Torch igniter

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

FIELD OF THE INVENTION

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

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.

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.

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

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.

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

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:

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;

FIG. 2 is a longitudinal section view of the torch igniter of FIG. 1;

FIG. 3 is a longitudinal section view similar to that of FIG. 2 but illustrating the flow aerodynamics and operation of the torch igniter;

FIG. 4 is a sectional view taken along the line 4—4 of FIG. 2;

FIG. 5 is a sectional view similar to that of FIG. 4 but illustrating a first alternate arrangement of the fuel and oxidizer conduits;

FIG. 6 is a sectional view similar to that of FIG. 4 but illustrating a second alternate arrangement of the fuel and oxidizer conduits;

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

FIG. 8 is a sectional view of an alternately constructed tip for the torch igniter of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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.

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 30a and 30b 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.

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.

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.

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.

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.

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.

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.

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 92a that is aligned concentrically to the tip bore 90 and a second orifice 92b that is aligned generally perpendicular to the first orifice 92a.

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.

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.

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 80a 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 80a 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, to 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.

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.

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.

Claims

1. A method for forming a torch igniter, comprising: providing a torch igniter housing having a combustion chamber therein, the combustion chamber having an upstream area and a downstream area; forming a first independent path in said housing for supplying a fuel radially into said combustion chamber; forming a second independent path in said housing for supplying an oxidizer into said combustion chamber, the combustion chamber being of sufficient volume to permit a degree of mixing of said fuel and oxidizer within said combustion chamber; and further disposing the independent paths relative to the combustion chamber to create first and second recirculation zones within said combustion chamber on opposite longitudinal sides of said first independent path, with at least one of the first and second recirculation zones being in said upstream area, said recirculation zones operating to pilot combustion of said fuel and oxidizer within said combustion chamber, when said mixture is ignited, such that a mixture of said fuel and oxidizer flows through said combustion chamber.

2. The method of claim 1, further comprising forming said first recirculation zone at an area upstream of said fuel and oxidizer paths, relative to a direction of flow of said fuel and oxidizer mixture in said combustion chamber.

3. The method of claim 1, further comprising forming said second recirculation zone at an area downstream of said fuel and oxidizer paths, relative to a direction of flow of said fuel and oxidizer mixture in said combustion chamber.

4. The method of claim 1, further comprising forming the fuel and oxidizer paths at a right angle relative to one another.

5. The method of claim 1, further comprising forming a pair of fuel flow paths in said housing non-parallel to one another.

6. The method of claim 1, further forming a pair of oxidizer paths in said housing non-parallel to one another.

7. The method of claim 1, further forming a plurality of fuel paths and a plurality of oxidizer paths in said housing, and further arranging said paths such that each said fuel path is bordered on opposite sides thereof by a pair of oxidizer paths.

8. The method of claim 1, further comprising forming said housing as a circumferential housing, and forming a plurality of fuel paths and a plurality of oxidizer paths radially around said housing, said fuel and oxidizer paths further being arranged such that a plurality of pairs of paths each including one fuel path and one oxidizer path are arranged radially around said housing.

9. A method for forming a torch igniter, comprising: providing a torch igniter housing having a generally circumferential combustion chamber therein, the combustion chamber having an upstream area and a downstream area; forming a plurality of first independent paths in said housing spaced radially around said housing and communicating with said combustion chamber, for supplying a fuel radially into said combustion chamber; forming a plurality of second independent paths in said housing spaced radially around said housing and communicating with said combustion chamber, for supplying an oxidizer into said combustion chamber, further disposing the independent fuel and oxidizer paths to each open into the combustion chamber at an intermediate point along a length of the combustion chamber to create a first recirculation zone upstream of said paths, relative to a direction of flow within said combustion chamber, and a second recirculation zone downstream of said paths, the recirculation zones operating to pilot combustion of said fuel and oxidizer within said combustion chamber, when said mixture is ignited, such that a mixture of said fuel and oxidizer flows through said combustion chamber to an output end thereof.

10. The method of claim 9, further comprising forming the fuel and oxidizer paths at a right angle relative to one another.

11. The method of claim 9, further comprising forming said fuel flow paths in said housing such that no two ones of said fuel flow paths extend parallel to one another.

12. The method of claim 9, further comprising forming said oxidizer flow paths in said housing such that no two ones of said oxidizer paths in said housing extend parallel to one another.

13. The method of claim 9, further forming said fuel paths and said oxidizer paths in said housing, and further arranging said paths such that each said fuel path is bordered on opposite sides thereof by a pair of said oxidizer paths.

14. The method of claim 9, further comprising forming said housing to include an igniter disposed at least partially in said housing upstream of said first recirculation zone.

15. A method of igniting a fuel/oxidizer mixture comprising: injecting a fuel radially into a combustion chamber within a torch igniter housing at a point intermediate first and second ends of said combustion chamber; injecting an oxidizer into said combustion chamber within a housing at point intermediate said first and second ends; forming an upstream recirculation zone in said combustion chamber for a portion of fuel and a portion of oxidizer injected into said combustion chamber at an area upstream of said point at which said fuel is injected, relative to a direction of flow through said combustion chamber; and forming a downstream recirculation zone in said combustion chamber downstream of said upstream recirculation zone, and downstream of said point at which said fuel is injected; and using said upstream and downstream recirculation zones to cooperatively pilot and stabilize combustion of intermixed fuel and oxidizer within said combustion chamber when said intermixed fuel and oxidizer is ignited by an igniter.

16. The method of claim 15, further comprising injecting said fuel into said combustion chamber at a plurality of points spaced radially apart from one another.

17. The method of claim 15, further comprising injecting said oxidizer into said combustion chamber at a plurality of points spaced radially apart from one another.

18. The method of claim 15, further comprising injecting each of said fuel and oxidizer at a plurality of points spaced radially about said combustion chamber such that each fuel and oxidizer streams are injected into said combustion chamber at alternating points arranged radially about said combustion chamber.

19. The method of claim 15, further comprising demarcating said upstream and downstream recirculation zones at said points where said fuel and said oxidizer are injected into said combustion chamber.

20. The method of claim 15, further comprising arranging injecting said fuel and said oxidizer into said combustion chamber within a common plane extending orthogonally to a direction of flow through said combustion chamber.