RU2754572C1 - High-pressure metal-composite cylinder with large-diameter necks - Google Patents

Abstract

FIELD: gas equipment.SUBSTANCE: invention relates to the field of gas equipment and can be applied to high-pressure vessels used, in particular, in portable products of cryogenic and fire-fighting equipment, gas supply systems, automotive equipment, pneumatic systems and other devices. A metal-composite high-pressure cylinder with large-diameter necks contains an internal cylindrical thin-walled metal tube, metal connecting flanges inserted into it and a power shell made of high-strength composite materials. The surface of the connecting flanges on one side is made in the form of a part of a nodoid or unduloid of rotation with a maximum diameter equal to the inner diameter of the tube, and with a ratio of a smaller diameter to the diameter of the tube 0.71 - 0.83 and has an end section in the form of a polyhedral prism of a non-circular cylinder separated from the surface of the nodoid or unduloid by an annular groove, and the ends of the tube are compressed by plastic deformation along the surfaces of the flanges in the form of nodoids or unduloids, and are fixed in the annular grooves of threaded flanges, at the same time, the power shell made of composite materials consists of layers of high-strength and high-modulus spiral reinforcement threads with reinforcement angles of 45-56° with a ratio between the membrane stiffness of a thin-walled metal tube and a power composite shell in the annular direction in the range of 0.56-0.58 and tightly covers the end sections of the connecting flanges of non-circular shape with the formation of a strong connection with them.EFFECT: simplicity of technological implementation.6 cl, 6 dwg

Description

The present invention relates to the field of gas equipment and can be applied to pressure vessels used, in particular, in portable products for cryogenic and fire-fighting equipment, gas supply systems, automotive equipment, pneumatic systems and other devices.

Among the requirements for gas cylinders, the priority is to reduce the specific material consumption of the cylinder, determined by the ratio of the cylinder mass to its volume, and to ensure a high resource in terms of the number of loading cycles during safe operation of the cylinder.

The practical attractiveness of cylinders with a body made of a composite material lies in the fact that they have a fairly low weight, are easily transported and are able to withstand significant pressure (300-450 bar) with multiple loading cycles.

Such cylinders (vessels), as a rule, are subject to repeated high pressure cyclic loads. In cylinders of this type, in order to avoid fluid leaks or leakage, particular importance is attached to the material and construction of the sealing shell - liner, which, depending on the type and nature of the fluid filling the vessel, is made of thermoplastic, aluminum or steel. Currently, the most widespread are cylinders using metal liners, which is determined by a number of advantages of metals over plastics.

Currently produced metal-plastic high-pressure cylinders contain an inner metal hermetic shell - a liner and an external power plastic shell formed by winding a bundle of high modulus fiber (for example, glass fiber, carbon fiber, organic fiber) impregnated with a binder onto the surface of the liner.

There are numerous examples of creating pressure cylinders from a composite material using a metal liner made of various alloys (see, for example, patents: US 5494188, US 5538680, US 5653358, US 5862938, US 5938209, US 5979692, US 6190598, US 6202674, US 6202674, US 6230922, US 2003111473, US 6810567). There are also known numerous examples of creating composite pressure cylinders using thin-walled metal liners from various alloys (see, for example, patents US 3066822, US 3446385, US 5292027, US 5,822,838, US 5918759, WO 03/029718, RU 2255829, JP 2005133847, WO 2005022026, RU 2149126, RU 2094695. RU 2077682, RU 2001115743, RU 2000123739, RU 2140602, RU 2187746, RU 93049863, RU 2065544, RU 2001115191, RU 2003115384, RU 2002101904, GB 1161846, EP 0497687 US 5287988).

The method of manufacturing such structures, as a rule, is the method of winding, which is considered in sufficient detail in a number of patent and technical literature (Bulanov I.M., Vorobey V.V. Technology of aerospace structures from composite materials, Moscow, Publishing house of the Moscow State Technical University named after N. E. Bauman, 1998; Composite materials, Handbook, Edited by V.V. Vasiliev, Yu.M. Tarnopolsky - M, Mechanical Engineering, 1990; Composite materials, T 1-7, (translated from English) Edited by, L Brautman, R Kroca, M. Mechanical Engineering, 1978; Handbook of Composite Materials (translated from English) / Edited by J. Lubin. M .. Mechanical Engineering, 1988; Balakirev BC et al. Automated production of products from composite materials - M .: Chemistry, 1990; Obraztsov I.O., Vasiliev V.V., Bunakov V.A. . Composite pressure cylinders., Moscow, Mashinostroenie, 2015).

The efficiency of using composite pressure vessels is determined by the degree of perfection of the reinforcement technology - the continuous winding process. This method provides for the determination of the rational structure of the material, i.e. the number and order of alternation of layers, orientation angles and the type of reinforcing materials in them, their relative content in the composition and other parameters. In this case, layers should be understood as layers with a corresponding arrangement of reinforcing fibers (annular or spiral laying direction) of the composite material during winding. The thickness of the annular or spiral layers is to be understood as the total plurality of reinforcing fibers with a corresponding arrangement, referred to the unit of length of the sheath section. In this case, the order of arrangement of layers with an annular and spiral arrangement of reinforcing fibers along the thickness of the shell wall can be different.

However, the existing designs of balloons and the above-mentioned patents, the recommended solutions are not always feasible in the manufacture of balloons in which the ratio of the diameter of the neck opening to the diameter of the balloon is higher than 0.7. A feature of such structures is that with an increase in the ratio of the diameter of the throat hole to the diameter of the cylinder above 0.7, the shape of the bottom surface begins to degenerate into a cylindrical shape, and at the same time, the geometric dimensions of the contacting surface of the neck connecting flange, necessary for its design, which are presented in the known solutions for the execution of composite cylinders, practically disappear. ...

In this case, great difficulties arise both in design and in the technological implementation of the composite shell, which significantly complicate and increase the cost of the design.

Known is a high-pressure cylinder with large-diameter necks containing an inner cylindrical thin-walled metal tube, metal connecting flanges (bushings) inserted into it, and a load-bearing shell made of high-strength composite materials (RU 2338955 C1, 20.11.2008, prototype). The disadvantage of the known cylinder is its low efficiency at any level of cyclic high pressure loading.

The objective of the invention is to create such a design of the cylinder with the ratio of the diameters of the throat openings to the diameter of the cylinder above 0.7, which would provide highly efficient performance at any level of cyclic high pressure loading with minimum weight and manufacturing cost.

The technical result of the invention is the simplicity of its technological implementation and consumer appeal, since the consumer has the opportunity not to be afraid of the destruction of the high-pressure cylinder when the maximum loads are reached, due to the splinter-free form of its destruction under these loads. This expands the possibilities of using the vessel according to the invention, especially in domestic conditions and on vehicles where compressed gases are used.

The technical result is achieved due to the fact that a metal-composite high-pressure cylinder with large-diameter necks contains an inner cylindrical thin-walled metal tube, inserted metal connecting flanges (bushings) and a load-bearing shell made of high-strength composite materials, the surface of the connecting flanges (bushings) is made on one side in the form of a part of a nodoid (unduloid) of rotation with a maximum diameter equal to the inner diameter of the tube and ensuring the ratio of the smaller diameter to the diameter of the tube 0.71 - 0.83 and has an end section in the form of a polyhedral prism (non-circular cylinder) separated from the surface of the nodoid (unduloid) by an annular groove, and the ends of the tube by plastic deformation are compressed along the surfaces of the flanges in the form of unduloid nodoids and fixed in the annular grooves of the threaded flanges (bushings), while the load-bearing shell made of composite materials consists of layers of high-strength and high-modulus threads spiral reinforcement with reinforcement angles of 45-56 ° ensuring the ratio between the membrane stiffness of the thin-walled metal tube and the load-bearing composite shell in the annular direction in the range of 0.56 - 0.58 and tightly covers the end sections of the non-circular connecting flanges with the formation of a strong connection with them. (last).

In the resulting space between the surfaces of the connecting flanges in the form of nodoids and the surfaces of the deformed ends of the tube with a tight contact, a pressure transducer is placed in the form of a set of interlayers of variable thickness, unfastened to each other, made of an elastic incompressible material of different density, such as rubber.

The total volume of the elastic incompressible material of the pressure transducer exceeds by 10-15% the increment in the volume of the bottom of the force shell during its deformation.

Sealing interlayers or elastic sealing rings are installed between the contact surfaces of the connecting flanges (bushings) and the surfaces of the deformed ends of the tube.

Sealing sealing rings are installed in the annular grooves of the connecting flanges (bushings).

Sealing sealing rings between the contacting surfaces of the bushings and the ends of the thin-walled tube are installed in the section of the transitions of the cylindrical surface of the tube into the surface of nodoids (unduloids).

The technical result is achieved only within the specified ranges and alternatives.

The invention is illustrated in the following in detail by describing examples of execution with reference to the drawings.

FIG. 1 shows a general view of a pressure vessel.

FIG. 2 is a diagram of flange installation using a pressure transducer.

FIG. 3 and FIG. 4 - options for installing the O-ring.

FIG. 5 shows typical shapes of bottom profiles of known composite shells.

FIG. 6 shows typical forms of the generating profiles of nodoid and uduloid shells of revolution.

As shown in FIG. 1, in one embodiment, the pressure vessel contains a strong load-bearing shell 2, for example, of a composite material in the form of a multilayer frame consisting of layers of unidirectional reinforcing threads of glass fiber or carbon fiber of spiral reinforcement impregnated with a polymer binder. The force shell 2 in the process of its manufacture covers a thin-walled metal tube 1, in which connecting flanges 3 are pre-installed and plastic deformation of its ends. The surfaces of the connecting flanges and deformed ends of the tube have the shape of nodoids. In the process of implementing the assembly of the tube and connecting flanges, a pressure transducer 4 of variable thickness is installed between them, consisting of a set of interlayers of viscoelastic material separated from each other. As the material of the pressure transducer 4, it is proposed to use elastic incompressible materials such as rubber with different densities for each layer. The wall thickness of the pressure transducer 4 varies linearly along the generating surface of the connecting flange and has a maximum value in the section of the annular groove of the latter. The total volume of material forming the pressure transducer 4 exceeds by 10-15% the increment in the volume of the bottom of the containment shell 2 when it is loaded with a test pressure.

Alternatively, instead of a pressure transducer, the installation of elastic sealing rings 5, which are located in different sections along the contacting surfaces of the connecting flanges and the deformed ends of the thin-walled tube, can be used.

The essence of the operation of this cylinder device is illustrated by the following example.

As a rule, the creation of a cylinder structure requires solving the problem of optimal design of a combined structure, i.e. selection of the optimal ratio of the thickness of the composite, selection of the appropriate reinforcement scheme for the composite and selection of the appropriate shape of the bottom profile.

In view of the fact that the main load during the operation of the cylinder is the internal pressure of the medium, when choosing the shape of the bottom profile of the shell 2, it is necessary to require the uniform tension of the reinforcing threads of the composite throughout the entire volume of the shell. This condition is equivalent to meeting the requirement of constant deformations of the cylinder structure in the axial and annular directions at all points of the considered shell, i.e.

where

ε _α = ε _β = ε _ν ,

ε _α - meridional deformation of the considered point of the bottom

ε _β - tangential deformation of the considered point of the bottom

ε _ν - deformation along the reinforcing fibers of the composite.

In the particular case of the execution of the design of the cylinder with the laying of the reinforcing threads of the composite along geodetic trajectories and using the above criterion, the shape of the bottom profile for it can be determined from the solution of the differential equation of the following form

obtained when considering the geometric, static and physical conditions for the behavior of the metal-composite shell.

The following designations are adopted here:

r, y - current coordinates of the profile defining the shape of the shell;

y ', y' '- the first and second differential (derivative) of the y coordinate;

R is the radius of the cylindrical part of the shell (maximum radius);

r ₀ is the radius of the pole hole in the composite shell.

- параметр учитывающий отношение прочностных характеристик используемого металла и материала армирующих волокон.

- a parameter that takes into account the ratio of the strength characteristics of the metal used and the material of the reinforcing fibers.

Where:

σ _m is the yield point of the used liner material;

δ _m is the thickness of the used liner material;

σ _ν is the ultimate strength of the composite used;

δ _R - thickness of the used composite material on the cylinder.

Typical bottom profile shapes obtained by solving this equation are shown in FIG. 5.

The analysis of the obtained shapes of the bottom profiles shows that for a wide class of composite materials used, the profile depth is 0.6 - 0.75 of the radius of the cylindrical part of the shell. However, with an increase in the diameter (r0 / Rc) of the neck of the balloon, the depth of the profile increases sharply, and the bottom shell practically degenerates into a cylindrical shape when the ratio r0 / Rc is greater than 0.8. In this case, the geometric dimensions of the contacting surface of the neck connecting flange, which are necessary for its structural design, which are presented in the known solutions of the execution of composite cylinders, practically disappear.

Obviously, in this case, it is necessary to use a different shape of the surface profile of the bottom of the cylinder, different from the previously known ones, ensuring its operability under the influence of the contact load arising between the connecting flange and the load-bearing shell. In this case, it is necessary to take into account the peculiarities of the contact interaction between the surface of the connecting flange and the surface of the shell. As a first approximation, the reaction of this interaction can be represented in the form of a linearly varying pressure along the generatrix of the bottom profile. To implement such a change in the contact pressure, it is advisable in the structure between the contacting surfaces to install a pressure transducer 4 with a thickness linearly varying along the generatrix of the bottom profile and made of an elastic incompressible material, for example rubber. To ensure the accepted nature of the contact pressure change, it is necessary to provide the wall thickness of the pressure transducer 4 linearly varying along the generatrix of the connecting flange surface with a maximum value in the section of the annular groove of the latter. In this case, the total volume of material forming the pressure transducer 4 must exceed by 10-15% the increment in the volume of the bottom of the power shell 2 when it is loaded with the test pressure. The given values of the material thickness of the transducer 4 are obtained from the condition of displacement of the connecting flange as a rigid body without mutual penetration under variable deformation of the bottom profile and ensuring its equilibrium under the conditions of loading by constant pressure acting from the side of the inner cavity of the cylinder and linearly varying will of the bottom forming pressure acting from the side contact.

In this case, it is advisable to use the profiles of special surfaces as the shape of the bottom profile.

Such surfaces include surfaces that are called nodoid or unduloid in mechanics. The generators of the nodoid and unduloid shells are shown in Fig. 5 and are described in parametric form as follows:

- модуль эллиптического интеграла,

- дополнительный модуль, F, Е - эллиптические интегралы 1-го и 2-го рода,

- текущая координата, λ - параметр, характеризующий кривую образующей, r₁ - радиус цилиндрической части оболочки.where

- elliptic integral modulus,

- additional module, F, E - elliptic integrals of the 1st and 2nd kind,

is the current coordinate, λ is a parameter characterizing the curve of the generatrix, r ₁ is the radius of the cylindrical part of the shell.

For 0 <λ <r _{1/2, the} shell is called unduloid, for r _1/2 <λ <r _{1, the} shell is called nodoid, and for λ = r _{1/2, 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 the maximum volume, have the minimum surface area, and the angle of inclination of the tangent to the generatrix in them tends to zero as it approaches the junction with a cylindrical or some other shell.

Nodoid, unduloid shells, when loaded by their internal pressure, have the property of uniform strength and have an advantage in strength in comparison with elliptical and spherical shells, the level of stress arising in them for this type of loading is much lower. One of the characteristic properties of the shell under consideration, as it is easy to see, is that as we approach the junction with the cylinder, there is a fairly smooth conjugation of the shell with it and bending stresses at the junction are practically absent, that is, the influence of edge effects is completely excluded.

Based on the above in the proposed solution, the design of the surface of the connecting flanges (bushings) on one side in the form of a part of a nodoid (unduloid) of rotation with a maximum diameter equal to the inner diameter of the tube and ensuring the ratio of the smaller diameter to the tube diameter 0.71 - 0.83 is also due to the degree of compression of the tube ends at carrying out the operation of plastic deformation with limiting the maximum deformations of the tube material to 28% to exclude the loss of stability of its shape.

As a rule, a cylinder, in addition to being loaded by internal pressure, is subjected to a load such as a torque arising during the installation of fittings or valves, as well as during the operation of winding the load-bearing shell. To ensure the operability of the structure under the influence of this load on the connecting flanges 3, end sections are provided in the form of a multifaceted prism (non-circular cylinder) separated from the surface of the nodoid (unduloid) by an annular groove, providing strong adhesion to the composite shell according to the principle of a spline connection.

Due to the fact that the relative radii of the bottle necks are greater than 0.7 for the implementation of the winding method in the manufacture of the load-bearing shell with the laying of reinforcing fibers along geodetic trajectories, the obtained reinforcement angles should be in the range of 45-56 degrees. This design of the reinforcement scheme makes it possible to significantly simplify the process of manufacturing the load-bearing shell due to the absence of reinforcement in the circumferential direction.

To ensure the operability of the cylinder under multi-cycle loading by internal pressure and based on the limitations imposed on the ultimate deformations of the tube material (as a rule, 0.37-0.4%) and the criterion assessment in the Menson-Coffin form, the ratio between the membrane stiffness of the thin-walled metal tube and the force composite shell in the annular direction in the range should be 0.56 - 0.58. This ratio makes it possible to determine the choice of the reinforcing material of the composite shell with a known tube material and to establish specific values for the thicknesses of both the tube and the composite material. And thus to carry out a rational design of the design of the cylinder.

The operation of the device according to the invention has been described in the description of the variants of its construction and does not require further special explanation in this case.

With the creation of the proposed device, it became possible to use high-pressure cylinders (vessels) made of a composite material and a thin-walled metal inner shell. Manufacturing and testing of pressure vessels with the proposed solution confirmed their high reliability and efficiency.

The invention is not limited to the above-described embodiments, which are given only to illustrate the invention, and may vary within the scope of the claims.

Claims (6)

1. A metal-composite high-pressure cylinder with large-diameter necks, containing an inner cylindrical thin-walled metal tube, metal connecting flanges inserted into it and a load-bearing shell made of high-strength composite materials, characterized in that the surface of the connecting flanges on one side is made in the form of a part of a nodoid or unduloid of revolution with a maximum diameter equal to the inner diameter of the tube and ensuring the ratio of the smaller diameter to the tube diameter of 0.71 - 0.83 and has an end section in the form of a multifaceted prism of a non-circular cylinder, separated from the surface of the nodoid or unduloid by an annular groove, and the ends of the tube are compressed along the surfaces by plastic deformation flanges in the form of nodoids or unduloids and are fixed in the annular grooves of the threaded flanges, while the load-bearing shell made of composite materials consists of layers of high-strength and high-modulus spiral reinforcement threads with reinforcement corners 45-56 ° with the provision of the ratio between the membrane stiffness of the thin-walled metal tube and the load-bearing composite shell in the annular direction in the range of 0.56 - 0.58 and tightly covers the end sections of the connecting flanges of a non-circular shape with the formation of a strong connection with them. 2. A metal-composite balloon according to claim 1, characterized in that a pressure transducer is placed in the resulting space between the surfaces of the connecting flanges in the form of nodoids and the surfaces of the deformed ends of the tube with a tight contact, in the form of a set of interlayers of variable thickness, interleaved with each other, made of an elastic incompressible material of different density, for example rubber. 3. A metal-composite balloon according to claim 2, characterized in that the total volume of the elastic incompressible material of the pressure transducer exceeds by 10-15% the increment in the volume of the bottom of the force shell during its deformation. 4. A metal-composite cylinder according to claim 2, characterized in that between the contact surfaces of the connecting flanges and the surfaces of the deformed ends of the tube, sealing interlayers or sealing elastic rings are installed. 5. A metal-composite cylinder according to claim 4, characterized in that the sealing sealing rings are installed in the annular grooves of the connecting flanges. 6. A metal-composite cylinder according to claim 4, characterized in that the sealing sealing rings between the contacting surfaces of the bushings and the ends of the thin-walled tube are installed in the cross-section of the transitions of the cylindrical surface of the tube into the surface of the nodoids or unduloids.

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