WO2019012559A1

WO2019012559A1 - An additive manufacturing process for combustion chamber

Info

Publication number: WO2019012559A1
Application number: PCT/IN2018/050456
Authority: WO
Inventors: Babasaheb KALYANI; Jagdish SHERKAR; Shreyans KHOT; Dattaprasad LOMATE; Pravin PAWAR; Swapnil PAWAR; Chaitanya GHODAKE; Sandeep THAKARE; Sachin Patil
Original assignee: Bharat Forge Limited
Priority date: 2017-07-12
Filing date: 2018-07-12
Publication date: 2019-01-17

Abstract

The present invention relates to a 3D printed combustion chamber assembly and an additive manufacturing of the combustion chamber assembly. The process involves spreading metal powder layer by layer on a predetermined platform followed by fusion, heat treatment, wire cutting operation, shot blasting and buffing operation to obtain a combustion chamber and flame tube parts with pre-detrmined surface finish; and press fitting the combustion chamber and flame tube parts to obtain the combustion chamber assembly.

Description

AN ADDITIVE MANUFACTURING PROCESS FOR

COMBUSTION CHAMBER

FIELD OF THE INVENTION:

The present invention relates to the field of manufacturing of aerospace parts. Particularly, the present invention relates to the field of additive manufacturing of aerospace parts.

More particularly the present invention relates to a method of additive manufacturing of a combustion chamber.

BACKGROUND OF THE INVENTION:

Gas turbine engines typically include an air intake, a compressor, a combustion chamber, a turbine, and an exhaust nozzle. Air goes in the front air intake, passes through a bunch of compressor blades, gets compressed, and delivers high pressure compressed air into the combustion chamber. Fuel injectors are fitted on the inlet of the combustion chamber to direct the fuel and mix it with compressed air. Then a mixture of fuel and the compressed air is ignited. It burns inside the combustion chamber and creates an immense amount of pressure which is then passed through to the turbine blades at the back of the engine that spin and create thrust.

Traditionally, the combustion chamber is made by sheet metal forming operations like punching, slitting, bending, etc., followed by precision joining process.

These traditionally manufactured parts have the following drawbacks: 1. Heavier and more powerful equipment with special tooling's are required.

2. In traditional manufacturing methods, the parts have to be made separately and then joined using precise joining processes.

3. The manufacturing processes demand mass quantity for economic production of these parts.

4. Enormous initial investments are required for these processes. Some of the prior art documents disclose additive manufacturing of few parts of combustion chamber. For instance:

EP2977133 discloses a method of producing cooling apertures in a combustion chamber head. It comprises mechanically drilling a plurality of cooling apertures through the combustion chamber head from the downstream side of the combustion chamber head. A tool is inserted through at least one aperture for a fuel injector from the downstream side of the combustion chamber head and the tool is rotated about its axis whilst within the aperture for a fuel injector.

US2016356245 discloses a rocket motor produced by additive manufacturing. It further discloses that the fuel element is made in an additive manufacturing process that defines the one or more chambers as fuel material is added to the fuel element.

EP3048370 discloses a combustion chamber for a gas turbine. It focuses on new design for the walls of a combustion chamber for gas turbines, which efficiently provide the required degree of acoustic dampening and wall cooling. US2016230646 discloses a combustion system, nozzle for prechamber assembly, and method of making same. It further discloses manufacturing of the nozzle body. The first orifice and the second orifice are defined via additive manufacturing.

None of these documents discloses manufacturing of combustion chamber assembly as a whole by an additive manufacturing method.

Accordingly, it is envisaged to provide an additive manufacturing method which can overcome the drawbacks of known methods.

OBJECTS OF THE INVENTION:

It is an object of the present invention to provide an additive manufacturing process for producing combustion chamber parts.

It is another object of the invention to reduce total number of parts.

It is yet another object of the present invention to eliminate number of manufacturing processes required to produce combustion chamber assembly.

It is still another object of the present invention to design combustion chamber in a single building block and in a single printing cycle, thereby eliminating excessive inventory which results in cost saving.

It is a further object of the present invention to provide a 3D printed combustion chamber assembly. It is a further object of the present invention to provide an optimised support for holding the combustion chamber being printed and dissipating heat to surrounding.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a process for manufacturing of a combustion chamber assembly; said process comprises additive manufacturing of combustion chamber assembly, said additive manufacturing comprises the following steps:

a. providing metal powder as a raw material;

b. providing a 3D printing device;

c. spreading said metal powder layer by layer on a predetermined platform;

d. selectively fusing said metal powder using at least one energy source at predetermined conditions to perform a printing operation to obtain a combustion chamber and flame tube parts separately;

e. heat treating said combustion chamber and said flame tube parts in a furnace separately at a predetermined temperature to obtain heat treated combustion chamber and flame tube parts followed by cooling to room temperature;

f. subjecting said treated combustion chamber and said flame tube parts to wire cutting operation to separate the combustion chamber and the flame tube parts from the platform, followed by shot blasting to generate compressive residual stresses on the surfaces of the combustion chamber and the flame tube parts, and buffing operation to achieve the combustion chamber and the flame tube parts with pre- detrmined surface finish; and

g. press fitting the combustion chamber and flame tube parts to obtain the combustion chamber assembly.

In one preferred embodiment, the process comprises a pre-step of printing a support having predetermined configuration meant for holding said combustion chamber assembly parts and transferring heat from the part/s being 3D printed to the platform during printing operation, wherein said printing operation comprises spreading metal powder layer by layer on a predetermined platform followed by fusing said powder using at least one energy source at predetermined conditions.

In another aspect of the present invention, there is provided a combustion chamber assembly for a jet engine; said combustion chamber assembly (100) comprises a 3D printed combustion chamber (10); and 3D printed flame tube parts (20) press fitted with the 3D printed combustion chamber (10),

wherein said combustion chamber comprises an inner casing wall (12) delimiting an inner volume (V) of the combustion chamber in a cone shape with integrated features, through which combustion gas flow; an outer casing wall (14) with specified holes of different sizes to cool down the inner portion of combustion chamber (10); cooling holes (16) on outer casing wall (14) acting as a cooling medium flowing outside the inner volume (V) in thermal contact with the inner casing wall (12); a lower wall (18) comprising structured slots acting as a bridge between the inner casing wall (12) and the outer casing wall (14); wherein the inner casing wall (12) is spaced apart from the outer casing wall (14),

wherein said flame tube parts (20) comprise flame tubes (22) and an upper wall/ring (24) adapted to hold the flame tubes (22), wherein the flame tube covers micro-fuel tubes and guides combustible gases which needs to be passed over turbine.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

The invention will now be described in relation to the accompanying drawings, in which:

Figure 1 illustrates the three dimensional image of 3D Printed combustion chamber assembly (100) in accordance with the present invention;

Figure 2 illustrates the outer casing wall (14) of the combustion chamber;

Figure 3 illustrates the inner casing wall (12) of the combustion chamber;

Figure 4 illustrates the lower wall (18) of the combustion chamber;

Figure 5 illustrates the upper wall/ring (24) for flame tube holding; Figure 6 illustrates the flame tube (22); and

Figure 7 illustrates the combustion chamber assembly parts (10 and 20) printed by additive manufacturing method of the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

3D printing, also known as additive manufacturing, refers to a process used to create a three-dimensional object in which layers of material are formed under computer control to create an object. Parts that are to be manufactured are made so by this process directly from digital model by using layer by layer material build-up approach. This tool-less manufacturing method can produce fully dense metallic parts in a short time period with high precision. Features of additive manufacturing like freedom of part design, part complexity, light weighting, part consolidation and design for function are garnering particular interests in metal additive manufacturing for aerospace, oil & gas, marine and automobile applications.

According to this invention, there is provided a method of additive manufacturing for making combustion chamber. There is also provided a combustion chamber assembly made by the method of additive manufacturing. The following non-limiting figures illustrate the combustion chamber made in accordance with one of the embodiments of the present invention. Figure 1 illustrates the three dimensional image of 3D printed combustion chamber assembly. This is referenced by numeral 100;

Figure 2 illustrates the outer casing wall (14) of combustion chamber;

Figure 3 illustrates the inner casing wall (12) of combustion chamber;

Figure 4 illustrates the lower wall (18) of combustion chamber;

Figure 5 illustrates the upper wall/ring (24) for holding the flame tubes;

Figure 6 illustrates the flame tube (22); and

Figure 7 (A & B) illustrates the combustion chamber parts printed by additive manufacturing method of the present invention.

In one aspect of the present invention, there is provided a combustion chamber assembly (100) for a jet engine; said combustion chamber assembly (100) comprises a 3D printed combustion chamber (10); and 3D printed flame tube parts (20) press fitted with the 3D printed combustion chamber (10), wherein said combustion chamber (10) comprises an inner casing wall (12) delimiting an inner volume (V) of the combustion chamber in a cone shape with integrated features, through which combustion gas flow; an outer casing wall (14) with specified holes of different sizes to cool down the inner portion of combustion chamber; cooling holes (16) on the outer casing wall (14) acting as a cooling medium flowing outside the inner volume (V) in thermal contact with the inner casing wall (12); a lower wall (18) comprising structured slots acting as a bridge between the inner casing wall and the outer casing wall; wherein the inner casing wall (12) is spaced apart from the outer casing wall (14),

wherein said flame tube parts comprise flame tubes (22) and an upper wall/ring (24) adapted to hold the flame tubes, wherein the flame tube covers micro-fuel tubes and guides combustible gases which needs to be passed over turbine.

In at least an embodiment of this invention, the combustion chamber assembly comprising these above-mentioned features are designed and rendered using a rendering software which is then used as an input for the additive manufacturing process.

The outer casing wall comprises complex geometry with predefined and structured features. With the use of this additive manufacturing process, there is reduction in tooling for making holes and for welding of thin wall to make the cylinder.

Additionally, due to the additive manufacturing process, the upper slots and half round holes and purging holes are provided on a conic shape of the inner casing wall which is manufactured in a single print.

According to another embodiment the space provided between outer casing wall and inner casing wall at one end is bridged by lower wall with structured slots integrated in model.

In at least an embodiment, clamping hooks (26) may be provided on the free end of outer casing wall which is integrated to outer casing wall design and manufactured within the assembly of additive manufacturing.

In one embodiment of the present invention, there is provided flame tubes (22) for covering fuel supply micro tubes which is integrated with upper wall design (24) and manufactured within the assembly of additive manufacturing.

These two parts (combustion chamber (10) and flame tubes parts (20)) are press fitted to form a combustion chamber assembly (100).

In accordance with another aspect, the present invention provides a process for manufacturing of combustion chamber assembly. The process involves additive manufacturing of combustion chamber assembly. The additive manufacturing according to the present invention involves the following steps:

In the first step, metal powder as a raw material and a 3D printing device is provided or kept ready. In the next step, the metal powder is spread layer by layer on a predetermined platform.

Typically, the layer has a thickness in the range of 0.02 to 0.08 mm and a laser strip width in the range of 5 to 10mm. Typically, the overlap between the layers is in the range of 0.01 to 0.15mm.

In one embodiment, the spreading comprises controlled deposition of the layers of metal powder to form holes, apertures and slots in the wall. In one embodiment, the spreading comprises depositing layers of a metal powder sequentially one upon the other to form features. After spreading, the powder is selectively fused using at least one energy source at predetermined conditions to perform a printing operation to obtain a combustion chamber and flame tube parts separately. Typically, the energy source is selected from the group consisting of laser beam and electron beam. The energy source has a scanning speed of about 1000 to 1400 mm/second and has power of 190 to 200 watt.

In the next step, the combustion chamber and the flame tube parts are heated in a furnace at a predetermined temperature to obtain heat treated combustion chamber and flame tube parts followed by cooling to room temperature.

In one preferred embodiment, the heat treatment step involves the following steps:

Step 1: annealing the combustion chamber parts at a temperature ranging from 1000 to 1200 °C for a period ranging from 30 minutes to 120 minutes followed by cooling to room temperature.

Step 2: ageing the combustion chamber parts by holding the parts at a temperature ranging from 700 to 800°C for a time period ranging from 5 to 15 hours followed by cooling to a temperature ranging from 625 to 675 °C in 1 to 3 hours and holding at a temperature ranging from 625-675 °C for 6 to 10 hours; and c) air cooling said parts to room temperature.

Typically, the temperature of said platform is set in the range of 110 to 130°C. Step 3: subjecting the treated combustion chamber and the flame tube parts to wire cutting operation to separate the combustion chamber and the flame tube parts from the platform.

Step 4: subjecting the combustion chamber and the flame tube parts to shot blasting to generate compressive residual stresses on the surfaces of the combustion chamber and the flame tube parts.

Step 5: performing a buffing operation to achieve the combustion chamber and the flame tube parts with pre-detrmined surface finish. Step 6: press fitting the combustion chamber and flame tube parts to obtain the combustion chamber assembly.

In accordance with a preferred embodiment of the present invention the process comprises a pre-step of printing a support having predetermined configuration meant for holding said combustion chamber assembly parts and transferring heat from the part/s being 3D printed to the platform during printing operation, wherein said printing operation comprises spreading metal powder layer by layer on a predetermined platform followed by fusing said powder using at least one energy source at predetermined conditions.

The 3D printing or additive manufacturing process consists of making a part layer by layer. The required amount of a layer of powder is fused using an energy source. Each new layer of fused powder requires support from layer beneath it (formed previously). Combustion chamber parts have overhang or bridge thus needs use of 3D printed support structures to ensure a successful print. The support structures found to have both positive as well as negative effects on the 3D printing process. On the one hand the support structures help in transfer of heat, prevent extreme powder inclusion, support the overhanging part of the product and secures the part against detachment during the building process. On the other hand the support structure leads to waste of material, may affect the surface finish of the product and leads to requirement of post processing operations to remove it. Hence, it is found that the selection of type and geometry of support structure is critical for defect less manufacturing, ease of manufacturing and economic manufacturing.

According to the present invention several types of supports which can be used during the 3D printing are tried. The type of support to be used is decided based on the quantity of material required for supports, heat dissipation of product to surrounding, geometry of model etc. Different types of supports which are tried include Block type, Line type, Point type, Web Type, Contour type, Gusset type, volume type etc. The support structure with different features like hatching, hatching teeth, fragmentation, borders, border teeth, perforations, gusset borders etc are experimented.

Based on the considerations and experimentations, during the manufacturing of the combustion chamber assembly, the preferred type of support used is "Block Support with hatching teeth and perforation".

Figure 1 illustrates combustion chamber assembly printed in an additive manufacturing process. According to the present invention, the manufacturing process starts with a metal powder as a raw material. The metal material includes but is not limited to IN718, IN713C, IN625 material and the like. The metal powder is spread on bed layer by layer and selectively fused by using an energy source like a laser or electron beam. After completion of the print, part is transferred to the furnace, where heat treatment is conducted and required properties are achieved. The final parts are separated from the build platform by using wire cutting operation. The final parts are then transferred to shot blasting to generate compressive residual stresses on the surface. Then buffing is carried out on the final parts to achieve the required surface finish. Finally, two parts are assembled.

The combustion chamber manufacturing process is described, in detail, as below.

1. CAD Model generation:

Producing a digital model of the parts (i. e. the combustion chamber) is the first step in the additive manufacturing process. A digital model is produced by using computer aided design. Then, this CAD model is converted into a Surface Tesselation Language / Standard Triangulation Language file (STL) which is used by further portions and processes of this invention.

2. Additive Manufacturing program generation:

Once an STL file has been generated, the file is imported into a MAGICS MATERIALISE software. MAGICS is used for defining part orientation and generating support. Then, STL file sent to the slicer software for slicing. After slicing, the file is imported in EOSPRINT software. EOSPRINT software is used for assigning the build parameters and these further are optimized for CAD data. Then after-parameters like laser power, scanning speed, hatch distance and layer thickness are designed. Finally, the file is exported to the 3D printing machine for producing the parts.

3. Additive Manufacturing or 3D printing:

Different types of materials can be used for manufacturing combustion chamber parts which include but are not limited to IN718, IN713C, IN625 material and the like. Material is provided in the form of powder. Powder is spread on the build-up platform layer by layer with a layer thickness of 0.020 mm. During this activity platform temperature is maintained 120 °C throughout the process. After each layer, powder is selectively fused by using a laser with a scanning speed of 1200 mm/Sec for parts and 500 mm/Sec for support in an Argon environment. The output of this process is a combustion chamber parts with a build platform. The summary of parameters used to produce the combustion chamber parts in additive manufacturing are mentioned in table 1.

Table 1

Parameters Value

Part

Layer thickness 0.020 mm

Platform temperature 120°C

Chamber environment Argon

Skip layer 0

Scanning speed 1200 mm/Sec

Laser Power 195 Watt

Laser Strip Width 5 mm

Beam offset 0.015

Strip Overlap 0.12 mm

Support Layer thickness 0.020 mm

Platform temperature 120°C

Chamber environment Argon

Skip layer 1

Scanning speed 500 mm/Sec

Laser Power 90 Watt

4. Heat treatment:

Heat treatment is carried out on the combustion chamber parts to achieve the mechanical properties and de-stress the parts. Firstly, parts are solution annealed. The combustion chamber parts are solution treated at 1065 °C for one hour, followed by air cooling to room temperature. The second heat treatment is ageing. In this treatment, parts are held at 760 °C for ten hours, after that it is furnace cooled to 650 °C in two hours and then held at 650 °C for eight hours. Finally, the parts are air cooled to the room temperature. The above heat treatment is performed for IN718. The mechanical properties achieved after heat treatment are summarized in table 2. (Material: IN718)

Table 2

Mechanical properties Value

Tensile strength Min 1241 Mpa

Yield strength 1150 Mpa

Elongation 12 %

Hardness 47 RC

5. Wire cutting and support removal:

The heat treated combustion chamber parts are separated from the build platform by using a wire cutting operation. Next, the support formed during the 3D printing operation are machined off. 6. Polishing:

After that, buffing operation is performed to achieve the desired finish.

7. Press Fitting:

After that the part 1 and 2 are press fitted to make the complete combustion assembly.

The TECHNICAL ADVANCEMENT of this invention lies in provide a method of additive manufacturing which processes input data into a 3D printed chamber of the above-mentioned design in a single building block and in a single printing cycle, thereby eliminating excessive inventory and thereby resulting in cost saving and thereby eliminating wastage.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

A process for manufacturing of a combustion chamber assembly; said process comprises additive manufacturing of combustion chamber assembly, said additive manufacturing comprises the following steps:

a) providing metal powder as a raw material;

b) providing a 3D printing device;

c) spreading said metal powder layer by layer on a predetermined platform;

d) selectively fusing said metal powder using at least one energy source at predetermined conditions to perform a printing operation to obtain a combustion chamber and flame tube parts separately;

e) heat treating said combustion chamber and said flame tube parts in a furnace at a predetermined temperature to obtain heat treated combustion chamber and flame tube parts followed by cooling to room temperature; f) subjecting said treated combustion chamber and said flame tube parts to wire cutting operation to separate the combustion chamber and the flame tube parts from the platform, followed by shot blasting to generate compressive residual stresses on the surfaces of the combustion chamber and the flame tube parts, and buffing operation to achieve the combustion chamber and the flame tube parts with pre-detrmined surface finish; and

1 g) press fitting the combustion chamber and flame tube parts to obtain the combustion chamber assembly.

2. The process as claimed in claim 1, wherein the process comprises a pre-step of printing a support having predetermined configuration meant for holding said combustion chamber assembly parts and transferring heat from the part/s being 3D printed to the platform during printing operation, wherein said printing operation comprises spreading metal powder layer by layer on a predetermined platform followed by fusing said powder using at least one energy source at predetermined conditions.

3. The process as claimed in claim 2, wherein the support is block support with hatching teeth and perforation/s.

4. The process as claimed in claim 1, wherein the process comprises a step of producing a digital model of the combustion chamber using computer aided design.

5. The process as claimed in claim 1, wherein said combustion chamber comprises an inner casing wall delimiting an inner volume (V) of the combustion chamber in a cone shape with integrated features, through which combustion gas flow; an outer casing wall with specified holes of different sizes to cool down the inner portion of combustion chamber; cooling holes

2 on outer casing wall; a lower wall comprising structured slots acting as a bridge between the inner casing wall and the outer casing wall; wherein the inner casing wall is spaced apart from the outer casing wall.

6. The process as claimed in claim 1, wherein said flame tube part comprises flame tubes and an upper wall, wherein the flame tube covers micro-fuel tubes and guides combustible gases which needs to be passed over turbine; and wherein the upper wall adapted to hold flame tubes.

7. The process as claimed in claim 1, wherein the metal powder is selected from the group consisting of IN718, IN713C, and IN625 materials.

8. The process as claimed in claim 1, wherein the energy source is selected from the group consisting of laser beam and electron beam.

9. The process as claimed in claim 1, wherein the heat treatment step comprises a) annealing said combustion chamber parts at a temperature ranging from 1000 to 1200 °C for a period ranging from 30 minutes to 120 minutes followed by cooling to room temperature; b) ageing said combustion chamber parts by holding said parts at a temperature ranging from 700 to 800° C

3 for a time period ranging from 5 to 15 hours followed by cooling to a temperature ranging from 625 to 675 °C in 1 to 3 hours and holding at a temperature ranging from 625-675 °C for 6 to 10 hours; and c) air cooling said parts to room temperature.

10. The process as claimed in claim 1, wherein the layer has a thickness in the range of 0.02 to 0.08 mm and a laser strip width in the range of 5 to 10mm.

11. The process as claimed in claim 1, wherein the overlap between the layers is in the range of 0.01 to 0.15mm

12. The process as claimed in claim 1, wherein the energy source has a scanning speed of about 1000 to 1400mm/second and has power of 190 to 200 watt.

13. The process as claimed in claim 1, wherein the temperature of said platform is in the range of 110 to 130°C.

14. The process as claimed in claim 1, wherein the spreading comprises controlled deposition of the layers of metal to form holes, apertures and slots in the wall.

15. The process as claimed in claim 1, wherein the spreading comprises depositing layers of a metal sequentially one upon

4 the other to form features.

16. A combustion chamber assembly (100) for a jet engine; said combustion chamber assembly (100) comprises a 3D printed combustion chamber (10); and 3D printed flame tube parts (20) press fitted with the 3D printed combustion chamber (10),

wherein said combustion chamber comprises an inner casing wall (12) delimiting an inner volume (V) of the combustion chamber in a cone shape with integrated features, through which combustion gas flow; an outer casing wall (14) with specified holes of different sizes to cool down the inner portion of combustion chamber; cooling holes (16) on outer casing wall (14) acting as a cooling medium flowing outside the inner volume (V) in thermal contact with the inner casing wall; a lower wall (18) comprising structured slots acting as a bridge between the inner wall (12) and the outer casing wall (14); wherein the inner casing wall (12) is spaced apart from the outer casing wall (14),

17. The combustion chamber assembly as claimed in claim 16, wherein said outer casing wall (14) is provided with at least one clamping hook (26) at free end of said outer casing wall.

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