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Title:
METHOD FOR MANUFACTURING A WALL STRUCTURE
Document Type and Number:
WIPO Patent Application WO/2008/010748
Kind Code:
A1
Abstract:
Method for manufacturing a wall structure comprising the steps of providing two walls (106, 110) at least substantially in parallel to one another and at least two webs (107, 109) that connect the two walls and delimit a cooling channel (115) between said walls, said cooling channel extending in a divergent manner from a narrow cooling channel section (111). The method further comprises the step of providing an intermediate web (108) between said two webs (107, 109) so that it connects the two walls (106, 110) and divides a single diverging cooling channel (115) into two separate cooling channels (215, 315) and positioning the intermediate web (108) so that it ends at a distance from the narrow cooling channel section. The method further comprises the step of depositing material (119) on an outer surface of one of said walls (110) opposite an end position (117) of the intermediate web.

Inventors:
HAEGGANDER JAN (SE)
Application Number:
PCT/SE2006/000895
Publication Date:
January 24, 2008
Filing Date:
July 19, 2006
Export Citation:
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Assignee:
VOLVO AERO CORP (SE)
HAEGGANDER JAN (SE)
International Classes:
F02K9/64; B23K26/28; F02K9/97
Domestic Patent References:
WO2000020749A12000-04-13
Foreign References:
US4781019A1988-11-01
EP1564398A12005-08-17
EP0122071A11984-10-17
Attorney, Agent or Firm:
FRÖHLING, Werner (Corporate Patents 0682, M1.7 Göteborg, SE)
Download PDF:
Claims:

CLAIMS

1. Method for manufacturing a wall structure (101) comprising the steps of

- providing two walls (106,110) at least substantially in parallel to one another and at least two webs

(107.109) that connect the two walls and delimit a cooling channel (115) between said walls, said cooling channel extending in a divergent manner from a narrow cooling channel section (111) , - providing an intermediate web (108) between said two webs (107,109) so that it connects the two walls

(106.110) and divides a single diverging cooling channel (115) into two separate cooling channels (215,315), positioning the intermediate web (108) so that it ends at a distance from the narrow cooling channel section, and

- depositing material (119) on an outer surface of one of said walls (110) opposite an end position (117) of the intermediate web.

2. Method according to claim 1, comprising the step of depositing the material (119) to about the same thickness as the wall thickness.

3. Method according to claim 1 or 2, comprising the step of depositing the material (119) in at least two layers on top of each other.

4. Method according to any preceding claim, comprising the step of attaching the intermediate web (108) to at least one of the walls (110) before the step of depositing said material (119) .

5. Method according to claim 4, comprising the step of attaching the intermediate web (108) to at least one of the walls (110) via affecting the wall from an outside of the wall relative to the cooling channels .

6. Method according to claim 4, comprising the step of attaching the intermediate web (108) to at least one of the walls (110) by welding from an outside of the wall relative to the cooling channels .

7. Method according to any of claims 4-6, comprising the step of depositing the material (119) so that the deposited material covers an attachment stop (401) .

8. Method according to any preceding claim, comprising the step of providing the webs (107,108,109) so that they extend at right angles with regard to the walls (106,110) .

9. Method according to any preceding claim, comprising the step of machining a surface of a sheet work-piece so that one of said walls (106) is formed with the webs (107,108,109) in one-piece.

10. Method according to claim 9, comprising the step of using a cutter with two spaced cutting wheels arranged at a mutual distance corresponding to a desired web thickness .

11. Method according to claim 10, comprising the step of cutting the webs (107,108,109) from the work piece so that a distance between the adjacent webs (107,109) forming the single diverging cooling channel is about

the same as a width of the cutter at a position of the intermediate web end (117) .

12. Method according to any of claims 9-11, comprising the step of positioning the other of said walls (110) in parallel to the machined wall (106) and in contact with the edges of the webs (107,108,109), and thereafter attaching the other wall (110) to the edges of the webs.

13. Method according to any preceding claim, forming the wall structure so that it encompasses a gas duct (105).

14. Method according to claim 13, comprising the steps of providing a plurality of intermediate webs (108) , each between two adjacent webs (107,109), so that a plurality of the intermediate webs end at substantially the same position in the direction of a wall structure centre axis (103), and depositing the material (119) in a continuous manner around the wall structure.

15. Method according to any preceding claim, forming the wall structure to withstand a high thermal load during operation.

16. Method according to any preceding claim, wherein the wall structure (101) is shaped to form a tubular wall structure with a varying diameter along a centre axis, wherein the walls (106,110) form an inner wall and an outer wall and the webs (107,108,109) are circumferentially spaced between the inner and outer wall so that the cooling channels extend in a divergent manner from a narrow section (111) of the wall structure

to a wide section of the wall structure, and depositing the material on a radially outer surface of the wall structure.

17. Method according to any preceding claim, forming the wall structure to form an engine wall structure.

18. Method according to any preceding claim, forming the wall structure to form a rocket engine member.

19. Method according to any preceding claim, forming the wall structure to form an outlet nozzle for use in a liquid fuel rocket engine.

20. A wall structure (101) comprising two walls (106,110) at least substantially in parallel to one another and at least two webs (107,109) that connect the two walls and delimit a cooling channel (115) , between said walls, said cooling channel extending in a divergent manner from a narrow cooling channel section

(111), wherein an intermediate web (108) is located between said two webs so that it connects the two walls and divides a single diverging cooling channel into two separate cooling channels (215,315), wherein the intermediate web ends at a distance from the narrow cooling channel section (111) , and wherein material

(119) is deposited on an outer surface of one of said walls opposite an end position of the intermediate web.

21. A wall structure according to claim 20, wherein the deposited material has about the same thickness as the wall thickness .

22. A wall structure according to claim 20 or 21, wherein the wall structure is adapted to encompass a gas duct (105) .

23. A wall structure according to claim 22, wherein the wall structure comprises a plurality of intermediate webs, each between two adjacent webs, and that a plurality of the intermediate webs end at substantially the same position in the direction of a wall structure centre axis, and that deposited material is arranged in a continuous manner around the wall structure.

24. A wall structure according to any of claims 20-23, wherein the wall structure is adapted to withstand a high thermal load.

25. A wall structure according to any of claims 20-24, wherein the wall structure is adapted to form an engine wall structure.

26. A wall structure according to any of claims 20-25, wherein the wall structure is adapted to form a rocket engine member .

27. A wall structure according to any of claims 20-26, wherein the wall structure is adapted to form an outlet nozzle for use in a liquid fuel rocket engine.

Description:

Method for manufacturing a wall structure

TECHNICAL FIELD

The present invention relates to a method for manufacturing a wall structure. The method is particularly directed to manufacturing a wall structure, which is capable of withstanding a high thermal load, and especially to an engine wall structure. The method is specifically directed to manufacturing the wall structure of a combustion chamber or an outlet nozzle for use in rocket engines . The invention is further directed to a corresponding wall structure.

BACKGROUND OF THE INVENTION

During operation, a rocket nozzle is subjected to very high stresses, for example in the form of a very high temperature on its inside (in the magnitude of 800 °K) and a very low temperature on its outside (in the magnitude of 50 °K) . As a result of this high thermal load, stringent requirements are placed upon the choice of material, design and manufacture of the outlet nozzle. At least there is a need for effective cooling of the outlet nozzle.

The wall structure forming the outlet nozzle has a tubular shape with a varying diameter along a centre axis . More specifically, the outlet nozzle wall structure has a conical or parabolic shape. The outlet nozzle normally has a diameter ratio from the aft or large outlet end to the forward or small inlet end in the interval from 2:1 to 4:1.

The outlet nozzle wall structure comprises cooling channels extending between an upstream end and a downstream end of the nozzle. The outlet nozzle wall structure comprises an inner wall, to which hot gas is admitted during engine operation and an outer wall, which is colder than the inner wall during engine operation.

There is a plurality of elongated webs connecting the inner wall to the outer wall dividing the space between the walls into a plurality of cooling channels.

During engine operation, any cooling medium may be used to flow through the cooling channels . Regarding a rocket engine, the rocket engine fuel is normally used as a cooling medium in the outlet nozzle. The rocket engine may be driven with hydrogen or a hydrocarbon, i.e. kerosene, as a fuel. Thus, the fuel is introduced in a cold state into the wall structure, delivered through the cooling channels while absorbing heat via the inner wall and is subsequently used to generate the thrust. Heat is transferred from the hot gases to the inner wall, further on to the fuel, from the fuel to the outer wall, and, finally, from the outer wall to any medium surrounding it. Heat is also transported away by the coolant as the coolant temperature increases by the cooling. The hot gases may comprise a flame generated by a combustion of gases and/or fuel.

The strength and the life of the cooling channel walls are limited by the width of the cooling channel. The wall structure is loaded from internal pressure and thermal

loads . There are further restrictions on wall thickness from thermal stresses and from a weight point of view.

According to a known rocket engine outlet nozzle, the wall structure is formed by helically arranged tubes. Such a spiral winding of the tubes means that the cooling channels are long and hence give rise to a large pressure drop in the flow of cooling medium.

A further known rocket engine outlet nozzle is described in WO 00/20749. According to a method for manufacturing the nozzle, the webs are integrated in and project from the channel inner wall . A channel outer wall is positioned around the inner wall, and joined to the edges of the webs by welding. In this manner, the cooling channels may be parallel to the longitudinal axis of the nozzle. Such straight cooling channels have a shorter length relative to the above described helically arranged tubes. In order to obtain the desired diameter ratio of the nozzle, the cross sectional area of the cooling channels must increase towards the part of the nozzle with a larger diameter. The nozzle is therefore normally built in several sections in the axial direction. The number of webs is larger in the nozzle section with larger diameter. Adjacent axial sections are joined by a weld at the inner wall . The webs are interrupted and a manifold is arranged in a tangential direction between the ends of the webs forming a tangential cooling duct. The duct allows a tangential flow, which makes it difficult to control the flow accurately along the full length of the cooling channel. This leads to that the manifold is normally located close to the nozzle exit. This increases the weight since the manifold will have a

large diameter and the cooling channels from the engine to the nozzle manifold will be long, which leads to that the manifold and cooling channels become more exposed to vibrations and heat loads .

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for manufacturing a wall structure provided with cooling channels which extend in a diverging manner, which creates conditions for an increased stability of the wall structure during operation and/or a long cyclic life. The invention is especially adapted for manufacturing a tubular wall structure with an increasing diameter with axial position and particularly for a rocket engine member. Especially, there is a desire to provide a method that creates conditions for eliminating the joint between adjacent sections.

This object is achieved with a method according to claim 1. Thus, it is achieved by the the steps of providing two walls at least substantially in parallel to one another and at least two webs that connect the two walls and delimit a cooling channel between said walls, said cooling channel extending in a divergent manner from a narrow cooling channel section, providing an intermediate web between said two webs so that it connects the two walls and divides a single diverging cooling channel into two separate cooling channels, positioning the intermediate web so that it ends at a distance from the narrow cooling channel section, and depositing material on an outer surface of one of said walls opposite an end position of the intermediate web.

In this way, all parts can be made from the same material, or similar materials, which is advantageous for heat treatment, for corrosion problems and repairability. Further, due to the fact that there are no additional parts, the invention creates conditions for a facilitated manufacturing with regard to logistics, an easier handling in the tools, and fitting of parts. Further, metal deposition can easily be performed with varying thickness in order to achieve different functionality in different portions.

According to a preferred embodiment of the invention, the method comprises the step of attaching the intermediate web to at least one of the walls before the step of depositing said material.

Thus, a metal deposition (MD) reinforcement is introduced to allow for a stop of a web attachment line (for example a weld) to the wall at a distance from the wall structure end. In this way, a simple start/stop of the attachment (for example welding) process is feasible. Further, the metal deposition reduces stresses from outer loads during operation and induces a compressive stress in the attachment stop area. Further, the MD reinforcement forms a solid structure that provides additional crack growth path before leakage. Further, the inner wall thickness may be decreased or maintained while improving or maintaining the stability and cyclic life of the wall structure. Further, the method creates conditions for a wall structure with a high pressure capacity, a low coolant pressure drop and an advantageous area ratio.

According to a further preferred embodiment of the invention, the method comprises the step of attaching the intermediate web to at least one of the walls by welding from an outside of the wall relative to the cooling channels . Preferably, the material is positioned so that it covers a weld stop.

According to a further preferred embodiment of the invention, the method comprises the step of providing a plurality of intermediate webs, each between two adjacent webs, so that a plurality of the intermediate webs end at substantially the same position in the direction of a wall structure centre axis, and depositing the material in a continuous manner around the wall structure.

The invention is further directed to a corresponding wall structure.

Advantageous embodiments of the invention can be derived from the following description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in the following, in a non-limiting way with reference to the accompanying drawings in which:

FIG 1 is a partly cut, perspective view showing a wall structure defining a rocket engine nozzle,

FIG 2 is a partial sectional view along the line A-A in Fig. 1, showing a plurality of cooling channels at the inlet end of the nozzle,

FIG 3 is a cut, perspective view of the wall structure welds in the vicinity of the intermediate web ends,

FIG 4 is a cut side view of the intermediate web ends in the circumferential direction of the wall structure, and

FIG 5 is a cut front view of the intermediate web ends in the radial direction of the wall structure.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a diagrammatic and somewhat simplified perspective view of a wall structure 101 that is produced according to the present invention. The wall structure 101 is tubular with a varying diameter along a centre axis 103 and encompasses a gas duct 105. Thus, the wall structure 101 forms a hollow component. More specifically, the wall structure 101 presents a rotational symmetric outer surface that internally defines the gas duct 105. The diameter of the wall structure 101 increases with axial position.

Further, the wall structure 101 is adapted to withstand a high thermal load. The wall structure 101 is therefore provided with cooling channels for internal cooling. More specifically, the wall structure 101 forms an engine wall structure. The wall structure 101 forms a rocket engine member for a thrust chamber. The thrust chamber is a combustion chamber with an outlet nozzle for expansion of the combustion gases. More specifically, the wall structure forms an outlet nozzle for use in a liquid fuel rocket engine.

One embodiment of the method for manufacturing the wall structure 101 will be described below, see figure 1-5. A surface of a sheet work-piece is machined so that an inner wall 106 is formed with circumferentialIy spaced elongated

webs 107,108,109 projecting from the inner wall 106 and at right angles to the wall. In other words, the method comprises milling a plurality of grooves in the outer surface of a monolithic channel wall section. The inner wall 106 forms a cylinder and is preferably continuous in a circumferential direction. The webs 107,108,109 are parallel to the longitudinal centre axis 103 of the wall structure 101.

The webs 107,108,109 are adapted to form mid walls between the inner wall 106 and an outer wall 110. Thus, the webs form distancing elements for keeping a distance between the inner and outer walls 106,110.

Preferably, a cutter is used with two spaced cutting wheels arranged at a mutual distance corresponding to a desired web thickness. Thus, the webs 107,108,109 are integrated in the inner wall 106. In other words, the inner wall 106 and the webs 107,108,109 are formed in one- piece.

A tubular outer wall 110 is positioned around the inner wall, see figure 2, and thereafter joined to the edges of the webs 107,108,109 by welding from an outer side of the outer wall relative to the cooling channels, see figure 3. The outer wall 110 forms a cylinder and is preferably continuous in a circumferential direction. Thus, the wall structure 101 forms a welded sandwich structure.

Preferably, laser-welding is used for joining the outer wall 110 to the webs. The welding is performed in such a way that the joined-together portions of the wall 110 and each web 107 form a T-shaped joint 301, see figure 3.

Suitable selection of material parameters and welding parameters makes it possible to obtain a T-shaped joint with rounded corners, or at least a relatively smooth transition, between the wall and the respective web. This results in a high-strength construction and thus an extended life. Alternatively, a construction with thinner wall thicknesses and thus reduced weight can be obtained.

In order that the welded joint comes to lie in exactly the correct position, a previously known joint-tracking technique can be used.

Every second web 107,109 extends all the way from an inlet end 111 of the nozzle 101 to an outlet end 113 of the nozzle. Two adjacent webs 107,109 at the inlet end 111 delimit a single diverging cooling channel 115 between the inner wall 106 and the outer wall 110. An intermediate web 108 is provided between said two longer webs 107,109 so that it divides the single diverging cooling channel 115 into two separate cooling channels 215,315. Thus, the intermediate web 108 ends at a distance from the inlet end 111 of the nozzle 101. In other words, the intermediate webs 108 form additional mid walls.

Thus, a cooling channel cross section area increases progressively in direction from the inlet end 111 of the wall structure 101 to the position of the intermediate web end 117, where the channel is split in two. Further, a cooling channel cross section area increases progressively in direction from the position of the intermediate web end 117 and then towards its outlet end 113. Further, the cooling channels 115,215,315 extend substantially in parallel to the longitudinal axis 103 of

the nozzle 101 from the inlet end 111 of the nozzle to its outlet end 113.

The webs 203,205 are cut from the work piece so that a distance between the adjacent webs 107,109 forming the single diverging cooling channel 115 is about the same as a width of the complete cutter at a position of an end 117 of the intermediate web 108.

The ends 117 of the intermediate webs 108 are machined so that the ends are chamfered. In other words, the end 117 presents a gentle slope from a top edge of the web 108 to the surface of the wall 106. The method comprises the step of welding the intermediate web 108 to a position 401 at a distance from the start of the slope 117, see figure 4. Thus, the position 401 defines a weld stop. The welding is preferably realized by means of continuous fusion welding.

Further, material 119 is deposited on an outer surface of the outer wall 110 opposite the end position 117 of the intermediate web 108. More specifically, the material is deposited so that it covers the weld stop 401, see figure 4. The material is preferably deposited symmetrically with regard to the weld stop 401. Thus, the layers of deposited material 119 are centered on the same axial position of the wall structure 101 as the weld stop 401 and extend a distance in both directions in the axial direction.

A plurality of the intermediate webs 108 ends at substantially the same position in the direction of the wall structure centre axis 103. The material 119 is therefore deposited in a continuous manner around the wall structure 101. The material 119 is deposited to about the

same thickness as the wall thickness. Further, the material 119 is deposited in a plurality of layers on top of each other, see figure 4.

The nozzle 101 is intended for use in rocket engines of the type using liquid fuel, for example liquid hydrogen. The nozzle 101 is cooled with the aid of a cooling medium that is preferably also used as fuel in the particular rocket engine. The invention is however not limited to outlet nozzles of this type but can also be used in those cases in which the cooling medium is dumped after it has been used for cooling.

The materials used for the walls 106,110 and webs 107,108,109 consist of weldable materials, such as stainless steel, for example of the type 347 or A286. Use can alternatively be made of nickel-based alloys such as, for example, INCO600, INCO625, INCO718 and Hastaloy x.

According to other variants, cobalt-based alloys, for example of the type HAYWES 188 and HAYNES 230, can be used. Various types of aluminum alloys can also be used.

Combinations of different materials are also possible.

For the welding operation, laser-welding is preferably used, but other types of welding arrangement, for example an electro-beam welder, can also be used according to the invention.

By accurate matching of the welding procedure, material selection and dimensions of walls and webs, the laser- welding produces the T-shape at the joint and also a softly rounded shape on the inner corners between the outer wall 110 and the web edge. Welding is suitably

effected by means of a continuous weld. The rounded shape of the welded joints results in a high-strength construction and thus a long life of the component. This type of joining together affords opportunities for complete fusion of the welded joint and fine transitions between the parts .

The invention is not limited to the above-described embodiments, but several modifications are possible within the scope of the following claims. For example, the joining of two sections may be performed differently than described.

According to an alternative to laser welding, soldering may be used to attach the outer wall 110 to the webs 107,108,109. Further, solid state welding, e.g. friction welding may be used. According to a further alternative, the outer wall 110 is built up via an electrochemical process, such as plating.

According to an alternative method step, the full length webs and/or the shorter intermediate webs may be applied on the inner wall by depositing material on the wall surface. After the metal deposition, excess material may be removed by a machining process in order to create the desired shape of the webs.

According to a further alternative method step, the wall structure may be formed by providing a plurality of preprocessed, elongated, curved profile members, arranging the profile members next to each other and joining the profile members to each other, preferably by welding. Each profile member has a diverging cross sectional shape in

its longitudinal direction. Each profile member in cross section has a web and flanges extending from opposite sides of the web at right angles to the web, wherein the cooling channels are formed by adjacent webs and adjacent pairs of flanges . The profile member may have a cross section shape of a C and/or an E. Profile members of different cross sectional shapes may be attached next to each others . At least some of the profile members are processed to present said intermediate web ending at a distance from the end of the complete wall structure. The profile members may be formed by forging. Alternatively, the profile members are preprocessed by forming a sheet metal plate.