Patent Publication Number: US-9423125-B2

Title: Burner with lance

Description:
FIELD OF THE INVENTION 
     The present invention relates to a burner for a second combustion chamber of a gas turbine plant with sequential combustion having a first and a second combustion chamber, said burner being equipped with a lance. 
     BACKGROUND OF THE INVENTION 
     Conventional burners as for example known from the DE10128063 may be equipped with a lance for introducing gaseous and/or liquid fuels into the burner. The introduction of fuel via the lance may be utilized, for example, for pilot operation or for stabilizing a combustion reaction in the combustion space of a combustion chamber. Usually, a shaft of such a lance has at least one nozzle for introducing fuel into the burner. An example for such a fuel lance is given in the DE4326802. 
     Conventional burners preferably operate with natural gas as gaseous fuel. In this case, it is customary to provide the lance shaft along its circumference with a plurality of nozzles, through which the fuel gas can flow out essentially radially with respect to a longitudinal mid-axis of the shaft. A main injection direction of the respective nozzle is thereby oriented essentially radially onto a burner wall. In conjunction with an oxidizer gas flow present in the burner during operation, the fuel gas emerging radially from the lance is entrained in the main flow direction of the oxidizer gas, thus resulting in the desired intermixing between the oxidizer gas and fuel gas. 
     In modern combustion chambers, other gaseous fuels may also be used, which are distinguished by increased reactivity, as compared with a natural gas. These are, for example, fuel gases which contain hydrogen gas and, moreover, may contain carbon monoxide gas. Such a fuel gas containing hydrogen gas and carbon monoxide gas can be generated, for example, by means of the partial oxidation of long-chain hydrocarbons. A fuel gas of this type may also be designated as synthesis gas or syngas. If, then, a synthesis gas of this type is used as fuel gas in a conventional burner, this may lead to difficulties, since conventional burners are not suitable per se for use with fuel gases having such high reactivity. For example, reactive fuel gases of this type ignite even at lower temperatures and therefore with markedly shorter dwell times in the burner. In order in this case to avoid a hazardous flashback, for example, the mass flow of fuel gas can be increased correspondingly. Further, these gases have a lower calorific value than natural gas. Thus, higher mass and volume flows are needed, resulting in changed fuel distribution when fuel is injected from conventional natural gas holes. With an increased fuel mass flow, however, an undesirable enrichment of fuel gas in the region of the burner wall may occur, with the result that an intensive intermixing with the oxidizer gas, which is preferably air, takes place only inadequately. Inadequate intermixing, however, may lead to increased combustion temperatures, thus ultimately entailing increased pollutant values. Further, if fuel is concentrated near the wall, a flame can stabilize in the wall region due to low flow velocities in the wall, which can quickly lead to severe damages on the hardware. 
     SUMMARY OF THE INVENTION 
     The invention is concerned with the problem of specifying for a burner of the type initially mentioned an improved embodiment which is distinguished, in particular, in that, with it, a relatively good intermixing of the introduced fuel gas with the oxidizer gas is achieved and/or consequently reduced pollutant emissions are implemented, while, moreover, the burner is to be capable of being operated with a fuel gas containing hydrogen gas. 
     The invention is based on the general idea of equipping the burner in the region of its burner wall with an introduction device for a diverting fluid, which introduction device can introduce, in each case in a wall portion onto which a main injection direction of a nozzle of the lance is oriented, a diverting fluid which redirects the fuel flow before it impinges onto the burner wall. As a result of this design, the fuel gas introduced into the burner by the lance-side nozzle flows counter to a directionally oriented diverting fluid, with the result that the fuel gas flow can be stagnated and, in conjunction with the oxidizer gas flow prevailing in the burner, can be deflected to an increased extent in its main flow direction. A concentration of the fuel gas in regions of the burner wall can thereby be avoided or at least reduced. Overall, therefore, an improved homogenization of the fuel gas and oxidizer gas can be achieved by means of the proposed measure. This leads to improved emission values, even when a fuel gas containing hydrogen gas is used. Different gases can be used as diverting fluid. For example oxidizer gas, which is typically air, can be used as diverting fluid. Steam or inert gases are also suitable as diverting fluids. Further, depending on its reactivity and the flow field, fuel gas can also be used as diverting fluid. A combination of the different gas types or the use of fine water spay is also conceivable. 
     An embodiment is particularly advantageous in which the introduction device has in the burner wall, for each shaft nozzle oriented onto the burner wall, itself a directionally oppositely directed nozzle for introducing the diverting fluid. As a result, in particular, an individual adaptation of the individual nozzle pairings to one another can be implemented. This is advantageous particularly when the flow conditions within the burner vary in the circumferential direction. This is the case, for example, when the shaft is positioned in the burner via a base angled at right angles to said shaft. Different flow conditions necessarily exist in the wake of the base from those outside the wake. 
     In case of dual fuel applications, i.e. burners, which are capable of burning gaseous and liquid fuels additional injection means for injection of the liquid fuel have to be provided. Typically these means are nozzles for the injection of liquid fuel, which are arranged in the lance and for example inject fuel in the main flow direction from the downstream end of the shaft, as known for example from the DE4326802. 
     Further important features and advantages of the present invention may be gathered from the subclaims, from the drawing and from the accompanying figure description with reference to the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some preferred exemplary embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description. 
         FIG. 1  shows a greatly simplified longitudinal section through a burner with a lance; and 
         FIG. 2  shows a longitudinal section through a burner with a lance having a nozzle for introduction of liquid fuel in the main flow direction and arranged at the downstream end of the shaft. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to  FIG. 1 , a burner  1  has a burner wall  2  which laterally delimits a mixing space  3  of the burner  1 . The burner  1  usually forms an integral part of a combustion chamber, otherwise not illustrated here, of a gas turbine plant. The burner  1  has an inlet side  4  through which an oxidizer gas, preferably air, enters the mixing space  3 . A corresponding oxidizer gas flow is indicated by arrows  5 . Furthermore, the burner  1  has an outlet side  6  through which gas flows out of the mixing space  3  and, in particular, enters a combustion space  7  of the combustion chamber. A corresponding gas flow is indicated by arrows  8 . The throughflow of the burner  1  or of the mixing space  3  mainly takes place in a longitudinal direction of the burner  1 , with the result that a main throughflow direction or main flow direction  9  of the burner is defined, which is indicated in  FIG. 1  by an arrow. 
     The burner  1 , moreover, has a lance  10 , with the aid of which a gaseous fuel can be introduced into the burner  1  or into the mixing space  3 . The lance  10  has a shaft  11  which preferably has a cylindrical body and possesses a longitudinal mid-axis  12 . The lance  10  is expediently arranged in the burner  1  such that the shaft  11  is oriented with its longitudinal mid-axis  12  parallel to the main flow direction  9  prevailing in the burner  1 . In the example shown, moreover, the lance  10  has a base  13 , from which the shaft  11  is angled at 90°. The base  13  extends transversely with respect to the main flow direction  9  of the burner  1  and is fastened to the burner wall  2  in a suitable way. The base  13  thus positions the shaft  11  in the burner  1 . 
     The lance shaft  11  is equipped with at least one nozzle  14 , with the aid of which gaseous fuel can be introduced into the burner  1  or into the mixing space  3 . In the example, the shaft  11  possesses a plurality of such nozzles  14  which are arranged in the circumferential direction of the shaft  11  along a row  15  which extends annularly and coaxially with respect to the longitudinal mid-axis  12  of the shaft  11 . Within the row  15 , the individual nozzles  14  are arranged adjacently, spaced apart from one another. 
     The respective nozzle  14  is configured such that it injects the fuel gas into the burner  1  in a main injection direction  16 . The respective nozzle  14  usually generates a conical spray jet which emerges from a corresponding outlet orifice  17  of the respective nozzle  14 . The longitudinal mid-axis of the respective conical body then forms the main injection direction  16  of the respective nozzle  14 . In the example shown, purely by way of example, two arrows are depicted which symbolize the main injection directions  16  of two nozzles  14  lying diametrically opposite one another. It is notable, here, that the nozzles  14  are configured such that the main injection directions  16  are oriented radially with respect to the main flow direction  9  or with respect to the longitudinal mid-axis  12 . 
     In any event, the nozzles  14  are configured such and/or arranged on the shaft  14  such that the associated main injection direction  16  is oriented onto a portion  18 , identified here by a curly bracket, of the burner wall  2 . This means that the respective fuel jet would impinge upon the burner wall  2  in said portion  18  in the absence of an oxidizer gas flow  5 . In the presence of an oxidizer gas flow  5 , a pronounced deflection of the fuel gas in the direction of the oxidizer gas flow occurs. The resulting direction in which part of the fuel gas could reach the burner wall is indicated by a straight line designated  19 . If this dotted line  19  is followed, this gives rise on the burner wall  2  to a region  20 , symbolized by a curly bracket, in which, in the presence of an oxidizer flow  5 , the fuel gas could impinge onto the burner wall  2  if an increased inflow velocity is set for the fuel gas. An increased flow velocity of this kind is required, for example, when an increased volume flow is to be implemented for the reliable use of a fuel gas containing hydrogen gas. The contacting of fuel gas with the burner wall  2  could lead in the region  20  to an enrichment of fuel gas, and this may lead subsequently in the combustion space  7  or even in the mixing space  3  to an unfavorable combustion reaction with increased pollutant values. In worst case this can even result in a flash back. 
     The burner  1 , moreover is equipped with an introduction device  21 , with the aid of which a diverting fluid, which may be, for example, oxidizer gas, that is to say preferably air, can be introduced into the burner  1  or into the mixing space  3  through the burner wall  2 . While fuel gas can thus be introduced into the mixing space  3  virtually from inside by means of the lance  10 , the introduction device  21  makes it possible to introduce diverting fluid into the mixing space  3  virtually from outside. The introduction device  21 , then, allows a directed introduction of diverting fluid in said wall portion  18  in such a way as thereby to give rise, according to arrows  22 , to a diverting fluid flow which redirects the fuel flow and counteracts an impingement of the fuel flow  16  on the burner wall  2 . This results, for example, in a deflection of the fuel flow leads past the burner wall  2  as indicated by the dotted straight line  23 , with the result that contacting between the fuel gas and burner wall  2  can be avoided effectively. 
     The introduction device  21  for the diverting fluid expediently generates a main introduction direction which is likewise represented here by the arrows  22  and is likewise designated below by  22 . The embodiment shown here is particularly advantageous, in which the introduction device  21  is configured such that the main introduction direction  22  consequently generated coincides with the main injection direction  16  of the respective nozzle  14  and is directed opposite to this. In the best case, a compensation of the flows can be achieved, so that the deflection of the fuel flow leads to the straight line  23  running essentially parallel to the main flow direction  9 . 
     An embodiment is particularly advantageous in which the introduction device  21  has at least one nozzle  24 , with the aid of which the diverting fluid can be introduced into the mixing space  3  and which, in particular, can generate the abovementioned main introduction direction  22  for the diverting fluid flow. The respective nozzle  24  of the introduction device  21  is preferably arranged opposite the respective nozzle  14  of the shaft  11  on or in the burner  1 . 
     An embodiment is particularly advantageous in which for each nozzle  14  arranged on the shaft  11  a nozzle  24  is arranged on the burner wall  2 . It is further possible to assign to each nozzle  14  arranged on the shaft one nozzle  24  arranged on the burner wall  2 , which is aligned with it. In the example shown, therefore, a plurality of nozzles  24  are arranged, distributed in the circumferential direction of the burner  1 , along the burner wall  2 . These burner wall-side nozzles  24  are preferably arranged next to one another along an annular row  25  which extends coaxially with respect to the main flow direction  9  or coaxially with respect to the longitudinal mid-axis  12  of the shaft  11 . 
     In the case of shaft-side nozzles  14  which generate a radial main injection direction  16 , the burner wall-side nozzles  24  are expediently configured such that they generate a main introduction direction  22  oriented radially with respect to the main flow direction  9  or radially with respect to the longitudinal mid-axis  12  of the shaft  11 . 
     It is clear that the shaft  11  may basically also have a plurality of rows  15  of nozzles  14 . The introduction device  21 , too, may likewise have a plurality of rows  25  of nozzles  24 . Alternatively, the introduction device  21  may have, instead of singular nozzles  24 , large-area introduction zones for generating a more or less directed diverting fluid flow. In particular, the introduction of diverting fluid then does not have to be limited to the wall portion  18 , but can be extended to downstream wall portions or shifted into these. 
     Instead of the plurality of nozzles  14 , in another embodiment, at least one single slit-shaped opening extending circumferentially around the shaft  11  is used for introduction of the fuel. Complementarily to this, the introduction device  21  may also have at least one corresponding slit-shaped opening extending in circumferential direction around the burner wall  2  for introducing the diverting fluid. 
     While only certain features and embodiments of the invention have been shown and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.