Fuel injector

A fuel injector (1) having a chamber (7) with a fuel inlet (8) and a plurality of fuel outlets (10), and including a fuel distributor (18) that is arranged in the chamber (7) for the purpose of distributing fuel introduced into the chamber (7) via the fuel inlet (8) to the outlets (10). The fuel distributor (18) includes a generally rotary symmetric distributor body (19).

BACKGROUND OF INVENTION

Technical Field

The present invention relates to a fuel injector, comprising a chamber with a fuel inlet and a plurality of fuel outlets, and comprising a fuel distributor that is arranged in the chamber for the purpose of distributing fuel introduced into the chamber via the fuel inlet to the outlets.

The invention also relates to a method of manufacturing such a fuel injector and an engine that comprises a combustion chamber and such a fuel injector for injecting fuel into the combustion chamber via the outlets of the chamber of the fuel injector. It should be understood that, according to the invention, the fuel could be injected either directly or indirectly via the fuel outlets of the fuel injector into the combustion chamber (or chambers).

“Fuel injector” should be understood in a broad sense and includes what is normally referred to as a spray bar in jet engine technology. Such spray bars are then provided for the purpose of injecting fuel into the afterburner of the engine in question.

“Engine” may include any engine which for its operation uses a fuel that is injected either in liquid or gaseous state into one or more combustion chambers and where there is a need of distributing the fuel in precise pre-determined amounts to the combustion chamber or chambers via the outlets of the fuel injector.

However, a particularly relevant application according the invention, includes jet engines equipped with an afterburner into which fuel needs to be injected with high precision during operation. Therefore, the invention will be described by way of example with reference to such a preferred application.

BACKGROUND

In the spray bar head of a jet engine equipped with an afterburner there is provided a chamber or a collector volume into which fuel, in liquid and/or gaseous state, is introduced via a fuel inlet provided in a wall portion of the spray bar head. The spray bar head also comprises a plurality of fuel outlets from the collector volume, said outlets being provided in another wall portion of the spray bar head than the fuel inlet. In the collector volume the fuel introduced via the inlet is primarily distributed to the outlets in pre-determined amounts. Specific restriction elements may be provided at one or more outlets for the purpose of affecting the fuel flow rate individually for one or more outlets.

According to prior art, the collector volume is delimited by a cylinder and opposite end walls that are provided at opposite ends of the cylinder. The cylinder may comprise one or more portions with restricted width as well as one or more truncated portions. Typically the inlet is arranged in the cylinder wall and the outlets are provided in one of the end walls. For such a spray bar head geometry it has been found that, without any kind of fuel distributor provided inside the collector volume, there will be static pressure oscillations inside the collector volume, resulting in corresponding velocity fluctuations in of the fuel exiting via the fuel outlets, which in itself is a drawback with respect to the need of precise control of the fuel flow via the outlets.

Therefore, prior art suggests the use of a fuel distributor or a fuel distributing body arranged inside the collector volume. According to prior art, fuel distributors comprise one or more distributor bodies that are produced by way of casting, preferably in one piece with any one of the walls of the spray bar head, that wall then being attached to the adjacent wall or walls by means of welding or brazing.

SUMMARY OF INVENTION

The object of the invention is achieved by means of the initially defined fuel injector, characterized in that fuel distributor comprises a generally rotary symmetric distributor body. Rotary symmetric is referred to as presenting a generally circular outer periphery.

According to a preferred embodiment of the invention, the fuel injector chamber is delimited by at least one side wall, and said fuel distributor defines a lid or plug that forms an end wall in relation thereto. These features further enhances the production-related advantage of the design according to the invention.

Preferably, the fuel inlet is provided in the side wall and that the outlets are provided in an end wall.

According to the invention, the fuel outlets should be provided in an end wall opposite to an end wall that is formed by the fuel distributor or to which the distributor body is attached.

In further accordance with the invention, the fuel injector comprises a cylinder that defines the side wall, and the cylinder has a generally circular inner periphery.

Moreover, it is preferred, both from a production and a fuel flow point of view, that the distributor body is concentric with the cylinder.

The distributor body should be located in front of the fuel and cover the fuel inlet, in order to sufficiently affect the incoming flow of fuel in order to avoid any irregularities in the flow pattern that might induce flow wave oscillations in the collector chamber. In accordance with this feature the distributor body is both longer in length direction and wider in its width direction than the corresponding length and width of the fuel inlet or each individual fuel inlet to the collector chamber.

The object of the invention is also to present a method of manufacturing a fuel injector according to the invention that is advantageous from a production cost-saving point of view with regard to methods of producing corresponding fuel injectors according to prior art. This object is achieved by means of a method of manufacturing a fuel injector according to the invention, characterized in that the distributor body is produced by subjecting a work piece to a turning operation. Here, machining by way of a turning operation is regarded as favorable from production technical reasons when compared to casting. The rotary symmetric design of the distributor body promotes turning operation as the preferred production technique.

Preferably, the distributor body is formed to its final shape by the turning operation, meaning that virtually no further shaping of the one and only distributor body is needed before positioning it in its operational position.

According to a preferred embodiment of the inventive method, the distributor body is attached to an adjacent side wall of the fuel injector by means of welding or brazing. Preferably, the side wall is formed by a cylinder with a circular inner periphery, as described above for the preferred embodiment of the fuel injector. Then, the circular outer periphery of the part of the distributor that defines an end wall can easily be fitted into or on the end of the cylinder and be attached thereto.

The object of the invention is also achieved by means of an engine comprising a combustion chamber, characterized in that it comprises a fuel injector according to the invention for the injection of fuel into the combustion chamber via the fuel outlets of the fuel injector. It should be understood that any motor or engine with a combustion chamber is included in the scope of protection thereby claimed. The motor/engine may comprise one or more combustion chambers, and the outlets from the collector chamber of the fuel injector may lead to a single combustion chamber for injection of fuel into the latter via a plurality of injection locations, for example for even distribution of fuel as in the case of a spray bar in a jet engine afterburner. The fuel may also be distributed to a plurality of combustion chambers, one or more outlets thereby communicating with or leading to each combustion chamber, and different outlets leading to different combustion chambers.

According to a preferred embodiment, the engine it is a jet engine and the combustion chamber is an afterburner chamber. Preferably, the jet engine is positioned in an airplane.

Such a jet engine then comprises a plurality of fuel injection tubes connected to said plurality of outlets of the fuel injector and extending into the afterburner chamber. The afterburner chamber defines a channel with a radial direction and a longitudinal direction. The fuel injection tubes are directed from an outer radial position inwards towards the longitudinal axis of the afterburner, and they should be angularly evenly distributed around said axis or around the periphery of the afterburner wall.

In the preferred embodiment described above, the engine further comprises a radial flame holder and the fuel injector tubes extend into the afterburner chamber upstream the radial flame holder as seen in the gas flow direction in the afterburner.

Further features and advantages of the present invention will be presented in the following detailed description of a preferred embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1shows a jet engine1equipped with a plurality of fuel injectors2one of which is shown in the figure. The engine comprises a gas turbine section3and an afterburner section4, the gas turbine section3being arranged upstream the afterburner section4as seen in a gas flow direction through the engine1. The fuel injectors are arranged in a circular arrangement around the inner periphery of the afterburner4for the purpose of injecting fuel into the interior of the afterburner4, that is the afterburner chamber5. Here, the engine1comprises twenty four fuel injectors2in said circular arrangement.

The gas turbine section1comprises a plurality of rows of turbine blades6arranged in a way known per se. Hot gases are emitted from the turbine section3into the afterburner section4.

Each fuel injector2comprises a fuel collector chamber7, a fuel inlet8into the collector chamber7, a fuel inlet pipe9, a plurality of fuel outlets10from the collector chamber9and a corresponding plurality of outlet tubes or injector tubes11that lead from said outlets10into the afterburner chamber5. Here, each fuel injector2comprises four outlets and four injector tubes11. However, it is also contemplated to equip each fuel injector2with only two or three injector tubes11, or more than four such tubes.

Adjacent to and downstream the row of fuel injectors2, as seen in the gas flow direction in the engine1, there is provided a radial flame holder12. The flame holder12has the task of regulating the gas flow conditions, in particular to reduce the flow velocity, in the afterburner4in order to permit optimal combustion of the fuel introduced into the latter via the injector tubes11. The flame holder12comprises a row of stays or struts13each of which extends radially from an outer peripheral connection14with the inner periphery of the afterburner wall to an inner ring15. In a preferred embodiment there are two fuel injectors2located in each angle sector between two of the struts or stays13.

With reference toFIG. 3andFIG. 4a more detailed description of the fuel injector2will now be given.

The collector chamber7of the injector2is delimited by a cup-shaped body that has a cylindrical side wall with a circular inner periphery16and a generally flat, circular end wall17. The angle between the side wall16and the plane of the end wall17is 90 degrees. Preferably, the cup-shaped body16,17has been produced by pin milling a work piece. The cup-shaped body16,17has a width of 11.5 cm and a substantially smaller wall thickness, for example in the order of 1–5 mm. It is made of a metal or metal alloy. The fuel inlet8is provided in the side wall16and the fuel outlets11are provided in the end wall17. The center axis of the inlet pipe9is directed towards the center axis of the cup-shaped body16,17, such that the fuel introduced via the inlet8has a flow direction generally towards the center of the collector chamber7.

The fuel injector2further comprises a fuel distributor18that protrudes into the collector chamber7from an opposite end of the chamber7with regard to the first end wall17mentioned above. The fuel distributor comprises a fuel distributor body19that has a diameter that is smaller than the inner diameter of the side wall16, thereby leaving a spacing between side wall16and distributor body19free for flow of the fuel introduced via the inlet8. The spacing is larger than 0.5, preferably approximately 1 mm for the injector in question. The distributor18, or at least the body19, is rotary symmetric in the respect that it has a generally circular outer periphery along its entire length. When mounted, it is coaxial (coinciding rotational and center axis) with the cylinder that defines the side wall16and, thus, positioned in the center of the latter.

The distributor body19ends at a given distance from the first end wall17, thereby leaving a sufficient spacing between the body19and the end wall17to guarantee a sufficient and stable flow of fuel out of the outlets10. Nevertheless, the distributor body19shall extend such a distance towards the first end wall17that it, if projected on the side wall16, shall cover the inlet8in order to suppress fuel jet oscillations in the collector chamber7. The free end of the body19that points at the first end is rounded, chamfered or beveled, such that the free end of the body19defines a truncated cone20, in order to further improve the flow conditions in the collector chamber7.

Opposite to the free end of the distributor body19the fuel distributor18presents a circular flange21that has a diameter that is equal to or larger than the inner diameter of the cylindrical side wall16at its end portion opposite to the end where the first end wall17is located. The flange21defines a second end wall that is located opposite to the first end wall17. The flange21and the distributor body19defines a solitaire formed by turning of one and the same work piece in a lathe. The flange is then attached to the side wall16, preferably by means of welding. Thus the collector chamber7is delimited by the two opposite end walls, defined by the first end wall17and the fuel distributor18, and the cylindrical side wall16.

It should be stated that, according to this preferred embodiment, the distributor body19has generally the same diameter along its whole length, apart from the truncated cone part20and the smooth transition region in which the body19transits to the flange21.

Thanks to the distributor body19, the incoming fuel jet is broken up within a rather short distance from the inlet8, the generation of fuel wave oscillations is suppressed, and the fuel mass flow rate out of the collector chamber8and the injector2becomes stable. A further advantage of the geometrical features of the distributor18is that it becomes unnecessary to adjust the angular position of the distributor body19in relation to the inlet8and the outlets10when the distributor is attached to the adjacent wall16.

It should be realized that the above presentation of the invention has been made by way of example, and that alternative embodiments will be obvious for a man skilled in the art without going beyond the scope of protection as claimed in the annexed patent claims supported by the description and the annexed drawings.

For example, the invention is not restricted to only one inlet8into the collector chamber9, but could consist of more than one such inlet.

It should be understood that, according to the invention, each of a plurality of fuel injectors or spray bars arranged around an after-burner chamber should be provided with the kind of fuel distributor that has been described above.

It should also be realized that, apart from its oscillation-suppressing function, the distributor body19also acts as a mixer in the sense that it improves the mixing of gaseous and liquid fuel that is introduced into the collector chamber7.