Fuel injectors and methods of making fuel injectors

Abstract

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 is axially offset from the retention tab and fixes the inner body within the outer body.

Claims

1. A method of making a fuel injector, comprising: positioning an inner body within an outer body; engaging a retention tab of the inner body within a retention groove defined within an inner surface of the outer body; retaining the inner body relative to the outer body; heating the inner body and the outer body to define a joint axially offset from the retention tab along the inner body, wherein the joint is located radially between the inner body and the outer body; and redundantly retaining the inner body within the outer body with the joint, wherein the retention groove is a recess configured to receive the retention tab therein to prevent axial movement of the inner body in both an upstream and a downstream direction.

2. The method as recited in claim 1, further comprising seating a braze ring on the inner body at a location axially offset from the retention tab along the inner body.

3. The method as recited in claim 1, wherein heating the inner body and the outer body includes interfusing material from the outer body with the inner body in a welding operation.

4. A method of making a fuel injector, comprising: positioning an inner body within an outer body; engaging a retention tab of the inner body within a retention groove defined within an inner surface of the outer body; retaining the inner body relative to the outer body; heating the inner body and the outer body to define a joint axially offset from the retention tab along the inner body; redundantly retaining the inner body within the outer body with the joint; positioning one or more intermediate body within the outer body; and pressing the intermediate body within the outer body such that a retention tab of the intermediate body seats within a second retention groove defined within the fuel injector, wherein the heating includes heating the inner body, the intermediate body, and the 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.

5. A method of making a fuel injector, comprising: positioning an inner body within an outer body; engaging a retention tab of the inner body within a retention groove defined within an inner surface of the outer body; retaining the inner body relative to the outer body; seating a braze ring on the inner body at a location axially offset from the retention tab along the inner body; heating the inner body and the outer body to define a joint axially offset from the retention tab along the inner body, wherein the joint includes a braze structure disposed between an outer surface of the inner body and an inner surface of the outer body; and redundantly retaining the inner body within the outer body with the joint, wherein the retention groove is a recess configured to seat the retention tab therein to prevent axial movement of the inner body in both an upstream and a downstream direction, wherein the retention groove is a recess configured to receive the retention tab therein to prevent axial movement of the inner body in both an upstream and a downstream direction.

6. A method of making a fuel injector, comprising: positioning an inner body within an outer body; engaging a retention tab of the inner body within a retention groove defined within an inner surface of the outer body; retaining the inner body relative to the outer body; heating the inner body and the outer body to define a joint axially offset from the retention tab along the inner body; and redundantly retaining the inner body within the outer body with the joint, wherein heating the inner body and the outer body includes interfusing material from the outer body with the inner body in a welding operation, wherein the joint includes a weld structure disposed between the interior surface of the outer body and the outer surface of the inner body wherein the retention groove is a recess configured to receive the retention tab therein to prevent axial movement of the inner body in both an upstream and a downstream direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 is an exploded view of a fuel injector constructed in accordance with the present disclosure, showing an outer body with a retention groove and an inner body with retention tabs arranged on a first end of the inner body;

(3) FIGS. 2-4 are cross-sectional views of the fuel injector of FIG. 1, showing the inner body being positioned within the inner body, pressed therein, and retained therein by engagement of the retention tabs in the retention groove, respectively;

(4) FIG. 5 is a cross-sectional views of the fuel injector of FIG. 1, showing a brazed joint being formed between a second end of the inner body and the outer body while the retention tabs retain the inner body relative to the outer body;

(5) FIG. 6 is a cross-sectional view a fuel injector according to a second embodiment, showing retention tabs retaining an inner body relative to an outer body subsequent to the inner body being positioned and pressed within the outer body;

(6) FIG. 7 is a cross-sectional view of the fuel injector of FIG. 6, showing a welded joint being formed between the second end of the inner body and the outer body while the retention tabs retain the inner body relative to the outer body;

(7) FIG. 8 is an exploded view of a fuel injector according to a third embodiment, showing an inner body with retention tabs arranged on the second end of the inner body;

(8) FIGS. 9 and 10 are cross-sectional views of fuel injector of FIG. 8, showing the inner body being positioned and pressed within the outer body;

(9) FIG. 11 is a cross-sectional views of the fuel injector of FIG. 8, showing a brazed joint being formed between the second end of the inner body and outer body while the retention tabs retain the inner body relative to the outer body;

(10) FIG. 12 is an exploded view of a fuel injector according to a fourth embodiment, showing an inner body with retention tabs arranged on the second end of the inner body and a weld target arranged on the first end of the inner body;

(11) FIG. 13 is a cross-sectional view of fuel injector of FIG. 12, showing the inner body positioned and retained within the outer body by engagement of the retention tabs in the retention groove;

(12) FIG. 14 is a cross-sectional views of the fuel injector of FIG. 12, showing a welded joint being formed between the first end of the inner body and the outer body while the retention tabs retain the inner body relative to the outer body; and

(13) FIG. 15 is cross-sectional side view of a fuel injector, showing inner and intermediate bodies positioned within an outer body and retained therein by inner body and intermediate body retention tabs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(14) 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 FIG. 1 and is designated generally by reference character 100. Other embodiments of fuel injectors and methods of making fuel injectors in accordance with the present disclosure, or aspects thereof, are provided in FIGS. 2-15 as will be described. The systems and methods described herein can be used fuel injectors for gas turbine engines, where the tolerances and concentricity required by injectors can pose significant challenges to the manufacture of injectors for aircraft main engines and auxiliary power units, however the present disclosure is not limited to fuel injector aircraft gas turbine engines.

(15) Referring to FIG. 1, fuel injector 100 is shown. Fuel injector 100 includes an inner body 102 and an outer body 104. As shown in the illustrated exemplary embodiment, outer body 104 is a fuel injector housing and inner body 102 is a fuel injector heat shield. This is for illustration purposes only and is non-limiting. As will also be appreciated by those of skill in the art in view of the present disclosure, inner body 102 and outer body 104 can be any cylindrical element of fuel injector 100. For example, either (or both) of inner body 102 and outer body 104 can be a prefilmer, swirler, heat shield, or inlet fitting for a fuel injector.

(16) 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.

(17) Inner body 102 is configured to be retained within outer body 104 prior to forming a joint 152 (shown in FIG. 5) fixing inner body 102 within outer body 104. Inner body 102 has a first end 120 and an opposed second end 122 that are coupled to one another by an annular body. Inner body 102 also has a radially outer surface 124 and an opposed radially inner surface 126 separated by a thickness of inner body 102. It is contemplated that the outer body be formed from a metallic material 128, such as a stainless steel alloy, which may or may not be identical to metallic material 118 of outer body 104. One or more retention tab 130 is arranged about inner body 102 and extends therefrom along inlet end 120. Each of the one or more retention tabs 130 are bounded by axial slots 132 that extend partially along an axial length of inner body 102. In the illustrated exemplary embodiment inner body 102 has eight (8) retention tabs 130 separated by eight (8) axial slots 132. This is for illustration purposes only and is non-limiting. Those of skill in the art will appreciate in view of the present disclosure that fuel injector assemblies described herein can have inner bodies with fewer than eight retention tabs or more than eight retention tabs, as suitable for an intended application.

(18) With reference to FIGS. 2-5, positioning, retention, and fixation of inner body 102 within outer body 104 are shown. As shown in FIG. 2, inner body 102 is registered to outer body 104 along assembly axis 106 (shown in FIG. 1) and pressed into outer body 104. Registration can include centering inner body 102 within outer body 104 such inner body 102 is coaxial with outer body 104 along assembly axis 106. Registration can include clocking inner body 102 relative to outlet body 104 about assembly axis 106. Registration can include both centering and clocking inner body 102 relative to outer body 104 along and about assembly axis 106.

(19) 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 FIG. 1), and towards outlet end 110 of outer body 104. It is contemplated that inner body 102 have a radially outer dimension that exceeds a radial inner dimension of outer body 104. Accordingly, the pressing force can be applied such that an interference fit exists between inner body 102 and outer body 104. It is contemplated that the pressing force can be applied by a manual press. For example, an arbor press can be used to position inner body 102.

(20) 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 FIG. 2) to a deflected position (shown in FIG. 3). Having resiliency, resilient member 136 is arranged to urge barb 134 into a seated position (shown in FIG. 4) corresponding to axial of inner body 102 within outer body 104, wherein barb 134 seats in groove 116 (shown in FIG. 1).

(21) Referring to FIG. 3, as inner body 102 is pressed into outer body 104 barb 134 comes into sliding contact with inner surface 112 of outer body 104. Sliding contact of barb 134 with inner surface 112 of outer body 104 deflects resilient member 136, moving 134 radially inward relative to outer body 104 to the deflected position. Barb 134 retain the deflected position until inner body 102 is positioned within outer body 104 such that retention groove 116 radially overlaps 134 (shown in FIG. 4), at which point resilient member drives barb 134 into retention groove 116, retention tab 130 thereby engaging retention groove 116. Engagement of retention tab 130 with retention groove 116 forms an engagement joint 150 (shown in FIG. 4) between inner body 102 and outer body 104, engagement joint 150 retaining position of inner body 102 within outer body 104. In certain embodiments engagement of retention tab 130 is accompanied by an audible click, which signals to an assembler operating the press that inner body 102 is correctly positioned within outer body 104 and error-proofing position of inner body 102 within outer body 104.

(22) 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 FIG. 2) and the deflected position (shown in FIG. 3). It is contemplated that, once positioned, that inner body 102 be axially between ramp 174 and second end 110 of outer body 104, as shown in FIG. 4.

(23) With reference to FIG. 4, structures associated with formation of a brazed joint 152 (shown in FIG. 5) are shown. Outer surface 124 of inner body 102 has an optional braze stop 154, a braze target 156, and a groove 158. Braze stop 154 is arranged axially between retention tab 130 and braze target 156. Braze target 156 is arranged axially between braze stop 154 and groove 158. A braze ring 160 is seated within groove 158, extends circumferentially about inner body 102 within groove 158, and is in intimate mechanical contact with outer body inner surface 112. Braze ring 160 includes a metallic material 162, such as a gold-nickel alloy, suitable for forming brazed joint 152.

(24) With reference to FIG. 5, application of heat to braze ring 160 (shown in FIG. 4) causes metallic material 162 to melt. As metallic material 162 melts, molten metallic material 162 flows axially along braze target 156 (shown in FIG. 4) from groove 158 via capillary action. The flow of molten metallic material 162 ceases at about the location of braze stop 154. Once cooled metallic material 162 forms a braze structure 172. Braze structure 172 at least partially overlaps braze target 156 and groove 158, and is disposed between outer surface 124 of inner body 102 and inner surface 112 of outer body 104.

(25) In the illustrated exemplary embodiment flow of metallic material 162 is confined by braze stop 154. As shown in FIG. 2, braze stop 154 is bounded axially by a first shoulder 164 with a first radial height 166 and a second shoulder 168 with a second radial height 170. The first height can be substantially the same as the second owing to the axial separation of first shoulder and second shoulder, the radial depth of braze stop 154 being sufficient to prevent capillary action from conveying metallic material 162 across braze stop 154. Formation of brazed joint 152 can be, for example, as described in U.S. patent application Ser. No. 11/998,584, filed Nov. 30, 2007, the contents of which are incorporated herein by reference in their entirety.

(26) 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.

(27) Referring to FIGS. 6 and 7, a fuel injector 200 according to a second embodiment is shown. Fuel injector 200 is similar to fuel injector 100 (shown in FIG. 1), and additionally includes a welded joint 252 (shown in FIG. 7) with a weld structure 264 (shown in FIG. 7).

(28) As shown in FIG. 6, an inner body 202 includes a weld target 266. Weld target 266 is disposed on outer surface 224 of inner body 202 and may include a prepared surface portion, such as by etching or polishing. Weld target 266 projects radially from outer surface 224 to preferentially receive weld energy for forming weld structure 264.

(29) As shown in FIG. 7, upon application of heat from a weld source, weld structure 264 is formed between inner body 202 and outer body 204. Weld structure 264, which may comprise native material from either or both of inner body 202 and outer body 204, fuses inner body 202 within outer body 204 with a welded joint 252. Welded joint 252 thereafter cooperates with first joint 250 to retain inner body 202 within outer body 204.

(30) With reference to FIGS. 8-11, a fuel injector 300 according to a third embodiment is shown. Fuel injector 300 is similar to fuel injector 100 (shown in FIG. 1) and additionally includes an inner body 302. Inner body 302 has a retention tab 330 arranged on a second end 322 of inner body 302. Inner body 302 also has a groove 358 bounded by a first should 364 with a radial first height 366 and a second shoulder 370 with a radial second height 368. First height 366 is greater than second height 368. Because first height 366 is greater than second height 368, braze from a braze ring 360 (shown in FIG. 11) preferentially flows towards a braze target 356, which is arranged axially along outer surface 324 inner body 302, and which is arranged axially on a side of groove 358 opposite a braze stop 354. This causes brazed joint 352, and more particularly braze structure 372 (shown in FIG. 11), to be arranged on first end 320 of inner body 302.

(31) It is to be understood and appreciated that, in the illustrated exemplary embodiment, braze ring 360 (shown in FIG. 9) is itself optional. In this respect, once inner body 302 is retained within outer body 304 by the retention tab 330 being received within retention groove 316 (shown in FIG. 8), a semi-liquid braze 301 can be introduced into fuel injector 300 circumferentially about an interface of inner body 302 and outer body 304, e.g., at a location axially offset from engagement joint 330. It is contemplated that semi-liquid braze 301 can be introduced with the aid of conduit, like a hypodermic needle (or hypodermic needle segment) 303, retention of inner body 302 within outer body 304 by seating of the retention tabs within the retention grooves as described above maintaining the spatial relationship of each to the other for formation of a second joint with a braze structure from semi-liquid braze 301. With application of a suitable amount of heat, semi-liquid braze 301 would flow to the right (relative to FIG. 11) toward groove 358, groove 358 serving as an optional braze stop.

(32) Referring now to FIGS. 12-14, a fuel injector 400 according to a fourth embodiment is shown. Fuel injector 400 is similar to fuel injector 300 and additionally includes a welded joint 452. Welded joint 452 is on first end 420 of inner body 402 and is formed by application of weld energy to a weld target 466. Welded joint 452 can be formed subsequent to positioning inner body 402 relative outer body 404 and establishment of engagement joint 450 between second end 422 of inner body 402 and outer body 404. Welded joint 452 can include a weld structure 472, and can be a butt weld extending circumferentially about inner body 402 and outer body 404 by way of example.

(33) With reference to FIG. 15, a fuel injector 500 is shown. Fuel injector 500 is similar to fuel injector 100 (shown in FIG. 1) and additionally includes an intermediate body 502 arranged radially between an inner body 504 and an outer body 506. In the illustrated exemplary embodiment inner body 504 is a heat shield, intermediate body 502 is a prefilmer, and outer body 506 is an injector body. An air swirler 528 is arranged radially inward of intermediate body 502, intermediate body 502 (e.g., a heat shield) being arranged between outer body 506 and air swirler 528 for thermally insulating air swirler 528 from outer body 506. As will be appreciated by those of skill in the art, other arrangements of cylindrical fuel injector elements are possible, as suitable for an intended application.

(34) 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.

(35) 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.

(36) 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.

(37) 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.

(38) 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.

(39) 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.

(40) 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.

(41) 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.

(42) 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.