Pipeline components with air gap insulation

Abstract

The invention relates to a line element with air gap insulation, in particular to a line element (10) for an exhaust gas line, in which an inner pipe (IS) is surrounded by an outer pipe (AS) while forming an intermediate space (15). In a preferred embodiment, the inner pipe (IS) is produced from a wound, contoured strip (11) having at least one radial projection (RF) which protrudes into the intermediate space (15) as a spacer between the inner pipe (IS) and the outer pipe (AS).

Description

Technical Field

[0001] The invention relates to a tubular, double-walled pipeline element with air gap insulation in a preferred embodiment. The pipeline element can be produced in a straight form and can be bent in all spatial directions without using tools combined with shape memory. A bending machine is not required for this purpose. Background Art

[0002] The preferred field of application of the described subject matter is the use in the exhaust gas system (abgasanlage, sometimes referred to as exhaust system) of an internal combustion engine. This is mainly in the region of the exhaust gas-conducting system between the turbine outlet and the inlet into the exhaust gas aftertreatment system. The task of such line elements is to transport hot gaseous media without leakage, which have a significant temperature difference (>200° C.) with respect to the ambient temperature. The thermal insulation of this region of the exhaust gas-conducting system is becoming increasingly important.

[0003] The driving force (Treiber) is a legal provision in the field of exhaust gases all over the world. The legal provisions currently and in the future significantly regulate (sometimes referred to as constraints) the harmful substance emissions of PKW (passenger cars) and commercial vehicles. Exhaust gas equipment is increasingly equipped with aftertreatment modules such as soot particle filters and SCR systems (selective catalytic reduction systems). The functional capacity of the exhaust gas aftertreatment device depends to a large extent on the temperature of the exhaust gas, at which the exhaust gas enters the aftertreatment. This applies to the catalytic reaction in the case of the SCR system, which should lead to an almost complete reduction of nitrogen oxides as soon as possible after the start-up process. In the case of a particle filter, passive regeneration can only occur when the minimum exhaust gas temperature is exceeded. The higher the exhaust gas temperature, the more effectively active regeneration (for example, by injecting unburned diesel into the exhaust gas device to initialize the active regeneration) also works. This results in the following requirement, that the temperature loss in the exhaust gas on the path from the turbine outlet to the inlet into the aftertreatment device should be minimized. This is particularly applicable to the cold start phase. It is useful to keep the cold start phase as short as possible by suitable measures so that effective aftertreatment of the exhaust gases can begin as soon as possible after the engine is started.

[0004] Another driving force is the reduction of the average fuel consumption of the company and the associated reduction of CO2 emissions. In particular, there is a trend towards lower exhaust gas temperatures for diesel vehicles, since the combustion processes guided in this way lead to lower fuel consumption. Therefore, the ever-lower exhaust gas temperatures will require much better thermal insulation in the future in order for the aftertreatment to remain effective.

[0005] BACKGROUND OF THE INVENTION A method for producing a curved element insulated with a recess for exhaust gas guidance is known.

[0006] DE 19628797 C1 discloses an exhaust manifold insulated with a gap. Here, an inner pipe is surrounded by two half shells in such a way that a gap is created between the outer diameter of the pipe and the half shells. The resulting gap is defined by a plurality of distance devices (distanzmittel, sometimes called distance devices) or distance blocks (distanzstücke, sometimes called distance blocks).

[0007] DE 102012018470 A1 is a further development of DE 19628797 C1. In order to adjust the gap in a defined manner over the entire covering area, a mounting aid made of a unstable plastic is used. The plastic is either injected (angespritzt, sometimes called injection molding) onto the outer jacket or injection molded onto the exhaust pipe at room temperature.

[0008] DE 102011121383 A1 describes an assembly with two pipes inserted into each other. The annular gap between the two pipes is first filled with a pourable insulating material. In a subsequent step, the entire structure (consisting of the inner pipe, insulating material and outer pipe) is deformed by an internal high-pressure method.

[0009] In general, in the background art, straight or curved pipes for guiding exhaust gas are always required. A gap is created around the pipe. In order to ensure the gap height, a mechanical spacing device is used in DE 19628797 C1. In DE 102012018470 A1, the gap is adjusted by unstable plastic, which melts during later operation. DE 102011121383 A1 uses a pourable insulating material to ensure the distance between the inner pipe and the outer pipe. DE 19628797 C1, DE 102012018470 A1 and DE 102011121383 A1 require one or more curved pipes, which are manufactured in a previous process step. In addition, the measures for ensuring the gap are highly expensive and, despite this, the gap height cannot be ensured to the same extent in every area of ​​the pipeline element during another production process (bending, internal high-pressure deformation). Summary of the invention

[0010] Against the background described, the main object of the invention is to produce curved pipe elements for exhaust systems that are insulated with gaps without using bending tools or even bending machines combined with shape memory. A secondary object is to maintain a constant gap between the inner pipe and the outer pipe, which gap should be achieved without additional measures or auxiliary materials.

[0011] The main object is achieved by a pipeline element according to claim 1. Advantageous developments are contained in the dependent claims.

[0012] The piping element according to the invention therefore comprises the following components:

[0013] Internal piping.

[0014] An outer pipe surrounding an inner pipe with an intermediate space formed.

[0015] This applies to:

[0016] The inner and / or outer pipe is manufactured from a wound, profiled strip.

[0017] The aforementioned strip has at least one radial projection which projects into the intermediate space as a spacer between the inner pipe and the outer pipe.

[0018] In particular, the inner pipe can be wound from a profiled (metal) strip, wherein the strip has radial projections pointing radially outwards, i.e. in the direction of the outer pipe, which ensure a defined (minimum) distance between the inner pipe and the outer pipe. Additionally or alternatively, the outer pipe can be wound from a profiled (metal) strip, wherein the strip has radial projections pointing radially inwards, i.e. in the direction of the inner pipe, which ensure a defined (minimum) distance between the inner pipe and the outer pipe.

[0019] The radial projections extend in radial direction over the corresponding base diameter (inner diameter of the outer pipe or outer diameter of the inner pipe), wherein the base diameter in the case of corrugated pipes is located at the points of the troughs or peaks of the “normal” pipe geometry.

[0020] Furthermore, the radial projections may be present only locally at one location. Preferably, however, the radial projections extend continuously around the entire strip and thus also (helical) around the entire intermediate space. For an intermediate form to the variant described, there are a plurality of local radial projections, for example at equidistant distances along the entire strip.

[0021] Since one or more radial projections can be formed on the strip, when “radial projection” is mentioned below, it always means “at least one of the one or more radial projections”.

[0022] The inner duct or the outer duct (preferably both) may in particular be gas-tight.

[0023] In a preferred embodiment, the inner pipe and / or the outer pipe is designed as a spirally corrugated winding bellows. A spirally corrugated bellows is a spirally corrugated element connected in the contour edge region, which has a corrugation that is spiral with respect to the axis of rotation. The spirally corrugated tube structure can preferably be hooked in a form-fitting manner or welded in an overlapping or materially fitting manner. Such elements are described, for example, in DE 10 2008 001 297 A1 or DE 10 2011 053 131 A1.

[0024] The inner tube and / or the outer tube can optionally have a diameter that varies in a wave-like manner between adjacent radial projections formed thereon or alternatively have a substantially constant diameter.

[0025] The radial projection can be viewed in an axial cross-section and can be formed in principle at any arbitrary position of the strip, for example in the middle region of the strip. However, in a preferred embodiment, the radial projection is formed at the axial edge of the strip.

[0026] In particular, radial projections may be formed at both axial edges of the strip, wherein the radial projections of adjacent pipe spirals that abut against each other are connected to each other (for example welded).

[0027] In a preferred embodiment, both the inner pipe and the outer pipe are made of a coiled strip with a specific profile, in particular in the form of a spirally corrugated coiled bellows. Preferably, the pitch of the coils of the inner pipe and the outer pipe is identical to each other.

[0028] Preferably, the inner and outer pipes are screwed into one another. This is possible in particular when both the inner and outer pipes are each manufactured with a helically wavy geometry and the pitches of the geometries are substantially the same. The screwing into one another results in a particularly stable configuration.

[0029] In a further embodiment, the intermediate space between the inner pipe and the outer pipe is filled with a thermal insulation material. In addition to thermal insulation, the thermal insulation material can also contribute to the stability and reinforcement of the structure.

[0030] Additionally or alternatively, the inner pipe and / or the outer pipe can also have a thermally insulating coating.

[0031] Furthermore, the inner pipe and the outer pipe can optionally have different wall thicknesses. Preferably, the wall thickness of the inner pipe is smaller here. The ratio of the wall thickness of the inner pipe to the outer pipe is typically in the range of 1:N, where N>1 (preferably N=2; 3; 4; 5; 6; 8; 9 or 10). For example, the inner pipe can be approximately 0.2 mm thick and the outer pipe can be approximately 0.5 mm thick (N=2.5).

[0032] The free (distal) end of the radial projection can be optionally bent over to avoid sharp outer edges (see DE 10 2011 053 131 A1). In particular, the bend can be a 180° reverse bend which is, for example, openly U-shaped or results in overlapping of sections and doubling of material.

[0033] In addition, the outer pipe is wound with a strip material at its outer side. This can further stabilize the shape and in particular achieve additional thermal insulation. Preferably, a further intermediate space is constructed between the strip material and the outer pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention is explained below with reference to the figures according to an exemplary embodiment.

[0035] Figure 1 The pipeline element according to one embodiment of the invention is shown in an axial section through one of its walls along its axial extension (pipe center axis X), wherein the pipeline element has a corrugated bellows structure as basic geometry;

[0036] Figure 2 shows axial cross-sections through different ribbon geometries used for producing a tubular element;

[0037] Figure 3 shows a similar Figure 1 Axial cross-sectional view;

[0038] Figure 4 A cross-sectional view (left) and a perspective view (right) of a pipe element with a spatial bend are shown;

[0039] Figure 5 Similar to the example shown, a pipe element with a strip of material wrapped around the outside Figure 4 ;

[0040] Figure 6 A schematic diagram of the use of an intermediate space through which exhaust gas flows through a line element is shown. DETAILED DESCRIPTION

[0041] The object described at the outset is achieved according to the invention, for example, by means of two helically corrugated bellows geometries which can be screwed into one another ( Figure 1 ). The bellows geometry is firstly rolled from a flat metal strip (strip), the corners are rounded and then welded at the outer circumference similarly to a diaphragm bellows (see DE 10 2011 053 131 A1).

[0042] The outer bellows geometry (belt 12) has three undulations with a radial height b in the present example. The helical welding is carried out in the region (14) of the abutting edges of adjacent spiral band elements. The pitch of the helix corresponds to the profile width and is Figure 1 It is specified by p.

[0043] The inner bellows geometry (belt 11) in the present example also has three waves with a radial height a (wherein the distance of the wave crests from the pipe center axis X defines the basic outer diameter of the inner pipe). The helical welding is carried out in the region (13) of the abutting edges of adjacent spiral strip elements. The pitch of the helix corresponds to the profile width and is Figure 1 It is specified by q.

[0044] The two bellows geometries are first produced independently of one another and then screwed into one another. The resulting interspace (intermediate space 15) is helical and is sealed both internally with respect to the exhaust gas flow and externally with respect to the surroundings in a gas-tight manner. In a preferred embodiment, the interspace can be filled with insulating material. For example, a foamed, hardened (e.g. metallic) insulating material can be introduced using an injection device. The bellows undulations produce a mobility that can be used for bending and, if necessary, for extension and compression.

[0045] Especially from the attached Figure 2 As can be seen in , the two axial edges of the strip 11 of the inner pipe carry radial projections RF which, in the finished piping element, extend radially beyond the base outer diameter of the inner pipe into the intermediate space 15 and engage in the wave crests of the outer pipe.

[0046] The radial bridge length of the inner bellows geometry (radial projection RF 13 ) defines the radial height of the recess, also during and after bending to the final geometry.

[0047] Since the two bellows geometries are screwed into each other, the pitches p and q are identical in a preferred embodiment. In a preferred embodiment, this also applies to the wave heights a and b and to the number of waves spanning the profile widths p and q.

[0048] also Figure 2 Two different embodiments are shown in the outer region or at the profile ends. Strips 11 and 12 describe a simply deformed profile shape, while strips 11-II and 12-II have sheet metal folds in the outer region. The latter improve the feel and reduce structural stresses during operation.

[0049] The sheet thicknesses of the two bellows geometries can be selected independently of one another. The screwed-in and fixed fit can be optimized by suitable structural measures. In a preferred embodiment, the sheet thickness of the outer bellows geometry is significantly greater than the inner sheet thickness, for example in a ratio of 1:2 to 1:3. In this way, the outer bellows geometry produces stability, structural integrity, resistance to natural frequencies and protection from street influences such as stone impacts. The inner bellows geometry has a minimum sheet thickness in a preferred embodiment. The minimum sheet thickness produces a similarly minimum heat capacity. The heating time of the inner sheet layer in contact with the exhaust gas flow in this way is short and the pipeline element insulated with gaps according to the invention contributes to a rapid, fully functional aftertreatment after a short cold start phase.

[0050] The sheet thickness, profile width and wave height of the geometry according to the invention are variable so that heat and pressure losses across the length of the element can be optimized.

[0051] Figure 3 An embodiment with a wave height a=b=zero is shown. In particular, for straight line sections, the line elements separated by gaps can be designed in a weight-optimized and resource-saving manner. Optionally, only the inner or outer pipe can also be designed with such a wave height (zero).

[0052] Figure 4 The interspaced pipe element according to the invention is shown after the bending to the final geometry has been achieved. The diameter difference of the undulations (31) influences the pressure loss across the length.

[0053] Figure 5 A hollow-insulated pipe element is shown, which is mechanically reinforced by being wound with a strip material after being bent into the final geometry. The hollow-insulated pipe element with a specific shape is wrapped on the outside by the wound material. The material is made of a heat-resistant strip, for example of glass fiber roving (Glasfaser-Roving, sometimes called glass fiber roving). Other strip materials, which are not exhaustive in this list, are suitable for use at high temperatures:

[0054] Needle-punched nonwoven fabrics (Nadelvliese) made of alkali-free glass fiber (E-Glas), ceramic precursor materials or metal fabric composite materials (nonwovens)

[0055] Knitted ribbons made of alkali-free glass fiber, ceramic precursor material or metal fabric composite material

[0056] Knitted elements made of graphite fibers combined with absorbent fibers.

[0057] In a further step, the wound strip can be impregnated with a hardenable liquid. For example, polyester resins, vinyl ester resins or epoxy resins are suitable for this purpose. Ceramic materials such as CBPC (chemically bonded phosphate ceramic) can also be used. Production can be carried out in a parallel winding method or in a cross-winding method (see DE 10 2010 004 809 A1).

[0058] In this way the mechanical strength can be optimized. The second interspace produced beneath the wound tape layer increases the insulating capacity.

[0059] Figure 6 The recessed line element is shown with a connection for introducing a special medium into the recess ( 15 ).

[0060] For example, the separation of the exhaust gas flow before the pipeline element separated by the gap is suitable for improving the insulation effect. The thread-shaped gap (15) has a significantly greater length compared to the exhaust gas path located inside. The separation of the exhaust gas flow into the gap by means of a branch therefore ideally leads to a higher flow velocity and a lower pressure in the region of the gap. This can positively influence the insulation properties.

[0061] In the attached Figure 6 The exhaust gas convection in the inner pipe and in the intermediate space is shown, but the exhaust gas can also be guided in a parallel flow. In addition, the exhaust gas can be extracted optionally between the engine M and the pipeline element 50, after the pipeline element 50 and before the exhaust gas aftertreatment device AGN or after the exhaust gas aftertreatment device (see DE 10 2018 122658.6).

[0062] It is also possible to actively influence the exhaust gas temperature by using the flow gap through which a heating medium or also a cooling medium flows.

[0063] All embodiments described above are also usable in combination and the technical variants are described in detail, but not exhaustively.

Claims

1. Pipe elements for exhaust gas lines, including coaxial components: - Internal pipe (IS), - an outer pipe (AS) surrounding the inner pipe (IS) while forming an intermediate space (15), in - the inner tube (IS) and / or the outer tube (AS) are made from a coiled profiled strip, the strip has at least one radial projection (RF) which projects into the intermediate space (15) as a spacer between the inner pipe (IS) and the outer pipe (AS), - the radial protrusion (RF) is formed at the axial edge of the strip, and - Radial projections (RF) are formed at two axial edges of the strip, wherein the abutting radial projections (RF) of adjacent pipe spirals are connected to one another.

2. The piping element according to claim 1, characterized in that The inner tube (IS) and / or the outer tube (AS) are spirally corrugated coiled bellows.

3. The piping element according to claim 1, characterized in that The inner tube (IS) and / or the outer tube (AS) has a constant diameter between adjacent radial projections (RF).

4. Pipe element according to any one of the preceding claims, characterized in that The inner tube (IS) and the outer tube (AS) are manufactured from a coiled profiled strip.

5. The piping element according to claim 4, characterized in that The inner pipe (IS) and the outer pipe (AS) are screwed into each other.

6. Pipeline element according to any one of the preceding claims 1 to 3, characterized in that The intermediate space (15) between the inner pipe (IS) and the outer pipe (AS) is filled with a thermal insulation material.

7. Pipeline element according to any one of the preceding claims 1 to 3, characterized in that The inner tube (IS) and the outer tube (AS) have different wall thicknesses.

8. Pipeline element according to any one of the preceding claims 1 to 3, characterized in that The end of the radial protrusion (RF) is bent.

9. Pipeline element according to any one of the preceding claims 1 to 3, characterized in that The outer pipe (AS) is wound with a strip material (56) at its outer side.

10. The piping element according to claim 4, characterized in that The pitch of the windings of the inner tube (IS) and the outer tube (AS) are the same.

11. The piping element according to claim 7, characterized in that The wall thickness of the inner tube (IS) is smaller.

12. The piping element according to claim 9, characterized in that A further intermediate space is formed between the strip material (56) and the outer pipe (AS).

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