Abstract:
An improved torch igniter for use in devices such as thrust augmenters, gas turbine engines, ramjets, combined-cycle engines and industrial burners. The torch igniter includes a housing with a combustion chamber. Fuel and oxidizer are delivered into the combustion chamber and ignited by an electronic ignition source, such as a plasma jet igniter or a spark igniter, so that an upstream recirculation zone and a downstream recirculation zone are created. The upstream recirculation zone stabilizes and pilots combustion within the combustion chamber, while the downstream recirculation zone augments the combustion event. Byproducts of the combustion event within the torch igniter provide a high mass flux with high thermal energy and strong ignition source radicals that are discharged through a neck portion of the housing and are thereafter employed to initiate a primary combustion event in a primary combustor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a divisional of U.S. patent application Ser. No. 10/217,972 filed on Aug. 13, 2002. The disclosure of the above application is incorporated herein by reference in its entirety into the present application. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention generally relates torch igniters for initiating a combustion event in devices such as industrial burners or combustors for gas turbine engines, ramjets or combined-cycle engines, and more particularly to a torch igniter having increased mass flux and energy.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional aircraft engines, ramjets, combined-cycle engines and industrial burners typically include an electronically actuated ignition source for initiating a combustion event in a combustion chamber. Such electronically actuated ignition sources are usually of the spark igniter type or the plasma jet type.  
           [0004]    Spark igniters typically utilize a spark plug-like device for generating a discharge arc which is employed to generate a flame kernel that ignites a mixture of fuel and oxidizer (e.g., air or oxygen) in the combustion chamber. Plasma jet igniters typically employ a fuel source, such as hydrogen or jet fuel, that dissociates in a spark discharge to produce a kernel of various radicals that in turn initiate a combustion event in the combustion chamber.  
           [0005]    If the rate of heat loss from the kernel is less than the rate of heat production in the kernel, the ignition front advances leading to combustor light-off. Most conventional igniters require favorable aerodynamic conditions to advance the ignition front. Some combustors, however, are engineered to operate with inlet conditions (e.g., during supersonic pre-ignition flow) and/or fuel conditions (e.g., fuel type, fuel droplet size, the extent to which the fuel and air have mixed) that do not present the favorable aerodynamic conditions that are necessary for reliable ignition and flame propagation with conventional igniters. Further aggravating this situation, it may not be practical to place the igniter relative to the combustor in the position where it would be most effective as when, for example, the placement of the igniter is dictated by concerns for serviceability or the packaging of the combustor into an application. Accordingly, there remains a need in the art for an improved igniter.  
         SUMMARY OF THE INVENTION  
         [0006]    In one preferred form, the present invention provides a torch igniter having a housing and an electronic ignition source. The housing defines a combustion chamber, at least one fuel conduit and at least one oxidizer conduit. The fuel conduit or conduits intersect the combustion chamber forwardly of an end wall and are configured to dispense at least one stream of fuel into the combustion chamber. The oxidizer conduit or conduits intersect the combustion chamber forwardly of the end wall and are configured to dispense at least one stream of oxidizer into the combustion chamber. The streams of fuel and oxidizer mix to produce a fuel/oxidizer mixture. The fuel and oxidizer conduits are positioned relative to the combustion chamber so as to create an upstream recirculation zone and a downstream recirculation zone that stabilize and pilot combustion within the combustion chamber. The electronic ignition source is coupled to the housing and generates a kernel that is dispensed into the combustion chamber rearwardly of the fuel and oxidizer conduits. The kernel initially ignites the fuel/oxidizer mixture in the recirculation zone, which propagates throughout the combustion chamber.  
           [0007]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 is a sectional view of a thrust augmenter that includes a torch igniter constructed in accordance with the teachings of the present invention;  
         [0010]    [0010]FIG. 2 is a longitudinal section view of the torch igniter of FIG. 1;  
         [0011]    [0011]FIG. 3 is a longitudinal section view similar to that of FIG. 2 but illustrating the flow aerodynamics and operation of the torch igniter;  
         [0012]    [0012]FIG. 4 is a sectional view taken along the line  4 - 4  of FIG. 2;  
         [0013]    [0013]FIG. 5 is a sectional view similar to that of FIG. 4 but illustrating a first alternate arrangement of the fuel and oxidizer conduits;  
         [0014]    [0014]FIG. 6 is a sectional view similar to that of FIG. 4 but illustrating a second alternate arrangement of the fuel and oxidizer conduits;  
         [0015]    [0015]FIG. 7 is a sectional view similar to that of FIG. 4 but illustrating a third alternate arrangement of the fuel and oxidizer conduits; and  
         [0016]    [0016]FIG. 8 is a sectional view of an alternately constructed tip for the torch igniter of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    With reference to FIG. 1 of the drawings, a torch igniter constructed in accordance with the teachings of the present invention is generally indicated by reference numeral  10 . The torch igniter  10  is especially suited to produce a high concentration of free radicals at a high temperature and appropriate mass flux that is required for generating a robust ignition event in the combustor  12  of a device such as a thrust augmenter  14 , a turbojet engine, a ramjet engine, a combined-cycle engine or an industrial burner. In the particular embodiment provided, the torch igniter  10  utilizes an ethylene fuel and an air or oxygen oxidizer so as to produce free radicals such as OH, H and O and a robust output torch jet or kernel.  
         [0018]    With additional reference to FIGS. 2 and 3, the torch igniter  10  is illustrated to include a housing  20  and an electronic ignition source  22 , which is illustrated to be a conventional and commercially available plasma jet igniter  24 , such as a plasma jet igniter manufactured by Unison Industries, Jacksonville, Fla. The plasma jet igniter  24  is coupled to a gaseous plasma source  26  and an igniter controller  28 . The igniter controller  28  controls the operation of the plasma jet igniter  24  and more specifically, the discharge of electricity across a pair of electrodes  30   a  and  30   b  to dissociate the gaseous plasma source into a plasma jet or kernel  32  that emanates from a tip  34  of plasma jet igniter  24 . Alternatively, the electronic ignition source  22  may be a conventional spark igniter, such as a spark igniter manufactured by Champion Spark Plug Company, Toledo, Ohio.  
         [0019]    The housing  20  includes an igniter mounting portion  40 , a combustion chamber portion  42  and a neck portion  44 . In the particular example provided, the igniter mounting portion  40 , the combustion chamber portion  42  and the neck portion  44  are separately formed components that are formed from a suitable material, such as 304 stainless or nickel, and fixedly coupled to one another in an appropriate manner, such as with a plurality of threaded fasteners  46  or welds.  
         [0020]    The igniter mounting portion  40  includes an annular igniter housing  50  and an end wall  52 . The annular igniter housing  50  is removably coupled to the rear side of the combustion chamber portion  42  and defines an igniter aperture  54  that is configured to receive the electronic ignition source  22 . In the particular embodiment illustrated, the igniter aperture  54  includes an internally threaded portion  56  that threadably engages an externally threaded portion  58  of the electronic ignition source  22  to permit the electronic ignition source  22  to be fixedly but removably coupled to the igniter mounting portion  40 . Those skilled in the art will understand, however, that any known coupling mechanism may be employed to couple the electronic ignition source  22  to the igniter mounting portion  40 . The electronic ignition source  22  is disposed in the igniter aperture  54  such that a tip  34  of the electronic ignition source  22  extends at least partially through a tip aperture  58  formed through the end wall  52 . As those skilled in the art will appreciate, however, the tip  34  of the electronic ignition source need not extend through the tip aperture  58  in the end wall  52 ; recessing of the tip  34  inside the end wall  52  is beneficial where enhanced survivability of the electronic ignition source  22  is desired.  
         [0021]    The combustion chamber portion  42  defines a combustion chamber  60 , at least one fuel conduit  62  and at least one oxidizer conduit  64 . The combustion chamber  60  is arranged about the longitudinal axis  66  of the torch igniter  10  and is bounded at its opposite ends by the end wall  52  and a transition wall  70  that abuts the neck portion  44 . In the particular example provided, the transition wall  70  is shown to be frustoconically shaped to thereby guide the combustion byproducts into the neck portion  44 . Those skilled in the art will appreciate, however, that the transition wall  70  may be shaped in various other manners, including arcuately shaped, or may be omitted altogether such that the neck portion  44  confines the combustion chamber  60  in a manner like that of the end wall  52  (i.e., the neck portion  44  forms a wall that is generally perpendicular to the longitudinal axis of the combustion chamber  60 ). The fuel and oxidizer conduits  62  and  64  are spaced between the end wall  52  and the neck portion  44  to create an upstream recirculation zone  74  and a downstream recirculation zone  75 , both of which being discussed in greater detail, below.  
         [0022]    With additional reference to FIG. 4, the particular example shown includes a combustion chamber portion  42  that defines a pair of fuel conduits  62  which are disposed 180° apart from one another such that the fuel streams  76  produced by the fuel conduits  62  impinge upon one another. Similarly, the particular example provided includes a pair of oxidizer conduits  64  that are disposed 180° apart from one another and offset by 90° from the fuel conduits  62 . Accordingly, the oxidizer conduits  64  produce oxidizer streams  78  that impinge upon one another, as well as the fuel streams  76  to thereby produce a fuel/oxidizer mixture  80 . Those skilled in the art will understand, however, that the fuel and oxidizer streams  76  and  78  need not impinge upon one another about a common point as is illustrated in FIGS. 5 through 7.  
         [0023]    Returning to FIGS. 2 and 3, the neck portion  44  defines a neck barrel  84  that is in fluid communication with the combustion chamber  60 . The neck barrel  84  is illustrated to have diameter “d” that is about 20% to about 60% of the diameter “D” of the combustion chamber  60 . Accordingly, the neck barrel  84  is formed to have a lateral cross-section that is substantially smaller than the lateral cross-section of the combustion chamber  60 . In the particular embodiment provided, the diameter d is about 40% of the diameter D.  
         [0024]    In the example shown, the torch igniter  10  is also illustrated to include a tip  88  that is coupled to the neck portion  44  on a side opposite the combustion chamber portion  42 . The tip  88  serves to extend the neck portion  44  and may be integrally formed with the neck portion  44  or may be a discrete structure that is coupled, permanently or removably, to the neck portion  44 . If the tip  88  is formed as a discrete structure it may be formed from a material, such as 200 nickel, that is more appropriate for the environment in which it will be used.  
         [0025]    The tip  88  includes a longitudinally extending and generally cylindrical tip bore  90  and one or more orifices  92 , which intersect the tip bore  90  at a distal end of the tip  88 . The tip bore  90  is in fluid communication with the combustion chamber  60  and receives therefrom the byproducts of the combustion event in the combustion chamber  60 . These byproducts are subsequently expelled from the tip  88  through the orifice  92  as an output kernel  94  that is employed to ignite a recirculation zone. The orifice  92  is illustrated to have an arcuately shaped wall  96  that is disposed concentrically to the tip bore  90 , but may also be configured with a generally cylindrical wall. With brief reference to FIG. 8, one or more additional orifices  92  may be utilized to expel additional kernels for igniting the same and/or another recirculation zone. In the embodiment illustrated, the tip  88 ′ includes a first orifice  92   a  that is aligned concentrically to the tip bore  90  and a second orifice  92   b  that is aligned generally perpendicular to the first orifice  92   a.    
         [0026]    Although the tip bore  90  and neck barrel  84  are illustrated to be cylindrically shaped and identically sized, those skilled in the art will appreciate that other configurations are possible. For example, the neck barrel  84  and/or the tip bore  90  may have an arcuate or frustoconical shape. As another example, the tip bore  90  may be sized relatively smaller in diameter than the neck barrel  84 .  
         [0027]    In FIGS. 3 and 4, the operation of the torch igniter  10  is illustrated. The electronic ignition source  22  is operated to generate an ignition kernel  32  that is dispensed into the combustion chamber  60  rearwardly of the fuel and oxidizer conduits  62  and  64  (i.e., rearwardly of the point at which the fuel and oxidizer conduits  62  and  64  intersect the combustion chamber  60 ). A fuel and an oxidizer are dispensed into the combustion chamber  60  via the fuel and oxidizer conduits  62  and  64 , respectively, and thereafter mix to produce a fuel/oxidizer mixture  80 .  
         [0028]    While the majority of the fuel/oxidizer mixture  80  moves forwardly in the combustion chamber  60  toward the neck barrel  84 , a relatively small portion  80   a  of the fuel/oxidizer mixture  80  is diverted into the portion of the combustion chamber  60  between the end wall  52  and the fuel and oxidizer conduits  62  and  64  and ignited by the ignition kernel  32 . The fuel/oxidizer mixture inside the upstream recirculation zone  74  that is ignited by the ignition kernel  32  operates to ignite the fuel/oxidizer mixture  80 , which in turn ignites the downstream recirculation zone  75  that together ignite the remainder of the fuel/oxidizer mixture  80  that is disposed forwardly in the combustion chamber  60  and sustain a self-propagating flame. Accordingly, those skilled in the art will appreciate that the fuel and oxidizer conduits  62  and  64  are positioned relative to the combustion chamber  60  to create an upstream recirculation zone  74  and a downstream recirculation zone  75  that cooperate to stabilize and pilot combustion within the combustion chamber  60 . In the particular example provided, the streams of fuel and oxidizer  76  and  78  impinge upon one another so as to promote enhanced mixing and atomization of the fuel and oxidizer (when liquid fuel and/or oxidizer is used), which thereby produces a fuel/oxidizer mixture  80  within flammability limits that burns more completely, as well as to more fully control the flow and aerodynamic characteristics of the upstream recirculation zone  74  and downstream recirculation zone  75 .  
         [0029]    The byproducts  98  of the combustion event in the combustion chamber  60  are ejected in a jet output kernel  94  that travels through the neck barrel  84  and tip bore  90  and out the orifice  92  in the tip  88 . The high-temperature byproducts  98  of the output kernel  94  provide a discharge of high mass flux jet with copious ignition source radicals, such as H, OH and O, and as such, the torch igniter  10  is well suited for use in applications, such as combustors, that lack the favorable aerodynamic conditions that would be necessary to advance the ignition front if a conventional igniter were employed.  
         [0030]    While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.