METHOD OF ELECTROPOLISHING

Abstract

A method of electropolishing an internal passageway of a component, wherein the passageway has an inlet and an outlet; including: providing an electrode assembly including a flexible electrode, a shuttle and a guide cable extending between the flexible electrode and the shuttle; inserting the shuttle into the inlet; causing fluid to flow through the passageway to transport the shuttle through the passageway from the inlet towards the outlet; pulling the guide cable through the passageway to position the electrode in the passageway adjacent to a region of the passageway to be polished; and electropolishing the passageway using the electrode while moving the electrode within the passageway. Also, an electrode assembly for electropolishing an internal passageway of a component, including: a flexible electrode, a shuttle, and a guide cable extending between the flexible electrode and the shuttle.

Claims

1. A method of electropolishing an internal passageway passageway of a component, wherein the passageway has an internal inlet and an outlet; comprising: providing an electrode assembly comprising a flexible electrode; a shuttle and a guide cable extending between the flexible electrode and the shuttle; inserting the shuttle into the inlet; causing fluid to flow through the passageway to transport the shuttle through the passageway from the inlet towards the outlet; pulling the guide cable through the passageway to position the electrode in the passageway adjacent to a region of the passageway to be polished; and electropolishing the passageway using the electrode while moving the electrode within the passageway.

2. A method according to claim 1, wherein transporting the shuttle through the passageway by the fluid flow causes the guide cable to be pulled through the passageway to position the electrode adjacent to the region of the passageway to be polished.

3. A method according to claim 1, further comprising inserting a retainer through the outlet, and catching the shuttle with the retainer.

4. A method according to claim 3, wherein the retainer is controllable to close around the shuttle.

5. A method according to claim 3, wherein the guide cable is pulled through the passageway to position the electrode by using the retainer to pull the shuttle and thereby the guide cable.

6. A method according to claim 1, wherein the method further comprises guiding the transport of the shuttle within the passageway towards the outlet with a temporary guide located within the passageway.

7. A method according to claim 6, further comprising removing the temporary guide.

8. A method according to claim 7, wherein the temporary guide is removed by leaching or etching.

9. A method according to claim 6, wherein the guide is formed in the passageway by additive manufacturing.

10. A method according to claim 1, wherein the flexible electrode comprises a plurality of electrode segments which are independently selectable for electro-polishing by a controller, the method further comprising the controller selecting a proper subset of the electrode segments and electropolishing portions of the passageway local to the or each respective electrode segment.

11. A method according to claim 1, wherein an electrolyte is received in the passageway for electropolishing, and wherein the electrolyte comprises a deep eutectic solvent.

12. A method according to claim 1, wherein the component is a component of a gas turbine engine; optionally wherein the component is one of: a fuel injector nozzle; a stator vane such as a nozzle guide vane; a rotor blade such as a compressor blade or a turbine blade; a heat exchange element for a heat exchanger.

13. A kit for electropolishing an internal passageway of a component, comprising: a flexible electrode, a shuttle, and a guide cable extending between the flexible electrode and the shuttle.

14. A kit according to claim 13, wherein the electrode comprises a plurality of electrode segments, wherein each of the plurality of segments is configured to be independently selectable for electropolishing.

15. A kit according to claim 14, wherein each segment of the flexible electrode comprises an electrically conductive core covered by an insulating jacket, the jacket having at least one window exposing the core.

16. A method comprising: manufacturing a component by additive manufacture to form: a body defining an inlet, an outlet, and an internal passageway for flow between the inlet and the outlet; a temporary guide disposed within the internal passageway, wherein the temporary guide is configured to guide transport of a shuttle suspended in a fluid flow from the inlet and the outlet so that the shuttle moves towards the outlet; wherein the temporary guide and the body are formed from different materials, such that the temporary guide is removable by leaching or etching while the body remains intact.

17. A method according to claim 16, wherein the temporary guide is configured to at least partially block a portion of the internal passageway so as to direct fluid flow and/or the shuttle towards the outlet.

18. A method according to claim 16, further comprising electropolishing the internal passageway, comprising: providing an electrode assembly comprising a flexible electrode; a shuttle and a guide cable extending between the flexible electrode and the shuttle; inserting the shuttle into the inlet; causing fluid to flow through the passageway to transport the shuttle through the passageway from the inlet towards the outlet; pulling the guide cable through the passageway to position the electrode in the passageway adjacent to a region of the passageway to be polished; and electropolishing the passageway using the electrode while moving the electrode within the passageway.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Embodiments will now be described by way of example only, with reference to the Figures, in which:

[0059] FIG. 1 is a sectional side view of a gas turbine engine;

[0060] FIG. 2 is a close up sectional side view of an upstream portion of a gas turbine engine;

[0061] FIG. 3 is a partially cut-away view of a gearbox for a gas turbine engine;

[0062] FIG. 4 shows an example electrode assembly;

[0063] FIG. 5 is a cross-section of an example passageway of a component;

[0064] FIGS. 6a and 6b are cross-sections of an example passageway of a component showing the transport of a shuttle;

[0065] FIG. 7 is a cross-section of an example passageway of a component showing an example retainer;

[0066] FIG. 8 is a cross section of an example passageway of a component showing guides;

[0067] FIGS. 9a and 9b are cross-sections of an example passageway of a component showing positioning of an electrode within the passageway;

[0068] FIG. 10 is a cross-section of an example passageway of a component showing movement of the electrode within the passageway;

[0069] FIG. 11 is a cross-section of an example fuel injection nozzle having an example passageway;

[0070] FIG. 12 is a flowchart showing the method of electropolishing the component with reference to FIGS. 6a, 6b and 10; and

[0071] FIG. 13 is a flowchart showing the method of electropolishing the component with reference to FIGS. 6a, 6b, 8 and 10.

DETAILED DESCRIPTION

[0072] Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

[0073] FIG. 1 illustrates a gas turbine engine 10 having a principal rotational axis 9. The engine 10 comprises an air intake 12 and a propulsive fan 23 that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine 10 comprises a core 11 that receives the core airflow A. The engine core 11 comprises, in axial flow series, a low pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, a low pressure turbine 19 and a core exhaust nozzle 20. A nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The bypass airflow B flows through the bypass duct 22. The fan 23 is attached to and driven by the low pressure turbine 19 via a shaft 26 and an epicyclic gearbox 30.

[0074] In use, the core airflow A is accelerated and compressed by the low pressure compressor 14 and directed into the high pressure compressor 15 where further compression takes place. The compressed air exhausted from the high pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high pressure and low pressure turbines 17, 19 before being exhausted through the core exhaust nozzle 20 to provide some propulsive thrust. The high pressure turbine 17 drives the high pressure compressor 15 by a suitable interconnecting shaft 27. The fan 23 generally provides the majority of the propulsive thrust. The epicyclic gearbox 30 is a reduction gearbox.

[0075] An exemplary arrangement for a geared fan gas turbine engine 10 is shown in FIG. 2. The low pressure turbine 19 (see FIG. 1) drives the shaft 26, which is coupled to a sun wheel, or sun gear, 28 of the epicyclic gear arrangement 30. Radially outwardly of the sun gear 28 and intermeshing therewith is a plurality of planet gears 32 that are coupled together by a planet carrier 34. The planet carrier 34 constrains the planet gears 32 to precess around the sun gear 28 in synchronicity whilst enabling each planet gear 32 to rotate about its own axis. The planet carrier 34 is coupled via linkages 36 to the fan 23 in order to drive its rotation about the engine axis 9. Radially outwardly of the planet gears 32 and intermeshing therewith is an annulus or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.

[0076] Note that the terms “low pressure turbine” and “low pressure compressor” as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan 23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft 26 with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan 23). In some literature, the “low pressure turbine” and “low pressure compressor” referred to herein may alternatively be known as the “intermediate pressure turbine” and “intermediate pressure compressor”. Where such alternative nomenclature is used, the fan 23 may be referred to as a first, or lowest pressure, compression stage.

[0077] The epicyclic gearbox 30 is shown by way of example in greater detail in FIG. 3. Each of the sun gear 28, planet gears 32 and ring gear 38 comprise teeth about their periphery to intermesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated in FIG. 3. There are four planet gears 32 illustrated, although it will be apparent to the skilled reader that more or fewer planet gears 32 may be provided within the scope of the claimed invention. Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planet gears 32.

[0078] The epicyclic gearbox 30 illustrated by way of example in FIGS. 2 and 3 is of the planetary type, in that the planet carrier 34 is coupled to an output shaft via linkages 36, with the ring gear 38 fixed. However, any other suitable type of epicyclic gearbox 30 may be used. By way of further example, the epicyclic gearbox 30 may be a star arrangement, in which the planet carrier 34 is held fixed, with the ring (or annulus) gear 38 allowed to rotate. In such an arrangement the fan 23 is driven by the ring gear 38. By way of further alternative example, the gearbox 30 may be a differential gearbox in which the ring gear 38 and the planet carrier 34 are both allowed to rotate.

[0079] It will be appreciated that the arrangement shown in FIGS. 2 and 3 is by way of example only, and various alternatives are within the scope of the present disclosure. Purely by way of example, any suitable arrangement may be used for locating the gearbox 30 in the engine 10 and/or for connecting the gearbox 30 to the engine 10. By way of further example, the connections (such as the linkages 36, 40 in the FIG. 2 example) between the gearbox 30 and other parts of the engine 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have any desired degree of stiffness or flexibility. By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts from the gearbox and the fixed structures, such as the gearbox casing) may be used, and the disclosure is not limited to the exemplary arrangement of FIG. 2. For example, where the gearbox 30 has a star arrangement (described above), the skilled person would readily understand that the arrangement of output and support linkages and bearing locations would typically be different to that shown by way of example in FIG. 2.

[0080] Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gearbox styles (for example star or planetary), support structures, input and output shaft arrangement, and bearing locations.

[0081] Optionally, the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

[0082] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown in FIG. 1 has a split flow nozzle 18, 20 meaning that the flow through the bypass duct 22 has its own nozzle 18 that is separate to and radially outside the core exhaust nozzle 20. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct 22 and the flow through the core 11 are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have a fixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example. In some arrangements, the gas turbine engine 10 may not comprise a gearbox 30.

[0083] The geometry of the gas turbine engine 10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in FIG. 1), and a circumferential direction (perpendicular to the page in the FIG. 1 view). The axial, radial and circumferential directions are mutually perpendicular.

[0084] Some components in a gas turbine engine may include complex internal passageways with bends and narrow sections, such as pipes for conveying fuel from one location to another. Such components may be manufactured by a number of manufacturing techniques, and some of those techniques may result in rough surfaces that may be surface finished to improve performance and/or geometric compliance. For example, such components may be manufactured by additive manufacturing methods including additive layer manufacturing (ALM). It may be advantageous to smooth the surface of such internal passageways. For example, in the case of a fuel injector nozzle, the internal surfaces may advantageously be smoothed to ensure that fuel can be efficiently and reliably conveyed to the required location.

[0085] Electropolishing is an electrochemical process which removes material from the surface of a metal object to improve its surface finish. In a typical electropolishing process, the metal object is immersed in a bath of electrolyte and the object is connected to a positive terminal of a DC power supply, making it the anode. An electrode is also immersed in a bath of electrolyte and is connected to the negative terminal of the DC power supply, making it the cathode. An electrical current passes from the anode to the cathode, oxidising and removing material from the surface of the object.

[0086] FIG. 4 shows an example electrode assembly 42 for electropolishing an internal passageway of a component (such as a passageway 60 as first shown in FIG. 5).

[0087] The electrode assembly 42 comprises a flexible electrode 44, a shuttle 58 and a guide cable 56 extending between the electrode 44 and the shuttle 58. The electrode 44 comprises a plurality of electrode 44 segments 46. Each segment 46 has a central core 48 formed from an electrical conductor, which may be a multi-strand electrical wire. The central core 48 is covered by an insulating jacket 50. The insulating jacket 50 is formed from an insulating material which is flexible and/or resilient. The insulating jacket 50 has at least one window 52 exposing the core 48 within, such that in use an electrolyte may flow through the jacket to the core. Each segment 46 is connected to the adjacent segment 46 with a flexible electrical conductor 54, which may be multi-strand electrical wire. This enables each segment 46 of the electrode 44 to move relative to adjacent segments 46 (e.g. by relative pivoting and rotational movement) and therefore allows the electrode 44 to be flexible.

[0088] In this example, each segment 46 has two windows 52 in the insulating jacket 50. The effective conductive area of a segment 46 may differ between segments. For example, one or more of the segments 46 in the electrode 44 may have a relatively greater effective conductive area by having a larger window 52, and/or by having a relatively greater number of windows 52 to expose a relatively larger area of the core 48.

[0089] Each segment 46 of the electrode 44 is configured to be energised independently. For example, the electrode 44 may be configured so that when coupled to a controller, the controller can select which segments 46 to energise (i.e. by providing current to those segments) and which segments 46 to leave inactive (i.e. by preventing current to those segments). Therefore the electrode 44 can be partially energised at selected points along its length by energising only selected segments 46, or fully energised such that all segments 46 of the electrode 44 are energised.

[0090] The thickness of the insulating jacket 50 may be varied according to the size and shape of the passageway 60 to be polished and the level of polishing required on the surface of the passageway 60. For example, the thickness of the insulating jacket 50 may be relatively high for some segments 46 of the electrode 44, corresponding to regions of the passageway 60 which require a low degree of polishing; whereas other segments 46 of the electrode 44 may have a relatively lower insulating jacket 50 thickness, corresponding to regions of the passageway 60 which require a high degree of polishing.

[0091] A first end of the guide cable 56 is attached to an end of the electrode 44. In other examples, the guide cable 56 may be attached at other points along the length of the electrode 44, provided that the guide cable 56 extends from the electrode 44 to the shuttle 58. The shuttle 58 is attached at a second, opposite end of the guide cable 56. The shuttle 58 may be sized and shaped to pass through the passageway of the component. The shuttle 58 may be configured to be easily entrained within a fluid flow for transport, for example by being configured to be of comparable density to the fluid flow. The shuttle may be hollow. In this example, the shuttle 58 has a rounded shape to allow it to pass through the passageway 60 without being caught or obstructed by any internal corners or features present in the passageway 60. It will be appreciated that the shape of the shuttle 58 may be adapted to suit the size, shape and features within the particular passageway 60.

[0092] FIG. 5 shows a cross-section of an example internal passageway 60 of a component to be polished, and methods of positioning the example electrode 44 and electropolishing will now be described with reference to the example component.

[0093] For the purpose of illustration, the passageway 60 is shown as having a relatively simple profile. It will be appreciated that passageways 60 may be more complex than the profile shown.

[0094] The passageway 60 has an inlet 62 and an outlet 64. Initially a fluid flow 66 is established through the passageway 60. The fluid flows in a direction from the inlet 62 to the outlet 64. The fluid may be an electrolyte suitable for electropolishing; however any suitable fluid may be used, such as water.

[0095] The shuttle 58 of the electrode assembly 42 is to be inserted into the passageway 60 through the inlet 62, as shown in FIG. 6a. The direction of the fluid flow 66 causes the shuttle 58 to be transported through the passageway 60 from the inlet 62 towards the outlet 64, as shown in FIG. 6b. The shuttle 58 is entrained in the fluid flow 66. The flow rate of the fluid flow 66 may be controlled to enable the shuttle 58 to reach the outlet 64. For example, a flow rate which is too low may fail to entrain the shuttle 58. As the shuttle 58 moves towards the outlet 64, the guide cable 56 is consequently drawn into the passageway 60. In this example, the shuttle 58 exits the passageway 60 by passing through the outlet 64 under the action of the fluid flow 66.

[0096] FIG. 7 shows another example of how the shuttle 58 can reach the outlet 64 of the passageway 60. As described in relation to the previous example, a fluid flow 66 is established through the passageway 60 in a direction from the inlet 62 to the outlet 64. The shuttle 58 is inserted into the inlet 62 of the passageway 60 and the direction of the fluid flow 66 causes the shuttle 58 to be entrained in the fluid flow 66 and transported through the passageway 60 and towards the outlet 64.

[0097] A retainer 68 is inserted into the passageway 60 from the outlet 64. In this example, the retainer 68 comprises an arm having a retention feature 70 at an end of the arm. The retention feature 70 is configured to catch the shuttle 58 as it passes through the passageway 60 towards the outlet 64. The retention feature 70 may be a passive structure which allows the shuttle 58 to enter the retention feature 70 and prevents the shuttle 58 from leaving the retention feature 70, such as a narrowing conical tube. Alternatively, the retention feature 70 may comprise a mechanism which can be actuated to close around and capture the shuttle 58 as it moves towards the outlet 64 of the passageway 60. In another example, both the shuttle 58 and the retention feature 70 may have cooperating magnets, such that the shuttle 58 is drawn towards the retention feature 70 as it passes through the passageway 60.

[0098] The retainer 68 may be perforated to allow fluid to pass through the retainer 68, so as to minimise detrimental flow effects on the fluid flow 66 as a result of the presence of the retainer 68 in the passageway 60.

[0099] Once the shuttle 58 has been caught by the retainer 68, the retainer 68 is withdrawn from the outlet 64 to pull the shuttle 58 out of the passageway 60 and thereby draw the guide cable 56 through the passageway 60. The retainer 68 may be automatically controlled and actuated, for example by a robotic arm.

[0100] FIG. 8 shows another example of how the shuttle 58 can reach the outlet 64 of the passageway 60. In addition to the features described with reference to FIGS. 6a and 6b, the passageway 60 comprises temporary guides 72. The temporary guides 72 could be added to the passageway 60 during the manufacture of the component. For example, the temporary guides 72 could be produced in the same ALM process but using a different material to that of the body of the component (i.e. the part of the article manufactured by ALM which corresponds to the finished component). The temporary guides 72 could also be added to the passageway 60 in a secondary manufacturing operation after the component has been produced, for example in a subsequent ALM process or by affixing them in the passageway 60 with an adhesive. While this example includes multiple temporary guides 72, there could also be a single such temporary guide 72.

[0101] The temporary guides 72 are positioned in the passageway 60 to guide the transport of the shuttle 58 through the passageway 60 by the fluid flow 66. As the fluid flow 66 carries the shuttle 58 from the inlet 62 to the outlet 64, the guides 72 act to direct the shuttle 58 towards the outlet 64 by restricting the region of the passageway 60 in which the fluid flow 66 and thereby the shuttle 58 is able to travel. The guides 72 may block off particular areas of the passageway 60 to prevent the shuttle 58 from travelling past the outlet 64. The guides may do so by providing a physical obstruction to a portion of the passageway 60 and/or by redirecting the flow so that an entrained shuttle 58 would not pass to that portion of the passageway 60. The guides 72 may provide rounding on corners within the passageway 60 to prevent the shuttle 58 and/or guide cable 56 from becoming stuck.

[0102] Once the shuttle 58 has been transported to the outlet 64 (whether using a retainer or not), the guides 72 may be removed from the passageway 60. For example, the temporary guides 72 may be removed by leaching, etching or dissolution by the fluid or by the electrolyte.

[0103] FIGS. 9a and 9b show how the electrode 44 is drawn into the passageway 60. As described previously, the transport of the shuttle 58 through the passageway 60 to the outlet 64 causes the guide cable 56 to be drawn into the passageway 60. The electrode 44 is attached to the guide cable 56, and so as the guide cable 56 is drawn through the passageway the electrode 44 may also drawn into the passageway.

[0104] Whether or not the electrode is partially or wholly drawn into the passageway 60 by virtue of transporting the shuttle 58 through the passageway, there may be a separate step of positioning the electrode 44 within the passageway for electropolishing. In this step, the guide cable 56 is pulled through the passageway 60 and as a result, the electrode 44 is drawn into the passageway 60, as shown in FIG. 9a. The inlet 62 may be fluted or be provided with a funnel (e.g. a nozzle) to aid insertion of the electrode 44 into the passageway 60.

[0105] The guide cable 56 is pulled through the passageway 60 until the electrode 44 has been positioned adjacent to a region of the passageway 60 to be electropolished, as illustrated in FIG. 9b. For example, the position of the electrode 44 may be adjusted to ensure that the electrode 44 lies along a path corresponding to the curvature of the passageway 60. If the electrode 44 is drawing too far, it may be pulled back using a portion extending out of the inlet 62 (or a trailing guide cable, for example).

[0106] If the fluid used for originally transporting the shuttle 58 to the outlet 64 is not an electrolyte suitable for electropolishing, the fluid flow through the passageway 60 is terminated and a flow of suitable electrolyte 76 is established through the passageway 60 ready for electropolishing. This replacement (i.e. replacing the original fluid with an electrolyte) may take place at any time prior to commencing electropolishing. For example, the electrolyte flow may be established after the shuttle is retained at the outlet 64 and before final placement of the electrode 44 for electropolishing, or the electrolyte flow may be established after final placement of the electrode 44 for electropolishing. The electrolyte 76 flows in a direction from the inlet 62 to the outlet 64 of the passageway 60. The electrolyte may be any electrolyte that is suitable for electropolishing. In an example, the electrolyte may be a Deep Eutectic Solvent.

[0107] Once the electrode 44 is in position for electropolishing, the electrode 44 is connected to the negative terminal of a DC power supply, whilst the component is connected to the positive terminal, thus making the component to be the anode, and the electrode 44 to be the cathode. The electrode 44 is activated such that an electric current passes from the component to the electrode 44 and electropolishing of the passageway 60 commences. The material on the surface of the passageway 60 is dissolved into the electrolyte. The flow of the electrolyte 76 carries the dissolved material out of the passageway 60 through the outlet 64.

[0108] Whilst electropolishing, the electrode 44 is moved within the passageway 60. Moving the electrode 44 whilst electropolishing ensures that the regions of the passageway 60 to be polished are uniformly polished. Additionally, moving the electrode 44 reduces the occurrence of electrolyte flow stagnation in regions of the passageway 60. Electrolyte flow stagnation can occur when using a static electrode 44 in convoluted passageway 60s and can lead to certain regions of the passageway 60 being polished to a greater or lesser extent than required. By moving the electrode 44, the electrolyte can flow freely through the passageway 60 and uniform polishing of the surface can be achieved. The electrode 44 may be moved by pulling the electrode 44 in different directions, which may be done manually or actuated robotically. The electrode 44 may also be moved by the electrolyte flow 76 by controlling the speed and/or direction of the electrolyte flow through the passageway 60.

[0109] Electropolishing of a given region of the passageway 60 may continue until the potential difference between the electrode 44 and the given region reaches a target value corresponding to a target level of surface finishing required.

[0110] As described previously, each segment 46 of the electrode 44 is independently selectable for electropolishing. Each segment 46 may be selectively energised to achieve local polishing of selected regions of the passageway 60. For example, if a greater degree of surface finishing is required in a particular region of the passageway 60, only the segments 46 adjacent to that region may be energised and other segments 46 may not be energised. The degree of surface finishing of a particular region of the passageway 60 can also be varied by varying the time spent for electropolishing that region. The intensity of the electropolishing of a particular region may be also be varied by changing the size or number of windows 52 in the insulating jacket 50 of the segments 46 to expose a larger or smaller area of the core 48.

[0111] FIG. 11 shows an example fuel injection nozzle 80 for use in a gas turbine engine. The fuel injection nozzle 80 comprises an internal passageway 60 extending between a fuel inlet 82 and a fuel outlet 84. The passageway 60 has convoluted geometry, having variable curvature and variable cross-section along its length from the fuel inlet 82 and the fuel outlet 84. The passageway 60 of the fuel injection nozzle 80 is an example of an internal passageway that can be electropolished using the aforementioned method. Other examples to which the disclosure applies include an internal passageway of a heat exchanger.

[0112] A method 1000 of electropolishing an internal passageway 60 of a component will now be described with reference to FIG. 12, with further reference to FIGS. 6a, 6b and 10. In block 1002, an electrode assembly 42 comprising a flexible electrode 44, a shuttle 58 and a guide cable 56 extending between the flexible electrode 44 and the shuttle 58 is provided. At block 1004, the shuttle 58 is inserted into the inlet 62 of the passageway 60. In block 1006, fluid is caused to flow through the passageway 60 to transport the shuttle 58 through the passageway 60 from the inlet 62 towards the outlet 64. At block 1008, the guide cable 56 is pulled through the passageway 60 to position the electrode 44 in the passageway 60 adjacent to a region of the passageway 60 to be polished. At block 1010, the passageway 60 is electropolished using the electrode 44 while moving the electrode within the passageway 60.

[0113] An alternative method 2000 of electropolishing an internal passageway 60 of a component will be described with reference to FIG. 13 and with further reference to FIGS. 6a, 6b, 8 and 10. Reference is made to the method 1000 described in FIG. 12, with like reference numerals indicating like features. In block 2002, a component is manufactured by additive manufacture to form: a body defining an inlet 62, an outlet 64, and an internal passageway 60 for flow between the inlet 62 and outlet 64; and a temporary guide 72 disposed within the internal passageway 60. In block 1002, an electrode assembly 42 comprising a flexible electrode 44, a shuttle 58 and a guide cable 56 extending between the flexible electrode 44 and the shuttle 58 is provided. At block 1004, the shuttle 58 is inserted into the inlet 62 of the passageway 60. In block 1006, fluid is caused to flow through the passageway 60 to transport the shuttle 58 through the passageway 60 from the inlet 62 towards the outlet 64. At block 2004, the transport of the shuttle 58 within the passageway 60 is guided towards the outlet 64 with a temporary guide 72 located within the passageway. At block 1008, the guide cable 56 is pulled through the passageway 60 to position the electrode 44 in the passageway 60 adjacent to a region of the passageway 60 to be polished. At block 2006, the temporary guide 72 is removed. The temporary guide 72 may be removed by leaching or etching. At block 1010, the passageway 60 is electropolished using the electrode 44 while moving the electrode 44 within the passageway 60.

[0114] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.