements in the present exemplary embodiment. The end of the combustion chamber facing the turbine section  7  has a hot gas outlet opening  39 , through which the hot combustion gases produced in the interior of the combustion chamber  25  can flow to the turbine. A combustion chamber end wall formed from burner inserts  41  is present at the end of the annular combustion chamber  25  opposite the hot gas exit  39 . A burner  27  is housed in each burner insert  41 . In this situation, the burner inserts  41  are not connected directly to the outer combustion chamber wall  33  and the inner combustion chamber wall  35  but are arranged on a support structure  50  (schematically shown in  FIG. 8 ) which is in turn affixed on the housing of the gas turbine, as schematically represented by circles  52 . Between the individual burner inserts  41  on the one hand and also the outer wall  33  and the inner wall  35  on the other hand there remains a gap which enables cold air to flow in along the respective wall into the interior of the combustion chamber. Furthermore, the burner inserts  41  are arranged such that gaps also remain between them, in other words between edges of the burner inserts  41  which are adjacent in the circumferential direction, which gaps enable cold air to enter the combustion chamber interior. 
     A burner insert is illustrated in a partial sectional perspective view in  FIG. 4 . It comprises a burner insert wall  42  having a cold side  43  and also a hot side  44  which is to face the combustion chamber interior (the hot side cannot be seen in  FIG. 4 ). The cold side  43  has a flow connection with the output from the compressor which means that compressor air can be directed past the cold side  43  for cooling purposes in order to maintain the temperature of the hot side at an acceptable level for the material of the burner insert  41 . The hot side is furthermore provided with a heat-insulating coating, for example in the form of a ceramic coating, in order to reduce the demand for cold air. 
     At its center the burner insert  41  has an opening  45  into which the outlet from a burner  27  can be inserted. The opening  45  is delimited by a section  47  of the burner insert wall  42  projecting beyond the cold side  43 . From this projecting section  47  extends an annular bar  49  running in the radial direction of the opening  45 , by means of which the burner insert  41  can be affixed to a retaining structure. 
     In the present exemplary embodiment, the entire outer edge  46  of the burner insert  41  is provided with an edge strip  51  projecting beyond the cold side  43 , which gives the edge  46  an increased stiffness and ensures that the resonance frequency of the burner insert wall  42  is increased. Detail views of the edge  46  with the edge strip  51  are illustrated in  FIGS. 5 and 6 . 
     The edge strip  51  has castellations  53  which are formed by sections of the edge strip  51  which project further beyond the cold side  43  than the remaining sections  54  of the edge strip  51 . When the burner insert is affixed to a support structure and fauns a part of a combustion chamber end wall, the castellations  53  with their front surfaces  55  furthest away from the cold side  43  rest against a contact surface of the retaining structure with a zero gap. Between the castellations  53  are then faulted windows  57 , through which cold air which as a rule is delivered from the compressor in the region of the projecting wall section  47  can flow out into the combustion chamber. The cold air can then flow, providing cooling, along the cold side  43  which is completely flat in form apart from the edge strip  51  and the projecting wall region  47 . The windows  57  between the castellations  53  constitute openings having a defined flow-through cross-section for the flowing cold air because the front surfaces  55  of the castellations  53  rest against the contact structure with a zero gap. Through suitable choice of the width and height of the edge strip sections  54  between the castellations  53  in relation to the height and width of the castellations  53  it is possible to specifically set the cold air quantity flowing into the combustion chamber. On account of the increased stiffness which the edge strip  51  gives the edge  46 , there are also no significant deviations occurring in the gap between the castellation surfaces  55  and the contact surface, which means that the flow cross-section present for the cold air and defined by the windows is also largely maintained during operation of the gas turbine. Excess supplies of cold air resulting from increasing gap dimensions can be substantially reduced by this means in comparison with the prior art, which in turn leads to a decrease in the cold air entering the combustion chamber and thus ultimately to a lowering of pollutant levels and to higher turbine inlet temperatures. 
     Although the edge strip  51  in the exemplary embodiment shown in  FIGS. 4  to  6  is provided with castellations  53  in order to define window openings  57  for the cold air, it is also possible to allow the edge strip  51  to project uniformly beyond the cold side  43 . Cooling air passages can then be implemented by means of through-holes  59 , in the form of drilled holes for instance. A corresponding exemplary embodiment of the burner insert according to the invention is illustrated in  FIG. 7 . 
     Although the edge strip extends along the entire outer edge  46  of the burner insert  41  in the present exemplary embodiments, embodiment variants are conceivable in which regions of the outer edge  46  of the burner insert  41  have no edge strip  51 . Furthermore, embodiment variants for cylindrical combustion chambers are possible. In such an embodiment variant, the outer edge of the burner insert would essentially be circular and the edge strip would be present at least along a part of the circumference, preferably around the entire circumference. 
     The invention enables the resonance frequency of the burner insert to be increased and simultaneously allows the flow of cold air into the combustion chamber to be specifically set in such a manner that the cold air is only able to flow through the predefined gaps. Associated therewith, further advantages of the invention result, such as for example an extended useful life of the burner insert and through the cold air saved at the burner insert—a lowering of pollutant levels whilst offering the same performance of the gas turbine provided with burner inserts according to the invention when the saved cold air is delivered to the burner. Alternatively, an improved performance can be achieved at the same level of emissions.