Patent Application
20190024900
The present disclosure relates to gas turbine engines, and more particularly to fuel injectors and methods of making fuel injectors for gas turbine engines.
Gas turbine engines, such as in aircraft, commonly include fuel injectors with passages for directing fuel into combustors under high temperature conditions. Because of the high temperature conditions, fuel injectors typically include heat shielding to prevent the fuel from coking within the passages, which can occur when the wetted wall temperatures of the passage walls exceed a particular temperature. Coke in fuel injector fuel passages can accumulate, potentially restricting fuel flow to the nozzle and reduce the service life of the fuel injector.
One approach to insulating fuel injectors from heat is the use of stagnant air gaps between external walls, which are exposed to high temperature, and internal walls, which are in thermal contact with the relatively cool fuel. Establishing such gaps requires fastening the walls together such that the assembly can accommodate differing thermal expansion between the walls while holding the nozzle components together. Fastening is commonly accomplished by temporarily fastening the walls together with a fixture in a first operation, permanently fastening the walls together in a second operation, and thereafter removing the fixture in a third operation. The fixture, which can be a ball tack or wire tie down holds the walls in place while being permanently fastened to one another.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved fuel injector and methods of making fuel injectors. The present disclosure provides a solution for this need.
A fuel injector includes an outer body and an inner body. The outer body extends about an axis and has a radially inner surface and a retention groove defined in the inner surface of the outer body. The inner body is positioned within the outer body has an outer surface and a retention tab. The retention tab retains the inner body relative to the outer body by engagement of the retention tab within the retention groove. A joint is axially offset from the retention tab and fixes the inner body within the outer body.
In certain embodiments, inner body can define an axial slot. The axial slot can bound the retention tab. The retention tab can have a resilient member. The retention tab can have a barb. The barb can extend radially from the resilient member. The resilient member can extend axially between the barb and a first end of the inner body. The resilient member can extend axially between the barb and a second end of the inner body. The outer body can have a first end, an opposite second end, and a ramp. The ramp can be arranged on the first end of the outer body. The inner body can be retained relative to the outer body between the ramp and the second end of the outer body.
In accordance with certain embodiment, the joint can be a brazed joint. The joint can include a braze structure. The braze structure can be disposed between the outer surface of the inner body and the inner surface of the outer body. The inner body can have a groove in the outer surface of the inner body. The groove can be bounded by a first shoulder and a second shoulder. The first shoulder can be on a side of the groove opposite the retention tab. The first shoulder can have a radial height greater than a radial height of the second shoulder. The braze structure can overlay, at least in part, the groove. Prior to forming the joint, a braze ring can be seated in the groove.
It is contemplated that the inner body can have a braze target. The braze target can be on the outer surface of the inner body. The braze target can be axially offset from the retention tab. The braze structure can at least partially overlap the braze target. The inner body can have a braze stop. The braze stop can be arranged in the outer surface of the inner body. The braze stop can be arranged axially between the retention tab and the braze target. It is also contemplated the joint can be a welded joint. The joint can include a weld structure. The weld structure can be disposed between the interior surface of the outer body and exterior surface of the inner body.
It is further contemplated that, in accordance with certain embodiments, the inner body can include a heat shield. The outer body can include a prefilmer. One or more intermediate bodies can be arranged radially between the inner body and the outer body. The outer body, intermediate body, inner body can include a heat shield, a swirler, and a prefilmer. Each of the inner body, intermediate body, and outer body can be retained within the fuel injector by respective engagement joints and welded or brazed joints. The engagement joints can include the retention tab. The brazed or welded joints can include a braze structure or a weld structure.
A fuel injector includes an outer body as described above. The inner body includes a heat shield with an outer surface and a retention tab is positioned within the outer body. The retention tab of the heat shield retains the heat shield within the outer body. A joint is axially offset from the retention and retains the inner body to the outer body. The joint includes a braze structure that is disposed between the outer surface of the heat shield and the inner surface of the outer body.
A method of making a fuel injector includes inserting an inner body within an outer body. The inner body is pressed against the outer body such that an inner body retention tab seats within a retention groove defined within the inner surface of the outer body. A joint axially offset from the retention tab along the inner body is formed by heating the bodies, redundantly retaining the inner body within the outer body. In certain embodiments, the method can include seating a braze ring on the inner body at a location axially offset from the retention tab along the inner body prior to positioning the inner body within the outer body. In accordance with certain embodiments heating the inner body and the outer body includes interfusing material from the outer body with the inner body in a welding operation.
It is also contemplated that, in accordance with certain embodiments, the method can include inserting one or more intermediate bodies within an outer body. The intermediate body can be pressed within the outer body such that a retention tab of the intermediate body seats within a second retention groove defined within the fuel injector. Heating can include heating the inner body, intermediate body, and outer body to coincidently form a joint axially offset from the intermediate body retention tab along the intermediate body while the joint between the inner body and outer body is formed.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a fuel injector in accordance with the disclosure is shown in
Referring to
Outer body 104 defines an assembly axis 106, extends about assembly axis 106, and has an inlet end 108 and an outlet end 110 arranged on opposite ends of an annular body coupling inlet end 108 with outlet end 110. Outer body 104 also has a radially outer surface 114 and an opposed radially inner surface 112 separated by a thickness of outer body 104. A retention grove 116 is defined in inner surface 112. It is contemplated that outer body 104 be formed from a metallic material 118, such as a stainless steel alloy. In the illustrated exemplary embodiment retention groove 116 extends continuously about assembly axis 106.
Inner body 102 is configured to be retained within outer body 104 prior to forming a joint 152 (shown in
With reference to
Pressing inner body 102 within outer body 104 includes applying a pressing force against inner body 102. The pressing force is directed against inner body 102, along assembly axis 106 (shown in
First end 120 of inner body 102 includes retention tab 130. Retention tab 130 includes a resilient member 136 and a barb 134. In the illustrated embodiment resilient member 136 extends from first end 120 of inner body 102 and towards second end 122 of inner body 102. Barb 134 extends radially outward from resilient member 136. Resilient member 136 is cantilevered and flexible. Being flexible, resilient member deflects as inner body 102 is positioned within outer body 104, barb 134 moving radially inward from a nominal position (shown in
Referring to
Deflection can be assisted by a ramp 174. Ramp 174 is arranged axially between first end 108 and second end 110 of outer body 104. As inner body 102 is positioned within outer body 104 ramp 174 progressively deflects retention tab 130 according to the axial position of inner body 102 relative to outer body 104, limiting the pressing force necessary to move barb 134 from the nominal position (shown in
With reference to
With reference to
In the illustrated exemplary embodiment flow of metallic material 162 is confined by braze stop 154. As shown in
In certain embodiments, engagement joint 150 can be removed subsequent to the formation of brazed joint 152. For example, a material removal operation (shown with a dashed line) can be used to remove engagement joint 150. The material removal can be done without disturbing the position of inner body 102 within outer body 104 due to brazed joint 152, which is axially spaced apart from engagement joint 150. Material removal can reduce the weight of fuel injector 100.
Referring to
As shown in
As shown in
With reference to
It is to be understood and appreciated that, in the illustrated exemplary embodiment, braze ring 360 (shown in
Referring now to
With reference to
Inner body 504 is positioned within outer body 506. In particular, inner body 504 is retained within outer body 506 by an inner body retention joint 508 and an inner body brazed joint 510. Inner body retention joint 508 includes a retention tab 512 received within a retention groove 514. Inner body brazed joint 510 includes a braze structure 516 that is axially offset from inner body first joint 508 and disposed radially between and inner body 504 and outer body 506.
Intermediate body 502 is positioned within outer body 506 and retained therein by an intermediate body retention joint 518 and an intermediate body brazed joint 520. Intermediate body retention joint 518 includes an intermediate body retention tab 522 received within a second outer boy retention groove 524. Intermediate body brazed joint 520 includes a braze structure 526 axially offset from intermediate body retention joint 518 and disposed radially between and intermediate body 502 and outer body 506.
Advantageously, in certain embodiments, inner body 504 and intermediate body 502 can both be spatially located within outer body 506 prior to brazing. This enables both inner body brazed joint 510 and intermediate body brazed joint 520 to be formed coincidently, e.g., in the same heating operation, simplifying manufacture of fuel injector 500. Further, more than one intermediate body 502 can be positioned within fuel injector 500 prior to intermediate body braze joint 520 being formed. As will be appreciated by those of skill in the art in view of the present disclosure, this prevents reheating a pre-existing braze structure, avoiding application thermal stress or softening the braze material, which could otherwise potentially disrupt the braze joint. As will also be appreciated by those of skill in the art in view of the present disclosure, welded joints can also be employed in lieu of brazed joints.
When joining parts using brazing or welding techniques, such as heat shields and prefilmers for gas turbine engine fuel injector assemblies, it can be necessary retain the positional arrangement of the parts until the joining process is complete. Retention is typically accomplished by a temporary retaining arrangement such as a tack weld, a ball-tack, weights, wire tie downs, and/or fixtures. Once the parts are joined the temporary retaining arrangement must be removed. In the case where a temporary tack weld or ball-tack is employed it can be necessary to rework the surfaces where welding was formed in order to restore finish and function in a further operation.
In embodiments described herein integral retention features are provided on the parts to be joined, e.g., an inner body and an outer body. The retention feature retains the parts in a selected spatial registration by forming a retention joint during the assembly of the parts. For example, the inner body can be registered relative to the outer body, inserted into an outer body, and positioned by pressing the inner body into the outer body such that a retention tab arranged on the inner body engages a retention groove within the outer body.
The seating of the retention tab within the retention groove establishes a retention joint between the inner body and the outer body, which retains the positional relationship between the inner body and outer body while a redundant brazed or welded joint is formed between the inner body and the outer body. Although described in the exemplary embodiments herein as being arranged on the inner body, those of skill in the art will appreciate in view of the present disclosure that the retention tab can be arranged on the outer body and a cooperative retention groove defined within the inner body.
In certain embodiments the integral retention feature, such as a tab, is arranged to snap into the groove when the inner body is pressed into to the outer body when the inner body reaches a desired position and orientation relative to the outer body. It is contemplated that the tab can be a locking tab located on a flexible portion of the part or component, e.g., on a resilient member, such that a slight deformation during assembly does not damage or limit the capability of the part or component once assembled. In accordance with certain embodiments, a braze ring or braze band can be seated on the inner body and captured within a braze ring groove defined within the outer surface of the inner body prior to assembly such that braze alloy forming the braze ring or braze band will be in the correct location to flow and create a brazed joint fixing the inner body within the outer body.
It is contemplated that the retention feature allow for quick and repeatable assembly of the inner and outer bodies prior to fixing the inner body within the outer body with a brazed or welded joint. Assembly can be accomplished by pressing the inner body into the outer body in a single operation prior to brazing or welding, such as with an arbor press, to establish a retention joint between the inner and outer bodies. As will be appreciated by those of skill in the art in view of the present disclosure, two or more inner bodies can be positioned within an outer body prior to the brazing or welding process. In accordance with certain embodiments, no additional operations are necessary to retain the parts or components in spatial registration to one another, eliminating the need for to retain the parts or components with a temporary weld, a temporary ball tack, a temporary tie, or use of a fixture prior to brazing or welding the inner body to the outer body to redundantly fix the inner body within the outer body with a brazed or welded joint. It is also contemplated that the need for gauging or measuring the positional relationship of the inner and outer bodies can be eliminated as the inner and outer bodies can themselves report correct spatial registration by issuing an audible signal, e.g., a ‘click’, once the inner body reaches a selected position within the outer body.
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for fuel injector assemblies and methods of making fuel injector assemblies with superior properties including redundant joints and simplified assembly. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that change and/or modifications may be made thereto without departing from the scope of the subject disclosure.
