Patent Publication Number: US-6209327-B1

Title: Burner arrangement for a gas turbine including an inlet-air impingement plate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of gas-turbine technology. It relates to a burner arrangement for a gas turbine, where the burner arrangement comprises a interior space enclosed by a casing, in which interior space at least one burner is arranged, and into which interior space in each case a jet of a gaseous medium, in particular air, is sprayed through at least two nozzle openings against the direction of flow of the burner and along the inner wall of the casing, which jets, guided by the inner wall, meet one another from opposite directions and combine to form a secondary flow flowing off perpendicularly from the inner wall. 
     Such a burner arrangement has been disclosed, for example, by publication EP-A2-0 692 675 (see, for example, FIG. 1 there). 
     2. Discussion of Background 
     A double-cone burner of a gas turbine, to which double-cone burner fuel is fed via a fuel lance, is shown in the publication mentioned at the beginning (e.g. in FIG. 1 there). The burner is accommodated in the interior space of a dome-like casing. Main burner air flows into the casing against the direction of flow of the burner above and below the burner, is deflected by the inner wall of the casing and then enters the burner in order to be mixed with the fuel there. 
     Such a flow in a casing, which flow results from two or more jets striking one another, the jets entering the casing through corresponding nozzle openings, is generally extremely sensitive to fluctuations in the total pressure of the jets. This may be illustrated with reference to FIG.  1 . In the flow arrangement  10  according to FIG. 1, two jets  15 ,  16  are sprayed on two opposite sides through corresponding nozzle openings  13 ,  14  into an interior space  11 , which is defined by a boundary wall  12  (curved in a semicircle in this example), and these jets  15 ,  16 —guided by the boundary wall  12 —meet one another at an impingement point  18  and combine there to form a secondary flow  17 , which is directed perpendicularly to the boundary wall into the interior of the interior space  11 . 
     The velocity of the jets  15 ,  16  approaches zero at the impingement point  18 . Since the wall streamlines of the two jets  15  and  16  meet at the stagnation point  18 , the total pressures of the jets  15  and  16  must also correspond there. Since the friction at the boundary wall  12  typically does not lead to a rapid change in the total pressure, the impingement point  18  will regularly lie in the vicinity of one of the two nozzle openings  13 ,  14 , which produce the jets  15 ,  16 . In the extreme case, one of the jets  15 ,  16  may even block the nozzle opening which is intended to produce the other jet. Even in the cases in which the total pressures of the two jets are virtually the same, the position of the impingement point normally deviates greatly from the plane of symmetry which runs between the two nozzle openings. 
     This instability and uncertainty of such casing flows also has an effect in the case of a burner arrangement  20  as shown in FIG.  2 . The burner  21  (in this case a double-cone burner of known type of construction) is accommodated in a casing  23  in such a way as to lie in a plane of symmetry  19 . The burner  21  opens to the left into a combustion chamber  33 ; it is supplied with fuel from the right via a fuel feed  32 . Formed at the top and bottom between the combustion chamber  33  and the casing  23  are nozzle openings  24  and  25 , through which combustion air (from the compressor of the gas turbine) is sprayed in the form of jets  26 ,  27  into the interior space  22  enclosed by the casing  23 . The jets  26 ,  27  flow toward one another along the inner wall  23   a  of the casing  23  and, after striking one another, combine to form a secondary flow  28 , which flows toward the burner  21  and enters the burner  21  laterally. As indicated in FIG. 2, the impingement point and thus also the secondary flow generally lie at a varying point outside the plane of symmetry, which point cannot be predetermined and may change quickly due to geometric disturbances in the arrangement and due to pressure fluctuations. As a result, the uniform operation of the burner  21  under stable combustion conditions is considerably impaired. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the invention is to provide a novel burner arrangement in which stable flow conditions of the sprayed-in combustion air result, these flow conditions being essentially unaffected by geometric deviations and pressure fluctuations. 
     The object is achieved in a burner arrangement of the type mentioned at the beginning in that, to establish the impingement point of the jets, a dividing plate is placed in the flow path of the jets and arranged essentially perpendicular to the inner wall. The two jets strike the dividing plate, mounted in a fixed position, from both sides and are deflected parallel to the dividing plate into the interior space, where they are combined behind the dividing plate to form a secondary flow, which flows parallel to the dividing plate. 
     Depending on the arrangement of the dividing plate, the secondary flow may be produced at different points of the casing and with different directions. However, a preferred embodiment of the invention is defined in that the burner is arranged inside the casing in a plane of symmetry, in that the nozzle openings are arranged symmetrically to the plane of symmetry, and in that the dividing plate lies in the plane of symmetry. 
     Further embodiments follow from the dependent claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 shows a schematic representation of a basic flow arrangement having two wall-guided flows striking one another at an impingement point; 
     FIG. 2 shows a schematic representation of a burner arrangement having jets of combustion air according to the prior art which are directed inside a casing; 
     FIG. 3 shows a first preferred exemplary embodiment of a burner arrangement according to the invention having a dividing plate fastened directly to the casing; and 
     FIGS.  4 A,B show a second preferred exemplary embodiment of a burner arrangement according to the invention having an interchangeable burner in side view (FIG.  4 A), in which burner arrangement the dividing plate is fastened to a cover of an access opening for the burner (plan view of the cover with dividing plate in FIG.  4 B). 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, a first preferred exemplary embodiment of the burner arrangement according to the invention, based on the representation from FIG. 2, is reproduced in FIG.  3 . In this case, the same parts of the arrangement are provided with the same reference numerals as in FIG.  2 . Essential to the invention is the insertion of a dividing plate  29  into the burner arrangement. In the exemplary embodiment in FIG. 3, the dividing plate  29  lies in the plane of symmetry  19  and can therefore only be seen from the side. The dividing plate  29  is placed perpendicularly on the inner wall  23   a  of the casing  23  and is preferably mounted in a fixed position at this point on the inner wall  23   a , e.g. welded or screwed thereto. It is at the same time disposed perpendicularly to the jets  26  and  27  striking the dividing plate  29  at this point from both sides. Due to the effect of the dividing plate  29 , two partial flows  28   a  and  28   b  form at the location defined by the dividing plate  29 , and these partial flows  28   a  and  28   b  flow along the dividing plate  29  into the interior of the interior space  22  and combine at the end of the dividing plate  29  to form a secondary flow  28 . The dividing plate  29  according to the invention, at a defined point of the casing  23 , in particular in the plane of symmetry  19 , thus produces a secondary flow of defined direction, which meets the burner  21  symmetrically from the rear and essentially retains its configuration, even in the event of changes in the rest of geometry or in the pressures. In this way, very stable conditions are achieved during operation of the burner. 
     If, as assumed in FIG. 3, a burner  21  is installed in a fixed position in the casing  23 , the dividing plate  29  may be fastened directly to the inner wall  23   a  of the casing  23  without difficulty. If, for example, a plurality of burners are arranged side by side in an interchangeable manner in the casing  23 , and these burners, according to FIGS. 4A and B, are designed such that they can be pushed in or pulled out through an access opening  31  in the casing  23 , the access opening  31  being closable by an appropriate (disk-shaped) cover, the dividing plate  29  may be advantageously arranged and fastened on the inside of the cover  30 . 
     It has been possible to experimentally confirm the effect of such dividing plates in stabilizing and evening out the combustion-air flow in gas turbines of type GT13E2 from the applicant. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.