GAS TURBINE ENGINE

Abstract

A method of manufacturing a part comprises providing a component for cutting and directing a water jet at the component so as to cut the component. The water jet comprises water and abrasive particles having a nucleus made from a first substance and a second substance surrounding the nucleus, the first substance being denser than the second substance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This specification is based upon and claims the benefit of priority from UK Patent Application Number 1712479.3 filed on 3 Aug. 2017, the entire contents of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure concerns a method of manufacture and/or a method of water jet cutting.

Description of the Related Art

Gas turbine engines are typically employed to power aircraft. Typically a gas turbine engine will comprise an axial fan driven by an engine core. The engine core is generally made up of one or more turbines which drive respective compressors via coaxial shafts. The fan is usually driven off an additional lower pressure turbine in the engine core.

The fan includes a plurality of blades arranged around a hub. The blades may be metallic or composite blades. Composite blades generally include a body made from a carbon reinforced plastic matrix which may be reinforced in various ways. A metallic leading edge, and often a metallic trailing edge is provided on the body.

The metallic leading edge can be manufactured in a number of different ways, and in some examples the metallic leading edges need to be cut during the manufacturing process. This cutting can be done using water jet cutting. Water on its own is not sufficiently abrasive to cut the metal, so abrasive garnet particles are added to the water. However, the garnet can become embedded in the metal work contaminating the surface of the cut component. Garnet is chemically inert, so it is not readily removed using chemical processes and as such mechanical processes need to be employed to remove the embedded particles. Removal of the garnet particles from the surface of the component adds cost and time to the manufacturing process.

SUMMARY

According to an aspect there is provided a method of manufacturing a part, the method comprising providing a component for cutting and directing a water jet at the component so as to cut the component. The water jet comprises water and abrasive particles having a nucleus made from a first substance and a second substance surrounding the nucleus. The first substance may be denser than the second substance. The second substance may be a liquid at atmospheric temperature and pressure. The first substance may be solid at atmospheric temperature and pressure. The second substance may be a frozen liquid, e.g. the second substance may be ice. Ice refers to frozen water. Frozen water consists essentially of H₂O and any impurities. In alternative examples, the second substance may be an alternative frozen liquid.

The nucleus may comprise carbon. The nucleus may consist of or consist essentially of carbon or carbon fibre. The nucleus may comprise one or more carbon fibres or particles.

The nucleus may be defined by a single carbon fibre.

The nucleus may comprise acrylic. The acrylic nucleus may be 3D printed prior to being surrounded by the second substance.

The part may be a fan blade for a gas turbine engine, e.g. the component once cut may be a metal leading edge or trailing edge of a fan blade.

According to an aspect there is provided a method of water jet cutting a component, the method comprising providing a component for cutting and directing a water jet at the component so as to cut the component. The water jet comprises water and abrasive particles having a nucleus made from a first substance and a second substance surrounding the nucleus, the second substance being different to the first substance.

The method may comprise one or more features of the previous aspect.

According to an aspect there is provided a method of manufacturing a part, the method comprising providing a component for cutting and directing a water jet at the component so as to cut the component, the water jet comprising water and carbon particles.

The method may comprise one or more features of the previous aspect.

According to an aspect there is provided a method of water jet cutting comprising providing a component for cutting, and directing a water jet at the component so as to cut the component. The water jet comprises water and carbon particles.

The carbon particles may be surrounded in a substance that is liquid at atmospheric temperature and pressure. For example, the carbon particles may be surrounded by ice.

The method may comprise one or more features of the previous aspect.

The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

FIG. 2 is a schematic of a water jet cutting arrangement and component;

FIG. 3 illustrates water with particles suspended in it for use as a water jet;

FIG. 4 is a schematic of a feed of particles into a water jet;

FIG. 5 is a schematic of equipment used to make the particles illustrated in FIG. 3; and

FIG. 6 is a schematic of equipment used to grow abrasive particles

DETAILED DESCRIPTION

With reference to FIG. 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the air flow directed into it before delivering that air to 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 combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

The fan 13 includes a plurality of fan blades 24 arranged around a hub. In the present example, the fan blades are composite fan blades and include a metallic leading edge 25. The metallic leading edge is made from metal and is at least partially cut to size using water jet cutting.

The method of water jet cutting will now be described in more detail. Referring to FIG. 2, to cut a component 26 a water jet 28 is directed at the component. The water jet is delivered from cutting equipment 30.

Referring to FIG. 3, the water jet includes water 32 and abrasive particles 34. The abrasive particles include a nucleus 36 of a first substance. The nucleus is surrounded by a second substance 38. In the present example, the nucleus is made from carbon, more specifically in this example carbon fibre. The second substance in this example is ice, i.e. frozen water.

The carbon fibre is defined by short sharp lengths of carbon. These can be produced with a high aspect ratio. The carbon fibres can be bought off the shelf or may be manufactured from carbon rod stock. To manufacture the carbon fibres, conventional methods can be used such as a using a slotted cutting wheel or shearing jaws.

Referring now to FIG. 4, the cutting equipment 30 includes a hopper 40 for receiving solid particles (e.g. carbon fibre nuclei surrounded by ice). The equipment also includes a high pressure supply 42A, 42B of water. A water outlet 44 is provided through which the high pressure supply of water can flow. A focus tube 46 projects into the outlet from the hopper 40, such that a flow of solid particles from the hopper can mix with the water. A control orifice 48 is provided at the exit of the water outlet, so as to control the flow of water and solid particles.

To cut a component, solid particles are supplied to the hopper 40, either continuously or in batches. High pressure water is supplied through the inlets 42A, 42B. This water then flows to the water outlet 44. Simultaneously, particles are released from the hopper into the water in the outlet. The orifice 48 then funnels the water and particles to have the desired jet properties for a given application. For example, the orifice can be dimensioned for high speed cutting, high precision edge or super fine precision edge.

In the present example, the particles 34 having a carbon fibre nucleus and surrounding substance are made prior to being delivered to the hopper 40. The abrasive particles may be formed in a number of different ways, for example using sublimation, an atomiser or particles may be swirled in a super saturated liquid prior to be placed in a long drop condensing chamber.

Referring to FIG. 5, to manufacture the particles using one exemplary method an atomiser 50 (e.g. an ultrasonic atomiser) may be provided. The atomiser 50 may be connected to a mixing chamber 52. The mixing chamber is connected to a water supply 54 and a carbon fibre supply 56. The water supply and carbon fibre supply pass water and carbon fibre to the mixing chamber, where it is mixed. The mixing chamber then supplies the mixture of water and carbon fibre to the atomiser. A nitrogen supply 58 is also connected to the atomiser. Once the water has been atomised around the carbon fibre, liquid nitrogen from the nitrogen supply is used to freeze the water around the carbon fibre. If applicable, a further step of filtering any ice only particles from the carbon fibre and ice particles may be performed. Referring to FIG. 6, if sublimation is used to form the abrasive particles, the material to be crystallised is heated under reduced pressure or vacuum until it vaporizes where it then deposits on a cool area of the vessel. As the material is deposited on the cool surface, it converts into a crystalline form. A nuclei seed can be placed at the tip of a cooled finger prior to starting sublimation allowing the crystal to form around it. For example, the material to be crystallised may be heated under pressure in the pressure vessel 60. A nuclei seed 62 may be provided around which the crystal can form.

In alternative embodiments, the ice and carbon fibre particles may be made in situ within the cutting equipment. For example, referring to FIG. 4, the cutting equipment may be modified so that the hopper 40 supplies carbon to a mixing chamber where it is mixed with water. A supply of super cooled liquid can be passed around the mixing chamber as the carbon fibres enter so as to freeze water droplets surrounding the carbon fibre. The combined carbon fibre and ice particles are then directed through the focus tube 44 as previously described.

In the described example, the particles are less likely to embed in the surface of a cut component compared to the garnet particles of the prior art because of the ice surrounding the nucleus. Further, carbon fibre can be more easily removed from the surface of a component than garnet.

Provision of a nuclei, e.g. carbon fibre nuclei, means that the particles have increased momentum compared to particles made only from ice, which means that the cutting performance can be improved compared to water jet cutting using only ice particles.

As discussed previously, carbon can be more easily removed from a surface than garnet. As such, advantages over the conventional garnet water jet cutting process can be achieved by using carbon as the abrasive particle, i.e. carbon not surrounded by ice. To utilise carbon only particles a similar method to that described and illustrated in FIG. 4 may be used, but instead of the hopper containing carbon and ice particles, the hopper contains carbon only particles. These carbon particles may be propelled through the cartridge 40 by ultra-high pressure environmentally conditioned water feed 42A. At a certain point, e.g. puncture of a seal, a secondary encasement supply of ultra-high pressure environmentally conditioned water 42B is introduced to contain and direct the impregnated cutting solution through the orifice 48 onto the material that requires cutting.

In exemplary embodiments, the hopper may comprise a belt e.g. a multi-feed option. In examples of the described methods, the cartridge 40 may be oscillated at high frequency to improve distribution of the particles into the water stream. Cartridges are ideally disassembled and cleaned prior to replacement of media for repeated use.

In alternative examples, the nuclei may not be made from carbon fibre. For example the nuclei may be made from an acrylic. The acrylic may be produced in a colloidal dispersion using high-shear mixing or by 3D printing to form particles having a desired shape, for example angular particles with sharp edges. Selecting the desired shape of the particles can result in more favourable abrasive particle shapes (e.g. the shape of the acrylic nuclei and ice formed around the nuclei) for improved cutting.

In further alternative examples the nuclei may be formed from a crystalline solid, for example uric acid crystals or crystals of other organic acids e.g. diprotic acids, citric acid, malic acid, tartaric acid, or folic acid. In other examples the crystals may comprise calcium, for example calcium oxalate. The crystals may be formed from hydroxyapatite. The crystals may be formed from urea or derivatives thereof, for example heterocyclic urea, or hydroxycarbamide. In many examples it is desirable for the crystals to be formed from a heterocyclic compound. In alternative examples, the crystalline solids may comprise metal ions. For example, calcium, magnesium, sodium, lithium, or potassium may be added to the composition of the crystalline solids.

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.

Claims

1. A method of manufacturing a part, the method comprising: providing a component for cutting; anddirecting a water jet at the component so as to cut the component, the water jet comprising water and abrasive particles having a nucleus made from a first substance and a second substance surrounding the nucleus, the first substance being denser than the second substance.

2. The method according to claim 1, wherein the second substance is a liquid at atmospheric temperature and pressure.

3. The method according to claim 1, wherein the first substance is solid at atmospheric temperature and pressure.

4. The method according to claim 1, wherein the second substance is ice.

5. The method according to claim 1, wherein the nucleus comprises carbon.

6. The method according to claim 5, wherein the nucleus is defined by a single carbon fibre.

7. The method according to claim 1, wherein the nucleus comprises acrylic.

8. The method according to claim 7, wherein the acrylic nucleus is 3D printed prior to being surrounded by the second substance.

9. The method according to claim 1, wherein the part is a fan blade for a gas turbine engine.

10. A method of water jet cutting a component, the method comprising: providing a component for cutting; anddirecting a water jet at the component so as to cut the component, the water jet comprising water and abrasive particles having a nucleus made from a first substance and a second substance surrounding the nucleus, the second substance being different to the first substance.

11. A method of manufacturing a part, the method comprising: providing a component for cutting; anddirecting a water jet at the component so as to cut the component, the water jet comprising water and carbon particles.