WO2010131990A1

WO2010131990A1 - Metal-to-composite high-pressure cylinder

Info

Publication number: WO2010131990A1
Application number: PCT/RU2009/000232
Authority: WO
Inventors: Сергей Владимирович ЛУКЬЯНЕЦ; Николай Григорьевич МОРОЗ
Original assignee: Lukyanets Sergei Vladimirovich; Moroz Nikolai Grigorievich
Priority date: 2009-05-14
Filing date: 2009-05-14
Publication date: 2010-11-18
Also published as: EP2461081A4; EP2461081A1

Abstract

The invention is directed at preventing a ring welded joint between a cylindrical part and a bottom from being stressed. The metal-to-composite high-pressure cylinder comprises a thinwalled metal welded liner and an outer pressure shell that is made of a composite material and formed by the combination of the layers of high-modulus and low-modulus yarns of reinforcing materials, which yarns are oriented in helical and peripheral directions; furthermore, a ring lens compensator is made in the shell of the liner in the areas of a ring weld seam and at least one annular collar for limiting axial deformations is disposed in the structure of the wall of the composite pressure shell above the lens compensator, which annular collar is rigidly attached along the entire surface thereof to the independent groups of the continuous reinforcing yarns; furthermore, the width of the collar is greater than the width of the compensator and the number of the collars-limiters is determined according to a condition of limiting the value of the compensator axial deformation and the elasticity of the used material.

Description

Metal Composite High Pressure Cylinder

Technical field

The invention relates to the field of gas equipment, namely to metal composite high-pressure cylinders used, in particular, in portable oxygen breathing apparatus for climbers, rescuers, in portable products of cryogenic and fire fighting equipment, gas supply systems and other industries.

State of the art

Currently produced metal-composite high-pressure cylinders contain an internal thin-walled metal hermetic shell - a liner and an external power shell of composite material formed by winding high-modulus fiber bundles (e.g. carbon fiber) impregnated with a binder on the surface of the liner.

Among the requirements for high-pressure gas cylinders, priority are: reducing the specific material consumption of the cylinder, determined by the ratio of the mass of the cylinder to its volume, and ensuring a high resource in the number of loading cycles during safe operation of the cylinder.

Known metal-plastic high-pressure cylinder containing a stamped-welded sealed steel liner and an external power shell made of composite material. The liner contains the middle cylindrical part, two bottoms and has a wall thickness equal to (0.5-0.9) mm. The bottoms are connected to the middle part by welding through washers, providing a smooth outer surface of the liner in place of the weld. At least one fitting is welded to one of the bottoms (see RU 2077682 Cl, 04/20/1997).

For the manufacture of the liner using a steel billet of thin sheet metal. The cylindrical part of the liner is obtained from sheet steel billets rolled into a cylinder and butt welded, for example, by electron beam welding. The bottoms are performed by the known method of cold drawing from the same sheet metal. Moreover, since the depth of the bottoms is insignificant, as a rule, no more than 0.32 of the outer diameter, their thickness after drawing is comparable with the thickness of the cylindrical workpiece. Bottoms around the perimeter are welded to the cylindrical part through washers. When this is used, for example, electron beam or laser welding. Welded, stamped-welded technologies make it possible to manufacture steel liners with rather thin walls and, thereby, provide a relatively low specific material consumption of the cylinder.

However, the known design of metal-plastic cylinders with welded or stamped-welded steel liners have a relatively low resource in the number of loading cycles due to possible destruction of the liner in the area of the welded bottom.

A composite high-pressure cylinder is known, comprising a thin-walled metal welded liner and an external power shell made of composite material formed by a combination of groups of layers of high-modulus and low-modulus strands of reinforcing materials oriented in spiral and circumferential directions. The cylinder is equipped with stainless steel rings mounted on the outside and inside of the liner at the junctions of the cylindrical shell with bottoms (see RU 2140602 Cl, 10.27.1999).

A disadvantage of the known design of a cylinder with a welded steel liner is the relatively low resource in the number of loading cycles due to the possible destruction of the liner in the region of the welded bottom joint.

Disclosure of invention

The results of comprehensive studies of the fatigue characteristics of ring welds of steel pipes show that even small defects in the weld can have a significant impact on its performance. Important A feature of ring welded joints is the need for their alignment (adjustment). Any distortion in this case will lead to local secondary bending in the case of a load on the joint in the transverse direction relative to the weld and distortion in the joint of the parts is the main reason for the relatively low fatigue characteristics of the weld. Another significant point in the welding of circumferential joints is the nature of the residual welding stresses. There are no rigid and established rules that determine the nature of residual stresses in welded annular seams, but practical experience based on the measurement results, together with the analysis performed by the finite element method, shows that they are always tensile in the root zone of annular welds. In this case, even if the external stress cyclically changed from tension to compression, the actual stress range is practically tensile.

The present invention is based on the task of creating a metal-plastic high-pressure cylinder, which allows to exclude loading of the annular welded joint of the cylindrical part with the bottom and thereby increase the strength of the liner and the resource of the cylinder by the number of loading cycles while maintaining a low specific material consumption of the cylinder.

The technical result of the invention is:

- the fulfillment of the compatibility condition for deformations of materials in the local zone of the weld, in which the axial stiffness of the composite shell is changed and zero tensile or compressive axial deformations in the liner material are achieved and thereby exclude axial loading of the weld;

- the complete exclusion of deformation of the weld without introducing additional disturbances in the deformation of the liner in the circumferential direction;

- ensuring a uniform structure of the liner shell and eliminating the influence of the weld on the operability of the cylinder structure as a whole. The technical result is achieved due to the fact that the metal-composite pressure cylinder contains a thin-walled metal welded liner and an external power shell made of composite material formed by a combination of groups of layers of high-modulus and low-modulus threads of reinforcing materials oriented in spiral and circumferential directions, while in the zone of the ring weld an annular lens compensator is made in the liner shell, and in the wall structure of the composite power shell of the balloon above the lens compensator Credited at least one annular bracelet - axial deformation limiter fixedly bonded over the entire surface with independent groups of continuous reinforcing filaments with a width greater than the width of the compensator and the amount brasletov- constraints determined from the condition of axial strain limit value compensator and elasticity of the material used.

The forming surface of the lens compensator can be made in the form of a surface consisting of two nodoids connected by a weld.

The forming surface of the lens compensator can be made in the form of a surface consisting of parts of toroidal surfaces with radii of their cross sections amounting to 5-7 heights of the lens compensator.

The lens compensator may have at least one circumferential ridge located in the section of the weld.

The width of the lens compensator is at least 30-40 thicknesses of the liner shell

The forming surface of the lens compensator can be made cylindrical, while the compensator is partially embedded in the bracelet - axial strain limiter.

The first bracelet-limiter of axial deformations from the surface of the liner may have a meridional curvature that substantially coincides with the meridional curvature of the compensator, and subsequent limiters are parallel to the first in the structure of the composite material with dressing with reinforcing threads of the composite shell.

Ring bracelets - axial strain limiters can be made with different coefficients of longitudinal and transverse deformation.

Ring bracelets - axial deformation limiters can be made of single-strand high modulus cord fabric.

Ring bracelets - axial deformation limiters can be made from a combination of high-modulus and low-modulus groups of flexible continuous threads.

A group of high-modulus threads can be made of metal cord threads, and a group of low-modulus threads can be made of fiberglass threads.

A group of high-modulus threads can be made of high-modulus carbon threads, and a group of low-modulus threads can be made of polyamide threads.

Brief Description of the Drawings of the Invention

In FIG. 1 shows a general view of a high pressure cylinder.

In FIG. 2 shows a general view of the cylinder liner.

In FIG. 3 shows a general view of a high pressure cylinder.

In FIG. 4 - installation diagram of bracelets - axial deformation limiters.

In FIG. Figure 5 shows the pattern of changes in axial strains in the composite shell material along the length of the cylinder generatrix in the weld zone. In FIG. 6 shows the nodoid shape of the generatrix surface of the compensator.

Embodiments of the invention

As shown in FIG. 1, the high-pressure cylinder contains a liner 1 and a composite shell 2. Moreover, the liner consists of a cylindrical shell 3, welded bottoms 4 to it, and a fitting 5, also welded to one of the bottoms 4. In the welding zone of the cylindrical shell and the bottom, a lens compensator is made in the liner, as shown in FIG. 4 and FIG. 5.

Due to the fact that the main load during the operation of the container is the internal pressure of the medium, during the operation of the structure in the material of the liner and composite shell various levels of deformation can occur. Moreover, if in the circumferential direction the deformations in the material of the liner and the composite shell are compatible, then in the axial direction this condition is not always satisfactory, and the liner can slip relative to the composite shell. These slippage results in increased deformations in the liner material and are usually localized in the welded joint. To ensure the compatibility of axial deformations in the local zone of the liner weld, a lens compensator is made, which, due to changes in geometry and internal pressure support, provides this condition for the compatibility of the deformation of materials of the zone in question.

Obviously, the meridional deformation ε _ma in its material has a decisive influence on the operability of an annular weld in a liner.

When the conditions for compatibility of deformation of materials in the local zone of the weld are met, locally changing the axial stiffness of the composite shell, it is possible to achieve zero tensile or vice versa compressive axial deformations in the liner material and thereby completely eliminate the loading of the weld (see Fig. 5). To accomplish this task, it is advisable to introduce bracelets limiters of axial deformation into the structure of the composite material 6. The essence of the design of such a bracelet lies in the fact that its axial tensile stiffness, together with the axial stiffness of the composite shell, significantly reduces deformations in the local zone of the weld and, at the same time, does not introduce disturbances in the stiffness of the composite shell in the circumferential direction. Such design properties of the bracelets of axial deformation limiters make it possible to completely turn off the deformation of the weld without introducing additional disturbances in the deformation of the liner in the circumferential direction. In FIG. 5 shows a picture of changes in axial deformations in liner material in the presence of bracelets in the balloon design - axial deformation limiters.

To obtain designs of bracelets - limiters of axial deformations, it is possible to use various structural schemes. For example, it is possible to design a bracelet in the form of metal profile plates of lamellas connected in a circumferential direction by a low-modulus material. It is possible to design a bracelet in the form of a combination of high-modulus and low-modulus threads oriented in different directions, or a scheme for using a single-strand high-modulus cord fabric. Various joint combinations of the proposed schemes are also possible.

When the cylinder is loaded with internal pressure, the bracelets, the limiters, are subjected to pronounced deformation gradients, which lead to the appearance of longitudinal and transverse shear stresses between them and the intersecting layers of the composite material. These stresses can lead to cracking in the composite, adversely affecting the life of the balloon. It is known from mechanics that considering the pattern of inclusion of the axial stiffness of bracelets - stoppers and the composite material of the power shell, the minimum distance necessary to exclude marked cracking should be at least 3 - 5 wall thicknesses of the composite material or correlating with the wall thickness of the liner this ratio should be at least 15 - 20 For these reasons, the width of the local compensator in the liner should be at least 30 to 40 liner wall thicknesses.

Obviously, when performing the compensator, it is necessary to create a special shape of its surface, which would exclude the influence of moment strains in the liner material. Such surfaces include surfaces, which in mechanics are called nodoid and unduloid.

The generators of the nodoid and unduloid membranes are shown in FIG. 6 are described in parametric form as follows:

where '^ ^r i) / ^{/ "} i is the module of the elliptic integral, * is the additional module, F, E are elliptic integrals of the first and second kind,

Is the parameter characterizing the generatrix curve, i is the radius of the cylindrical part of the shell.

At 0

> ^r i

the shell is called a nodoid, when the shell becomes spherical. It should be noted that the generatrix of the nodoid (unduloid) is described by the focus of the ellipse (hyperbola), if you roll it in a straight line. Such shells have a maximum volume, a minimum surface area, and the angle of inclination of the tangent to the generatrix in them tends to zero as they approach the junction with a cylindrical or some other shell.

Nodoid, unduloid shells when loaded with internal pressure have the property of equal strength and have an advantage in strength compared with elliptical and spherical shells, the level of stresses arising in them with this type of loading is much lower. One of the characteristic properties of the shell under consideration, as it is easy to notice, is that when approaching the junction with the cylinder, there is a fairly smooth conjugation of the shell with it and bending stresses in the joint are practically absent, that is, the influence of edge effects is completely eliminated.

The use of such a shape of the surface of the compensator eliminates the appearance of local zones of deformation in the liner and thereby significantly increase its reliability in operation. Thus, performing the design of the cylinder according to the above diagram provides an almost completely homogeneous structure of the liner shell and excludes the influence of the weld on the operability of the cylinder structure as a whole.

The functioning of the high-pressure cylinder of the proposed design consists in filling it with a fluid / liquid or gas / to the required pressure level, storage, transportation, emptying, subsequent new filling, expenditure of fluid, i.e. in the repetition of actions and operations with multiple cyclic loading.

Industrial applicability

With the creation of the proposed device, there was a real opportunity to use high-pressure vessels of various materials using a welded thin-walled metal inner shell - liner. The manufacture and testing of pressure vessels with the proposed liner for their sealing confirmed their high reliability and efficiency. The present invention can be used in portable oxygen breathing apparatus of climbers, rescuers, in portable products of cryogenic and fire fighting equipment, gas supply systems and automotive equipment.

Claims

Claim

1. Metal-composite high-pressure cylinder, characterized in that it contains a thin-walled metal welded liner and an external power shell made of composite material formed by a combination of groups of layers of high-modulus and low-modulus threads of reinforcing materials oriented in spiral and circumferential directions, while in the zone of the annular weld an annular lens compensator is made in the liner shell, and is installed in the structure of the wall of the composite power shell of the cylinder above the lens compensator, shey least one annular bracelet - axial deformation limiter fixedly bonded over the entire surface with independent groups of continuous reinforcing filaments with a width greater than the width of the compensator and the amount brasletov- constraints determined from the condition of axial strain limit value compensator and elasticity of the material used.

2. The cylinder according to claim 1, wherein the forming surface of the lens compensator is made in the form of a surface consisting of two nodoids connected by a weld.

3. The cylinder according to claim 1, wherein the forming surface of the lens compensator is made in the form of a surface consisting of parts of toroidal surfaces with radii of their cross sections amounting to 5-7 heights of the lens compensator.

4. The cylinder according to claim 1, wherein the lens compensator has at least one circumferential ridge located in the section of the weld.

5. A cylinder according to claim 1 _λ or according to any one of claims 2 to 4, in which the width of the lens compensator is at least 30-40 liner shell thicknesses

6. The cylinder according to claim 1, wherein the forming surface of the lens compensator is cylindrical, and the compensator is partially embedded in the bracelet - axial strain limiter.

SUBSTITUTE SHEET (RULE 26)

7. The bottle according to claim 1, in which the first from the surface of the liner bracelet-limiter of axial deformation has a meridional curvature substantially coinciding with the meridional curvature of the compensator, and the subsequent stoppers are parallel to the first in the structure of the composite material with ligation of the composite shell reinforcing threads.

8. A cylinder according to claim 1, wherein the ring bracelets are axial strain limiters made with different longitudinal and transverse strain coefficients.

9. The bottle according to claim 1, wherein the ring bracelets are axial deformation limiters made of single-strand high-modulus cord fabric.

10. The cylinder according to claim 1, wherein the ring bracelets are axial deformation limiters made of a combination of high-modulus and low-modulus groups of flexible continuous threads.

11. The bottle of claim 10, in which the group of high-modulus threads is made of metal cord threads, and the group of low-modulus threads is made of fiberglass threads.

12. The cylinder of claim 10, in which the group of high-modulus threads is made of high-modulus carbon threads, and the group of low-modulus threads is made of polyamide threads.

SUBSTITUTE SHEET (RULE 26)