Abstract:
An injection nozzle ( 10 ), especially for injecting liquid fuel, preferably crude oil, into the combustion chamber of a gas turbine, includes an inner chamber ( 16 ) which extends along a nozzle axis ( 19 ), conically tapers to a concentric nozzle orifice ( 17 ), and to which the medium which is to be injected is fed from outside through a plurality of inlet ports ( 18 ) which are arranged in a distributed manner around the nozzle axis ( 19 ). The inlet ports ( 18 ) are oriented perpendicularly to the nozzle axis ( 19 ) and each lead tangentially into the inner chamber ( 16 ). With such an injection nozzle, an improved spray cone is achieved by the fact that a pin ( 14 ), which extends in the axial direction, is concentrically arranged in the inner chamber ( 16 ) and passes through the region of the mouths of the inlet ports ( 18 ) and extends right into the nozzle orifice ( 17 ).

Description:
This application claims priority under 35 U.S.C. §119 to Swiss application no. 00105/10, filed 29 Jan. 2010, the entirety of which is incorporated by reference herein. 
     BACKGROUND 
     1. Field of Endeavor 
     The present invention relates to the field of combustion technology, especially in connection with gas turbines. It relates to an injection nozzle and to a method for operating such an injection nozzle. 
     2. Brief Description of the Related Art 
     For the atomizing injection of liquid fuel into the combustion chamber of a gas turbine, a multiplicity of various injection nozzles, which differ with respect to their internal construction and the type of spray cone which is generated, are known from the prior art. 
     A fuel nozzle with swirl passage, which includes a sleeve and a pin, is known, for example, from WO 2009/095100. The pin is arranged in the sleeve so that the inner surface of the sleeve is connected in a positive manner to the outer generated surface of the pin. Along the outer generated surface of the pin extends a swirl passage in the form of a recess which winds in a helical manner around the center axis of the pin on the outer generated surface. As a result of the arrangement of the pin in the sleeve, a swirl passage is covered or delimited radially with regard to the center axis of the pin by the inner surface of the sleeve. The sleeve has a discharge orifice in the flow direction of the fuel which leaves the fuel nozzle. The pin is arranged in the sleeve so that the cover surface of the pin is recessed towards the discharge orifice of the sleeve. As a result, a swirl chamber is formed. In the swirl chamber, a mixing of the fuel—that is to say, of the oil in the present exemplary embodiment—with air takes place. As a result of the recessing, a film atomization instead of a jet atomization is furthermore enabled. It is also possible for the cover surface to align with the discharge orifice. In the case of the swirl chamber, the spray cone can only be adjusted with difficulty. If the cover surface aligns with the discharge orifice, the fuel only discharges at the ends of the swirl passages, that is to say is localized to a high degree. Furthermore, the production of the swirl passages is comparatively costly. 
     A liquid fuel nozzle for the combustion chamber of a gas turbine, which includes a nozzle cap  100 , a nozzle insert  101 , a pilot insert  102 , and a nozzle body  103 , is known from EP 1 793 165 ( FIG. 1  there). The pilot insert  102  is arranged inside the nozzle insert  101 . The nozzle insert  101  is, in turn, arranged inside the nozzle cap  100 . The nozzle has a pilot passage  105  which supplies the pilot insert  102  with fuel. The pilot insert  102  has a swirl chamber  110  into which a pilot swirl orifice  107  tangentially leads. Pilot fuel  32  flows via the pilot passage  105  from the vicinity of the pilot insert  102  through the pilot swirl orifice  107  and maintains a swirl there, by which it moves in the swirl chamber  110 . The pilot fuel  32  forms a film on the inner wall of the swirl chamber  110  and shoots from the pilot injection orifice  108  in fine droplets. 
     The construction and function of the pilot arrangement of EP 1 793 165 are comparable with a simplex swirl atomizer which has been described in an article by D. B. Kulshreshtha et al., Variations of Spray Cone Angle and Penetration Length of Pressure Swirl Atomizer Designed for Micro Gas Turbine Engine, Int. J. Dynamics of Fluids, Vol. 5, Number 2, pp. 165-172 (2009). In both cases, the fuel which is pressurized and provided with a swirl discharges from a circular hole. The swirl chamber, into which the fuel flows tangentially and perpendicularly to the nozzle axis, is formed as a simple chamber without devices which promote swirl. Both lead to a non-optimized design of the spray cone which, moreover, has a limited cone angle. 
     SUMMARY 
     One of numerous aspects of the present invention includes an injection nozzle for liquid fuels, especially in the form of crude oil, and methods for its operation. 
     Another aspect of the present invention includes that a pin, which extends in the axial direction, is concentrically arranged in the inner chamber of the injection nozzle, which pin passes through the region of the mouths of the inlet ports and extends right into the nozzle orifice. In the center of the inner chamber, the pin promotes swirl of the fuel which is introduced tangentially through the inlet ports. At the same time, the pin narrows the nozzle orifice to an annular gap, by which the forming of the spray cone is greatly improved. 
     One development includes that the nozzle orifice is formed with a circular shape, and that the pin has a circular cross section in the region of the nozzle orifice in such a way that an annular gap is formed between the pin and the boundary of the nozzle orifice. 
     The pin can especially be formed with a continuously cylindrical shape with a constant outside diameter. 
     It is also conceivable, however, for the pin to be formed with a cylindrical shape with a constant outside diameter and in the region of the nozzle orifice to have a shape which deviates from the cylindrical shape, especially being formed in a conically tapering manner. 
     Another development of the invention includes that the inner chamber, on the side opposite the nozzle orifice, is sealed off by a wall which is oriented perpendicularly to the nozzle axis, and that the pin extends up to the wall and is fastened on the wall. The pin can especially be formed in one piece together with the wall. 
     A further development includes that the inner chamber has a cylindrical section and a conically tapering section which adjoins the cylindrical section in an axial direction and leads into the nozzle orifice, and that the inlet ports lead into the cylindrical section of the inner chamber. 
     Another development of the invention includes that the inner chamber is concentrically encompassed by an outer chamber, and that the outer chamber is in communication with the inner chamber by the inlet ports. 
     The outer chamber in this case is preferably enclosed by a tubular housing which is open at one end and closed off at the other end by a nozzle plate, and the inner chamber is arranged in the nozzle plate. 
     The housing can especially include a cylindrical section and a conical section, and the nozzle plate with the inner chamber can be arranged in the cylindrical section of the housing. 
     Another development includes that at least three inlet ports are arranged in a uniformly distributed manner in one plane around the nozzle axis. 
     Good results are achieved if the nozzle orifice has an inside diameter of 3 mm and the pin has an outside diameter of 2 mm, and if three inlet ports are provided with an inside diameter of 1 mm in each case. 
     Good results are also achieved if the nozzle orifice has an inside diameter of 2.5 mm and the pin has an outside diameter of 2 mm, and if three inlet ports are provided with an inside diameter of 1 mm in each case. 
     The same also applies if the nozzle orifice has an inside diameter of 2.5 mm and the pin has an outside diameter of 1.8 mm, and if three inlet ports are provided with an inside diameter of 1 mm in each case. 
     In the case of a method according to principles of the present invention, the injection nozzle is pressurized with an injection pressure in the range of between 1 and 5 bar, or operated with a mass throughflow rate of between 40 and 120 kg/h. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention shall subsequently be explained in more detail based on exemplary embodiments in conjunction with the drawing. In the drawing 
         FIG. 1  shows, in longitudinal section ( FIG. 1   a ) and in lateral cross-section ( FIG. 1   b ), the construction of an injection nozzle with inner chamber and four tangential inlet ports, as is the starting point of the present invention; 
         FIG. 2  shows, in a rear elevational view ( FIG. 2   a ) and in longitudinal section ( FIG. 2   b ), an injection nozzle according to an exemplary embodiment of the invention; 
         FIG. 3  shows, in a rear elevational view ( FIG. 3   a ) and in longitudinal section ( FIG. 3   b ), the housing of the injection nozzle according to  FIG. 2 ; 
         FIG. 4  shows, in a side elevational view ( FIG. 4   a ) and in a front elevational view ( FIG. 4   b ), the insert with pin of the injection nozzle according to  FIG. 2 ; 
         FIG. 5  shows, in a side elevational view ( FIG. 5   a ), in longitudinal cross-section ( FIG. 5   b ), and in lateral cross-section ( FIG. 5   c ), the nozzle plate ( FIG. 5   c ) with the inner chamber and the nozzle orifice of the injection nozzle according to  FIG. 2 ; 
         FIG. 6  shows a graph of the dependency of the cone angle of the spray cone of an injection nozzle according to  FIG. 1  without a pin in dependence upon the mass throughflow, for two different sets of nozzle parameters; 
         FIG. 7  shows a graph of the dependency of the mass throughflow of injection pressure (p inj ) for an exemplary injection nozzle according to  FIG. 2 , for water and crude oil; 
         FIG. 8  shows a graph of the dependency of the cone angle of the spray cone of an injection nozzle according to  FIG. 2  with a pin in dependence upon the mass throughflow, for water and crude oil, and 
         FIG. 9  shows a graph of the dependency of the cone angle of the spray cone of an injection nozzle according to  FIG. 2  with a pin in dependence upon the mass throughflow, for two other sets of nozzle parameters. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In  FIG. 1 , in longitudinal section ( FIG. 1   a ) and in lateral cross section ( FIG. 1   b ), the construction of an injection nozzle with inner chamber is reproduced, as is the starting point of nozzles embodying principles of the present invention. The injection nozzle  20  is assembled from a rear section  21  and a front section  23  which abut against each other and therefore define an inner chamber  24 . The inner chamber  24  includes a cylindrical section, which is arranged in the rear section  21 , and a conically tapering section which is accommodated in the front section  23 . The pointed end of the conical section merges into a circular nozzle orifice  25  through which pressurized liquid fuel in the form of a spray cone can discharge outwards. 
     The fuel is introduced into the inner chamber  24  from outside through four inlet ports  22  which lie in one plane and lead tangentially into the inner chamber  24 . The tangential orientation of the inlet ports  22  ensures that the fuel which flows into the inner chamber  24  maintains a swirl around the nozzle axis ( 19  in  FIG. 3 ), which contributes to the forming of extremely fine droplets in the spray cone. 
     Starting from the configuration of  FIG. 1 , a pin is arranged in the inner chamber, which on the one hand promotes the swirl of the fuel which flows into the inner chamber, and on the other hand narrows the nozzle orifice to an annular gap. 
       FIG. 2  shows, in a rear elevational view ( FIG. 2   a ) and in longitudinal cross-section ( FIG. 2   b ), a corresponding injection nozzle according to an exemplary embodiment of the invention. The individual parts, from which the injection nozzle  10  of  FIG. 2  is assembled, are shown in  FIGS. 3 ,  4 , and  5  in different views. 
     The injection nozzle  10  has an outer chamber  12  and an inner chamber  16 . The outer chamber  12  is delimited on the outside by a tubular housing  11 , which, according to  FIG. 3 , lies concentrically to the nozzle axis  19  and includes a cylindrical section  11   a  and a (frusto-)conical section  11   b . On the side of the conical section  11   b , the housing  11  is open so that from there fuel can flow unhindered into the outer chamber  12 . On the opposite side, the housing  11  is sealed off on the outside by a circular disk-shaped nozzle plate  15  which is equipped with a disk  15   a  and a shoulder  15   b.    
     Inside a cylindrical section  15   c  ( FIG. 5 ), which is formed on the nozzle plate  15  and projects rearwards into the outer chamber  12 , provision is made for a concentric inner chamber  16 . The inner chamber  16 , by a conically tapering section which extends through the disk  15   a , leads to a circular nozzle orifice  17  which is arranged on the front side of the nozzle plate  15  and has an inside diameter F ( FIG. 5   b ). At the rear, a cylindrical section, which at the rear end is closed off by the disk  13   a  and a shoulder  13   b  of an insert  13 , adjoins the conical section of the inner chamber  16 . On the insert  13 , an axially oriented pin  14  is formed, which extends centrally through the inner chamber  16  up to the nozzle orifice  17  and closes off the nozzle orifice  17  except for an annular gap. Through the annular gap which has been left open, fuel which is in the inner chamber  16  can discharge outwards, forming a spray cone. 
     The fuel can flow from the outer chamber  12  into the inner chamber  16  through a plurality of inlet ports  18  which are distributed uniformly around the nozzle axis  19  and arranged in a plane which is oriented perpendicularly to the nozzle axis (in the example of  FIG. 2  there are three inlet ports altogether; see  FIG. 5   c ). The inlet ports  18  lead tangentially into the inner chamber  16  ( FIG. 5   c ) so that the inflowing fuel maintains a strong swirl around the pin  14 , which, inter alia, as a result of the pin  14  continues almost unhindered up to the nozzle orifice  17 . The inlet ports  18  have the inside diameter J in each case ( FIG. 5   c ). 
     With injection nozzles of the type which is shown in  FIG. 1  and  FIG. 2 , measurements were carried out, wherein specific parameters of the injection nozzle were varied. The results are reproduced in the form of graphs in  FIGS. 6 ,  7 ,  8 , and  9 .  FIG. 6  shows a graph of the dependency of the cone angle of the spray cone of an injection nozzle according to  FIG. 1  without a pin in dependence upon the mass throughflow for two different sets of nozzle parameters and for the medium of water at injection pressures of between 1 and 8 bar. The one injection nozzle (diamonds in  FIG. 6 ) had an inside diameter of the nozzle orifice  25  of 0.9 mm, an inside diameter of the inlet ports  22  of 1.5 mm, a diameter in the cylindrical section of the inner chamber  24  of 12.2 mm, and an axial length of the inner chamber  24  of 12.1 mm. The other injection nozzle (squares in  FIG. 6 ) had an inside diameter of the nozzle orifice  25  of 0.9 mm, an inside diameter of the inlet ports  22  of 1.0 mm, a diameter in the cylindrical section of the inner chamber  24  of 7 mm, and an axial length of the inner chamber  24  of 6 mm. It is apparent that the cone angle does not vary a great deal with the mass throughflow and remains below 60° even in the case of high mass throughflows of more than 55 kg/h. 
       FIG. 7  shows a graph of the dependency of the mass throughflow of injection pressure (p inj ) for an exemplary injection nozzle according to  FIG. 2 , for water and crude oil. The injection nozzle  10  in this case had three inlet ports  18  with an inside diameter of J=1 mm, the nozzle orifice  17  had an inside diameter of F=3 mm, and the pin  14  was continuously cylindrical with an outside diameter of F1=2 mm, so that an annular gap with a gap width of 0.5 mm resulted. 
     In comparison to  FIG. 6 ,  FIG. 8  shows a graph of the dependency of the cone angle of the spray cone of an injection nozzle according to  FIG. 2  with a cylindrical pin in dependence upon the mass throughflow for water and crude oil, wherein it concerns the same injection nozzle  10  as in  FIG. 7 . 
       FIG. 9  finally shows a graph of the dependency of the cone angle of the spray cone of an injection nozzle  10  according to  FIG. 2  with a cylindrical pin  14  in dependence upon the mass throughflow for two other sets of nozzle parameters, wherein the one injection nozzle (squares in  FIG. 9 ) has three inlet ports  18  with J=1 mm, a nozzle orifice  17  with F=2.5 mm, and an outside diameter of the pin  14  with F1=2 mm, while the other injection nozzle (diamonds in  FIG. 9 ) has three inlet ports  18  with J=1 mm, a nozzle orifice  17  with F=2.5 mm, and an outside diameter of the pin  14  with F1=1.8 mm. 
     It is apparent that compared with an injection nozzle without a central pin, significantly larger cone angles result both for water and for crude oil. Without the pin, the nozzle orifice  25  ( FIG. 1 ) is filled with the medium and the angle of the spray cone is largely constant. The rotational speed (in the swirl) is greatly reduced and the speed in the axial direction is increased. The pin  14  on the other hand forces a rotating flow (swirled flow) with a high rotational speed inside the nozzle orifice  17 . The injection nozzle is therefore especially suitable for use in the combustion chamber of a gas turbine with a multiplicity of different injection points. 
     An injection nozzle according to principles of the present invention is especially suitable for crude oil (high density). It is comparatively small and characterized by a large swirl in the inner chamber. This leads to the surface stress, which without the pin  14  is so great that the spray cone is only about 50-55° (“plain jet”; see  FIG. 6 ), losing its influence. As a result of the pin  14 , the spray angle can therefore be appreciably enlarged (to about 90-100°; see  FIGS. 8 ,  9 ). The shape of the pin  14 , as already mentioned, does not necessarily have to be cylindrical; a tapering shape or the like could also be possible. 
     LIST OF DESIGNATIONS 
     
         
         
           
               10 ,  20  Injection nozzle 
               11  Housing 
               11   a  Cylindrical section 
               11   b  Conical section 
               12  Outside diameter 
               13  Insert 
               13   a  Disk 
               13   b  Shoulder 
               14  Pin 
               15  Nozzle plate 
               15   a  Disk 
               15   b  Shoulder 
               15   c  Cylindrical section 
               16 ,  24  Inner chamber 
               17 ,  25  Nozzle orifice 
               18 ,  22  Inlet port 
               19  Nozzle axis 
               21  Rear section 
               23  Front section 
             F Inside diameter (nozzle orifice) 
             F 1  Outside diameter (pin) 
             J Inside diameter (inlet port) 
             p inj  Injection pressure 
           
         
       
    
     While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.